//
//  AppAppearanceManager.swift
//  App for Indeed
//

import AppKit

/// Persists and applies the user’s light / dark / system appearance preference.
@MainActor
final class AppAppearanceManager {
    static let shared = AppAppearanceManager()

    static let didChangeNotification = Notification.Name("AppAppearanceManager.didChange")

    enum Mode: String, CaseIterable {
        case light
        case dark
        case system

        var segmentIndex: Int {
            switch self {
            case .system: 0
            case .light: 1
            case .dark: 2
            }
        }

        init?(segmentIndex: Int) {
            switch segmentIndex {
            case 0: self = .system
            case 1: self = .light
            case 2: self = .dark
            default: return nil
            }
        }
    }

    private enum UserDefaultsKey {
        static let appearanceMode = "com.appforindeed.appearanceMode"
    }

    private var systemThemeObserver: NSObjectProtocol?

    private init() {
        systemThemeObserver = DistributedNotificationCenter.default().addObserver(
            forName: Notification.Name("AppleInterfaceThemeChangedNotification"),
            object: nil,
            queue: .main
        ) { [weak self] _ in
            guard let self, self.mode == .system else { return }
            self.apply()
            NotificationCenter.default.post(name: Self.didChangeNotification, object: self)
        }
    }

    /// Whether the app is currently rendering with a dark appearance (respects System mode).
    var isDark: Bool {
        NSApp.effectiveAppearance.bestMatch(from: [.darkAqua, .aqua]) == .darkAqua
    }

    var mode: Mode {
        get {
            guard let raw = UserDefaults.standard.string(forKey: UserDefaultsKey.appearanceMode),
                  let stored = Mode(rawValue: raw) else {
                return .system
            }
            return stored
        }
        set {
            guard newValue != mode else { return }
            UserDefaults.standard.set(newValue.rawValue, forKey: UserDefaultsKey.appearanceMode)
            apply()
            NotificationCenter.default.post(name: Self.didChangeNotification, object: self)
        }
    }

    /// Window backing color aligned with dashboard chrome for the active appearance.
    var windowChromeColor: NSColor {
        AppDashboardTheme.chromeBackground
    }

    func apply() {
        switch mode {
        case .light:
            NSApp.appearance = NSAppearance(named: .aqua)
        case .dark:
            NSApp.appearance = NSAppearance(named: .darkAqua)
        case .system:
            NSApp.appearance = nil
        }
        updateWindowChrome()
    }

    private func updateWindowChrome() {
        let color = windowChromeColor
        for window in NSApp.windows where window.isVisible || window.canBecomeKey {
            window.backgroundColor = color
        }
    }
}