using System.Runtime.InteropServices;

namespace Lumi.Companion.Overlay;

public sealed class GlobalHotkeyManager : IDisposable
{
    private const uint WmHotkey = 0x0312;
    private const uint WmQuit = 0x0012;
    private readonly Dictionary<int, Action> _actions = [];
    private readonly ManualResetEventSlim _ready = new();
    private readonly Thread _thread;
    private IntPtr _window;
    private uint _threadId;
    private int _nextId = 0x4C00;

    public GlobalHotkeyManager()
    {
        _thread = new Thread(MessageLoop) { IsBackground = true, Name = "Lumi Overlay hotkeys" };
        _thread.Start();
        _ready.Wait(TimeSpan.FromSeconds(3));
    }

    public bool Register(string chord, Action action)
    {
        if (!TryParse(chord, out var modifiers, out var key) || _window == IntPtr.Zero) return false;
        var id = Interlocked.Increment(ref _nextId);
        if (!RegisterHotKey(_window, id, modifiers | 0x4000, key)) return false;
        lock (_actions) _actions[id] = action;
        return true;
    }

    public void Clear()
    {
        lock (_actions)
        {
            foreach (var id in _actions.Keys) UnregisterHotKey(_window, id);
            _actions.Clear();
        }
    }

    private void MessageLoop()
    {
        _threadId = GetCurrentThreadId();
        _window = CreateWindowEx(0, "STATIC", "LumiOverlayHotkeys", 0, 0, 0, 0, 0, new IntPtr(-3), IntPtr.Zero, IntPtr.Zero, IntPtr.Zero);
        _ready.Set();
        while (GetMessage(out var message, IntPtr.Zero, 0, 0) > 0)
        {
            if (message.message == WmHotkey)
            {
                Action? action;
                lock (_actions) _actions.TryGetValue(message.wParam.ToInt32(), out action);
                try { action?.Invoke(); } catch { }
            }
            TranslateMessage(ref message);
            DispatchMessage(ref message);
        }
    }

    private static bool TryParse(string chord, out uint modifiers, out uint key)
    {
        modifiers = 0;
        key = 0;
        var parts = (chord ?? string.Empty).Split('+', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
        foreach (var part in parts)
        {
            if (part.Equals("Ctrl", StringComparison.OrdinalIgnoreCase)) modifiers |= 0x0002;
            else if (part.Equals("Alt", StringComparison.OrdinalIgnoreCase)) modifiers |= 0x0001;
            else if (part.Equals("Shift", StringComparison.OrdinalIgnoreCase)) modifiers |= 0x0004;
            else if (part.Equals("Win", StringComparison.OrdinalIgnoreCase)) modifiers |= 0x0008;
            else if (part.Length == 1 && char.IsAsciiLetterOrDigit(part[0])) key = char.ToUpperInvariant(part[0]);
            else if (part.StartsWith('F') && int.TryParse(part[1..], out var function) && function is >= 1 and <= 24) key = (uint)(0x70 + function - 1);
            else return false;
        }
        return key != 0;
    }

    public void Dispose()
    {
        Clear();
        if (_threadId != 0) PostThreadMessage(_threadId, WmQuit, IntPtr.Zero, IntPtr.Zero);
        _thread.Join(TimeSpan.FromSeconds(1));
        _ready.Dispose();
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct Msg { public IntPtr hwnd; public uint message; public IntPtr wParam; public IntPtr lParam; public uint time; public int x; public int y; }
    [DllImport("user32.dll", SetLastError = true)] private static extern bool RegisterHotKey(IntPtr hwnd, int id, uint modifiers, uint key);
    [DllImport("user32.dll", SetLastError = true)] private static extern bool UnregisterHotKey(IntPtr hwnd, int id);
    [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Unicode)] private static extern IntPtr CreateWindowEx(uint exStyle, string className, string windowName, uint style, int x, int y, int width, int height, IntPtr parent, IntPtr menu, IntPtr instance, IntPtr parameter);
    [DllImport("user32.dll")] private static extern int GetMessage(out Msg message, IntPtr hwnd, uint min, uint max);
    [DllImport("user32.dll")] private static extern bool TranslateMessage(ref Msg message);
    [DllImport("user32.dll")] private static extern IntPtr DispatchMessage(ref Msg message);
    [DllImport("kernel32.dll")] private static extern uint GetCurrentThreadId();
    [DllImport("user32.dll")] private static extern bool PostThreadMessage(uint threadId, uint message, IntPtr wParam, IntPtr lParam);
}