tubular/src/main.rs

//! A Ratatui YouTube browser backed by yt-dlp, with playback handed to Terebi.
//!
//! Run `cargo run -- "rust programming"`; default to the installed Terebi CLI on PATH.
//! Always start in normal mode; a CLI query searches automatically. Press i to edit the query.
//! Insert: Enter submits a changed query and returns to normal; Esc returns without searching.
//! Search and new-tag text: Option/Alt+Backspace or Ctrl-W deletes the previous whitespace word.
//! Cmd/Super+Backspace or Ctrl-U clears the line; plain Backspace removes one character.
//! The terminal must transmit modified Backspace; otherwise map it to Ctrl-W or Ctrl-U.
//! Active text fields show a steady block cursor at the scrolled end; other views hide it.
//! The terminal's configured default cursor shape is restored when the app exits.
//! Normal: j/k selects, Enter opens the video in Terebi, and i edits the query.
//! View tabs wrap whole labels into rows using terminal-cell widths and reflow on resize.
//! Short terminals keep the selected tab row visible while reserving space for the other panes.
//! A single label wider than the terminal is clipped rather than split across rows.
//! Normal-mode d opens video info; d expands the full description in place, then returns to info.
//! Both modes share one centered popup, up to 70% width and 60% height, capped at 96 by 20 cells.
//! Full descriptions scroll with Up/Down and PgUp/PgDn; j/k selects videos in either mode.
//! Esc closes the popup; i returns to editing. Mode toggles retain cached content and pending work.
//! Images use native terminal graphics when supported, otherwise colored half-block characters.
//! HQ thumbnails reserve their proportional 4:3 footprint before loading, avoiding metadata reflow.
//! Thumbnails align to the popup's left inner edge, with two columns before the left-aligned text.
//! A blank row separates the bold title from the dimmed author · publication date.
//! Description excerpts use normal brightness and retain a two-column right gutter.
//! Overflowing excerpts end with … without splitting wide glyphs; full descriptions preserve paragraphs.
//! Both modes share an in-memory LRU of 64 full descriptions, keyed by video ID across views.
//! Thumbnails retain eight recently used inactive decoded images plus the selected image.
//! Reopening or revisiting cached videos skips extraction/download/decoding; resize work stays off-thread.
//! Title, author, and publication metadata remain in loaded view rows; preview caches survive view/query changes.
//! Caches last for this session without a timer. A successful r refresh clears both preview buffers.
//! curl fetches JPEGs lazily into memory; decoding and image resizing/encoding run off-thread.
//! Channel tags live in `$XDG_CONFIG_HOME/tubular/config.toml`, or `~/.config/tubular/config.toml`.
//! `[categories]` stores flat, overlapping tags: one channel can appear in several arrays.
//! Checked tags save the creator's @handle; `[channels]` retains its canonical URL.
//! Mapped handles resolve to stable channel IDs; unmapped handles still work directly.
//! Deselecting removes the channel from that tag, preserving other creators and empty tags.
//! Missing handle/ID metadata or a conflicting mapping prevents saving rather than guessing.
//! Normal-mode s edits memberships: j/k moves, Space toggles, Enter commits, Esc cancels.
//! n prompts for a new tag; Enter stages it checked, Esc returns. Only list Enter writes the file.
//! Normal-mode S in a category view edits every saved channel, even with no videos loaded.
//! Shared tags start checked; Enter atomically replaces every target's tags with the checked set.
//! Unchecked tags lose only target channels; other creators, registrations, pins, and empty categories remain.
//! n stages a new shared tag; Esc cancels the whole edit. Changed source membership requires reopening.
//! Clearing all tags is refused for category-only channels, avoiding accidental unsubscription.
//! Search and Feed are permanent tabs. Normal-mode c opens the saved-category browser.
//! The category browser starts NORMAL: j/k or arrows move, i filters, Enter browses, p pins, Esc closes.
//! INSERT filters live with case-insensitive substring matching; arrows or Ctrl-J/K move, Enter browses.
//! Esc returns to NORMAL without clearing the filter; another Esc closes. Search input editing shortcuts apply.
//! Matching selections survive filter edits; no matches leaves Enter/p without an action.
//! Pinned categories stay visible; browsing another category replaces the single temporary tab.
//! Pinned category tab titles use a dimmed `p` suffix; Search, Feed, and temporary tabs do not.
//! The suffix stays dimmed when selected and counts toward whole-label wrapping without changing category names.
//! Browsing a pinned category focuses its existing tab and removes the temporary tab.
//! Top-level `pinned_categories = ["Favorites"]` persists pins; missing category names are ignored.
//! Tab/Shift-Tab cycle only visible tabs; hidden views retain cached rows and selection.
//! r reloads config and refreshes the current view.
//! Feed includes saved `[channels]` entries, even untagged, plus direct tag entries, without duplicates.
//! Untagging is not unsubscribing: remove mappings and tag references from the file to unsubscribe.
//! Search pages contain 20 results; Feed/tag pages request 20 uploads per channel's /videos tab.
//! In normal mode, approaching the loaded end fetches the next page without replacing rows/selection.
//! Loading result/preview panes animate a spinner after their title, including additional pages.
//! Info spinners cover image download/decode/resize and description fetching; errors stop them.
//! Feed rows use approximate upload dates; older rows wait until newer channel pages catch up.
//! Undated feed rows appear at exhaustion. Cached views retain their page position across switches.
//! Switching views cancels in-flight extraction; returning resumes the same pending range.
//! Errors keep loaded rows and stop automatic retries; r reloads config and restarts the current view.
//! Deep pages may slow down because yt-dlp offsets re-traverse earlier continuation pages.
//! Video tables show Published as YYYY-MM-DD; ~ marks estimated UTC dates, Unknown missing metadata.
//! Prefer exact upload dates and cache date labels during extraction, not on every redraw.
//! Terebi receives `--new-instance --url` and the canonical YouTube URL; each selection gets its own player.
//! `--player` overrides its CLI path; otherwise `terebi` is resolved through PATH.
//! The CLI exits after handoff, not playback completion. Later playback errors appear in Terebi.
//! Quitting cancels pending metadata/launch processes, not the separately running player.

mod config;
mod thumbnail;
mod youtube;

use std::{
    collections::{BTreeMap, HashSet},
    ffi::OsString,
    io,
    path::PathBuf,
    time::{Duration, Instant},
};

use clap::Parser;
use ratatui::{
    DefaultTerminal, Frame,
    crossterm::{
        cursor::SetCursorStyle,
        event::{self, Event, KeyCode, KeyEvent, KeyEventKind, KeyModifiers},
        execute,
    },
    layout::{Constraint, Layout, Rect},
    style::{Color, Style, Stylize},
    text::{Line, Span},
    widgets::{Block, Clear, List, ListState, Paragraph, Row, Table, TableState, Wrap},
};
use youtube::{Job, PAGE_SIZE, Page, PlayerLaunch, Video};

#[derive(Parser)]
#[command(
    version,
    about = "Browse YouTube and open selected videos in Terebi",
    after_help = "Requires yt-dlp for browsing; thumbnails also use curl. Playback requires Terebi and its own streaming dependencies.\nDefaults to terebi on PATH; --player overrides the CLI path.\nTerebi receives --new-instance --url followed by the canonical YouTube video URL and handles extraction, decoding, and playback itself; each selection opens an independent player instance without replacing existing playback.\nAlways start in NORMAL. A CLI query is searched automatically; otherwise press i to enter a query.\nINSERT: type to edit; Enter submits if changed and returns to NORMAL; Esc returns without submitting.\nTEXT EDITING (search, category filter, and new tag): Option/Alt+Backspace or Ctrl-W deletes the previous whitespace-delimited word, including trailing whitespace; Cmd/Super+Backspace or Ctrl-U clears the entire line. Plain Backspace removes one character.\nThe terminal must transmit modified Backspace. If it intercepts Option/Cmd, map those shortcuts to Ctrl-W/Ctrl-U respectively.\nNORMAL: j/k or arrows select; Enter opens the video in Terebi; i edits the query; d opens video info (again for full description); c browses saved categories; s edits channel tags; S edits all channels in the current category; q quits.\nSearch and Feed are permanent tabs. Pinned categories also stay visible; one temporary category tab is replaced by each new unpinned selection.\nTab/Shift-Tab cycle only visible tabs; r reloads config and refreshes the current view from its first page.\nCATEGORY BROWSER (c): starts NORMAL; j/k or arrows move; i enters INSERT to filter; Enter browses; p immediately saves pin/unpin; Esc closes. Choosing a pinned category focuses its existing tab and clears the temporary tab.\nCATEGORY FILTER INSERT: type a case-insensitive substring to filter live; arrows or Ctrl-J/K move; Enter browses the selected match; Esc returns to NORMAL with the filter retained. In NORMAL, j/k and pinning operate on the filtered list. No matches makes Enter/p a no-op. Reopening the selector clears the filter.\nHidden category views retain loaded rows, selection, and pagination for this session. Temporary tabs do not survive restarting; pins do.\nPUBLISHED: Every video view shows YYYY-MM-DD. Exact upload dates take precedence; ~ marks an estimated UTC date from flat metadata, and Unknown means unavailable. Dates are cached without fetching full metadata for every video.\nLOADING: Result/feed and preview titles show an animated spinner while content loads, including further pages and thumbnail decoding/resizing; it disappears when ready or on error.\nFeed sits immediately right of Search and combines every saved [channels] registration, including untagged channels, plus channels entered directly in tags.\nChannel URLs and videos are deduplicated; Feed keeps its cached selection and page position when only tag assignments change.\nSubscriptions: $XDG_CONFIG_HOME/tubular/config.toml, or ~/.config/tubular/config.toml when XDG_CONFIG_HOME is unset/empty/relative.\nExample TOML:\npinned_categories = [\"Favorites\"]\n[categories]\nCreators = [\"@jawed\"]\nFavorites = [\"@jawed\"]\n[channels]\n\"@jawed\" = \"https://www.youtube.com/channel/UC4QobU6STFB0P71PMvOGN5A\"\npinned_categories is a top-level array of category names; pins referencing removed categories are ignored.\n[categories] defines flat, overlapping tags, each with its own feed; there is no hierarchy or inheritance.\nEntries accept @handles, HTTPS YouTube channel URLs, or canonical UC channel IDs.\n[channels] registers saved handles with canonical channel URLs/IDs; feeds use these stable identities.\nChecked tags save the handle plus its mapping; existing URLs/aliases are replaced with the handle, preserving comments.\nUnchecked tags remove only that channel's tag assignment; other creators, omitted tags, empty tag arrays, saved registrations, and pins are retained.\nUntagging does not unsubscribe from Feed. To unsubscribe, remove all of that channel's [channels] mappings and tag entries, then press r.\nUnmapped handles work directly. Existing URL entries still load.\nSaving a single channel requires a handle and canonical ID; unavailable metadata or conflicting mappings are reported without changing the file.\nPAGINATION: Search loads 20 results per page; Feed and tags request 20 uploads per channel's /videos tab per page.\nMoving near the loaded end in NORMAL fetches more asynchronously, preserving existing rows, selection, and previews. Insert mode and open popups pause automatic prefetch.\nFeed views merge newest-first using approximate upload dates. Older uploads wait while newer channel pages catch up; undated uploads appear when the feed is exhausted.\nStatus shows the page and whether more is available or the end is reached. Switching views cancels pending extraction; returning resumes the same range with cached rows intact.\nPage errors retain loaded rows and stop automatic retries; r reloads config and restarts the current view from page one.\nDeep pages may take longer because yt-dlp offsets re-traverse earlier continuation pages.\nTAGS (s): existing assignments are checked; j/k or arrows move; Space toggles; Enter saves all staged memberships; n prompts for a new tag; Esc cancels without writing.\nBULK TAGS (S, category views only): edits all saved channels in the current category, not just channels with loaded videos. Tags shared by every target start checked; mixed memberships start unchecked. Enter atomically applies the exact checked tag set to every target, removing targets from all unchecked categories while leaving other channels untouched. Empty categories, registrations, pins, and comments remain. n stages a new category for all targets; Esc cancels without saving. If source channels changed while editing, close and reopen. Clearing all tags is refused if any target lacks a [channels] registration, so category-only subscriptions are not accidentally lost.\nNEW TAG: type a name; Enter stages it checked and returns to the list; Esc abandons the name; Ctrl-U clears.\nNew tags and membership changes reach disk only on Enter in the main tag list.\nVIDEO INFO: d opens thumbnail and details; d again expands the full description inside the same popup; another d returns to info. Esc closes.\nThe popup uses up to 70% width and 60% height, capped at 96 by 20 cells.\nFull descriptions preserve paragraphs; Up/Down scroll lines and PgUp/PgDn scroll pages. j/k selects videos in either mode.\nThumbnails stay left-aligned with two columns before the text. Image space is reserved before loading so metadata does not shift when decoding finishes.\nThe title is bold, only author/publication metadata is dimmed, and readable excerpts end with an ellipsis when clipped.\nImages fit proportionally on resize. Terminal graphics are detected at startup, falling back to colored half-blocks.\nDownloading, JPEG decoding, and image resizing/encoding do not block navigation.\nSwitching info/description retains in-flight work and cached content. Full descriptions have a session LRU of 64; thumbnails retain eight inactive images plus the selected image.\ni, c, s, S, view changes, and refresh dismiss the preview; successful refresh clears its caches. Typing d or t in INSERT edits text.\nCtrl-C quits in any mode or popup.\nThe player CLI exits once macOS accepts the handoff; Tubular reports launcher errors, while later extraction/playback errors appear in Terebi.\nSelecting another video opens a new Terebi player, leaving existing playback untouched. Quitting Tubular cancels only pending metadata/CLI work; Terebi continues playing independently.\nExample: tubular \"rust programming\""
)]
struct Options {
    /// Terebi CLI executable; accepts --new-instance --url followed by a YouTube video URL.
    #[arg(long, default_value = "terebi")]
    player: OsString,

    /// Optional initial YouTube search.
    query: Option<String>,
}

const DESCRIPTION_CACHE_SIZE: usize = 64;

fn cached_description<'a>(
    cache: &'a std::collections::VecDeque<(String, String)>,
    id: &str,
) -> Option<&'a str> {
    cache
        .iter()
        .find(|(cached, _)| cached == id)
        .map(|(_, text)| text.as_str())
}

#[derive(Debug, PartialEq, Eq)]
enum Mode {
    Insert,
    Normal,
}

struct View {
    name: String,
    title: String,
    videos: Vec<Video>,
    selection: TableState,
    loaded: bool,
    next_start: usize,
    has_more: bool,
    pending: Vec<Video>,
    page_error: Option<String>,
}

impl View {
    fn new(name: String) -> Self {
        Self {
            title: format!(" {name} "),
            name,
            videos: Vec::new(),
            selection: TableState::default(),
            loaded: false,
            next_start: 1,
            has_more: false,
            pending: Vec::new(),
            page_error: None,
        }
    }

    fn reset(&mut self) {
        self.videos.clear();
        self.selection = TableState::default();
        self.loaded = false;
        self.next_start = 1;
        self.has_more = false;
        self.pending.clear();
        self.page_error = None;
    }

    fn accept_page(&mut self, mut page: Page, feed: bool) -> Result<(), String> {
        let next_start = self
            .next_start
            .checked_add(PAGE_SIZE)
            .ok_or("Page offset exceeds the supported range")?;
        let mut videos = if feed {
            self.pending.append(&mut page.videos);
            std::mem::take(&mut self.pending)
        } else {
            page.videos
        };
        if feed {
            videos.sort_by(|a, b| b.timestamp.cmp(&a.timestamp));
        }
        if !videos.is_empty() {
            // Borrow IDs before moving rows, retaining the existing row data.
            let keep: Vec<_> = {
                let mut ids = HashSet::with_capacity(self.videos.len() + videos.len());
                ids.extend(self.videos.iter().map(|video| video.id.as_str()));
                videos
                    .iter()
                    .map(|video| ids.insert(video.id.as_str()))
                    .collect()
            };
            let mut keep = keep.into_iter();
            videos.retain(|_| keep.next().expect("one deduplication flag per video"));
        }
        let ready = if feed && page.has_more {
            page.cutoff.map_or(0, |cutoff| {
                videos.partition_point(|video| video.timestamp.is_some_and(|date| date >= cutoff))
            })
        } else {
            videos.len()
        };
        self.videos.extend(videos.drain(..ready));
        if feed {
            self.pending = videos;
        }
        if self.selection.selected().is_none() && !self.videos.is_empty() {
            self.selection.select(Some(0));
        }
        self.loaded = true;
        self.next_start = next_start;
        self.has_more = page.has_more;
        self.page_error = None;
        Ok(())
    }

    fn needs_page(&self) -> bool {
        self.loaded
            && self.has_more
            && self.page_error.is_none()
            && (self.videos.is_empty()
                || self
                    .selection
                    .selected()
                    .is_some_and(|index| index.saturating_add(5) >= self.videos.len()))
    }
}

enum CategoryTarget {
    Channel { handle: String, channel: String },
    Category { name: String, channels: Vec<String> },
}

struct CategoryDialog {
    target: CategoryTarget,
    label: String,
    tags: BTreeMap<String, bool>,
    selection: ListState,
    name: Option<String>,
    error: Option<String>,
}

struct CategoryBrowser {
    mode: Mode,
    query: String,
    search_names: Vec<String>,
    matches: Vec<usize>,
    selection: ListState,
    error: Option<String>,
}

impl CategoryBrowser {
    fn refilter(&mut self) {
        let selected = self
            .selection
            .selected()
            .and_then(|row| self.matches.get(row))
            .copied();
        let query = self.query.to_lowercase();
        self.matches.clear();
        self.matches.extend(
            self.search_names
                .iter()
                .enumerate()
                .filter(|(_, name)| name.contains(&query))
                .map(|(index, _)| index),
        );
        self.selection.select(
            selected
                .and_then(|index| self.matches.binary_search(&index).ok())
                .or_else(|| (!self.matches.is_empty()).then_some(0)),
        );
        self.error = None;
    }
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum PreviewMode {
    Info,
    Description,
}

struct App {
    options: Options,
    query: String,
    mode: Mode,
    submitted_query: String,
    config_path: PathBuf,
    config: config::Config,
    feed_channels: Vec<String>,
    views: Vec<View>,
    view_index: usize,
    category_dialog: Option<CategoryDialog>,
    category_browser: Option<CategoryBrowser>,
    temporary_category: Option<String>,
    preview: Option<PreviewMode>,
    thumbnail: thumbnail::Thumbnail,
    description_job: Option<(usize, Job)>,
    description_error: Option<String>,
    // ponytail: 64-entry linear lookup; use a keyed LRU if the buffer grows.
    descriptions: std::collections::VecDeque<(String, String)>,
    description_scroll: u16,
    description_max_scroll: u16,
    description_viewport: Option<(u16, u16)>,
    job: Option<Job>,
    player_launch: Option<PlayerLaunch>,
    status: String,
}

impl App {
    fn new(options: Options, config_path: PathBuf, config: config::Config) -> Self {
        let query = options.query.clone().unwrap_or_default();
        let feed_channels = config.subscriptions();
        let mut views = vec![View::new("Search".into()), View::new("Feed".into())];
        views.extend(config.categories.keys().cloned().map(View::new));
        Self {
            options,
            query,
            mode: Mode::Normal,
            submitted_query: String::new(),
            config_path,
            config,
            feed_channels,
            views,
            view_index: 0,
            category_dialog: None,
            category_browser: None,
            temporary_category: None,
            preview: None,
            thumbnail: thumbnail::Thumbnail::new(),
            description_job: None,
            description_error: None,
            descriptions: std::collections::VecDeque::with_capacity(DESCRIPTION_CACHE_SIZE),
            description_scroll: 0,
            description_max_scroll: 0,
            description_viewport: None,
            job: None,
            player_launch: None,
            status: "Press i to enter a query, then Enter to search.".into(),
        }
    }

    fn visible_views(&self) -> impl Iterator<Item = (usize, &View)> {
        self.views
            .iter()
            .enumerate()
            .filter(|(index, view)| {
                *index < 2 || self.config.pinned_categories.contains(&view.name)
            })
            .chain(self.temporary_category.as_ref().and_then(|name| {
                self.views.iter().enumerate().skip(2).find(|(_, view)| {
                    &view.name == name && !self.config.pinned_categories.contains(name)
                })
            }))
    }

    fn cycle_view(&mut self, backwards: bool) {
        let next = if backwards {
            self.visible_views()
                .map(|(index, _)| index)
                .take_while(|index| *index != self.view_index)
                .last()
                .or_else(|| self.visible_views().last().map(|(index, _)| index))
                .unwrap_or(0)
        } else {
            self.visible_views()
                .map(|(index, _)| index)
                .skip_while(|index| *index != self.view_index)
                .nth(1)
                .unwrap_or(0)
        };
        self.switch_view(next);
    }

    fn open_category_browser(&mut self) {
        self.close_preview();
        let mut selection = ListState::default();
        selection.select(
            self.config
                .categories
                .keys()
                .position(|name| self.view_index >= 2 && name == &self.views[self.view_index].name)
                .or_else(|| (!self.config.categories.is_empty()).then_some(0)),
        );
        let mut browser = CategoryBrowser {
            mode: Mode::Normal,
            query: String::new(),
            search_names: self
                .config
                .categories
                .keys()
                .map(|name| name.to_lowercase())
                .collect(),
            matches: Vec::with_capacity(self.config.categories.len()),
            selection: ListState::default(),
            error: None,
        };
        browser.refilter();
        browser.selection = selection;
        self.category_browser = Some(browser);
    }

    fn browse_category_key(&mut self, key: KeyEvent) {
        let mut browser = self
            .category_browser
            .take()
            .expect("category browser is open");
        if browser.mode == Mode::Insert {
            match key.code {
                KeyCode::Esc => browser.mode = Mode::Normal,
                KeyCode::Enter | KeyCode::Up | KeyCode::Down => {}
                KeyCode::Char('j' | 'k') if key.modifiers.contains(KeyModifiers::CONTROL) => {}
                _ if delete_input(&mut browser.query, key) => {
                    browser.refilter();
                    self.category_browser = Some(browser);
                    return;
                }
                KeyCode::Char(c)
                    if !key
                        .modifiers
                        .intersects(KeyModifiers::CONTROL | KeyModifiers::ALT) =>
                {
                    browser.query.push(c);
                    browser.refilter();
                    self.category_browser = Some(browser);
                    return;
                }
                _ => {
                    self.category_browser = Some(browser);
                    return;
                }
            }
            if key.code == KeyCode::Esc {
                self.category_browser = Some(browser);
                return;
            }
        }
        let count = browser.matches.len();
        match key.code {
            KeyCode::Esc => return,
            KeyCode::Char('i') if browser.mode == Mode::Normal => browser.mode = Mode::Insert,
            KeyCode::Down | KeyCode::Char('j') if count != 0 => {
                browser.selection.select(Some(
                    browser
                        .selection
                        .selected()
                        .unwrap_or(0)
                        .saturating_add(1)
                        .min(count - 1),
                ));
            }
            KeyCode::Up | KeyCode::Char('k') if count != 0 => {
                browser.selection.select(Some(
                    browser.selection.selected().unwrap_or(0).saturating_sub(1),
                ));
            }
            KeyCode::Enter | KeyCode::Char('p')
                if browser.mode == Mode::Normal || key.code == KeyCode::Enter =>
            {
                if let Some(name) = browser
                    .selection
                    .selected()
                    .and_then(|row| browser.matches.get(row))
                    .and_then(|index| self.config.categories.keys().nth(*index))
                    .cloned()
                {
                    if key.code == KeyCode::Enter {
                        self.temporary_category = None;
                        let index = self
                            .views
                            .iter()
                            .skip(2)
                            .position(|view| view.name == name)
                            .expect("configured category view exists")
                            + 2;
                        self.switch_view(index);
                        return;
                    }
                    let pinned = !self.config.pinned_categories.contains(&name);
                    match config::set_category_pinned(&self.config_path, &name, pinned) {
                        Ok(config) => {
                            let names_changed =
                                config.categories.keys().ne(self.config.categories.keys());
                            self.apply_config(config);
                            self.switch_view(self.view_index);
                            if names_changed {
                                browser.search_names.clear();
                                browser.search_names.extend(
                                    self.config
                                        .categories
                                        .keys()
                                        .map(|name| name.to_lowercase()),
                                );
                                browser.refilter();
                                browser.selection.select(
                                    self.config
                                        .categories
                                        .keys()
                                        .position(|key| key == &name)
                                        .and_then(|index| {
                                            browser.matches.binary_search(&index).ok()
                                        }),
                                );
                            }
                            browser.error = None;
                        }
                        Err(error) => browser.error = Some(error.to_string()),
                    }
                }
            }
            _ => {}
        }
        self.category_browser = Some(browser);
    }

    fn search(&mut self) {
        let query = self.query.trim();
        if query.is_empty() {
            self.status = "Press i to enter a query, then Enter to search.".into();
            return;
        }
        if query != self.submitted_query {
            self.submitted_query = query.to_owned();
            self.views[0].reset();
            self.job = None;
        }
        self.switch_view(0);
    }

    fn switch_view(&mut self, index: usize) {
        if index >= 2
            && !self
                .config
                .pinned_categories
                .contains(&self.views[index].name)
        {
            self.temporary_category = Some(self.views[index].name.clone());
        }
        if index != self.view_index {
            self.job = None;
            self.view_index = index;
        }
        self.close_preview();
        if !self.views[index].loaded && self.views[index].page_error.is_none() {
            if self.job.is_none() {
                self.load_page();
            }
        } else if self.job.is_none() {
            self.status = self.view_status();
        }
    }

    fn load_view(&mut self) {
        self.job = None;
        self.close_preview();
        self.views[self.view_index].reset();
        self.load_page();
    }

    fn load_page(&mut self) {
        if self.job.is_some() {
            return;
        }
        let view = &mut self.views[self.view_index];
        let page = (view.next_start - 1) / PAGE_SIZE + 1;
        let result = if self.view_index == 0 {
            if self.submitted_query.is_empty() {
                self.status = "Press i to enter a query, then Enter to search.".into();
                return;
            }
            self.status = format!("Searching for {} (page {page})...", self.submitted_query);
            Job::search(&self.submitted_query, view.next_start)
        } else {
            let channels = if self.view_index == 1 {
                &self.feed_channels
            } else {
                &self.config.categories[&view.name]
            };
            if channels.is_empty() {
                view.loaded = true;
                view.has_more = false;
                self.status = format!(
                    "{} has no channels. Press c on a search result to add one.",
                    view.name
                );
                return;
            }
            self.status = format!(
                "Loading {} page {page} ({} videos kept)...",
                view.name,
                view.videos.len()
            );
            Job::feed(channels, view.next_start)
        };
        match result {
            Ok(job) => self.job = Some(job),
            Err(error) => {
                view.page_error = Some(error.to_string());
                self.status = self.view_status();
            }
        }
    }

    fn view_status(&self) -> String {
        let view = &self.views[self.view_index];
        if let Some(error) = &view.page_error {
            return format!(
                "{} videos kept in {}. Page {} failed: {error}. Press r to refresh.",
                view.videos.len(),
                view.name,
                (view.next_start - 1) / PAGE_SIZE + 1
            );
        }
        if self.view_index != 0
            && (if self.view_index == 1 {
                &self.feed_channels
            } else {
                &self.config.categories[&view.name]
            })
            .is_empty()
        {
            return format!(
                "{} has no channels. Press s on a search result to add one.",
                view.name
            );
        }
        let continuation = if view.has_more {
            if view.videos.is_empty() && !view.pending.is_empty() {
                "newer pages pending"
            } else {
                "more available"
            }
        } else {
            "end"
        };
        format!(
            "{} videos in {} (page {}; {continuation}). Select a video to stream.",
            view.videos.len(),
            view.name,
            (view.next_start - 1) / PAGE_SIZE
        )
    }

    fn finish_page(&mut self, result: Result<String, String>) {
        self.job = None;
        let parsed = result.and_then(|output| {
            if self.view_index == 0 {
                youtube::search_results(&output)
            } else {
                youtube::feed_results(&output)
            }
        });
        if let Err(error) = parsed
            .and_then(|page| self.views[self.view_index].accept_page(page, self.view_index != 0))
        {
            self.views[self.view_index].page_error = Some(error);
        }
        self.status = self.view_status();
    }

    fn can_prefetch(&self) -> bool {
        self.job.is_none()
            && self.mode == Mode::Normal
            && self.category_dialog.is_none()
            && self.category_browser.is_none()
            && self.preview.is_none()
            && self.views[self.view_index].needs_page()
    }

    fn apply_config(&mut self, config: config::Config) {
        if config.categories == self.config.categories
            && config.channels == self.config.channels
            && config.pinned_categories == self.config.pinned_categories
        {
            return;
        }
        let active_index = self.view_index;
        let active_name = (active_index >= 2).then(|| self.views[active_index].name.clone());
        let feed_channels = config.subscriptions();
        let mut old = std::mem::take(&mut self.views).into_iter();
        self.views.push(old.next().expect("search view exists"));
        let mut feed = old.next().expect("feed view exists");
        if feed_channels != self.feed_channels {
            feed.reset();
        }
        self.views.push(feed);
        let mut old: Vec<_> = old.collect();
        // ponytail: category lookup is quadratic; use a keyed map if hundreds of categories matter.
        for name in config.categories.keys() {
            let mut view = if let Some(index) = old.iter().position(|view| &view.name == name) {
                old.swap_remove(index)
            } else {
                View::new(name.clone())
            };
            if config.categories.get(name) != self.config.categories.get(name) {
                view.reset();
            }
            self.views.push(view);
        }
        self.view_index = if active_index < 2 {
            active_index
        } else {
            active_name
                .and_then(|name| self.views.iter().skip(2).position(|view| view.name == name))
                .map(|index| index + 2)
                .unwrap_or(0)
        };
        self.feed_channels = feed_channels;
        self.config = config;
        if self.temporary_category.as_ref().is_some_and(|name| {
            !self.config.categories.contains_key(name)
                || self.config.pinned_categories.contains(name)
        }) {
            self.temporary_category = None;
        }
        if self.view_index >= 2
            && !self
                .config
                .pinned_categories
                .contains(&self.views[self.view_index].name)
        {
            self.temporary_category = Some(self.views[self.view_index].name.clone());
        }
        self.job = None;
        self.close_preview();
    }

    fn refresh(&mut self) {
        self.close_preview();
        match config::load(&self.config_path) {
            Ok(config) => {
                self.thumbnail.clear_cache();
                self.descriptions.clear();
                self.apply_config(config);
                self.load_view();
            }
            Err(error) => self.status = error.to_string(),
        }
    }

    fn open_category_picker(&mut self) {
        self.close_preview();
        let view = &self.views[self.view_index];
        let Some(video) = view
            .selection
            .selected()
            .and_then(|index| view.videos.get(index))
        else {
            self.status = "Select a video first.".into();
            return;
        };
        let Some(id) = video.channel_id.as_deref() else {
            self.status = "This video has no available channel identity.".into();
            return;
        };
        let Some(handle) = video
            .uploader_id
            .as_deref()
            .filter(|handle| handle.starts_with('@'))
        else {
            self.status =
                "This video's channel handle is unavailable; no channel was saved.".into();
            return;
        };
        let handle = handle.to_owned();
        let channel = format!("https://www.youtube.com/channel/{id}");
        let label = format!(" {} ({handle}) ", video.channel.as_deref().unwrap_or(id));
        match config::load(&self.config_path) {
            Ok(config) => self.apply_config(config),
            Err(error) => {
                self.status = error.to_string();
                return;
            }
        }
        let mut selection = ListState::default();
        let handle_url = format!("https://www.youtube.com/{handle}");
        let tags = self
            .config
            .categories
            .iter()
            .map(|(name, channels)| {
                (
                    name.clone(),
                    channels
                        .iter()
                        .any(|url| url == &channel || url == &handle_url),
                )
            })
            .collect();
        selection.select((!self.config.categories.is_empty()).then_some(0));
        self.category_dialog = Some(CategoryDialog {
            target: CategoryTarget::Channel { handle, channel },
            label,
            tags,
            selection,
            name: None,
            error: None,
        });
    }

    fn open_bulk_category_picker(&mut self) {
        if self.view_index < 2 {
            self.status = "Browse a category first to edit all its channels.".into();
            return;
        }
        let name = self.views[self.view_index].name.clone();
        let config = match config::load(&self.config_path) {
            Ok(config) => config,
            Err(error) => {
                self.status = error.to_string();
                return;
            }
        };
        let channels = config.categories.get(&name).cloned().unwrap_or_default();
        self.apply_config(config);
        if channels.is_empty() {
            self.status = format!("{name} has no saved channels to edit.");
            return;
        }
        let tags = self
            .config
            .categories
            .iter()
            .map(|(tag, members)| {
                (
                    tag.clone(),
                    channels.iter().all(|channel| members.contains(channel)),
                )
            })
            .collect();
        let mut selection = ListState::default();
        selection.select(self.config.categories.keys().position(|tag| tag == &name));
        self.close_preview();
        self.category_dialog = Some(CategoryDialog {
            label: format!(" {name} · {} channels ", channels.len()),
            target: CategoryTarget::Category { name, channels },
            tags,
            selection,
            name: None,
            error: None,
        });
    }

    fn category_key(&mut self, key: KeyEvent) {
        let mut dialog = self
            .category_dialog
            .take()
            .expect("category dialog is open");
        if let Some(name) = &mut dialog.name {
            match key.code {
                KeyCode::Esc => {
                    dialog.name = None;
                    dialog.error = None;
                }
                KeyCode::Enter => {
                    let name = name.trim().to_owned();
                    if name.is_empty() || name.chars().any(char::is_control) {
                        dialog.error =
                            Some("Enter a nonempty tag name without control characters.".into());
                    } else if dialog.tags.contains_key(&name) {
                        dialog.error = Some("That tag already exists.".into());
                    } else {
                        dialog.tags.insert(name.clone(), true);
                        dialog
                            .selection
                            .select(dialog.tags.keys().position(|tag| tag == &name));
                        dialog.name = None;
                        dialog.error = None;
                    }
                }
                _ if delete_input(name, key) => {}
                KeyCode::Char(c)
                    if !key
                        .modifiers
                        .intersects(KeyModifiers::CONTROL | KeyModifiers::ALT) =>
                {
                    name.push(c);
                }
                _ => {}
            }
        } else {
            let count = dialog.tags.len();
            match key.code {
                KeyCode::Esc => {
                    self.switch_view(self.view_index);
                    return;
                }
                KeyCode::Char('n') => {
                    dialog.name = Some(String::new());
                    dialog.error = None;
                }
                KeyCode::Char(' ') => {
                    if let Some((_, checked)) = dialog
                        .selection
                        .selected()
                        .and_then(|index| dialog.tags.iter_mut().nth(index))
                    {
                        *checked = !*checked;
                        dialog.error = None;
                    }
                }
                KeyCode::Down | KeyCode::Char('j') if count != 0 => {
                    dialog.selection.select(Some(
                        dialog
                            .selection
                            .selected()
                            .unwrap_or(0)
                            .saturating_add(1)
                            .min(count - 1),
                    ));
                }
                KeyCode::Up | KeyCode::Char('k') if count != 0 => {
                    dialog.selection.select(Some(
                        dialog.selection.selected().unwrap_or(0).saturating_sub(1),
                    ));
                }
                KeyCode::Enter => {
                    let result = match &dialog.target {
                        CategoryTarget::Channel { handle, channel } => config::set_channel_tags(
                            &self.config_path,
                            &dialog.tags,
                            handle,
                            channel,
                        ),
                        CategoryTarget::Category { name, channels } => config::set_category_tags(
                            &self.config_path,
                            name,
                            channels,
                            &dialog.tags,
                        ),
                    };
                    match result {
                        Ok(config) => {
                            self.apply_config(config);
                            self.switch_view(self.view_index);
                            self.status = match &dialog.target {
                                CategoryTarget::Channel { .. } => "Saved channel tags.".into(),
                                CategoryTarget::Category { channels, .. } => {
                                    format!("Saved tags for {} channels.", channels.len())
                                }
                            };
                            return;
                        }
                        Err(error) => dialog.error = Some(error.to_string()),
                    }
                }
                _ => {}
            }
        }
        self.category_dialog = Some(dialog);
    }

    fn close_preview(&mut self) {
        if self.preview.take().is_some() {
            self.thumbnail.cancel();
        }
        self.description_job = None;
        self.description_viewport = None;
    }

    fn load_description(&mut self) {
        self.description_job = None;
        self.description_error = None;
        self.description_scroll = 0;
        self.description_max_scroll = 0;
        self.description_viewport = None;
        let view = &self.views[self.view_index];
        let Some(index) = view
            .selection
            .selected()
            .filter(|&index| index < view.videos.len())
        else {
            return;
        };
        let video = &view.videos[index];
        if let Some(index) = self.descriptions.iter().position(|(id, _)| id == &video.id) {
            let hit = self
                .descriptions
                .remove(index)
                .expect("cache position exists");
            self.descriptions.push_back(hit);
            return;
        }
        match Job::description(&video.id) {
            Ok(job) => self.description_job = Some((index, job)),
            Err(error) => self.description_error = Some(error.to_string()),
        }
    }

    fn remember_description(&mut self, id: String, description: String) {
        if let Some(index) = self
            .descriptions
            .iter()
            .position(|(cached, _)| cached == &id)
        {
            self.descriptions.remove(index);
        }
        if self.descriptions.len() == DESCRIPTION_CACHE_SIZE {
            self.descriptions.pop_front();
        }
        self.descriptions.push_back((id, description));
    }

    fn play(&mut self) {
        let view = &self.views[self.view_index];
        let Some(video) = view
            .selection
            .selected()
            .and_then(|index| view.videos.get(index))
        else {
            return;
        };
        self.player_launch = None;
        match PlayerLaunch::start(&video.id, &self.options.player) {
            Ok(launch) => {
                self.status = format!(
                    "Opening {} in {}...",
                    video.title,
                    self.options.player.to_string_lossy()
                );
                self.player_launch = Some(launch);
            }
            Err(error) => self.status = error.to_string(),
        }
    }

    fn update(&mut self) {
        if let Some(result) = self.job.as_mut().and_then(Job::poll) {
            self.finish_page(result);
        }
        if let Some(result) = self
            .description_job
            .as_mut()
            .and_then(|(_, job)| job.poll())
        {
            let (index, _) = self
                .description_job
                .take()
                .expect("completed description job exists");
            if let Some(video) = self.views[self.view_index].videos.get(index) {
                match result.and_then(|output| youtube::full_description(&output, &video.id)) {
                    Ok(description) => self.remember_description(video.id.clone(), description),
                    Err(error) => self.description_error = Some(error),
                }
            }
            self.description_viewport = None;
        }
        if let Some(result) = self.player_launch.as_mut().and_then(PlayerLaunch::poll) {
            self.player_launch = None;
            self.status = match result {
                Ok(()) => "Video handed to player; playback continues in its window.".into(),
                Err(error) => error,
            };
        }
        if self.can_prefetch() {
            self.load_page();
        }
    }

    fn key(&mut self, key: KeyEvent) -> bool {
        if key.code == KeyCode::Char('c') && key.modifiers.contains(KeyModifiers::CONTROL) {
            return true;
        }
        if self.category_dialog.is_some() {
            self.category_key(key);
            return false;
        }
        if self.category_browser.is_some() {
            self.browse_category_key(key);
            return false;
        }
        let selected_before = self.views[self.view_index].selection.selected();
        let preview_was_open = self.preview.is_some();
        if self.mode == Mode::Insert {
            match key.code {
                KeyCode::Esc => self.mode = Mode::Normal,
                KeyCode::Enter => {
                    self.search();
                    self.mode = Mode::Normal;
                }
                _ if delete_input(&mut self.query, key) => {}
                KeyCode::Char(c)
                    if !key
                        .modifiers
                        .intersects(KeyModifiers::CONTROL | KeyModifiers::ALT) =>
                {
                    self.query.push(c);
                }
                _ => {}
            }
        } else {
            match key.code {
                KeyCode::Char('q') => return true,
                KeyCode::Char('i') => {
                    self.close_preview();
                    self.mode = Mode::Insert;
                }
                KeyCode::Char('d') => {
                    self.preview = match self.preview {
                        Some(PreviewMode::Info) => Some(PreviewMode::Description),
                        Some(PreviewMode::Description) => Some(PreviewMode::Info),
                        None => self.views[self.view_index]
                            .selection
                            .selected()
                            .filter(|&index| index < self.views[self.view_index].videos.len())
                            .map(|_| PreviewMode::Info),
                    };
                }
                KeyCode::Esc => self.close_preview(),
                KeyCode::Down if self.preview == Some(PreviewMode::Description) => {
                    self.description_scroll = self
                        .description_scroll
                        .saturating_add(1)
                        .min(self.description_max_scroll);
                }
                KeyCode::Up if self.preview == Some(PreviewMode::Description) => {
                    self.description_scroll = self.description_scroll.saturating_sub(1);
                }
                KeyCode::PageDown if self.preview == Some(PreviewMode::Description) => {
                    let page = self
                        .description_viewport
                        .map(|(_, height)| height)
                        .unwrap_or(1)
                        .max(1);
                    self.description_scroll = self
                        .description_scroll
                        .saturating_add(page)
                        .min(self.description_max_scroll);
                }
                KeyCode::PageUp if self.preview == Some(PreviewMode::Description) => {
                    let page = self
                        .description_viewport
                        .map(|(_, height)| height)
                        .unwrap_or(1)
                        .max(1);
                    self.description_scroll = self.description_scroll.saturating_sub(page);
                }
                KeyCode::Char('c') => self.open_category_browser(),
                KeyCode::Char('s') => self.open_category_picker(),
                KeyCode::Char('S') => self.open_bulk_category_picker(),
                KeyCode::Char('r') => self.refresh(),
                KeyCode::Tab => self.cycle_view(false),
                KeyCode::BackTab => self.cycle_view(true),
                KeyCode::Enter => self.play(),
                KeyCode::Down | KeyCode::Char('j') => {
                    self.views[self.view_index].selection.select_next()
                }
                KeyCode::Up | KeyCode::Char('k') => {
                    self.views[self.view_index].selection.select_previous()
                }
                KeyCode::Home | KeyCode::Char('g') => {
                    self.views[self.view_index].selection.select_first()
                }
                KeyCode::End | KeyCode::Char('G') => {
                    self.views[self.view_index].selection.select_last()
                }
                _ => {}
            }
        }
        let view = &mut self.views[self.view_index];
        if view.videos.is_empty() {
            view.selection.select(None);
        } else if let Some(index) = view.selection.selected() {
            view.selection
                .select(Some(index.min(view.videos.len() - 1)));
        }
        if self.preview.is_none() {
            self.description_job = None;
        } else if !preview_was_open
            || self.views[self.view_index].selection.selected() != selected_before
        {
            self.load_description();
        }
        if self.preview.is_some()
            && (!preview_was_open
                || self.views[self.view_index].selection.selected() != selected_before)
            && let Some(video) = self.views[self.view_index]
                .selection
                .selected()
                .and_then(|index| self.views[self.view_index].videos.get(index))
        {
            self.thumbnail.select(&video.id);
        }
        false
    }

    fn draw(&mut self, frame: &mut Frame, elapsed: Duration) {
        const SPINNER: [&str; 10] = ["⠋ ", "⠙ ", "⠹ ", "⠸ ", "⠼ ", "⠴ ", "⠦ ", "⠧ ", "⠇ ", "⠏ "];
        let spinner = SPINNER[(elapsed.as_millis() / 100 % SPINNER.len() as u128) as usize];
        let area = frame.area();
        let mut tab_lines = vec![Line::default()];
        let mut row_width = 0;
        let mut selected_row = 0;
        for (index, view) in self.visible_views() {
            let mut title = Span::raw(view.name.as_str());
            let pinned = index >= 2 && self.config.pinned_categories.contains(&view.name);
            let title_width = title.width() + 2 + if pinned { 2 } else { 0 }; // Padding and pin marker.
            if row_width != 0 && row_width + 1 + title_width > usize::from(area.width) {
                tab_lines.push(Line::default());
                row_width = 0;
            }
            if index == self.view_index {
                title.style = Style::new().fg(Color::Cyan).bold();
                selected_row = tab_lines.len() - 1;
            }
            let row = tab_lines.last_mut().expect("at least one tab row");
            if row_width != 0 {
                row.spans.push("│".into());
            }
            row.spans.extend([" ".into(), title]);
            if pinned {
                row.spans.push(Span::styled(" p", Style::new().dim()));
            }
            row.spans.push(" ".into());
            row_width += usize::from(row_width != 0) + title_width;
        }
        // Leave space for search, a usable results pane, status, and help.
        let tab_height = tab_lines
            .len()
            .min(usize::from(area.height.saturating_sub(10).max(1)))
            as u16;
        let first_row = selected_row.saturating_sub(usize::from(tab_height).saturating_sub(1));
        let [tabs, search, results, status, help] = Layout::vertical([
            Constraint::Length(tab_height),
            Constraint::Length(3),
            Constraint::Min(3),
            Constraint::Length(3),
            Constraint::Length(1),
        ])
        .areas(area);
        frame.render_widget(
            Paragraph::new(tab_lines).scroll((first_row.min(u16::MAX as usize) as u16, 0)),
            tabs,
        );
        let search_style = if self.mode == Mode::Insert {
            Style::new().fg(Color::Cyan)
        } else {
            Style::new()
        };
        // End-only editing; scroll long queries without counting UTF-8 bytes as columns.
        let query = ratatui::text::Line::raw(self.query.as_str());
        let query_width = query.width();
        let search_block = Block::bordered()
            .title(" tubular / YouTube search ")
            .border_style(search_style);
        let input = search_block.inner(search);
        let scroll = query_width.saturating_sub(input.width.saturating_sub(1) as usize);
        frame.render_widget(
            Paragraph::new(query)
                .scroll((0, scroll.min(u16::MAX as usize) as u16))
                .block(search_block),
            search,
        );
        if self.mode == Mode::Insert
            && self.category_dialog.is_none()
            && input.width != 0
            && input.height != 0
        {
            let cursor = query_width
                .saturating_sub(scroll)
                .min(usize::from(input.width - 1));
            frame.set_cursor_position((input.x + cursor as u16, input.y));
        }
        let view = &mut self.views[self.view_index];
        let table = Table::new(
            view.videos.iter().map(|video| {
                Row::new([
                    video.title.as_str(),
                    video.channel.as_deref().unwrap_or("Unknown"),
                    video.publication_date.as_deref().unwrap_or("Unknown"),
                ])
            }),
            [
                Constraint::Fill(3),
                Constraint::Fill(1),
                Constraint::Length(11),
            ],
        )
        .header(Row::new(["Video", "Channel", "Published"]).bold())
        .block(Block::bordered().title(loading_title(
            if self.view_index == 0 {
                " Results "
            } else {
                view.title.as_str()
            },
            "",
            self.job.is_some().then_some(spinner),
        )))
        .row_highlight_style(Style::new().fg(Color::Black).bg(Color::Cyan))
        .highlight_symbol("> ");
        frame.render_stateful_widget(table, results, &mut view.selection);
        frame.render_widget(
            Paragraph::new(self.status.as_str())
                .wrap(Wrap { trim: true })
                .block(Block::bordered().title(" Status ")),
            status,
        );
        let help_text = match self.mode {
            Mode::Insert => {
                "INSERT · Enter search → normal · Esc normal · Ctrl-U clear · Ctrl-C quit"
            }
            Mode::Normal
                if self
                    .category_browser
                    .as_ref()
                    .is_some_and(|browser| browser.mode == Mode::Insert) =>
            {
                "CATEGORIES INSERT · type filter · ↑/↓ or Ctrl-J/K move · Enter browse · Esc normal"
            }
            Mode::Normal if self.category_browser.is_some() => {
                "CATEGORIES NORMAL · j/k · i filter · Enter browse · p pin/unpin · Esc close"
            }
            Mode::Normal if self.preview == Some(PreviewMode::Description) => {
                "NORMAL · ↑/↓ PgUp/PgDn scroll · j/k video · d info · Esc close · i insert · q quit"
            }
            Mode::Normal if self.preview == Some(PreviewMode::Info) => {
                "NORMAL · j/k video · d description · Esc close · i insert · q quit"
            }
            Mode::Normal => {
                "NORMAL · j/k · Enter play · i search · c browse · s channel tags · S bulk tags · d info · Tab views · r refresh · q quit"
            }
        };
        frame.render_widget(Paragraph::new(help_text).dim(), help);
        if let Some(mode) = self.preview
            && let Some(video) = self.views[self.view_index]
                .selection
                .selected()
                .and_then(|index| self.views[self.view_index].videos.get(index))
        {
            let popup = preview_area(frame.area());
            frame.render_widget(Clear, popup);
            let block = Block::bordered().border_style(Style::new().fg(Color::Cyan));
            let block = if mode == PreviewMode::Description {
                block.title_bottom(Line::from(vec![
                    " ".into(),
                    video.title.as_str().into(),
                    " ".into(),
                ]))
            } else {
                block
            };
            let inner = block.inner(popup);
            let cached = cached_description(&self.descriptions, &video.id);
            let text = match cached {
                Some("") => "This video has no description.",
                Some(description) => description,
                None => self
                    .description_error
                    .as_deref()
                    .unwrap_or("Loading full description..."),
            };
            if mode == PreviewMode::Description {
                let paragraph = Paragraph::new(text).wrap(Wrap { trim: false });
                let viewport = (inner.width, inner.height);
                if self.description_viewport != Some(viewport) {
                    self.description_max_scroll = if viewport.0 == 0 || viewport.1 == 0 {
                        0
                    } else {
                        paragraph
                            .line_count(viewport.0)
                            .saturating_sub(viewport.1 as usize)
                            .min(u16::MAX as usize) as u16
                    };
                    self.description_viewport = Some(viewport);
                }
                self.description_scroll = self.description_scroll.min(self.description_max_scroll);
                frame.render_widget(paragraph.scroll((self.description_scroll, 0)), inner);
            } else {
                let [image, _, mut details] = Layout::horizontal([
                    Constraint::Fill(3),
                    Constraint::Length(2),
                    Constraint::Fill(2),
                ])
                .areas(inner);
                let image_width = self.thumbnail.draw(frame, image);
                let reclaimed = image.width - image_width;
                details.x -= reclaimed;
                details.width += reclaimed;
                details.width = details.width.saturating_sub(2);
                let metadata = Paragraph::new(vec![
                    Line::raw(video.title.as_str()).bold(),
                    Line::default(),
                    Line::from(vec![
                        video.channel.as_deref().unwrap_or("Unknown").into(),
                        " · ".into(),
                        video
                            .publication_date
                            .as_deref()
                            .unwrap_or("Unknown")
                            .into(),
                    ])
                    .dim(),
                ])
                .wrap(Wrap { trim: true });
                let height = if details.is_empty() {
                    0
                } else {
                    metadata
                        .line_count(details.width)
                        .min(details.height as usize) as u16
                };
                let mut excerpt = details;
                let gap = (excerpt.height - height).min(1);
                excerpt.y += height + gap;
                excerpt.height -= height + gap;
                details.height = height;
                frame.render_widget(metadata, details);
                let paragraph = Paragraph::new(text).wrap(Wrap { trim: false });
                let overflow = cached.is_some_and(|text| !text.is_empty())
                    && !excerpt.is_empty()
                    && paragraph.line_count(excerpt.width) > usize::from(excerpt.height);
                frame.render_widget(paragraph, excerpt);
                if overflow {
                    let buffer = frame.buffer_mut();
                    let y = excerpt.bottom() - 1;
                    let end = (excerpt.x..excerpt.right())
                        .rev()
                        .find_map(|x| {
                            let symbol = buffer
                                .cell((x, y))
                                .expect("excerpt is inside frame")
                                .symbol();
                            (!symbol.trim().is_empty())
                                .then(|| x.saturating_add(Span::raw(symbol).width() as u16))
                        })
                        .unwrap_or(excerpt.x);
                    let mut x = end.min(excerpt.right() - 1);
                    // Do not leave half of a wide character beneath the ellipsis.
                    if x > excerpt.x
                        && Span::raw(buffer.cell((x - 1, y)).unwrap().symbol()).width() > 1
                    {
                        x -= 1;
                    }
                    buffer
                        .cell_mut((x, y))
                        .unwrap()
                        .set_symbol("…")
                        .set_style(Style::new());
                }
            }
            frame.render_widget(
                block.title(loading_title(
                    if mode == PreviewMode::Info {
                        " Info "
                    } else {
                        " Description "
                    },
                    if mode == PreviewMode::Info {
                        "· d description · Esc close "
                    } else {
                        "· ↑/↓ PgUp/PgDn · d info · Esc close "
                    },
                    (self.description_job.is_some()
                        || (mode == PreviewMode::Info && self.thumbnail.is_loading()))
                    .then_some(spinner),
                )),
                popup,
            );
        }
        self.draw_category_dialog(frame);
        self.draw_category_browser(frame);
    }

    fn draw_category_browser(&mut self, frame: &mut Frame) {
        let Some(browser) = &mut self.category_browser else {
            return;
        };
        let popup = preview_area(frame.area());
        frame.render_widget(Clear, popup);
        let block = Block::bordered()
            .title(" Categories · i filter · Enter browse · p pin ")
            .border_style(Style::new().fg(Color::Cyan));
        let [input, list, error] = Layout::vertical([
            Constraint::Length(3),
            Constraint::Min(1),
            Constraint::Length(if browser.error.is_some() { 2 } else { 0 }),
        ])
        .areas(block.inner(popup));
        frame.render_widget(block, popup);
        let input_block = Block::bordered().title(if browser.mode == Mode::Insert {
            " Filter · INSERT "
        } else {
            " Filter · NORMAL "
        });
        let text_area = input_block.inner(input);
        let text = Line::raw(browser.query.as_str());
        let scroll = text
            .width()
            .saturating_sub(text_area.width.saturating_sub(1) as usize);
        let cursor = text.width().saturating_sub(scroll) as u16;
        frame.render_widget(
            Paragraph::new(text)
                .scroll((0, scroll.min(u16::MAX as usize) as u16))
                .block(input_block),
            input,
        );
        if browser.mode == Mode::Insert && text_area.width != 0 && text_area.height != 0 {
            frame.set_cursor_position((text_area.x + cursor.min(text_area.width - 1), text_area.y));
        }
        if self.config.categories.is_empty() {
            frame.render_widget(
                Paragraph::new("No categories yet. Use s on a video to save its channel.")
                    .wrap(Wrap { trim: true })
                    .dim(),
                list,
            );
        } else if browser.matches.is_empty() {
            frame.render_widget(Paragraph::new("No matching categories.").dim(), list);
        } else {
            let mut matches = browser.matches.iter().copied();
            let mut next = matches.next();
            let items = self
                .config
                .categories
                .keys()
                .enumerate()
                .filter_map(|(index, name)| {
                    if next != Some(index) {
                        return None;
                    }
                    next = matches.next();
                    Some(Line::from(vec![
                        if self.config.pinned_categories.contains(name) {
                            "[p] "
                        } else {
                            "[ ] "
                        }
                        .into(),
                        name.as_str().into(),
                    ]))
                });
            frame.render_stateful_widget(
                List::new(items)
                    .highlight_symbol("> ")
                    .highlight_style(Style::new().fg(Color::Black).bg(Color::Cyan)),
                list,
                &mut browser.selection,
            );
        }
        if let Some(message) = browser.error.as_deref() {
            frame.render_widget(
                Paragraph::new(message)
                    .wrap(Wrap { trim: true })
                    .style(Style::new().fg(Color::Red)),
                error,
            );
        }
    }

    fn draw_category_dialog(&mut self, frame: &mut Frame) {
        let Some(dialog) = &mut self.category_dialog else {
            return;
        };
        let area = frame.area();
        let bulk = matches!(&dialog.target, CategoryTarget::Category { .. });
        let width = area.width.saturating_sub(4).min(60);
        let height = area.height.saturating_sub(4).min(if dialog.name.is_some() {
            7
        } else {
            dialog
                .tags
                .len()
                .saturating_add(if bulk { 7 } else { 5 })
                .clamp(7, if bulk { 18 } else { 16 }) as u16
        });
        let popup = Rect::new(
            area.x + (area.width - width) / 2,
            area.y + (area.height - height) / 2,
            width,
            height,
        );
        frame.render_widget(Clear, popup);
        let block = Block::bordered()
            .title(if dialog.name.is_some() {
                " New tag "
            } else if bulk {
                " Bulk tags "
            } else {
                " Tags "
            })
            .title_bottom(dialog.label.as_str())
            .border_style(Style::new().fg(Color::Cyan));
        let [body, warning, error, help] = Layout::vertical([
            Constraint::Min(1),
            Constraint::Length(if bulk && dialog.name.is_none() { 2 } else { 0 }),
            Constraint::Length(if dialog.error.is_some() { 2 } else { 0 }),
            Constraint::Length(1),
        ])
        .areas(block.inner(popup));
        frame.render_widget(block, popup);
        if bulk && dialog.name.is_none() {
            frame.render_widget(Paragraph::new(
                "Saving replaces all memberships. Only tags shared by every channel start checked."
            ).wrap(Wrap { trim: true }).dim(), warning);
        }
        if let Some(name) = &dialog.name {
            let text = Line::raw(name.as_str());
            let scroll = text
                .width()
                .saturating_sub(body.width.saturating_sub(1) as usize);
            let cursor = text.width().saturating_sub(scroll) as u16;
            frame.render_widget(
                Paragraph::new(text).scroll((0, scroll.min(u16::MAX as usize) as u16)),
                body,
            );
            if body.width != 0 && body.height != 0 {
                frame.set_cursor_position((body.x + cursor.min(body.width - 1), body.y));
            }
        } else if dialog.tags.is_empty() {
            frame.render_widget(Paragraph::new("No tags. Press n to create one."), body);
        } else {
            frame.render_stateful_widget(
                List::new(dialog.tags.iter().map(|(name, checked)| {
                    Line::from(vec![
                        (if *checked { "[x] " } else { "[ ] " }).into(),
                        name.as_str().into(),
                    ])
                }))
                .highlight_symbol("> ")
                .highlight_style(Style::new().fg(Color::Black).bg(Color::Cyan)),
                body,
                &mut dialog.selection,
            );
        }
        if let Some(message) = &dialog.error {
            frame.render_widget(
                Paragraph::new(message.as_str())
                    .wrap(Wrap { trim: true })
                    .fg(Color::Red),
                error,
            );
        }
        frame.render_widget(
            Paragraph::new(if dialog.name.is_some() {
                "Enter create · Esc back · Ctrl-U clear"
            } else {
                "j/k move · Space toggle · Enter save · n new · Esc cancel"
            })
            .dim(),
            help,
        );
    }

    fn run(mut self, terminal: &mut DefaultTerminal) -> io::Result<()> {
        struct ResetCursorStyle;
        impl Drop for ResetCursorStyle {
            fn drop(&mut self) {
                let _ = execute!(io::stdout(), SetCursorStyle::DefaultUserShape);
            }
        }
        execute!(io::stdout(), SetCursorStyle::SteadyBlock)?;
        let _cursor_style = ResetCursorStyle;
        self.thumbnail.query_terminal();
        if !self.query.trim().is_empty() {
            self.search();
        }
        let started = Instant::now();
        loop {
            self.update();
            terminal.draw(|frame| self.draw(frame, started.elapsed()))?;
            if event::poll(Duration::from_millis(100))?
                && let Event::Key(key) = event::read()?
                && key.kind != KeyEventKind::Release
                && self.key(key)
            {
                return Ok(());
            }
        }
    }
}

fn loading_title<'a>(
    title: &'a str,
    controls: &'static str,
    spinner: Option<&'static str>,
) -> Line<'a> {
    let mut spans =
        Vec::with_capacity(1 + usize::from(!controls.is_empty()) + usize::from(spinner.is_some()));
    spans.push(title.into());
    if let Some(spinner) = spinner {
        spans.push(spinner.into());
    }
    if !controls.is_empty() {
        spans.push(controls.into());
    }
    Line::from(spans)
}

fn preview_area(area: Rect) -> Rect {
    let width = area
        .width
        .saturating_sub(4)
        .min((u32::from(area.width) * 70 / 100) as u16)
        .min(96);
    let height = area
        .height
        .saturating_sub(4)
        .min((u32::from(area.height) * 60 / 100) as u16)
        .min(20);
    Rect::new(
        area.x + (area.width - width) / 2,
        area.y + (area.height - height) / 2,
        width,
        height,
    )
}

fn delete_input(text: &mut String, key: KeyEvent) -> bool {
    match key.code {
        KeyCode::Backspace if key.modifiers.contains(KeyModifiers::SUPER) => text.clear(),
        KeyCode::Char('u') if key.modifiers.contains(KeyModifiers::CONTROL) => text.clear(),
        KeyCode::Backspace | KeyCode::Char('w')
            if key.modifiers.contains(if key.code == KeyCode::Backspace {
                KeyModifiers::ALT
            } else {
                KeyModifiers::CONTROL
            }) =>
        {
            let keep = text
                .char_indices()
                .rev()
                .skip_while(|(_, c)| c.is_whitespace())
                .find(|(_, c)| c.is_whitespace())
                .map_or(0, |(index, c)| index + c.len_utf8());
            text.truncate(keep);
        }
        KeyCode::Backspace => {
            text.pop();
        }
        _ => return false,
    }
    true
}

fn main() -> io::Result<()> {
    let options = Options::parse();
    let config_path = config::config_path()?;
    let config = config::load(&config_path)?;
    let app = App::new(options, config_path, config);
    ratatui::run(|terminal| app.run(terminal))
}

#[cfg(test)]
mod tests {
    use super::*;

    fn app(args: &[&str]) -> App {
        App::new(
            Options::parse_from(args),
            PathBuf::new(),
            config::Config::default(),
        )
    }

    #[test]
    fn bulk_picker_uses_all_saved_channels_and_commits_or_cancels_the_whole_group() {
        let path =
            std::env::temp_dir().join(format!("tubular-bulk-picker-{}.toml", std::process::id()));
        let original = "pinned_categories = ['Source']\n[channels]\n'@a' = 'UC4QobU6STFB0P71PMvOGN5A'\n'@b' = 'UCaYhcUwRBNscFNUKTjgPFiA'\n'@other' = 'UCBR8-60-B28hp2BmDPdntcQ'\n[categories]\nEmpty = []\nMixed = ['@a', '@other']\nShared = ['@a', '@b', '@other']\nSource = ['@a', '@b']\n";
        std::fs::write(&path, original).unwrap();
        let mut app = App::new(
            Options::parse_from(["tubular"]),
            path.clone(),
            config::load(&path).unwrap(),
        );
        app.key(KeyEvent::new(KeyCode::Char('S'), KeyModifiers::SHIFT));
        assert!(app.category_dialog.is_none());
        app.view_index = app
            .views
            .iter()
            .position(|view| view.name == "Source")
            .unwrap();
        app.views[app.view_index].loaded = true;
        app.views[1].loaded = true;
        app.views[1].next_start = 41;
        let subscriptions = app.feed_channels.clone();
        app.key(KeyEvent::new(KeyCode::Char('S'), KeyModifiers::SHIFT));
        let dialog = app.category_dialog.as_ref().unwrap();
        assert!(dialog.tags["Shared"] && dialog.tags["Source"]);
        assert!(!dialog.tags["Mixed"] && !dialog.tags["Empty"]);
        assert!(
            matches!(&dialog.target, CategoryTarget::Category { channels, .. } if channels.len() == 2)
        );
        assert!(app.views[app.view_index].videos.is_empty());
        app.key(KeyEvent::new(KeyCode::Char('n'), KeyModifiers::NONE));
        for c in "Staged".chars() {
            app.key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE));
        }
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
        assert_eq!(std::fs::read_to_string(&path).unwrap(), original);
        assert!(!app.config.categories.contains_key("Staged"));
        app.key(KeyEvent::new(KeyCode::Char('S'), KeyModifiers::SHIFT));
        app.key(KeyEvent::new(KeyCode::Char(' '), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert!(app.category_dialog.is_none());
        let saved = config::load(&path).unwrap();
        assert!(saved.categories["Source"].is_empty());
        assert_eq!(
            saved.categories["Mixed"],
            ["https://www.youtube.com/channel/UCBR8-60-B28hp2BmDPdntcQ"]
        );
        assert_eq!(saved.categories["Shared"].len(), 3);
        assert_eq!(saved.pinned_categories, ["Source"]);
        assert_eq!(app.feed_channels, subscriptions);
        assert!(app.views[1].loaded);
        assert_eq!(app.views[1].next_start, 41);
        app.key(KeyEvent::new(KeyCode::Char('S'), KeyModifiers::SHIFT));
        assert!(app.category_dialog.is_none());
        std::fs::remove_file(path).unwrap();
    }

    #[test]
    fn filtering_preserves_selected_categories_and_browses_the_filtered_row() {
        let mut app = app(&["tubular"]);
        app.query = "main search untouched".into();
        app.apply_config(config::Config {
            categories: [
                ("Alpha".into(), vec![]),
                ("Japanese immersion".into(), vec![]),
                ("Japanese news".into(), vec![]),
            ]
            .into(),
            ..config::Config::default()
        });
        app.key(KeyEvent::new(KeyCode::Char('c'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE));
        for c in "JAPANESE".chars() {
            app.key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE));
        }
        app.key(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::CONTROL));
        assert_eq!(
            app.category_browser.as_ref().unwrap().selection.selected(),
            Some(1)
        );
        for c in " news".chars() {
            app.key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE));
        }
        assert_eq!(
            app.category_browser.as_ref().unwrap().selection.selected(),
            Some(0)
        );
        app.key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
        assert_eq!(app.category_browser.as_ref().unwrap().mode, Mode::Normal);
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(app.views[app.view_index].name, "Japanese news");
        assert_eq!(app.query, "main search untouched");
        assert!(app.category_browser.is_none());
    }

    #[test]
    fn insert_filter_types_jk_handles_empty_matches_and_navigates_without_editing() {
        let mut app = app(&["tubular"]);
        app.apply_config(config::Config {
            categories: [
                ("Alpha".into(), vec![]),
                ("Jazz".into(), vec![]),
                ("Jokes".into(), vec![]),
                ("日本語だけで".into(), vec![]),
            ]
            .into(),
            ..config::Config::default()
        });
        app.key(KeyEvent::new(KeyCode::Char('c'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE));
        for c in "jk".chars() {
            app.key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE));
        }
        assert!(
            app.category_browser
                .as_ref()
                .unwrap()
                .selection
                .selected()
                .is_none()
        );
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert!(app.category_browser.is_some());
        assert_eq!(app.view_index, 0);
        app.key(KeyEvent::new(KeyCode::Backspace, KeyModifiers::NONE));
        for (code, modifiers, row) in [
            (KeyCode::Char('j'), KeyModifiers::CONTROL, 1),
            (KeyCode::Char('k'), KeyModifiers::CONTROL, 0),
            (KeyCode::Down, KeyModifiers::NONE, 1),
            (KeyCode::Up, KeyModifiers::NONE, 0),
        ] {
            app.key(KeyEvent::new(code, modifiers));
            assert_eq!(
                app.category_browser.as_ref().unwrap().selection.selected(),
                Some(row)
            );
        }
        assert_eq!(app.category_browser.as_ref().unwrap().query, "j");
        app.key(KeyEvent::new(KeyCode::Char('w'), KeyModifiers::CONTROL));
        for c in "日本".chars() {
            app.key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE));
        }
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(app.views[app.view_index].name, "日本語だけで");
        assert_eq!(app.mode, Mode::Normal);
    }

    #[test]
    fn category_browser_replaces_the_temporary_tab_and_cycles_only_visible_views() {
        let mut app = app(&["tubular"]);
        app.apply_config(config::Config {
            categories: [
                ("Alpha".into(), vec![]),
                ("Beta".into(), vec![]),
                ("Gamma".into(), vec![]),
            ]
            .into(),
            ..config::Config::default()
        });
        let visible = |app: &App| {
            app.visible_views()
                .map(|(_, view)| view.name.clone())
                .collect::<Vec<_>>()
        };
        assert_eq!(visible(&app), ["Search", "Feed"]);
        app.key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        assert_eq!(app.view_index, 0);
        app.key(KeyEvent::new(KeyCode::Char('c'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(app.views[app.view_index].name, "Beta");
        assert_eq!(visible(&app), ["Search", "Feed", "Beta"]);
        app.key(KeyEvent::new(KeyCode::Char('c'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(visible(&app), ["Search", "Feed", "Gamma"]);
        app.apply_config(config::Config {
            categories: app.config.categories.clone(),
            pinned_categories: vec!["Beta".into()],
            ..config::Config::default()
        });
        assert_eq!(visible(&app), ["Search", "Feed", "Beta", "Gamma"]);
        app.key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        assert_eq!(app.view_index, 0);
        app.key(KeyEvent::new(KeyCode::BackTab, KeyModifiers::SHIFT));
        assert_eq!(app.views[app.view_index].name, "Gamma");
        app.key(KeyEvent::new(KeyCode::BackTab, KeyModifiers::SHIFT));
        assert_eq!(app.views[app.view_index].name, "Beta");
        app.key(KeyEvent::new(KeyCode::Char('c'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(visible(&app), ["Search", "Feed", "Beta"]);
        app.key(KeyEvent::new(KeyCode::Char('c'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
        assert_eq!(visible(&app), ["Search", "Feed", "Beta"]);
        assert!(app.category_browser.is_none());
        app.key(KeyEvent::new(KeyCode::Char('c'), KeyModifiers::NONE));
        assert!(app.key(KeyEvent::new(KeyCode::Char('c'), KeyModifiers::CONTROL)));
    }

    #[test]
    fn categories_named_search_or_feed_are_distinct_from_permanent_views() {
        let mut app = app(&["tubular"]);
        app.apply_config(config::Config {
            categories: [
                ("Alpha".into(), vec![]),
                ("Feed".into(), vec![]),
                ("Search".into(), vec![]),
            ]
            .into(),
            ..config::Config::default()
        });
        app.key(KeyEvent::new(KeyCode::Char('c'), KeyModifiers::NONE));
        assert_eq!(
            app.category_browser.as_ref().unwrap().selection.selected(),
            Some(0)
        );
        app.key(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(app.view_index, 3);
        assert_eq!(app.views[app.view_index].name, "Feed");
        app.key(KeyEvent::new(KeyCode::Char('c'), KeyModifiers::NONE));
        assert_eq!(
            app.category_browser.as_ref().unwrap().selection.selected(),
            Some(1)
        );
    }

    #[test]
    fn descriptions_are_shared_across_views_and_evict_least_recently_used_entries() {
        let mut app = app(&["tubular"]);
        let output = r#"{"entries":[{"id":"jNQXAC9IVRw","title":"Shared video"}]}"#;
        for view in &mut app.views {
            view.videos = youtube::search_results(output).unwrap().videos;
            view.selection.select(Some(0));
            view.loaded = true;
        }
        app.remember_description("jNQXAC9IVRw".into(), "Shared full description".into());
        for index in 1..DESCRIPTION_CACHE_SIZE {
            app.remember_description(format!("video{index:06}"), format!("Description {index}"));
        }
        app.switch_view(1);
        app.load_description(); // A hit in Feed promotes the Search video's description.
        assert!(app.description_job.is_none());
        app.remember_description("new00000000".into(), "New description".into());
        assert_eq!(
            cached_description(&app.descriptions, "jNQXAC9IVRw"),
            Some("Shared full description")
        );
        assert_eq!(cached_description(&app.descriptions, "video000001"), None);
        assert_eq!(
            cached_description(&app.descriptions, "video000002"),
            Some("Description 2")
        );
        // Updating an existing entry, including a known empty description, must not evict another.
        app.remember_description("jNQXAC9IVRw".into(), String::new());
        app.load_description();
        assert!(app.description_job.is_none());
        assert_eq!(
            cached_description(&app.descriptions, "jNQXAC9IVRw"),
            Some("")
        );
        assert_eq!(
            cached_description(&app.descriptions, "video000002"),
            Some("Description 2")
        );
    }

    #[test]
    fn thumbnail_ellipsis_marks_only_hidden_content_and_preserves_wide_characters() {
        use ratatui::{Terminal, backend::TestBackend};

        let mut app = app(&["tubular"]);
        app.views[0].videos = youtube::search_results(
            r#"{"entries":[{"id":"jNQXAC9IVRw","title":"Heading","channel":"Creator","upload_date":"20050423"}]}"#,
        ).unwrap().videos;
        app.views[0].selection.select(Some(0));
        app.preview = Some(PreviewMode::Info);
        for (last_line, hidden, marker) in [
            ("line", false, None),
            ("line", true, Some(50)),
            ("abcdefghijklmnopqrs", true, Some(64)),
            ("a界界界界界界界界界", true, Some(63)),
            ("", true, Some(46)),
        ] {
            app.remember_description(
                "jNQXAC9IVRw".into(),
                format!(
                    "{}{last_line}{}",
                    "line\n".repeat(6),
                    if hidden { "\nhidden content" } else { "" },
                ),
            );
            let mut terminal = Terminal::new(TestBackend::new(80, 24)).unwrap();
            terminal
                .draw(|frame| app.draw(frame, Duration::ZERO))
                .unwrap();
            let buffer = terminal.backend().buffer();
            // The blank row separates the title from its byline.
            for x in 46..65 {
                assert_eq!(buffer.cell((x, 7)).unwrap().symbol(), " ");
            }
            assert_eq!(buffer.cell((46, 8)).unwrap().symbol(), "C");
            if let Some(x) = marker {
                assert_eq!(buffer.cell((x, 17)).unwrap().symbol(), "…");
                if last_line.starts_with("a界") {
                    assert_eq!(buffer.cell((61, 17)).unwrap().symbol(), "界");
                    assert_eq!(buffer.cell((64, 17)).unwrap().symbol(), " ");
                }
            } else {
                let row: String = (46..65)
                    .map(|x| buffer.cell((x, 17)).unwrap().symbol())
                    .collect();
                assert_eq!(row.trim_end(), "line");
            }
            assert_eq!(buffer.cell((65, 17)).unwrap().symbol(), " ");
            assert_eq!(buffer.cell((66, 17)).unwrap().symbol(), " ");
        }
    }

    #[test]
    fn thumbnail_text_has_contrast_a_right_gutter_and_a_clipped_excerpt() {
        use ratatui::{Terminal, backend::TestBackend, style::Modifier};

        let mut app = app(&["tubular"]);
        app.views[0].videos = youtube::search_results(
            r#"{"entries":[{"id":"jNQXAC9IVRw","title":"First second third fourth fifth","channel":"Creator","upload_date":"20050423"}]}"#,
        ).unwrap().videos;
        app.remember_description(
            "jNQXAC9IVRw".into(),
            format!("{}CLIPPED SENTINEL", "Excerpt line\n".repeat(30)),
        );
        app.views[0].selection.select(Some(0));
        app.preview = Some(PreviewMode::Info);
        for (width, height) in [(80, 24), (120, 40), (20, 10)] {
            let mut terminal = Terminal::new(TestBackend::new(width, height)).unwrap();
            terminal
                .draw(|frame| app.draw(frame, Duration::ZERO))
                .unwrap();
            let buffer = terminal.backend().buffer();
            let popup = preview_area(Rect::new(0, 0, width, height));
            let mut excerpt_rows = Vec::new();
            for y in popup.y + 1..popup.bottom() - 1 {
                for x in popup.right() - 3..popup.right() - 1 {
                    assert_eq!(buffer.cell((x, y)).unwrap().symbol(), " ");
                }
                let row: String = (popup.x + popup.width / 2..popup.right() - 3)
                    .map(|x| buffer.cell((x, y)).unwrap().symbol())
                    .collect();
                assert!(!row.contains("CLIPPED SENTINEL"));
                if row.contains("Excerpt line") {
                    excerpt_rows.push(y);
                }
            }
            if width == 20 {
                assert!(excerpt_rows.is_empty()); // Heading takes all available height.
                continue;
            }
            let title = buffer
                .cell((if width == 80 { 46 } else { 69 }, popup.y + 1))
                .unwrap();
            assert_eq!(title.symbol(), "F");
            assert!(title.modifier.contains(Modifier::BOLD));
            assert!(!title.modifier.contains(Modifier::DIM));
            let excerpt_y = *excerpt_rows
                .last()
                .expect("description fills remaining space");
            assert_eq!(excerpt_y, popup.bottom() - 2);
            let excerpt = buffer
                .cell((if width == 80 { 46 } else { 69 }, excerpt_y))
                .unwrap();
            assert_eq!(excerpt.symbol(), "E");
            assert!(!excerpt.modifier.contains(Modifier::DIM));
            assert!(!excerpt.modifier.contains(Modifier::BOLD));
        }
    }

    #[test]
    fn view_tabs_wrap_whole_labels_and_keep_the_selected_row_visible() {
        use ratatui::{Terminal, backend::TestBackend};

        let mut app = app(&["tubular"]);
        app.views = ["Search", "Feed", "Language immersion", "日本語だけ", "中文"]
            .into_iter()
            .map(|name| View::new(name.into()))
            .collect();
        app.config.pinned_categories = app
            .views
            .iter()
            .skip(2)
            .map(|view| view.name.clone())
            .collect();
        app.view_index = 4;
        app.mode = Mode::Insert;
        for (width, height) in [(30, 20), (56, 20), (55, 20), (9, 20), (30, 12)] {
            let mut terminal = Terminal::new(TestBackend::new(width, height)).unwrap();
            terminal
                .draw(|frame| app.draw(frame, Duration::ZERO))
                .unwrap();
            let tab_height = terminal.get_cursor_position().unwrap().y - 1;
            let buffer = terminal.backend().buffer();
            let locate = |symbol: &str| {
                (0..tab_height)
                    .flat_map(|y| (0..width).map(move |x| (x, y)))
                    .find(|&position| buffer.cell(position).unwrap().symbol() == symbol)
            };
            let chinese = locate("中").expect("selected category remains visible");
            assert_eq!(buffer.cell(chinese).unwrap().fg, Color::Cyan);
            assert_eq!(
                buffer.cell((chinese.0 + 2, chinese.1)).unwrap().symbol(),
                "文"
            );
            if width >= 16 {
                let japanese = locate("日").expect("neighboring category remains visible");
                for (offset, character) in "日本語だけ".chars().enumerate() {
                    assert_eq!(
                        buffer
                            .cell((japanese.0 + offset as u16 * 2, japanese.1))
                            .unwrap()
                            .symbol(),
                        character.to_string(),
                        "category label must not split across rows"
                    );
                }
                assert_ne!(buffer.cell(japanese).unwrap().fg, Color::Cyan);
            }
            if width >= 24 {
                assert!(
                    (0..tab_height).any(|y| {
                        (0..width)
                            .map(|x| buffer.cell((x, y)).unwrap().symbol())
                            .collect::<String>()
                            .contains("Language immersion")
                    }),
                    "whole category label must fit after wrapping"
                );
            }
        }
    }

    #[test]
    fn search_pages_preserve_relevance_and_selection() {
        let mut view = View::new("Search".into());
        let mut first = youtube::search_results(
            r#"{"entries":[{"id":"jNQXAC9IVRw","title":"First","timestamp":100},{"id":"rQ_J9WH6CGk","title":"Second","timestamp":200}]}"#,
        )
        .unwrap();
        first.has_more = true;
        view.accept_page(first, false).unwrap();
        view.selection.select(Some(1));
        let mut next = youtube::search_results(
            r#"{"entries":[{"id":"rQ_J9WH6CGk","title":"Duplicate"},{"id":"l-GaaivVJCE","title":"Relevant","timestamp":50},{"id":"l-GaaivVJCE","title":"Repeated"},{"id":"aaaaaaaaaaa","title":"Later","timestamp":300}]}"#,
        )
        .unwrap();
        next.has_more = true;
        view.accept_page(next, false).unwrap();
        assert_eq!(
            view.videos
                .iter()
                .map(|video| video.id.as_str())
                .collect::<Vec<_>>(),
            ["jNQXAC9IVRw", "rQ_J9WH6CGk", "l-GaaivVJCE", "aaaaaaaaaaa"]
        );
        assert_eq!(view.videos[1].title, "Second");
        assert_eq!(view.selection.selected(), Some(1));
        assert_eq!(view.next_start, 41);
        assert!(view.has_more);
    }

    #[test]
    fn feed_pages_hold_short_channel_tails_until_newer_long_histories_finish() {
        let mut view = View::new("Feed".into());
        let long_page = |base: i64| {
            serde_json::json!({
                "entries": (0..PAGE_SIZE).map(|index| serde_json::json!({
                    "id": format!("long{:07}", base + index as i64),
                    "title": "Long channel",
                    "timestamp": base + index as i64,
                })).collect::<Vec<_>>()
            })
            .to_string()
        };
        let short = r#"{"entries":[{"id":"jNQXAC9IVRw","title":"Short old tail","timestamp":100},{"id":"rQ_J9WH6CGk","title":"Unknown date"}]}"#;
        let first = youtube::feed_results(&format!("{}\n{short}", long_page(200))).unwrap();
        view.accept_page(first, true).unwrap();
        assert_eq!(view.videos.len(), PAGE_SIZE);
        assert_eq!(view.videos.last().unwrap().timestamp, Some(200));
        assert_eq!(view.pending.len(), 2);
        view.selection.select(Some(PAGE_SIZE - 1));
        let second = youtube::feed_results(&format!("{}\n{short}", long_page(180))).unwrap();
        view.accept_page(second, true).unwrap();
        assert_eq!(view.videos.len(), PAGE_SIZE * 2);
        assert_eq!(view.videos.last().unwrap().timestamp, Some(180));
        assert_eq!(view.pending.len(), 2);
        assert_eq!(view.selection.selected(), Some(PAGE_SIZE - 1));
        view.accept_page(
            youtube::feed_results(
                r#"{"entries":[{"id":"l-GaaivVJCE","title":"Long last row","timestamp":179}]} {"entries":[]}"#,
            ).unwrap(),
            true,
        ).unwrap();
        assert_eq!(
            view.videos[PAGE_SIZE * 2..]
                .iter()
                .map(|video| video.id.as_str())
                .collect::<Vec<_>>(),
            ["l-GaaivVJCE", "jNQXAC9IVRw", "rQ_J9WH6CGk"]
        );
        assert!(view.pending.is_empty());
        assert!(!view.has_more);
        assert!(!view.needs_page());
    }

    #[test]
    fn unavailable_full_channel_pages_do_not_release_other_channels_ahead_of_newer_uploads() {
        let mut view = View::new("Feed".into());
        let dated = |base: i64| {
            serde_json::json!({
                "entries": (0..PAGE_SIZE).map(|index| serde_json::json!({
                    "id": format!("dated{:06}", base + index as i64),
                    "title": "Dated upload",
                    "timestamp": base + index as i64,
                })).collect::<Vec<_>>()
            })
        };
        let unavailable = serde_json::json!({
            "entries": vec![serde_json::Value::Null; PAGE_SIZE]
        });
        let page = youtube::feed_results(&format!("{}\n{unavailable}", dated(100))).unwrap();
        view.accept_page(page, true).unwrap();
        assert!(view.videos.is_empty());
        assert_eq!(view.selection.selected(), None);
        assert!(view.needs_page());
        let page = youtube::feed_results(&format!("{{\"entries\":[]}}\n{}", dated(200))).unwrap();
        view.accept_page(page, true).unwrap();
        assert_eq!(view.videos.first().unwrap().timestamp, Some(219));
        assert_eq!(view.videos.last().unwrap().timestamp, Some(200));
        view.accept_page(youtube::feed_results(r#"{"entries":[]}"#).unwrap(), true)
            .unwrap();
        assert_eq!(view.videos[PAGE_SIZE].timestamp, Some(119));
        assert_eq!(view.videos.last().unwrap().timestamp, Some(100));
        assert!(!view.has_more);
    }

    #[test]
    fn undated_full_feed_pages_stay_pending_and_do_not_look_exhausted() {
        let mut app = app(&["tubular", "rust"]);
        app.view_index = 1;
        app.feed_channels
            .push("https://www.youtube.com/@jawed".into());
        app.config
            .channels
            .insert("@jawed".into(), app.feed_channels[0].clone());
        let entries: Vec<_> = (0..PAGE_SIZE)
            .map(|index| {
                serde_json::json!({
                    "id": format!("unknown{index:04}"),
                    "title": "Undated",
                })
            })
            .collect();
        app.finish_page(Ok(serde_json::json!({"entries": entries}).to_string()));
        assert!(app.views[1].videos.is_empty());
        assert_eq!(app.views[1].pending.len(), PAGE_SIZE);
        assert_eq!(app.views[1].next_start, 21);
        assert!(app.views[1].loaded);
        assert!(app.can_prefetch());
        app.key(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE));
        assert_eq!(app.views[1].selection.selected(), None);
        assert!(app.job.is_none());
        app.finish_page(Err("Continuation failed".into()));
        assert_eq!(app.views[1].pending.len(), PAGE_SIZE);
        assert_eq!(app.views[1].next_start, 21);
        assert!(!app.can_prefetch());
        app.finish_page(Ok(r#"{"entries":[]}"#.into()));
        assert_eq!(app.views[1].videos.len(), PAGE_SIZE);
        assert!(app.views[1].pending.is_empty());
        assert_eq!(app.views[1].selection.selected(), Some(0));
        assert!(!app.can_prefetch());
        app.views[1].next_start = 81;
        app.views[1].has_more = true;
        app.views[1].page_error = Some("Refresh resets this".into());
        app.key(KeyEvent::new(KeyCode::Char('r'), KeyModifiers::NONE));
        assert_eq!(app.views[1].next_start, 1);
        assert!(app.views[1].videos.is_empty());
        assert!(app.views[1].pending.is_empty());
        assert!(!app.views[1].has_more);
        assert!(app.views[1].page_error.is_none());
        assert!(app.job.is_none());
    }

    #[test]
    fn page_failures_and_view_switches_preserve_the_successful_cursor_until_reset() {
        let mut app = app(&["tubular", "rust"]);
        app.submitted_query = "rust".into();
        app.finish_page(Err("First request failed".into()));
        assert_eq!(app.views[0].next_start, 1);
        assert!(!app.views[0].loaded);
        assert!(app.views[0].page_error.is_some());
        app.switch_view(0);
        app.update();
        assert!(app.job.is_none());
        app.views[0].reset();
        let entries: Vec<_> = (0..PAGE_SIZE)
            .map(|index| {
                serde_json::json!({
                    "id": format!("search{index:05}"),
                    "title": "Result",
                })
            })
            .collect();
        app.finish_page(Ok(serde_json::json!({"entries": entries}).to_string()));
        assert_eq!(app.views[0].next_start, 21);
        app.views[0].selection.select(Some(17));
        app.remember_description(app.views[0].videos[17].id.clone(), "Cached.".into());
        app.switch_view(1);
        app.switch_view(0);
        assert_eq!(app.views[0].next_start, 21);
        assert_eq!(app.views[0].selection.selected(), Some(17));
        app.finish_page(Ok("not JSON".into()));
        app.update();
        assert!(app.job.is_none());
        assert_eq!(app.views[0].videos.len(), PAGE_SIZE);
        assert_eq!(
            cached_description(&app.descriptions, &app.views[0].videos[17].id),
            Some("Cached.")
        );
        assert_eq!(app.views[0].next_start, 21);
        assert!(!app.views[0].needs_page());
        let view = &mut app.views[0];
        view.pending =
            youtube::search_results(r#"{"entries":[{"id":"jNQXAC9IVRw","title":"Pending"}]}"#)
                .unwrap()
                .videos;
        view.reset();
        assert!(view.videos.is_empty());
        assert!(view.pending.is_empty());
        assert_eq!(view.selection.selected(), None);
        assert_eq!(view.next_start, 1);
        assert!(!view.loaded);
        assert!(!view.has_more);
        assert!(view.page_error.is_none());
    }

    #[test]
    fn prefetch_only_runs_near_the_end_in_an_unobstructed_normal_view() {
        let mut app = app(&["tubular"]);
        app.key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE));
        let mut page =
            youtube::search_results(r#"{"entries":[{"id":"jNQXAC9IVRw","title":"Result"}]}"#)
                .unwrap();
        page.has_more = true;
        app.views[0].accept_page(page, false).unwrap();
        assert!(!app.can_prefetch());
        app.mode = Mode::Normal;
        assert!(app.can_prefetch());
        app.preview = Some(PreviewMode::Description);
        assert!(!app.can_prefetch());
        app.preview = Some(PreviewMode::Info);
        assert!(!app.can_prefetch());
        app.preview = None;
        app.category_dialog = Some(CategoryDialog {
            target: CategoryTarget::Channel {
                channel: String::new(),
                handle: String::new(),
            },
            label: String::new(),
            tags: BTreeMap::new(),
            selection: ListState::default(),
            name: None,
            error: None,
        });
        assert!(!app.can_prefetch());
        app.category_dialog = None;
        let entries: Vec<_> = (0..PAGE_SIZE)
            .map(|index| {
                serde_json::json!({
                    "id": format!("search{index:05}"),
                    "title": "Next result",
                })
            })
            .collect();
        app.views[0]
            .accept_page(
                youtube::search_results(&serde_json::json!({"entries": entries}).to_string())
                    .unwrap(),
                false,
            )
            .unwrap();
        assert_eq!(app.views[0].selection.selected(), Some(0));
        assert!(!app.can_prefetch());
        app.views[0].selection.select(Some(15));
        assert!(!app.can_prefetch());
        app.key(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE));
        assert!(app.can_prefetch());
        assert!(app.job.is_none());
        app.views[0].page_error = Some("Stop retrying".into());
        assert!(!app.can_prefetch());
        app.views[0].page_error = None;
        app.views[0].videos.clear();
        app.views[0].selection.select(None);
        assert!(app.can_prefetch());
    }

    #[test]
    fn input_cursor_tracks_display_width_and_stays_inside_scrolled_fields() {
        use ratatui::{Terminal, backend::TestBackend};

        let mut app = app(&["tubular"]);
        app.key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE));
        let mut terminal = Terminal::new(TestBackend::new(24, 20)).unwrap();
        for (text, x) in [
            ("", 1),
            ("ab", 3),
            ("日本語", 7),
            ("e\u{301}", 2),
            ("abcdefghijklmnopqrstuvwxyz", 22),
        ] {
            app.query = text.into();
            terminal
                .draw(|frame| app.draw(frame, Duration::ZERO))
                .unwrap();
            assert_eq!(terminal.get_cursor_position().unwrap(), (x, 2).into());
        }
        app.category_dialog = Some(CategoryDialog {
            target: CategoryTarget::Channel {
                channel: String::new(),
                handle: String::new(),
            },
            label: String::new(),
            tags: BTreeMap::new(),
            selection: ListState::default(),
            name: Some(String::new()),
            error: None,
        });
        for (text, x) in [("", 3), ("日本語", 9), ("abcdefghijklmnopqrstuvwxyz", 20)] {
            app.category_dialog.as_mut().unwrap().name = Some(text.into());
            terminal
                .draw(|frame| app.draw(frame, Duration::ZERO))
                .unwrap();
            assert_eq!(terminal.get_cursor_position().unwrap(), (x, 7).into());
        }
    }

    #[test]
    fn deletion_shortcuts_edit_search_and_tag_names_without_submitting() {
        for tag_input in [false, true] {
            for (input, code, modifiers, expected) in [
                (
                    "first 日本語  ",
                    KeyCode::Backspace,
                    KeyModifiers::ALT,
                    "first ",
                ),
                (
                    "first\u{3000}cafe\u{301}  ",
                    KeyCode::Char('w'),
                    KeyModifiers::CONTROL,
                    "first\u{3000}",
                ),
                ("word", KeyCode::Backspace, KeyModifiers::ALT, ""),
                (" \u{3000} ", KeyCode::Backspace, KeyModifiers::ALT, ""),
                ("", KeyCode::Backspace, KeyModifiers::ALT, ""),
                ("first 日本語", KeyCode::Backspace, KeyModifiers::SUPER, ""),
                (
                    "first 日本語",
                    KeyCode::Backspace,
                    KeyModifiers::SUPER | KeyModifiers::ALT,
                    "",
                ),
                (
                    "first 日本語",
                    KeyCode::Char('u'),
                    KeyModifiers::CONTROL,
                    "",
                ),
                (
                    "first 日本語",
                    KeyCode::Backspace,
                    KeyModifiers::NONE,
                    "first 日本",
                ),
            ] {
                let mut app = app(&["tubular"]);
                if tag_input {
                    app.mode = Mode::Normal;
                    app.category_dialog = Some(CategoryDialog {
                        target: CategoryTarget::Channel {
                            channel: "https://www.youtube.com/channel/UC4QobU6STFB0P71PMvOGN5A"
                                .into(),
                            handle: "@jawed".into(),
                        },
                        label: "jawed".into(),
                        tags: BTreeMap::new(),
                        selection: ListState::default(),
                        name: Some(input.into()),
                        error: None,
                    });
                } else {
                    app.key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE));
                    app.query = input.into();
                }
                app.key(KeyEvent::new(code, modifiers));
                let edited = app
                    .category_dialog
                    .as_ref()
                    .and_then(|dialog| dialog.name.as_deref())
                    .unwrap_or(&app.query);
                assert_eq!(
                    edited, expected,
                    "{tag_input}: {input:?} {code:?} {modifiers:?}"
                );
                assert!(app.job.is_none());
                assert_eq!(
                    app.mode,
                    if tag_input {
                        Mode::Normal
                    } else {
                        Mode::Insert
                    }
                );
            }
        }
        let mut app = app(&["tubular"]);
        app.query = "keep this query".into();
        app.mode = Mode::Normal;
        for (code, modifiers) in [
            (KeyCode::Backspace, KeyModifiers::ALT),
            (KeyCode::Backspace, KeyModifiers::SUPER),
            (KeyCode::Char('w'), KeyModifiers::CONTROL),
        ] {
            app.key(KeyEvent::new(code, modifiers));
            assert_eq!(app.query, "keep this query");
        }
    }

    #[test]
    fn modal_keys_edit_or_navigate_without_submitting_on_escape() {
        let mut app = app(&["tubular"]);
        app.key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE));
        app.views[0].videos = vec![
            Video {
                id: "jNQXAC9IVRw".into(),
                title: "Me at the zoo".into(),
                channel: None,
                channel_id: None,
                uploader_id: None,
                timestamp: None,
                publication_date: None,
            },
            Video {
                id: "rQ_J9WH6CGk".into(),
                title: "Rust course".into(),
                channel: None,
                channel_id: None,
                uploader_id: None,
                timestamp: None,
                publication_date: None,
            },
        ];
        app.views[0].selection.select(Some(0));

        for c in ['j', 'k', 'q'] {
            assert!(!app.key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE)));
        }
        app.update();
        assert_eq!(app.query, "jkq");
        assert_eq!(app.views[0].selection.selected(), Some(0));
        assert!(app.job.is_none());

        app.key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
        assert_eq!(app.mode, Mode::Normal);
        assert!(app.job.is_none());
        app.key(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE));
        assert_eq!(app.views[0].selection.selected(), Some(1));
        app.key(KeyEvent::new(KeyCode::Char('k'), KeyModifiers::NONE));
        assert_eq!(app.views[0].selection.selected(), Some(0));
        app.key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE));
        assert_eq!(app.mode, Mode::Insert);
        app.key(KeyEvent::new(KeyCode::Char('u'), KeyModifiers::CONTROL));
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(app.mode, Mode::Normal);
        assert!(app.query.is_empty());
        assert!(app.job.is_none());
    }

    #[test]
    fn category_dialog_is_modal_and_views_keep_independent_selections() {
        let mut app = app(&["tubular", "rust"]);
        let videos = r#"{"entries":[{"id":"l-GaaivVJCE","title":"Rust video","channel":"Rust","channel_id":"UCaYhcUwRBNscFNUKTjgPFiA","uploader_id":"@RustVideos"},{"id":"rQ_J9WH6CGk","title":"Another video"}]}"#;
        app.views[0].videos = youtube::search_results(videos).unwrap().videos;
        app.views[0].loaded = true;
        app.views[0].selection.select(Some(1));
        // The selected channel is unavailable; do not save a guessed display-name identity.
        app.key(KeyEvent::new(KeyCode::Char('s'), KeyModifiers::NONE));
        assert!(app.category_dialog.is_none());
        app.views[0].selection.select(Some(0));
        let handle = app.views[0].videos[0].uploader_id.take();
        app.key(KeyEvent::new(KeyCode::Char('s'), KeyModifiers::NONE));
        assert!(app.category_dialog.is_none());
        app.views[0].videos[0].uploader_id = handle;
        app.key(KeyEvent::new(KeyCode::Char('s'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char('n'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert!(app.category_dialog.as_ref().unwrap().error.is_some());
        for c in ['j', 'k', 'q', 'i', 't', 'd', ' '] {
            assert!(!app.key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE)));
        }
        assert_eq!(
            app.category_dialog.as_ref().unwrap().name.as_deref(),
            Some("jkqitd ")
        );
        assert_eq!(app.query, "rust");
        assert_eq!(app.views[0].selection.selected(), Some(0));
        app.key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
        assert!(app.category_dialog.as_ref().unwrap().name.is_none());
        app.key(KeyEvent::new(KeyCode::Char('n'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char('A'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert!(app.category_dialog.as_ref().unwrap().name.is_none());
        assert!(app.category_dialog.as_ref().unwrap().tags["A"]);
        assert!(app.config.categories.is_empty());
        app.key(KeyEvent::new(KeyCode::Char(' '), KeyModifiers::NONE));
        assert!(!app.category_dialog.as_ref().unwrap().tags["A"]);
        app.key(KeyEvent::new(KeyCode::Char('n'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
        assert!(!app.category_dialog.as_ref().unwrap().tags["A"]);
        app.key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
        assert!(app.category_dialog.is_none());
        assert_eq!(app.mode, Mode::Normal);
        assert!(app.config.categories.is_empty());

        let rust = vec!["https://www.youtube.com/@RustVideos".into()];
        app.apply_config(config::Config {
            categories: [("Rust".into(), rust.clone())].into(),
            channels: BTreeMap::new(),
            pinned_categories: vec!["Rust".into()],
        });
        app.views[0].selection.select(Some(1));
        app.views[1].videos = youtube::feed_results(videos).unwrap().videos;
        app.views[1].loaded = true;
        app.views[1].selection.select(Some(0));
        app.views[2].videos = youtube::feed_results(videos).unwrap().videos;
        app.views[2].loaded = true;
        app.views[2].selection.select(Some(0));
        app.key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        assert_eq!(app.view_index, 1);
        assert_eq!(app.views[1].name, "Feed");
        app.key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        assert_eq!(app.view_index, 2);
        app.key(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE));
        assert_eq!(app.views[2].selection.selected(), Some(1));
        assert_eq!(app.views[1].selection.selected(), Some(0));
        app.key(KeyEvent::new(KeyCode::BackTab, KeyModifiers::SHIFT));
        assert_eq!(app.view_index, 1);
        assert_eq!(app.views[1].selection.selected(), Some(0));
        app.key(KeyEvent::new(KeyCode::BackTab, KeyModifiers::SHIFT));
        assert_eq!(app.view_index, 0);
        assert_eq!(app.views[0].selection.selected(), Some(1));
        app.key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        app.apply_config(config::Config {
            categories: [
                (
                    "Books".into(),
                    vec!["https://www.youtube.com/@example".into()],
                ),
                ("Rust".into(), rust),
            ]
            .into(),
            channels: BTreeMap::new(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.view_index, 3);
        assert_eq!(app.views[3].name, "Rust");
        assert_eq!(app.views[3].selection.selected(), Some(1));
        assert!(app.views[3].loaded);
        app.apply_config(config::Config {
            categories: [("Rust".into(), vec![])].into(),
            channels: BTreeMap::new(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.views[app.view_index].name, "Rust");
        assert!(app.views[app.view_index].videos.is_empty());
        assert!(app.views[app.view_index].selection.selected().is_none());
        assert!(!app.views[app.view_index].loaded);
        assert!(app.job.is_none());
    }

    #[test]
    fn feed_cache_tracks_subscriptions_not_tag_memberships() {
        let registered = "https://www.youtube.com/channel/UCaYhcUwRBNscFNUKTjgPFiA";
        let direct = "https://www.youtube.com/channel/UC4QobU6STFB0P71PMvOGN5A";
        let added = "https://www.youtube.com/channel/UCBR8-60-B28hp2BmDPdntcQ";
        let mut app = App::new(
            Options::parse_from(["tubular", "rust"]),
            PathBuf::new(),
            config::Config {
                channels: [("@RustVideos".into(), registered.into())].into(),
                categories: [
                    ("Direct".into(), vec![direct.into()]),
                    ("Tagged".into(), vec![registered.into()]),
                ]
                .into(),
                pinned_categories: Vec::new(),
            },
        );
        let videos = r#"{"entries":[{"id":"l-GaaivVJCE","title":"New","timestamp":200},{"id":"rQ_J9WH6CGk","title":"Old","timestamp":100}]}"#;
        assert_eq!(app.feed_channels, vec![direct, registered]);
        app.views[1].videos = youtube::feed_results(videos).unwrap().videos;
        app.views[1].selection.select(Some(1));
        app.views[1].loaded = true;
        app.views[1].next_start = 41;
        app.views[1].has_more = true;
        app.views[1].pending = youtube::feed_results(
            r#"{"entries":[{"id":"jNQXAC9IVRw","title":"Buffered","timestamp":50}]}"#,
        )
        .unwrap()
        .videos;
        app.views[1].page_error = Some("Retained page error".into());
        app.remember_description(
            app.views[1].videos[1].id.clone(),
            "Retained description".into(),
        );
        app.views[3].videos = youtube::feed_results(videos).unwrap().videos;
        app.views[3].selection.select(Some(0));
        app.views[3].loaded = true;
        app.views[3].next_start = 61;
        app.views[3].has_more = true;
        app.views[3].pending = youtube::feed_results(
            r#"{"entries":[{"id":"jNQXAC9IVRw","title":"Tag pending","timestamp":50}]}"#,
        )
        .unwrap()
        .videos;
        app.views[3].page_error = Some("Tag page failed".into());
        app.switch_view(1);

        app.apply_config(config::Config {
            channels: app.config.channels.clone(),
            categories: [
                ("Direct".into(), vec![direct.into()]),
                ("Renamed".into(), vec![registered.into()]),
                ("Tagged".into(), vec![]),
            ]
            .into(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.view_index, 1);
        assert!(app.views[1].loaded);
        assert_eq!(app.views[1].videos[1].id, "rQ_J9WH6CGk");
        assert_eq!(app.views[1].selection.selected(), Some(1));
        assert_eq!(app.views[1].next_start, 41);
        assert!(app.views[1].has_more);
        assert_eq!(app.views[1].pending[0].id, "jNQXAC9IVRw");
        assert_eq!(
            app.views[1].page_error.as_deref(),
            Some("Retained page error")
        );
        assert_eq!(
            cached_description(&app.descriptions, &app.views[1].videos[1].id),
            Some("Retained description")
        );
        assert!(!app.views[4].loaded);
        assert!(app.views[4].videos.is_empty());
        assert_eq!(app.views[4].selection.selected(), None);
        assert_eq!(app.views[4].next_start, 1);
        assert!(!app.views[4].has_more);
        assert!(app.views[4].pending.is_empty());
        assert!(app.views[4].page_error.is_none());

        app.apply_config(config::Config {
            channels: app.config.channels.clone(),
            categories: [
                ("Direct".into(), vec![direct.into()]),
                ("Renamed".into(), vec![]),
                ("Tagged".into(), vec![]),
            ]
            .into(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.feed_channels, vec![direct, registered]);
        assert!(app.views[1].loaded);
        assert_eq!(app.views[1].videos.len(), 2);
        assert_eq!(app.views[1].selection.selected(), Some(1));
        assert_eq!(app.views[1].next_start, 41);
        assert!(app.views[1].has_more);
        assert_eq!(app.views[1].pending.len(), 1);
        assert!(app.views[1].page_error.is_some());

        let mut channels = app.config.channels.clone();
        channels.insert("@YouTube".into(), added.into());
        app.apply_config(config::Config {
            channels,
            categories: app.config.categories.clone(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.feed_channels, vec![direct, added, registered]);
        assert!(!app.views[1].loaded);
        assert!(app.views[1].videos.is_empty());
        assert_eq!(app.views[1].selection.selected(), None);
        assert_eq!(app.views[1].next_start, 1);
        assert!(!app.views[1].has_more);
        assert!(app.views[1].pending.is_empty());
        assert!(app.views[1].page_error.is_none());
        assert_eq!(app.view_index, 1);
        assert!(app.job.is_none());

        app.views[1].videos = youtube::feed_results(videos).unwrap().videos;
        app.views[1].selection.select(Some(1));
        app.views[1].loaded = true;
        let mut channels = app.config.channels.clone();
        channels.remove("@YouTube");
        app.apply_config(config::Config {
            channels,
            categories: app.config.categories.clone(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.feed_channels, vec![direct, registered]);
        assert!(!app.views[1].loaded);
        assert!(app.views[1].videos.is_empty());
        assert_eq!(app.views[1].selection.selected(), None);
        assert_eq!(app.view_index, 1);
        assert!(app.job.is_none());
    }

    #[test]
    fn builtins_and_same_named_tags_keep_distinct_identities() {
        let mut app = app(&["tubular", "rust"]);
        app.apply_config(config::Config {
            channels: [(
                "@RustVideos".into(),
                "https://www.youtube.com/channel/UCaYhcUwRBNscFNUKTjgPFiA".into(),
            )]
            .into(),
            categories: [("Feed".into(), vec![]), ("Search".into(), vec![])].into(),
            pinned_categories: Vec::new(),
        });
        let videos = r#"{"entries":[{"id":"l-GaaivVJCE","title":"First"},{"id":"rQ_J9WH6CGk","title":"Second"}]}"#;
        for (index, view) in app.views.iter_mut().enumerate() {
            view.videos = youtube::feed_results(videos).unwrap().videos;
            view.loaded = true;
            view.selection.select(Some(usize::from(index % 2 == 0)));
        }
        app.switch_view(1);
        app.apply_config(config::Config {
            channels: app.config.channels.clone(),
            categories: [
                ("Alpha".into(), vec![]),
                ("Feed".into(), vec![]),
                ("Search".into(), vec![]),
            ]
            .into(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.view_index, 1);
        assert_eq!(app.views[1].selection.selected(), Some(0));
        assert_eq!(app.views[3].name, "Feed");
        assert_eq!(app.views[3].selection.selected(), Some(1));
        assert_eq!(app.views[0].selection.selected(), Some(1));
        assert_eq!(app.views[4].selection.selected(), Some(0));

        app.switch_view(0);
        app.apply_config(config::Config {
            channels: app.config.channels.clone(),
            categories: [("Feed".into(), vec![]), ("Search".into(), vec![])].into(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.view_index, 0);
        app.switch_view(2);
        app.apply_config(config::Config {
            channels: app.config.channels.clone(),
            categories: [
                ("Alpha".into(), vec![]),
                ("Feed".into(), vec![]),
                ("Search".into(), vec![]),
            ]
            .into(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.view_index, 3);
        assert_eq!(app.views[3].selection.selected(), Some(1));

        app.switch_view(4);
        app.apply_config(config::Config {
            channels: app.config.channels.clone(),
            categories: [
                ("Alpha".into(), vec![]),
                ("Beta".into(), vec![]),
                ("Feed".into(), vec![]),
                ("Search".into(), vec![]),
            ]
            .into(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.view_index, 5);
        assert_eq!(app.views[5].selection.selected(), Some(0));
        app.apply_config(config::Config {
            channels: app.config.channels.clone(),
            categories: [
                ("Alpha".into(), vec![]),
                ("Beta".into(), vec![]),
                ("Feed".into(), vec![]),
            ]
            .into(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.view_index, 0);
        assert_eq!(app.views[0].selection.selected(), Some(1));
        app.switch_view(4);
        app.apply_config(config::Config {
            channels: app.config.channels.clone(),
            categories: [("Alpha".into(), vec![]), ("Beta".into(), vec![])].into(),
            pinned_categories: Vec::new(),
        });
        assert_eq!(app.view_index, 0);
        assert_eq!(app.views[1].name, "Feed");
        assert_eq!(app.views[1].selection.selected(), Some(0));
        assert!(app.job.is_none());
    }

    #[test]
    fn empty_feed_is_informative_and_navigation_wraps_without_extraction() {
        let mut app = app(&["tubular"]);
        assert_eq!(app.views.len(), 2);
        app.key(KeyEvent::new(KeyCode::Tab, KeyModifiers::CONTROL));
        assert_eq!(app.view_index, 1);
        assert!(app.views[1].loaded);
        assert!(app.views[1].videos.is_empty());
        assert_eq!(app.views[1].selection.selected(), None);
        assert!(app.job.is_none());
        app.key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        assert_eq!(app.view_index, 0);
        app.key(KeyEvent::new(KeyCode::BackTab, KeyModifiers::SHIFT));
        assert_eq!(app.view_index, 1);
        assert!(app.job.is_none());
    }

    #[test]
    fn channel_tags_stage_memberships_and_commit_only_from_the_list() {
        let path = std::env::temp_dir().join(format!(
            "tubular-tag-editor-test-{}.toml",
            std::process::id()
        ));
        struct TestFile(PathBuf);
        impl Drop for TestFile {
            fn drop(&mut self) {
                let _ = std::fs::remove_file(&self.0);
            }
        }
        std::fs::OpenOptions::new()
            .write(true)
            .create_new(true)
            .open(&path)
            .unwrap();
        let _file = TestFile(path.clone());
        let original = "[categories]\nAlias = [\"@RustVideos\"]\nCanonical = [\"UCaYhcUwRBNscFNUKTjgPFiA\"]\nEmpty = []\n";
        std::fs::write(&path, original).unwrap();
        let mut app = app(&["tubular", "rust"]);
        app.config_path = path.clone();
        app.views[0].videos = youtube::search_results(
            r#"{"entries":[{"id":"l-GaaivVJCE","title":"Rust video","channel_id":"UCaYhcUwRBNscFNUKTjgPFiA","uploader_id":"@RustVideos"}]}"#,
        )
        .unwrap().videos;
        app.views[0].loaded = true;
        app.views[0].selection.select(Some(0));
        app.key(KeyEvent::new(KeyCode::Char('s'), KeyModifiers::NONE));
        assert_eq!(
            app.category_dialog.as_ref().unwrap().tags,
            [
                ("Alias".into(), true),
                ("Canonical".into(), true),
                ("Empty".into(), false),
            ]
            .into()
        );
        app.key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
        assert!(app.category_dialog.as_ref().unwrap().tags["Alias"]);
        app.key(KeyEvent::new(KeyCode::Up, KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char(' '), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char(' '), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char('n'), KeyModifiers::NONE));
        for c in "Empty".chars() {
            app.key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE));
        }
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert!(app.category_dialog.as_ref().unwrap().error.is_some());
        app.key(KeyEvent::new(KeyCode::Char('u'), KeyModifiers::CONTROL));
        for c in "  Added  ".chars() {
            app.key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE));
        }
        app.key(KeyEvent::new(KeyCode::Backspace, KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(
            app.category_dialog.as_ref().unwrap().selection.selected(),
            Some(0)
        );
        assert!(app.category_dialog.as_ref().unwrap().tags["Added"]);
        assert_eq!(std::fs::read_to_string(&path).unwrap(), original);
        app.category_dialog.as_mut().unwrap().error = Some("Previous save failed".into());
        app.key(KeyEvent::new(KeyCode::Char(' '), KeyModifiers::NONE));
        assert!(app.category_dialog.as_ref().unwrap().error.is_none());
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert!(app.category_dialog.is_none());
        let saved = config::load(&path).unwrap();
        let canonical = vec!["https://www.youtube.com/channel/UCaYhcUwRBNscFNUKTjgPFiA".to_owned()];
        assert!(saved.categories["Alias"].is_empty());
        assert!(saved.categories["Added"].is_empty());
        assert_eq!(saved.categories["Canonical"], canonical);
        assert_eq!(saved.categories["Empty"], canonical);
        let committed = std::fs::read_to_string(&path).unwrap();
        app.key(KeyEvent::new(KeyCode::Char('s'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char(' '), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
        assert_eq!(std::fs::read_to_string(&path).unwrap(), committed);
        std::fs::write(&path, "[categories]\n").unwrap();
        app.key(KeyEvent::new(KeyCode::Char('s'), KeyModifiers::NONE));
        assert!(
            app.category_dialog
                .as_ref()
                .unwrap()
                .selection
                .selected()
                .is_none()
        );
        app.key(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Char(' '), KeyModifiers::NONE));
        app.key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert!(app.category_dialog.is_none());
        assert!(config::load(&path).unwrap().categories.is_empty());
    }

    #[test]
    fn preview_cycles_without_reloading_and_selection_resets_scrolling() {
        use ratatui::{Terminal, backend::TestBackend};

        let mut app = app(&["tubular"]);
        app.views[0].videos = youtube::search_results(
            r#"{"entries":[{"id":"jNQXAC9IVRw","title":"First"},{"id":"9bZkp7q19f0","title":"Second"}]}"#,
        ).unwrap().videos;
        // Invalid fixture IDs keep thumbnail failure deterministic without invoking curl.
        app.views[0].videos[0].id = "first".into();
        app.views[0].videos[1].id = "second".into();
        app.remember_description("first".into(), "First paragraph\n\n".repeat(40));
        app.remember_description("second".into(), "Second paragraph\n\n".repeat(40));
        app.views[0].selection.select(Some(0));
        app.views[0].loaded = true;
        let mut terminal = Terminal::new(TestBackend::new(120, 40)).unwrap();
        let press = |app: &mut App, code| {
            app.key(KeyEvent::new(code, KeyModifiers::NONE));
        };
        press(&mut app, KeyCode::Char('t'));
        assert_eq!(app.preview, None);
        press(&mut app, KeyCode::Char('d'));
        assert_eq!(app.preview, Some(PreviewMode::Info));
        assert!(app.description_job.is_none());
        terminal
            .draw(|frame| app.draw(frame, Duration::ZERO))
            .unwrap();
        let info = terminal.backend().buffer().clone();
        press(&mut app, KeyCode::Char('d'));
        assert_eq!(app.preview, Some(PreviewMode::Description));
        terminal
            .draw(|frame| app.draw(frame, Duration::ZERO))
            .unwrap();
        press(&mut app, KeyCode::PageDown);
        assert!(app.description_scroll > 0);
        let scroll = app.description_scroll;
        press(&mut app, KeyCode::Char('d'));
        assert_eq!(app.preview, Some(PreviewMode::Info));
        assert_eq!(app.description_scroll, scroll);
        assert!(app.description_job.is_none());
        terminal
            .draw(|frame| app.draw(frame, Duration::ZERO))
            .unwrap();
        // Includes the failed thumbnail text: cancellation would remove that image state.
        assert_eq!(terminal.backend().buffer(), &info);
        press(&mut app, KeyCode::Char('d'));
        press(&mut app, KeyCode::Char('j'));
        assert_eq!(app.preview, Some(PreviewMode::Description));
        assert_eq!(app.views[0].selection.selected(), Some(1));
        assert_eq!(app.description_scroll, 0);
        assert_eq!(app.description_viewport, None);
        assert!(app.description_error.is_none());
        assert!(app.description_job.is_none());
        terminal
            .draw(|frame| app.draw(frame, Duration::ZERO))
            .unwrap();
        let buffer = terminal.backend().buffer();
        let popup = preview_area(buffer.area);
        let caption: String = (popup.x..popup.right())
            .map(|x| buffer[(x, popup.bottom() - 1)].symbol())
            .collect();
        assert!(caption.contains(" Second "));
        press(&mut app, KeyCode::Down);
        assert_eq!(app.description_scroll, 1);
        assert_eq!(app.views[0].selection.selected(), Some(1));
        press(&mut app, KeyCode::Char('d'));
        press(&mut app, KeyCode::Up);
        assert_eq!(app.views[0].selection.selected(), Some(0));
        assert_eq!(app.description_scroll, 0);
        press(&mut app, KeyCode::Esc);
        assert_eq!(app.preview, None);
        assert_eq!(
            cached_description(&app.descriptions, "first"),
            Some("First paragraph\n\n".repeat(40).as_str())
        );
        press(&mut app, KeyCode::Char('i'));
        press(&mut app, KeyCode::Char('t'));
        press(&mut app, KeyCode::Char('d'));
        assert_eq!(app.query, "td");
        assert_eq!(app.preview, None);
    }
}