use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
use ratatui::{
    Frame,
    layout::{Constraint, Layout, Rect},
    style::{Color, Modifier, Style},
    text::Line,
    widgets::{Block, Cell, Paragraph, Row, Table, TableState},
};

use crate::{
    Result,
    connection::Input,
    db::{Column, Database, PAGE_SIZE, Page, QueryResult, Relation},
    error_text, sql,
};

#[derive(Clone, Copy, PartialEq, Eq)]
pub(crate) enum Focus {
    Explorer,
    Query,
    Rows,
}

pub struct App {
    db: Database,
    pub(crate) relations: Vec<Relation>,
    active: Option<usize>,
    columns: Vec<Column>,
    page: Page,
    page_index: usize,
    rows_state: TableState,
    schema_state: TableState,
    column_offset: usize,
    show_schema: bool,
    query: Input,
    query_insert: bool,
    query_highlights: sql::Highlights,
    query_result: Option<QueryResult>,
    error: Option<String>,
}

impl App {
    pub fn new(mut db: Database) -> Result<Self> {
        let relations = db.relations()?;
        let selected = (!relations.is_empty()).then_some(0);
        let mut app = Self {
            db,
            relations,
            active: None,
            columns: Vec::new(),
            page: Page {
                rows: Vec::new(),
                has_next: false,
            },
            page_index: 0,
            rows_state: TableState::default(),
            schema_state: TableState::default(),
            column_offset: 0,
            show_schema: false,
            query: Input::default(),
            query_insert: false,
            query_highlights: Vec::new(),
            query_result: None,
            error: None,
        };
        app.open_relation(selected);
        Ok(app)
    }

    pub(crate) fn provider(&self) -> &'static str {
        self.db.name()
    }

    pub(crate) fn database_name(&self) -> &str {
        self.db.display_name()
    }

    pub(crate) fn query_insert_mode(&self) -> bool {
        self.query_insert
    }

    pub(crate) fn leave_query_insert(&mut self) -> bool {
        std::mem::replace(&mut self.query_insert, false)
    }

    pub(crate) fn query_position(&self) -> (usize, usize) {
        self.query.position()
    }

    pub(crate) fn handle_key(&mut self, key: KeyEvent) {
        match key.code {
            KeyCode::Down | KeyCode::Char('j') => self.move_selection(1),
            KeyCode::Up | KeyCode::Char('k') => self.move_selection(-1),
            KeyCode::Home | KeyCode::Char('g') => self.move_selection(isize::MIN),
            KeyCode::End | KeyCode::Char('G') => self.move_selection(isize::MAX),
            KeyCode::Char('s') if self.query_result.is_none() => {
                self.show_schema = !self.show_schema;
                self.column_offset = 0;
            }
            KeyCode::Left | KeyCode::Char('h') => self.move_column(-1),
            KeyCode::Right | KeyCode::Char('l') => self.move_column(1),
            KeyCode::Char('n') | KeyCode::PageDown
                if self.query_result.is_none() && !self.show_schema && self.page.has_next =>
            {
                self.load_page(self.page_index + 1);
            }
            KeyCode::Char('p') | KeyCode::PageUp
                if self.query_result.is_none() && !self.show_schema && self.page_index > 0 =>
            {
                self.load_page(self.page_index - 1);
            }
            KeyCode::Char('r') => self.refresh(),
            _ => {}
        }
    }

    pub(crate) fn handle_query_key(&mut self, key: KeyEvent) {
        let previous_len = self.query.value.len();
        match key.code {
            KeyCode::F(5) => self.execute_query(),
            KeyCode::Enter if key.modifiers.contains(KeyModifiers::CONTROL) => self.execute_query(),
            KeyCode::Esc => {
                self.leave_query_insert();
            }
            KeyCode::Enter if self.query_insert => self.query.paste_multiline("\n"),
            _ if self.query_insert => self.query.edit(key),
            KeyCode::Left
            | KeyCode::Right
            | KeyCode::Up
            | KeyCode::Down
            | KeyCode::Home
            | KeyCode::End => self.query.edit(key),
            KeyCode::Char(character)
                if !key
                    .modifiers
                    .intersects(KeyModifiers::CONTROL | KeyModifiers::ALT) =>
            {
                let movement = match character {
                    'h' => Some(KeyCode::Left),
                    'j' => Some(KeyCode::Down),
                    'k' => Some(KeyCode::Up),
                    'l' => Some(KeyCode::Right),
                    'a' => {
                        let (line, column) = self.query_position();
                        self.query
                            .value
                            .split('\n')
                            .nth(line - 1)
                            .filter(|text| column <= text.chars().count())
                            .map(|_| KeyCode::Right)
                    }
                    'I' => Some(KeyCode::Home),
                    'A' => Some(KeyCode::End),
                    _ => None,
                };
                if let Some(code) = movement {
                    self.query.edit(KeyEvent::new(code, KeyModifiers::NONE));
                }
                self.query_insert = matches!(character, 'i' | 'a' | 'I' | 'A');
            }
            _ => {}
        }
        self.highlight_query(previous_len);
    }

    pub(crate) fn paste_query(&mut self, text: &str) {
        if !self.query_insert {
            return;
        }
        let previous_len = self.query.value.len();
        self.query.paste_multiline(text);
        self.highlight_query(previous_len);
    }

    fn highlight_query(&mut self, previous_len: usize) {
        // Editing inserts or removes bytes; cursor movement does not invalidate syntax.
        if self.query.value.len() != previous_len {
            self.query_highlights = sql::highlight(&self.query.value, self.db.name() == "SQLite");
        }
    }

    fn execute_query(&mut self) {
        match self.db.query(&self.query.value) {
            Ok(result) => {
                self.rows_state = TableState::default()
                    .with_selected((!result.page.rows.is_empty()).then_some(0))
                    .with_selected_column((!result.headers.is_empty()).then_some(0));
                self.column_offset = 0;
                self.show_schema = false;
                self.query_result = Some(result);
                self.error = None;
            }
            Err(error) => self.error = Some(error_text(error.as_ref())),
        }
    }

    fn move_selection(&mut self, delta: isize) {
        if self.show_schema {
            let next = moved_index(self.schema_state.selected(), self.columns.len(), delta);
            self.schema_state.select(next);
        } else {
            let count = self
                .query_result
                .as_ref()
                .map_or(self.page.rows.len(), |result| result.page.rows.len());
            let next = moved_index(self.rows_state.selected(), count, delta);
            self.rows_state.select(next);
        }
    }

    fn column_count(&self) -> usize {
        if self.show_schema {
            5
        } else {
            self.query_result
                .as_ref()
                .map_or(self.columns.len(), |result| result.headers.len())
        }
    }

    fn move_column(&mut self, delta: isize) {
        let count = self.column_count();
        let state = if self.show_schema {
            &mut self.schema_state
        } else {
            &mut self.rows_state
        };
        state.select_column(moved_index(state.selected_column(), count, delta));
    }

    pub(crate) fn open_relation(&mut self, index: Option<usize>) {
        self.active = index;
        self.query_result = None;
        self.columns.clear();
        self.page = Page {
            rows: Vec::new(),
            has_next: false,
        };
        self.page_index = 0;
        self.column_offset = 0;
        self.rows_state = TableState::default();
        self.schema_state = TableState::default();
        self.error = None;
        if let Some(index) = self.active {
            match self.db.columns(&self.relations[index]) {
                Ok(columns) => {
                    self.columns = columns;
                    self.schema_state
                        .select((!self.columns.is_empty()).then_some(0));
                    self.schema_state
                        .select_column((!self.columns.is_empty()).then_some(0));
                    self.load_page(0);
                }
                Err(error) => self.error = Some(error_text(error.as_ref())),
            }
        }
    }

    fn load_page(&mut self, index: usize) {
        if let Some(active) = self.active {
            // ponytail: synchronous reads block input; use a worker if responsiveness matters.
            match self.db.page(&self.relations[active], &self.columns, index) {
                Ok(page) => {
                    self.rows_state = TableState::default()
                        .with_selected((!page.rows.is_empty()).then_some(0))
                        .with_selected_column(
                            self.rows_state
                                .selected_column()
                                .or_else(|| (!self.columns.is_empty()).then_some(0)),
                        );
                    self.page = page;
                    self.page_index = index;
                    self.error = None;
                }
                Err(error) => self.error = Some(error_text(error.as_ref())),
            }
        }
    }

    fn refresh(&mut self) {
        match self.db.relations() {
            Ok(relations) => {
                let id = self.active.map(|index| self.relations[index].id);
                let selected = relations
                    .iter()
                    .position(|relation| Some(relation.id) == id)
                    .or_else(|| (!relations.is_empty()).then_some(0));
                self.relations = relations;
                self.open_relation(selected);
            }
            Err(error) => self.error = Some(error_text(error.as_ref())),
        }
    }

    pub(crate) fn draw(&mut self, frame: &mut Frame, area: Rect, focus: Focus) {
        if area.width < 38 || area.height < 10 {
            frame.render_widget(
                Paragraph::new("Enlarge terminal to at least 70×17. Ctrl-C to quit."),
                area,
            );
            return;
        }
        let [error_area, body] = Layout::vertical([
            Constraint::Length(u16::from(self.error.is_some())),
            Constraint::Min(4),
        ])
        .areas(area);
        let [query, content] =
            Layout::vertical([Constraint::Ratio(1, 2), Constraint::Min(4)]).areas(body);
        self.query.draw(
            frame,
            query,
            " Query · F5 execute ",
            false,
            focus == Focus::Query,
            Some(sql::text(&self.query.value, &self.query_highlights)),
        );
        let title = if self.query_result.is_some() {
            " Results "
        } else if self.show_schema {
            " Schema · s for rows "
        } else {
            " Rows · s for schema "
        };
        let count = self.column_count();
        let capacity = usize::from(content.width.saturating_sub(2) / 21).max(1);
        let selected = if self.show_schema {
            self.schema_state.selected_column()
        } else {
            self.rows_state.selected_column()
        };
        if let Some(selected) = selected {
            self.column_offset = self.column_offset.min(selected);
            if selected >= self.column_offset + capacity {
                self.column_offset = selected + 1 - capacity;
            }
        }
        let visible = capacity.min(count.saturating_sub(self.column_offset));
        let widths = (0..visible).map(|index| {
            if index + 1 == visible {
                Constraint::Min(1)
            } else {
                Constraint::Length(20)
            }
        });
        let description = if let Some(result) = &self.query_result {
            format!(
                " Query · {} rows{} · columns {}–{}/{}",
                result.page.rows.len(),
                if result.page.has_next {
                    " (first 100)"
                } else {
                    ""
                },
                if count > 0 { self.column_offset + 1 } else { 0 },
                self.column_offset + visible,
                count,
            )
        } else if let Some(index) = self.active {
            let relation = &self.relations[index];
            if self.show_schema {
                format!(
                    " [{}] · {} columns · fields {}–{}/5",
                    relation.kind,
                    self.columns.len(),
                    self.column_offset + 1,
                    self.column_offset + visible
                )
            } else {
                let start = if self.page.rows.is_empty() {
                    0
                } else {
                    self.page_index * PAGE_SIZE + 1
                };
                let end = self.page_index * PAGE_SIZE + self.page.rows.len();
                format!(
                    " [{}] · rows {start}–{end} · page {}{} · columns {}–{}/{}",
                    relation.kind,
                    self.page_index + 1,
                    if self.page.has_next { " (more)" } else { "" },
                    if count > 0 { self.column_offset + 1 } else { 0 },
                    self.column_offset + visible,
                    count
                )
            }
        } else {
            " No readable relations. r to refresh.".into()
        };
        let mut content_block =
            panel(title, focus == Focus::Rows).title_bottom(Line::from(description).left_aligned());
        if self.query_result.is_none()
            && let Some(index) = self.active
        {
            content_block = content_block.title_top(
                Line::from(format!(" {} ", self.relations[index].label)).right_aligned(),
            );
        }
        let page = self
            .query_result
            .as_ref()
            .map_or(&self.page, |result| &result.page);
        if self.active.is_none() && self.query_result.is_none() {
            frame.render_widget(
                Paragraph::new("Choose a relation and press Enter.").block(content_block),
                content,
            );
        } else if self.show_schema {
            let headers = ["Column", "Type", "Nullable", "Key", "Default"];
            let rows = self.columns.iter().map(|column| {
                Row::new(
                    [
                        column.label.as_str(),
                        column.data_type.as_str(),
                        if column.nullable { "yes" } else { "no" },
                        if column.primary_key { "PK" } else { "" },
                        column.default.as_str(),
                    ]
                    .into_iter()
                    .skip(self.column_offset)
                    .take(visible),
                )
            });
            let table = Table::new(rows, widths)
                .header(
                    Row::new(headers.into_iter().skip(self.column_offset).take(visible))
                        .style(header_style()),
                )
                .block(content_block)
                .cell_highlight_style(selected_style());
            self.schema_state
                .select_column(selected.map(|column| column - self.column_offset));
            frame.render_stateful_widget(table, content, &mut self.schema_state);
            self.schema_state.select_column(selected);
        } else if page.rows.is_empty() {
            frame.render_widget(
                Paragraph::new(if self.error.is_some() {
                    "Could not load rows. See error above."
                } else {
                    "No rows."
                })
                .block(content_block),
                content,
            );
        } else {
            let headers = (self.column_offset..self.column_offset + visible).map(|index| {
                self.query_result.as_ref().map_or_else(
                    || self.columns[index].label.as_str(),
                    |result| result.headers[index].as_str(),
                )
            });
            let rows = page.rows.iter().map(|row| {
                Row::new(
                    row.iter()
                        .skip(self.column_offset)
                        .take(visible)
                        .map(|value| match value {
                            Some(value) => Cell::from(value.as_str()),
                            None => Cell::from("NULL").style(
                                Style::default()
                                    .fg(Color::DarkGray)
                                    .add_modifier(Modifier::ITALIC),
                            ),
                        }),
                )
            });
            let table = Table::new(rows, widths)
                .header(Row::new(headers).style(header_style()))
                .block(content_block)
                .cell_highlight_style(selected_style());
            self.rows_state
                .select_column(selected.map(|column| column - self.column_offset));
            frame.render_stateful_widget(table, content, &mut self.rows_state);
            self.rows_state.select_column(selected);
        }
        if let Some(error) = &self.error {
            frame.render_widget(
                Paragraph::new(error.as_str()).style(Style::default().fg(Color::Red)),
                error_area,
            );
        }
    }
}

fn panel(title: &str, focused: bool) -> Block<'_> {
    Block::bordered()
        .title(title)
        .border_style(Style::default().fg(if focused {
            Color::Cyan
        } else {
            Color::DarkGray
        }))
}

fn selected_style() -> Style {
    Style::default().bg(Color::Blue).fg(Color::White)
}

fn header_style() -> Style {
    Style::default()
        .fg(Color::Cyan)
        .add_modifier(Modifier::BOLD)
}

fn moved_index(selected: Option<usize>, count: usize, delta: isize) -> Option<usize> {
    if count == 0 {
        return None;
    }
    Some(
        selected
            .unwrap_or(0)
            .saturating_add_signed(delta)
            .min(count - 1),
    )
}

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

    #[test]
    fn navigation_clamps_to_available_items() {
        assert_eq!(moved_index(None, 0, 1), None);
        assert_eq!(moved_index(None, 3, 1), Some(1));
        assert_eq!(moved_index(Some(0), 3, -1), Some(0));
        assert_eq!(moved_index(Some(2), 3, 1), Some(2));
        assert_eq!(moved_index(Some(1), 3, isize::MIN), Some(0));
        assert_eq!(moved_index(Some(1), 3, isize::MAX), Some(2));
    }

    #[test]
    fn query_modes_preserve_literal_text_and_navigation() -> crate::Result<()> {
        use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
        let file = tempfile::NamedTempFile::new()?;
        let mut app = super::App::new(crate::db::Database::open_sqlite(file.path())?)?;
        let key = |character| KeyEvent::new(KeyCode::Char(character), KeyModifiers::NONE);
        assert!(!app.query_insert_mode());
        app.paste_query("ignored");
        app.handle_query_key(key('q'));
        assert!(app.query.value.is_empty());
        assert!(!app.leave_query_insert());
        app.handle_query_key(key('i'));
        for character in ['q', 'i', 'h'] {
            app.handle_query_key(key(character));
        }
        app.handle_query_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        app.paste_query("界é");
        assert_eq!(app.query.value, "qih\n界é");
        assert_eq!(app.query_position(), (2, 3));
        assert!(app.leave_query_insert());
        app.paste_query("ignored");
        app.handle_query_key(key('h'));
        assert_eq!(app.query_position(), (2, 2));
        app.handle_query_key(key('k'));
        assert_eq!(app.query_position(), (1, 2));
        app.handle_query_key(key('a'));
        assert!(app.query_insert_mode());
        assert_eq!(app.query_position(), (1, 3));
        app.leave_query_insert();
        app.handle_query_key(key('I'));
        assert_eq!(app.query_position(), (1, 1));
        assert!(app.query_insert_mode());
        app.leave_query_insert();
        app.handle_query_key(key('A'));
        assert_eq!(app.query_position(), (1, 4));
        assert!(app.query_insert_mode());
        app.leave_query_insert();
        app.handle_query_key(key('a'));
        assert_eq!(app.query_position(), (1, 4));
        app.handle_query_key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
        assert!(!app.query_insert_mode());
        assert_eq!(app.query.value, "qih\n界é");
        Ok(())
    }

    #[test]
    fn execution_shortcuts_work_in_both_query_modes() -> crate::Result<()> {
        use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
        let file = tempfile::NamedTempFile::new()?;
        let mut app = super::App::new(crate::db::Database::open_sqlite(file.path())?)?;
        app.handle_query_key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE));
        app.paste_query("SELECT\n42");
        for insert in [true, false] {
            if !insert {
                app.leave_query_insert();
            }
            for key in [
                KeyEvent::new(KeyCode::F(5), KeyModifiers::NONE),
                KeyEvent::new(KeyCode::Enter, KeyModifiers::CONTROL),
            ] {
                app.query_result = None;
                app.handle_query_key(key);
                assert_eq!(app.query_insert_mode(), insert);
                assert_eq!(
                    app.query_result.as_ref().unwrap().page.rows[0][0].as_deref(),
                    Some("42")
                );
            }
        }
        Ok(())
    }

    #[test]
    fn cell_selection_scrolls_and_survives_paging_and_schema_switches() -> crate::Result<()> {
        use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
        use ratatui::{Terminal, backend::TestBackend, style::Color};
        let file = tempfile::NamedTempFile::new()?;
        rusqlite::Connection::open(file.path())?.execute_batch(
            "CREATE TABLE cells (a, b, c, d, e, f);
             WITH RECURSIVE n(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM n WHERE x<101)
             INSERT INTO cells SELECT x, x, x, x, x, x FROM n;",
        )?;
        let mut app = super::App::new(crate::db::Database::open_sqlite(file.path())?)?;
        let mut terminal = Terminal::new(TestBackend::new(60, 20))?;
        let key = |character| KeyEvent::new(KeyCode::Char(character), KeyModifiers::NONE);
        assert_eq!(app.rows_state.selected_cell(), Some((0, 0)));
        terminal.draw(|frame| app.draw(frame, frame.area(), super::Focus::Rows))?;
        assert_eq!(terminal.backend().buffer()[(1, 12)].bg, Color::Blue);
        assert_ne!(terminal.backend().buffer()[(22, 12)].bg, Color::Blue);
        app.handle_key(key('l'));
        app.handle_key(key('l'));
        app.handle_key(key('j'));
        terminal.draw(|frame| app.draw(frame, frame.area(), super::Focus::Rows))?;
        assert_eq!(app.rows_state.selected_cell(), Some((1, 2)));
        assert_eq!(app.column_offset, 1);
        assert_eq!(terminal.backend().buffer()[(22, 13)].bg, Color::Blue);
        assert_ne!(terminal.backend().buffer()[(1, 13)].bg, Color::Blue);
        assert_ne!(terminal.backend().buffer()[(22, 12)].bg, Color::Blue);
        app.handle_key(key('n'));
        assert_eq!(app.page_index, 1);
        assert_eq!(app.rows_state.selected_cell(), Some((0, 2)));
        app.handle_key(key('s'));
        app.handle_key(key('l'));
        app.handle_key(key('j'));
        terminal.draw(|frame| app.draw(frame, frame.area(), super::Focus::Rows))?;
        assert_eq!(app.schema_state.selected_cell(), Some((1, 1)));
        assert_eq!(app.column_offset, 0);
        assert_eq!(terminal.backend().buffer()[(22, 13)].bg, Color::Blue);
        assert_ne!(terminal.backend().buffer()[(1, 13)].bg, Color::Blue);
        app.handle_key(key('s'));
        terminal.draw(|frame| app.draw(frame, frame.area(), super::Focus::Rows))?;
        assert_eq!(app.rows_state.selected_cell(), Some((0, 2)));
        assert_eq!(app.column_offset, 1);
        app.handle_key(KeyEvent::new(KeyCode::Left, KeyModifiers::NONE));
        assert_eq!(app.rows_state.selected_column(), Some(1));
        Ok(())
    }

    #[test]
    fn query_colors_survive_editing_and_scrolling() -> crate::Result<()> {
        use super::{App, Focus};
        use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
        use ratatui::{Terminal, backend::TestBackend, style::Color};
        let file = tempfile::NamedTempFile::new()?;
        let mut app = App::new(crate::db::Database::open_sqlite(file.path())?)?;
        let mut terminal = Terminal::new(TestBackend::new(60, 14))?;
        app.handle_query_key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE));
        app.paste_query("SELECT '界', 42;\n-- comment");
        terminal.draw(|frame| app.draw(frame, frame.area(), Focus::Query))?;
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(1, 1)].fg, Color::Cyan);
        assert_eq!(buffer[(8, 1)].fg, Color::Green);
        assert_eq!(buffer[(1, 2)].fg, Color::DarkGray);
        app.handle_query_key(KeyEvent::new(KeyCode::Char('u'), KeyModifiers::CONTROL));
        app.handle_query_key(KeyEvent::new(KeyCode::Char('\''), KeyModifiers::NONE));
        app.paste_query("unfinished\nstring");
        terminal.draw(|frame| app.draw(frame, frame.area(), Focus::Query))?;
        assert_eq!(terminal.backend().buffer()[(1, 2)].fg, Color::Green);
        app.handle_query_key(KeyEvent::new(KeyCode::Char('u'), KeyModifiers::CONTROL));
        app.paste_query(&format!("{}--{}", "-- line\n".repeat(12), "x".repeat(90)));
        terminal.draw(|frame| app.draw(frame, frame.area(), Focus::Query))?;
        let cursor = terminal.get_cursor_position()?;
        let buffer = terminal.backend().buffer();
        assert_eq!(cursor.x, 58);
        assert_eq!(buffer[(cursor.x - 1, cursor.y)].symbol(), "x");
        assert_eq!(buffer[(1, cursor.y)].fg, Color::DarkGray);
        Ok(())
    }

    #[test]
    fn queries_replace_rows_and_preserve_results_on_error() -> crate::Result<()> {
        use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
        let file = tempfile::NamedTempFile::new()?;
        rusqlite::Connection::open(file.path())?.execute_batch(
            "CREATE TABLE comments (id INTEGER); INSERT INTO comments VALUES (9);",
        )?;
        let mut app = super::App::new(crate::db::Database::open_sqlite(file.path())?)?;
        app.handle_query_key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE));
        app.paste_query("SELECT '界é' AS note,\nNULL AS missing UNION ALL SELECT 'next', 2;");
        app.handle_query_key(KeyEvent::new(KeyCode::F(5), KeyModifiers::NONE));
        let result = app.query_result.as_ref().unwrap();
        assert_eq!(result.headers, ["note", "missing"]);
        assert_eq!(result.page.rows[0], [Some("界é".into()), None]);
        assert_eq!(app.rows_state.selected_cell(), Some((0, 0)));
        app.handle_key(KeyEvent::new(KeyCode::Right, KeyModifiers::NONE));
        assert_eq!(app.rows_state.selected_cell(), Some((0, 1)));
        app.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
        assert_eq!(app.rows_state.selected(), Some(1));
        app.handle_query_key(KeyEvent::new(KeyCode::Char('u'), KeyModifiers::CONTROL));
        app.paste_query("SELECT missing FROM nowhere");
        app.handle_query_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::CONTROL));
        assert!(app.error.is_some());
        assert_eq!(
            app.query_result.as_ref().unwrap().page.rows[0][0].as_deref(),
            Some("界é")
        );
        app.open_relation(Some(0));
        assert!(app.query_result.is_none());
        assert!(app.error.is_none());
        assert_eq!(app.page.rows, [vec![Some("9".into())]]);
        assert_eq!(app.query.value, "SELECT missing FROM nowhere");
        Ok(())
    }

    #[test]
    fn relation_status_is_in_the_bottom_border() -> crate::Result<()> {
        let file = tempfile::NamedTempFile::new()?;
        rusqlite::Connection::open(file.path())?.execute_batch(
            "CREATE TABLE comments (id INTEGER); INSERT INTO comments VALUES (1);",
        )?;
        let mut app = super::App::new(crate::db::Database::open_sqlite(file.path())?)?;
        let mut terminal = ratatui::Terminal::new(ratatui::backend::TestBackend::new(100, 20))?;
        for (schema, error) in [(false, None), (true, None), (false, Some("Read failed"))] {
            app.show_schema = schema;
            app.error = error.map(str::to_owned);
            terminal.draw(|frame| app.draw(frame, frame.area(), super::Focus::Rows))?;
            let buffer = terminal.backend().buffer();
            let border: String = (0..100).map(|x| buffer[(x, 19)].symbol()).collect();
            assert!(border.ends_with('┘'), "{border}");
            assert!(!border.contains("main.comments"));
            assert!((0..19).any(|y| {
                let line: String = (0..100).map(|x| buffer[(x, y)].symbol()).collect();
                line.ends_with(" main.comments ┐")
            }));
            assert!(border.contains(if schema {
                "fields 1–4/5"
            } else {
                "rows 1–1"
            }));
            if let Some(error) = error {
                let message: String = (0..100).map(|x| buffer[(x, 0)].symbol()).collect();
                assert!(message.starts_with(error), "{message}");
            }
        }
        Ok(())
    }
}