import Cocoa
import Combine
import SwiftUI

class AppDelegate: NSObject, NSApplicationDelegate {
    var window: NSWindow!
    var appState: AppState!
    private var titleCancellable: AnyCancellable?
    private var titleBarView: TitleBarView?
    private var focusTitleObserver: NSObjectProtocol?

    func applicationDidFinishLaunching(_ notification: Notification) {
        appState = AppState()

        let contentView = ContentView(state: appState)
        let hostingView = NSHostingView(rootView: contentView)

        window = NSWindow(
            contentRect: NSRect(x: 0, y: 0, width: 1200, height: 800),
            styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
            backing: .buffered,
            defer: false
        )
        window.titlebarAppearsTransparent = true
        window.titleVisibility = .hidden
        window.backgroundColor = Theme.current.base
        window.title = "Swiftly"
        window.contentView = hostingView
        window.center()
        window.setFrameAutosaveName("SwiftlyMainWindow")
        window.makeKeyAndOrderFront(nil)

        setupTitleBar()
        setupMenuBar()
        observeDocumentTitle()
    }

    func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
        return true
    }

    func applicationWillTerminate(_ notification: Notification) {
        appState.saveNote()
    }

    // MARK: - Menu bar

    private func setupMenuBar() {
        let mainMenu = NSMenu()

        mainMenu.addItem(buildAppMenu())
        mainMenu.addItem(buildFileMenu())
        mainMenu.addItem(buildEditMenu())
        mainMenu.addItem(buildViewMenu())
        mainMenu.addItem(buildWindowMenu())

        NSApp.mainMenu = mainMenu
    }

    private func buildAppMenu() -> NSMenuItem {
        let item = NSMenuItem()
        let menu = NSMenu()
        menu.addItem(withTitle: "About Swiftly", action: #selector(NSApplication.orderFrontStandardAboutPanel(_:)), keyEquivalent: "")
        menu.addItem(.separator())
        menu.addItem(withTitle: "Quit Swiftly", action: #selector(NSApplication.terminate(_:)), keyEquivalent: "q")
        item.submenu = menu
        return item
    }

    private func buildFileMenu() -> NSMenuItem {
        let item = NSMenuItem()
        let menu = NSMenu(title: "File")

        let newItem = NSMenuItem(title: "New Note", action: #selector(newNote), keyEquivalent: "n")
        newItem.target = self
        menu.addItem(newItem)

        let openItem = NSMenuItem(title: "Open...", action: #selector(openNote), keyEquivalent: "o")
        openItem.target = self
        menu.addItem(openItem)

        menu.addItem(.separator())

        let saveItem = NSMenuItem(title: "Save", action: #selector(saveNote), keyEquivalent: "s")
        saveItem.target = self
        menu.addItem(saveItem)

        let saveAsItem = NSMenuItem(title: "Save As...", action: #selector(saveNoteAs), keyEquivalent: "S")
        saveAsItem.target = self
        menu.addItem(saveAsItem)

        item.submenu = menu
        return item
    }

    private func buildEditMenu() -> NSMenuItem {
        let item = NSMenuItem()
        let menu = NSMenu(title: "Edit")
        menu.addItem(withTitle: "Undo", action: Selector(("undo:")), keyEquivalent: "z")
        menu.addItem(withTitle: "Redo", action: Selector(("redo:")), keyEquivalent: "Z")
        menu.addItem(.separator())
        menu.addItem(withTitle: "Cut", action: #selector(NSText.cut(_:)), keyEquivalent: "x")
        menu.addItem(withTitle: "Copy", action: #selector(NSText.copy(_:)), keyEquivalent: "c")
        menu.addItem(withTitle: "Paste", action: #selector(NSText.paste(_:)), keyEquivalent: "v")
        menu.addItem(withTitle: "Select All", action: #selector(NSText.selectAll(_:)), keyEquivalent: "a")
        menu.addItem(.separator())

        let findItem = NSMenuItem(title: "Find...", action: #selector(NSTextView.performFindPanelAction(_:)), keyEquivalent: "f")
        findItem.tag = Int(NSTextFinder.Action.showFindInterface.rawValue)
        menu.addItem(findItem)

        item.submenu = menu
        return item
    }

    private func buildViewMenu() -> NSMenuItem {
        let item = NSMenuItem()
        let menu = NSMenu(title: "View")
        let toggleItem = NSMenuItem(title: "Toggle Sidebar", action: #selector(toggleSidebar), keyEquivalent: "b")
        toggleItem.keyEquivalentModifierMask = .control
        toggleItem.target = self
        menu.addItem(toggleItem)
        item.submenu = menu
        return item
    }

    private func buildWindowMenu() -> NSMenuItem {
        let item = NSMenuItem()
        let menu = NSMenu(title: "Window")
        menu.addItem(withTitle: "Minimize", action: #selector(NSWindow.miniaturize(_:)), keyEquivalent: "m")
        menu.addItem(withTitle: "Zoom", action: #selector(NSWindow.zoom(_:)), keyEquivalent: "")
        item.submenu = menu
        NSApp.windowsMenu = menu
        return item
    }

    // MARK: - Actions

    @objc private func newNote() {
        appState.newNote()
    }

    @objc private func openNote() {
        let panel = NSOpenPanel()
        panel.allowedContentTypes = [.plainText]
        panel.canChooseFiles = true
        panel.canChooseDirectories = false
        panel.allowsMultipleSelection = false
        panel.beginSheetModal(for: window) { [weak self] response in
            guard response == .OK, let url = panel.url else { return }
            self?.appState.loadNoteFromFile(url)
        }
    }

    @objc private func saveNote() {
        appState.saveNote()
    }

    @objc private func saveNoteAs() {
        let panel = NSSavePanel()
        panel.allowedContentTypes = [.plainText]
        panel.nameFieldStringValue = "note.txt"
        panel.beginSheetModal(for: window) { [weak self] response in
            guard response == .OK, let url = panel.url else { return }
            self?.appState.saveNoteToFile(url)
        }
    }

    @objc private func toggleSidebar() {
        NotificationCenter.default.post(name: .toggleSidebar, object: nil)
    }

    private func setupTitleBar() {
        let accessory = TitleBarAccessoryController()
        window.addTitlebarAccessoryViewController(accessory)

        let tbv = accessory.titleView
        tbv.onCommit = { [weak self] rawTitle in
            guard let self = self else { return }
            let lines = self.appState.documentText.components(separatedBy: "\n")
            var rest = Array(lines.dropFirst())
            if rest.isEmpty && self.appState.documentText.isEmpty { rest = [] }
            self.appState.documentText = ([rawTitle] + rest).joined(separator: "\n")
        }

        titleBarView = tbv

        focusTitleObserver = NotificationCenter.default.addObserver(
            forName: .focusTitle, object: nil, queue: .main
        ) { [weak self] _ in
            self?.titleBarView?.beginEditing()
        }
    }

    private func observeDocumentTitle() {
        titleCancellable = appState.$documentText
            .receive(on: RunLoop.main)
            .sink { [weak self] text in
                guard let self = self else { return }
                let firstLine = text.components(separatedBy: "\n").first?
                    .trimmingCharacters(in: .whitespaces) ?? ""
                let clean = firstLine.replacingOccurrences(
                    of: "^#+\\s*", with: "", options: .regularExpression
                )
                let displayTitle = clean.isEmpty ? "Swiftly" : String(clean.prefix(60))
                self.window.title = displayTitle
                self.titleBarView?.title = firstLine
            }
    }
}