import AppKit
import ConjureKit

@MainActor
final class EmojiPickerController: NSViewController, NSCollectionViewDataSource, NSCollectionViewDelegateFlowLayout {
    private let collection = NSCollectionView()
    private let category = NSPopUpButton()
    private let status = NSTextField(labelWithString: "")
    private let empty = NSTextField(labelWithString: "No matching emoji")
    private let copyButton = NSButton(title: "Copy and Paste", target: nil, action: nil)
    private let actionsButton = NSButton(title: "Actions", target: nil, action: nil)
    private let actions = ApplicationActionsController()
    private var favoriteCount = 0
    private var splitFavorites: Bool { favoriteCount > 0 && favoriteCount < results.count }
    private let defaults: UserDefaults
    private let pasteboard: NSPasteboard
    private var results: [Emoji] = []
    private var selected = 0
    var input: (() -> String)?
    var closed: (() -> Void)?
    var copied: (() -> Void)?
    var pasteRequested: (() -> Void)?
    var focusSearch: (() -> Void)?

    init(defaults: UserDefaults = .standard, pasteboard: NSPasteboard = .general) {
        self.defaults = defaults
        self.pasteboard = pasteboard
        super.init(nibName: nil, bundle: nil)
    }

    required init?(coder: NSCoder) { fatalError("Conjure creates its emoji picker programmatically") }

    override func loadView() {
        view = NSView()
        category.addItems(withTitles: ["All Emoji", "Recently Used"] + EmojiCatalog.categories)
        category.setAccessibilityLabel("Emoji category")
        category.target = self
        category.action = #selector(categoryChanged)
        let layout = NSCollectionViewFlowLayout()
        layout.itemSize = NSSize(width: 64, height: 56)
        layout.minimumInteritemSpacing = 6
        layout.minimumLineSpacing = 6
        layout.sectionInset = NSEdgeInsets(top: LauncherScrollView.fadeHeight, left: 16, bottom: 12, right: 16)
        collection.collectionViewLayout = layout
        collection.backgroundColors = [.clear]
        collection.dataSource = self
        collection.delegate = self
        collection.register(EmojiItem.self, forItemWithIdentifier: NSUserInterfaceItemIdentifier("emoji"))
        collection.setAccessibilityLabel("Emoji grid")
        let scroll = LauncherScrollView()
        scroll.documentView = collection
        scroll.hasVerticalScroller = true
        scroll.autohidesScrollers = true
        scroll.scrollerStyle = .overlay
        scroll.drawsBackground = false
        scroll.contentView.drawsBackground = false
        empty.textColor = SunsetPalette.secondaryText
        status.font = .systemFont(ofSize: 12)
        status.textColor = SunsetPalette.secondaryText
        status.lineBreakMode = .byTruncatingTail
        status.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        copyButton.target = self
        copyButton.action = #selector(copyAndPasteSelection)
        copyButton.keyEquivalent = "\r"
        copyButton.isBordered = false
        copyButton.font = .systemFont(ofSize: 12, weight: .medium)
        copyButton.contentTintColor = SunsetPalette.text
        actionsButton.target = self
        actionsButton.action = #selector(showActions)
        actionsButton.keyEquivalent = "k"
        actionsButton.keyEquivalentModifierMask = .command
        actionsButton.isBordered = false
        actionsButton.font = copyButton.font
        actionsButton.contentTintColor = SunsetPalette.text
        let pill = NSStackView(views: [copyButton, ShortcutIndicator("↵"), actionsButton, ShortcutIndicator("⌘", "K")])
        pill.spacing = 8
        pill.edgeInsets = NSEdgeInsets(top: 0, left: 14, bottom: 0, right: 12)
        pill.wantsLayer = true
        pill.layer?.cornerRadius = 18
        pill.layer?.borderWidth = 0.5
        pill.layer?.borderColor = SunsetPalette.accent.withAlphaComponent(0.35).cgColor
        pill.layer?.backgroundColor = SunsetPalette.background.withAlphaComponent(0.25).cgColor
        let footer = NSStackView(views: [status, NSView(), pill])
        pill.heightAnchor.constraint(equalToConstant: 36).isActive = true
        actions.closed = { [weak self] in
            self?.copyButton.keyEquivalent = "\r"
            self?.focusSearch?()
        }
        footer.spacing = 8
        for child in [category, scroll, empty, footer] {
            child.translatesAutoresizingMaskIntoConstraints = false
            view.addSubview(child)
        }
        NSLayoutConstraint.activate([
            category.topAnchor.constraint(equalTo: view.topAnchor),
            category.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 16),
            scroll.topAnchor.constraint(equalTo: category.bottomAnchor, constant: 4),
            scroll.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            scroll.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            scroll.bottomAnchor.constraint(equalTo: footer.topAnchor, constant: -4),
            empty.centerXAnchor.constraint(equalTo: scroll.centerXAnchor),
            empty.centerYAnchor.constraint(equalTo: scroll.centerYAnchor),
            footer.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 16),
            footer.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -16),
            footer.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -8),
            footer.heightAnchor.constraint(equalToConstant: 36),
        ])
        inputChanged()
    }

    @objc private func categoryChanged() { inputChanged() }
    @objc func goBack() {
        if actions.isShown { actions.close() } else { closed?() }
    }
    func close() {
        actions.close()
        closed?()
    }
    override func cancelOperation(_ sender: Any?) { goBack() }

    func inputChanged(preservingSelection: Bool = false) {
        let previous = preservingSelection && results.indices.contains(selected) ? results[selected].value : nil
        let recent = defaults.stringArray(forKey: "recentEmoji") ?? []
        let matches = EmojiCatalog.search(input?() ?? "", category: category.indexOfSelectedItem > 1 ? category.titleOfSelectedItem : nil)
        if category.indexOfSelectedItem == 1 {
            results = recent.compactMap { value in matches.first { $0.value == value } }
        } else if category.indexOfSelectedItem == 0, (input?() ?? "").isEmpty {
            let recentSet = Set(recent)
            results = recent.compactMap { value in matches.first { $0.value == value } }
                + matches.filter { !recentSet.contains($0.value) }
        } else {
            results = matches
        }
        let favorites = Set(defaults.stringArray(forKey: "favoriteEmoji") ?? [])
        let favored = results.filter { favorites.contains($0.value) }
        results = favored + results.filter { !favorites.contains($0.value) }
        favoriteCount = (input?() ?? "").trimmingCharacters(in: .whitespacesAndNewlines).isEmpty ? favored.count : 0
        selected = previous.flatMap { value in results.firstIndex { $0.value == value } } ?? 0
        collection.reloadData()
        collection.scroll(NSPoint.zero)
        updateSelection()
    }

    func moveSelection(by offset: Int) {
        guard !results.isEmpty else { return }
        let old = selected
        selected = min(max(selected + offset, 0), results.count - 1)
        (collection.item(at: indexPath(for: old)) as? EmojiItem)?.highlight(false)
        updateSelection()
        collection.scrollToItems(at: [indexPath(for: selected)], scrollPosition: .nearestVerticalEdge)
    }

    private var columns: Int { max(1, Int((collection.bounds.width - 32 + 6) / 70)) }

    private func indexPath(for index: Int) -> IndexPath {
        splitFavorites && index >= favoriteCount
            ? IndexPath(item: index - favoriteCount, section: 1) : IndexPath(item: index, section: 0)
    }

    private func index(for path: IndexPath) -> Int { path.item + (path.section == 1 ? favoriteCount : 0) }

    private func moveVertically(_ direction: Int) {
        guard !results.isEmpty else { return }
        let path = indexPath(for: selected)
        let count = collectionView(collection, numberOfItemsInSection: path.section)
        let column = path.item % columns
        var target = path
        if direction < 0 {
            if path.item >= columns { target = IndexPath(item: path.item - columns, section: path.section) }
            else if path.section > 0 {
                let previousCount = favoriteCount
                target = IndexPath(item: min(((previousCount - 1) / columns) * columns + column, previousCount - 1), section: 0)
            }
        } else if path.item / columns < (count - 1) / columns {
            target = IndexPath(item: min(path.item + columns, count - 1), section: path.section)
        } else if splitFavorites && path.section == 0 {
            target = IndexPath(item: min(column, results.count - favoriteCount - 1), section: 1)
        }
        moveSelection(by: index(for: target) - selected)
    }

    func handleControlKey(_ key: String) -> Bool {
        if actions.isShown {
            guard key == "j" || key == "k" else { return false }
            actions.moveSelection(by: key == "j" ? 1 : -1)
            return true
        }
        switch key {
        case "h": moveSelection(by: -1)
        case "j": moveVertically(1)
        case "k": moveVertically(-1)
        case "l": moveSelection(by: 1)
        default: return false
        }
        return true
    }

    @objc func showActions() {
        guard results.indices.contains(selected) else { return }
        let emoji = results[selected]
        actions.isFavorite = (defaults.stringArray(forKey: "favoriteEmoji") ?? []).contains(emoji.value)
        actions.open = { [weak self] in self?.copyAndPasteSelection() }
        actions.copyEmoji = { [weak self] in self?.copySelection() }
        actions.toggleFavorite = { [weak self] in self?.toggleFavorite() }
        actions.showEmoji(named: emoji.name, relativeTo: actionsButton)
        copyButton.keyEquivalent = actions.isShown ? "" : "\r"
    }

    func toggleFavorite() {
        guard results.indices.contains(selected) else { return }
        let value = results[selected].value
        var favorites = defaults.stringArray(forKey: "favoriteEmoji") ?? []
        if favorites.contains(value) { favorites.removeAll { $0 == value } }
        else { favorites.append(value) }
        defaults.set(favorites, forKey: "favoriteEmoji")
        inputChanged(preservingSelection: true)
    }
    func handle(_ selector: Selector) -> Bool {
        if actions.isShown { return actions.handle(selector) }
        switch selector {
        case #selector(NSResponder.moveLeft(_:)): moveSelection(by: -1)
        case #selector(NSResponder.moveRight(_:)): moveSelection(by: 1)
        case #selector(NSResponder.moveUp(_:)): moveVertically(-1)
        case #selector(NSResponder.moveDown(_:)): moveVertically(1)
        case #selector(NSResponder.insertNewline(_:)): copyAndPasteSelection()
        case #selector(NSResponder.cancelOperation(_:)): goBack()
        default: return false
        }
        return true
    }

    private func updateSelection() {
        empty.isHidden = !results.isEmpty
        if results.isEmpty {
            empty.stringValue = category.indexOfSelectedItem == 1 ? "No recently used emoji match" : "No matching emoji"
        }
        copyButton.isEnabled = !results.isEmpty
        actionsButton.isEnabled = !results.isEmpty
        status.stringValue = results.isEmpty ? "0 emoji" : "\(results[selected].name) · \(results.count) emoji"
        (collection.item(at: indexPath(for: selected)) as? EmojiItem)?.highlight(true)
    }

    @objc func copySelection() { copySelection(pasting: false) }
    @objc func copyAndPasteSelection() { copySelection(pasting: true) }

    private func copySelection(pasting: Bool) {
        guard results.indices.contains(selected) else { return }
        let value = results[selected].value
        pasteboard.clearContents()
        guard pasteboard.setString(value, forType: .string) else {
            status.stringValue = "Couldn’t copy emoji. Try again."
            return
        }
        var recent = defaults.stringArray(forKey: "recentEmoji") ?? []
        recent.removeAll { $0 == value }
        defaults.set(Array(([value] + recent).prefix(30)), forKey: "recentEmoji")
        closed?()
        if pasting { pasteRequested?() } else { copied?() }
    }

    func numberOfSections(in collectionView: NSCollectionView) -> Int { splitFavorites ? 2 : 1 }

    func collectionView(_ collectionView: NSCollectionView, numberOfItemsInSection section: Int) -> Int {
        splitFavorites ? (section == 0 ? favoriteCount : results.count - favoriteCount) : results.count
    }

    func collectionView(_ collectionView: NSCollectionView, layout collectionViewLayout: NSCollectionViewLayout, insetForSectionAt section: Int) -> NSEdgeInsets {
        NSEdgeInsets(top: section == 1 ? 18 : LauncherScrollView.fadeHeight, left: 16, bottom: splitFavorites && section == 0 ? 0 : 12, right: 16)
    }

    func collectionView(_ collectionView: NSCollectionView, itemForRepresentedObjectAt indexPath: IndexPath) -> NSCollectionViewItem {
        let item = collectionView.makeItem(withIdentifier: NSUserInterfaceItemIdentifier("emoji"), for: indexPath) as! EmojiItem
        let index = index(for: indexPath)
        let emoji = results[index]
        item.button.title = emoji.value
        item.button.toolTip = emoji.name
        item.button.setAccessibilityLabel((defaults.stringArray(forKey: "favoriteEmoji") ?? []).contains(emoji.value) ? "\(emoji.name), Favorite" : emoji.name)
        item.highlight(index == selected)
        item.clicked = { [weak self] in
            self?.selected = index
            self?.copyAndPasteSelection()
        }
        return item
    }
}

@MainActor
private final class EmojiItem: NSCollectionViewItem {
    let button = NSButton()
    var clicked: (() -> Void)?

    override func loadView() {
        button.font = .systemFont(ofSize: 32)
        button.isBordered = false
        button.target = self
        button.action = #selector(copyEmoji)
        button.wantsLayer = true
        button.layer?.cornerRadius = 10
        view = button
    }

    func highlight(_ selected: Bool) {
        button.layer?.backgroundColor = selected ? SunsetPalette.accent.withAlphaComponent(0.22).cgColor : nil
        button.setAccessibilitySelected(selected)
    }

    @objc private func copyEmoji() { clicked?() }
}