using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using AppLog = ytLive.Helpers.AppLog;

namespace ytLive.Services;

public enum HotkeyId
{
    SceneStarting = 1,
    SceneLive = 2,
    SceneBrb = 3,
    SceneChat = 4,
    SceneEnding = 5,
    StartStopStream = 6,
    ToggleMicMute = 7,
    ToggleGameMute = 8,
    TraxPlayPause = 9,
}

/// <summary>Registers/revokes the OS-level hotkeys. Seam so tests never touch
/// user32 (a real registration is global to the machine and needs a pump).</summary>
public interface IHotkeyRegistrar
{
    bool Register(IntPtr hwnd, HotkeyId id, uint virtualKey);
    void Unregister(IntPtr hwnd, HotkeyId id);
}

public sealed class Win32HotkeyRegistrar : IHotkeyRegistrar
{
    public bool Register(IntPtr hwnd, HotkeyId id, uint virtualKey)
        => RegisterHotKey(hwnd, (int)id, 0, virtualKey);

    public void Unregister(IntPtr hwnd, HotkeyId id)
        => UnregisterHotKey(hwnd, (int)id);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, uint vk);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool UnregisterHotKey(IntPtr hWnd, int id);
}

/// <summary>
/// TASK 20: global hotkeys — work while the app is unfocused (streamers are in-game).
/// Defaults: F1-F5 stage/transition the five canonical scenes, F6 start/end stream,
/// F7 mute mic, F8 mute desktop audio, F9 TRAX play/pause.
/// Attach after the window has a source (OnSourceInitialized); Detach on close.
/// </summary>
public sealed class GlobalHotkeyManager
{
    public const int WM_HOTKEY = 0x0312;

    internal static Func<IHotkeyRegistrar>? RegistrarOverride;

    private static readonly Dictionary<HotkeyId, uint> Defaults = new()
    {
        [HotkeyId.SceneStarting] = 0x70, // F1
        [HotkeyId.SceneLive] = 0x71,     // F2
        [HotkeyId.SceneBrb] = 0x72,      // F3
        [HotkeyId.SceneChat] = 0x73,     // F4
        [HotkeyId.SceneEnding] = 0x74,   // F5
        [HotkeyId.StartStopStream] = 0x75, // F6
        [HotkeyId.ToggleMicMute] = 0x76,   // F7
        [HotkeyId.ToggleGameMute] = 0x77,  // F8
        [HotkeyId.TraxPlayPause] = 0x78,   // F9
    };

    private readonly IHotkeyRegistrar _registrar;
    private readonly List<HotkeyId> _registered = new();
    private IntPtr _hwnd;
    private System.Windows.Interop.HwndSource? _source;

    /// <summary>Raised on the UI thread for each WM_HOTKEY that carries a known id.</summary>
    public event Action<HotkeyId>? Activated;

    public GlobalHotkeyManager()
        : this(RegistrarOverride?.Invoke() ?? new Win32HotkeyRegistrar())
    {
    }

    internal GlobalHotkeyManager(IHotkeyRegistrar registrar) => _registrar = registrar;

    public void Attach(System.Windows.Window window)
    {
        _hwnd = new System.Windows.Interop.WindowInteropHelper(window).Handle;
        _source = System.Windows.Interop.HwndSource.FromHwnd(_hwnd);
        _source?.AddHook(WndProc);
        foreach (var (id, vk) in Defaults)
        {
            if (_registrar.Register(_hwnd, id, vk))
                _registered.Add(id);
            else
                AppLog.Write($"Hotkey: {(HotkeyId)id} (vk {vk}) not registered — likely owned by another app");
        }
        window.Closed += OnWindowClosed;
        AppLog.Write($"hotkey: attached, {_registered.Count} registered");
    }

    private void OnWindowClosed(object? sender, EventArgs e) => Detach();

    private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        if (msg != WM_HOTKEY) return IntPtr.Zero;
        var raw = wParam.ToInt64();
        if (raw is < 1 or > int.MaxValue || !Enum.IsDefined(typeof(HotkeyId), (int)raw))
            return IntPtr.Zero;
        Activated?.Invoke((HotkeyId)raw);
        handled = true;
        return IntPtr.Zero;
    }

    private void Detach()
    {
        if (_hwnd != IntPtr.Zero)
            foreach (var id in _registered)
                _registrar.Unregister(_hwnd, id);
        _registered.Clear();
        _source?.RemoveHook(WndProc);
        _source = null;
        _hwnd = IntPtr.Zero;
    }
}