import AppKit
import ConjureKit
import Highlighter

@MainActor
final class NotesController: NSViewController, NSTextViewDelegate {
    private let createButton = NSButton(title: "New Note", target: nil, action: nil)
    private let actionsButton = NSButton(title: "Actions", target: nil, action: nil)
    private let noteMenu = NSMenu(title: "Notes")
    private let editor = NSTextView()
    private let status = NSTextField(labelWithString: "")
    private let defaults: UserDefaults
    private var store: NotesStore?
    private var selectedID: UUID?
    private var isDirty = false
    private var loadError: Error?
    var closed: (() -> Void)?

    init(defaults: UserDefaults = .standard, directory: URL? = nil) {
        self.defaults = defaults
        super.init(nibName: nil, bundle: nil)
        do {
            store = try directory.map { try NotesStore(directory: $0) } ?? NotesStore()
        } catch {
            loadError = error
        }
    }

    required init?(coder: NSCoder) { fatalError("Conjure creates Notes programmatically") }

    override func loadView() {
        view = NSView()
        createButton.target = self
        createButton.action = #selector(newNote)
        createButton.toolTip = "Create a note (Command-N)"
        actionsButton.target = self
        actionsButton.action = #selector(showActions)
        actionsButton.setAccessibilityLabel("Choose a note")
        actionsButton.toolTip = "Choose a note (Command-K)"
        actionsButton.menu = noteMenu
        let pill = ActionPill(primaryButton: createButton, actionsButton: actionsButton, primaryCommand: "n")
        let footer = NSStackView(views: [status, NSView(), pill])
        footer.orientation = .horizontal
        footer.alignment = .centerY
        footer.spacing = 12

        editor.delegate = self
        editor.isRichText = true
        editor.importsGraphics = true
        editor.allowsUndo = true
        editor.drawsBackground = false
        editor.textColor = SunsetPalette.text
        editor.insertionPointColor = SunsetPalette.accent
        editor.font = .systemFont(ofSize: 14)
        editor.isAutomaticQuoteSubstitutionEnabled = false
        editor.isAutomaticDashSubstitutionEnabled = false
        editor.isAutomaticTextReplacementEnabled = false
        editor.isVerticallyResizable = true
        editor.isHorizontallyResizable = false
        editor.autoresizingMask = [.width]
        editor.textContainer?.widthTracksTextView = true
        editor.textContainerInset = NSSize(width: 10, height: 10)
        editor.setAccessibilityLabel("Note editor")
        let scroll = NSScrollView()
        scroll.documentView = editor
        scroll.hasVerticalScroller = true
        scroll.autohidesScrollers = true
        scroll.drawsBackground = false
        scroll.wantsLayer = true
        scroll.layer?.cornerRadius = 8
        scroll.layer?.borderWidth = 0.5
        scroll.layer?.borderColor = SunsetPalette.secondaryText.withAlphaComponent(0.22).cgColor
        status.font = .systemFont(ofSize: 12)
        status.textColor = SunsetPalette.secondaryText
        status.setAccessibilityLabel("Notes save status")
        status.lineBreakMode = .byTruncatingTail
        status.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        for control in [scroll, footer] {
            control.translatesAutoresizingMaskIntoConstraints = false
            view.addSubview(control)
        }
        NSLayoutConstraint.activate([
            scroll.topAnchor.constraint(equalTo: view.topAnchor),
            scroll.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 16),
            scroll.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -16),
            scroll.bottomAnchor.constraint(equalTo: footer.topAnchor, constant: -8),
            footer.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 16),
            footer.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -8),
            footer.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -8),
            footer.heightAnchor.constraint(equalToConstant: 36),
        ])
        guard let store else {
            editor.isEditable = false
            for control in [createButton, actionsButton] { control.isEnabled = false }
            showError(loadError!)
            return
        }
        do {
            let savedID = defaults.string(forKey: "selectedNote").flatMap(UUID.init(uuidString:))
            let id = store.notes.first { $0.id == savedID }?.id ?? store.notes.first?.id
            select(try id ?? store.create())
        } catch {
            editor.isEditable = false
            showError(error)
        }
    }

    func focusEditor() { view.window?.makeFirstResponder(editor) }

    func textDidChange(_ notification: Notification) {
        isDirty = true
        MarkdownHighlighting.apply(to: editor)
        _ = save()
    }

    @discardableResult
    func save() -> Bool {
        guard isDirty, let store, let selectedID else { return true }
        do {
            try store.update(id: selectedID, contents: editor.attributedString())
            isDirty = false
            updateActions()
            status.stringValue = "Saved locally · Markdown · Paste or drop images"
            status.textColor = SunsetPalette.secondaryText
            return true
        } catch {
            showError(error)
            return false
        }
    }

    func goBack() {
        guard save() else { return }
        closed?()
    }

    @objc private func newNote() {
        guard save(), let store else { return }
        do { select(try store.create()); focusEditor() }
        catch { showError(error) }
    }

    @objc private func switchNote(_ sender: NSMenuItem) {
        guard let value = sender.representedObject as? UUID, save() else { return }
        select(value)
        focusEditor()
    }

    private func select(_ id: UUID) {
        guard let note = store?.notes.first(where: { $0.id == id }) else { return }
        selectedID = id
        defaults.set(id.uuidString, forKey: "selectedNote")
        editor.textStorage?.setAttributedString(note.contents)
        editor.undoManager?.removeAllActions()
        editor.isEditable = true
        editor.setSelectedRange(NSRange(location: editor.string.utf16.count, length: 0))
        MarkdownHighlighting.apply(to: editor)
        updateActions()
        status.stringValue = "Saved locally · Markdown · Paste or drop images"
        status.textColor = SunsetPalette.secondaryText
    }

    private func updateActions() {
        noteMenu.removeAllItems()
        for note in store?.notes ?? [] {
            let item = noteMenu.addItem(withTitle: note.title, action: #selector(switchNote(_:)), keyEquivalent: "")
            item.target = self
            item.representedObject = note.id
            item.state = note.id == selectedID ? .on : .off
        }
    }

    private func showError(_ error: Error) {
        status.stringValue = "Couldn’t save or load notes: \(error.localizedDescription)"
        status.toolTip = status.stringValue
        status.textColor = .systemRed
    }

    @objc private func showActions() {
        noteMenu.popUp(positioning: nil, at: NSPoint(x: 0, y: actionsButton.bounds.maxY + 4), in: actionsButton)
        focusEditor()
    }
}

@MainActor
enum MarkdownHighlighting {
    // ponytail: whole-note highlighting; incremental parsing if large notes make typing slow.
    private static let rules: [(NSRegularExpression, [NSAttributedString.Key: Any])] = [
        (try! NSRegularExpression(pattern: "(?m)^#{1,6} .+$"), [.font: NSFont.systemFont(ofSize: 17, weight: .semibold), .foregroundColor: SunsetPalette.accent]),
        (try! NSRegularExpression(pattern: "\\*\\*[^\\n]+?\\*\\*|__[^\\n]+?__"), [.font: NSFont.boldSystemFont(ofSize: 14)]),
        (try! NSRegularExpression(pattern: "(?<!\\*)\\*(?!\\*)[^*\\n]+\\*(?!\\*)|(?<!_)_(?!_)[^_\\n]+_(?!_)"), [.font: NSFontManager.shared.convert(.systemFont(ofSize: 14), toHaveTrait: .italicFontMask)]),
        (try! NSRegularExpression(pattern: "!?\\[[^\\]\\n]+\\]\\([^\\n)]+\\)|(?m)^\\s*(?:[-+*]|[0-9]+\\.)\\s"), [.foregroundColor: SunsetPalette.accent]),
        (try! NSRegularExpression(pattern: "`[^`\\n]+`"), [.font: NSFont.monospacedSystemFont(ofSize: 14, weight: .regular), .foregroundColor: NSColor.systemGreen]),
    ]

    private static let highlighter: Highlighter = {
        guard let value = Highlighter() else { preconditionFailure("Missing bundled syntax highlighter") }
        value.setTheme("atom-one-dark", withFont: "Menlo-Regular", ofSize: 14)
        return value
    }()
    private static let openingFence = try! NSRegularExpression(pattern: "(?m)^ {0,3}(`{3,}|~{3,})([^\\r\\n]*)\\r?\\n")

    private static func codeBlocks(in text: String) -> [(range: NSRange, body: NSRange, language: String?)] {
        let source = text as NSString
        var blocks: [(NSRange, NSRange, String?)] = []
        var cursor = 0
        while let opening = openingFence.firstMatch(in: text, range: NSRange(location: cursor, length: source.length - cursor)) {
            let fence = source.substring(with: opening.range(at: 1))
            let marker = NSRegularExpression.escapedPattern(for: String(fence.first!))
            let closing = try! NSRegularExpression(pattern: "(?m)^ {0,3}\(marker){\(fence.count),}[ \\t]*\\r?$")
            let start = NSMaxRange(opening.range)
            let end = closing.firstMatch(in: text, range: NSRange(location: start, length: source.length - start))
            let bodyEnd = end?.range.location ?? source.length
            cursor = end.map { NSMaxRange($0.range) } ?? source.length
            let language = source.substring(with: opening.range(at: 2)).split(whereSeparator: { $0.isWhitespace }).first.map(String.init)
            blocks.append((NSRange(location: opening.range.location, length: cursor - opening.range.location),
                           NSRange(location: start, length: bodyEnd - start), language))
            if cursor == source.length { break }
        }
        return blocks
    }

    static func apply(to editor: NSTextView) {
        guard let storage = editor.textStorage else { return }
        let text = editor.string
        let range = NSRange(location: 0, length: text.utf16.count)
        storage.beginEditing()
        defer { storage.endEditing() }
        storage.enumerateAttribute(.attachment, in: range) { value, _, _ in
            guard let attachment = value as? NSTextAttachment,
                  let cell = attachment.attachmentCell as? NSTextAttachmentCell,
                  let image = cell.image else { return }
            let size = image.size
            let scale = min(1, 460 / max(size.width, 1), 240 / max(size.height, 1))
            if scale < 1 { image.size = NSSize(width: size.width * scale, height: size.height * scale) }
        }
        storage.addAttributes([.font: NSFont.systemFont(ofSize: 14), .foregroundColor: SunsetPalette.text], range: range)
        let blocks = codeBlocks(in: text)
        for (expression, attributes) in rules {
            for match in expression.matches(in: text, range: range) {
                guard !blocks.contains(where: { NSIntersectionRange($0.range, match.range).length > 0 }) else { continue }
                storage.addAttributes(attributes, range: match.range)
            }
        }
        for block in blocks {
            storage.addAttributes([.font: NSFont.monospacedSystemFont(ofSize: 14, weight: .regular),
                                   .foregroundColor: SunsetPalette.secondaryText], range: block.range)
            storage.addAttribute(.foregroundColor, value: SunsetPalette.text, range: block.body)
            let code = (text as NSString).substring(with: block.body)
            guard let highlighted = highlighter.highlight(code, as: block.language),
                  highlighted.string == code else { continue }
            highlighted.enumerateAttribute(.foregroundColor, in: NSRange(location: 0, length: highlighted.length)) { color, range, _ in
                if let color {
                    storage.addAttribute(.foregroundColor, value: color,
                                         range: NSRange(location: block.body.location + range.location, length: range.length))
                }
            }
        }
        editor.typingAttributes = [.font: NSFont.systemFont(ofSize: 14), .foregroundColor: SunsetPalette.text]
    }
}