import AppKit
import ConjureKit

@MainActor
final class EmojiPickerController: NSViewController, NSCollectionViewDataSource {
    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 Emoji", target: nil, action: nil)
    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)?

    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: 12, left: 16, bottom: 12, right: 16)
        collection.collectionViewLayout = layout
        collection.backgroundColors = [.clear]
        collection.dataSource = 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(copySelection)
        copyButton.keyEquivalent = "\r"
        copyButton.isBordered = false
        copyButton.font = .systemFont(ofSize: 12, weight: .medium)
        copyButton.contentTintColor = SunsetPalette.text
        let footer = NSStackView(views: [status, NSView(), copyButton, ShortcutIndicator("↵")])
        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() { closed?() }
    override func cancelOperation(_ sender: Any?) { goBack() }

    func inputChanged() {
        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
        }
        selected = 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(item: old, section: 0)) as? EmojiItem)?.highlight(false)
        updateSelection()
        collection.scrollToItems(at: [IndexPath(item: selected, section: 0)], scrollPosition: .nearestVerticalEdge)
    }

    func handle(_ selector: Selector) -> Bool {
        let columns = max(1, Int((collection.bounds.width - 32 + 6) / 70))
        switch selector {
        case #selector(NSResponder.moveLeft(_:)): moveSelection(by: -1)
        case #selector(NSResponder.moveRight(_:)): moveSelection(by: 1)
        case #selector(NSResponder.moveUp(_:)): moveSelection(by: -columns)
        case #selector(NSResponder.moveDown(_:)): moveSelection(by: columns)
        case #selector(NSResponder.insertNewline(_:)): copySelection()
        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
        status.stringValue = results.isEmpty ? "0 emoji" : "\(results[selected].name) · \(results.count) emoji"
        (collection.item(at: IndexPath(item: selected, section: 0)) as? EmojiItem)?.highlight(true)
    }

    @objc func copySelection() {
        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?()
        copied?()
    }

    func collectionView(_ collectionView: NSCollectionView, numberOfItemsInSection section: Int) -> Int { results.count }

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