using System;
using System.Numerics;
using Godosa.Core.Diagnostics;
using Godosa.Core.Input;
using Silk.NET.SDL;

namespace Godosa.Gamepad;

/// <summary>
/// Reads the first attached game controller through windowless SDL. Returns raw
/// held state; each game maps it (and applies deadzones). Any SDL failure disables
/// the pad for the session and the game stays keyboard-only.
/// </summary>
public sealed unsafe class SdlGamepadSource : IDisposable
{
    private Sdl? _sdl;
    private GameController* _pad;
    private bool _failed;

    public GamepadState? Poll()
    {
        if (_failed) return null;
        try
        {
            if (_sdl is null && !Init()) return null;
            var sdl = _sdl!;
            sdl.GameControllerUpdate(); // also detects hot-plug (~1.4 µs/call)

            if (_pad != null && sdl.GameControllerGetAttached(_pad) != SdlBool.True)
            {
                sdl.GameControllerClose(_pad);
                _pad = null;
                if (EngineDebug.Input) EngineDebug.Write("input", "gamepad detached");
            }
            if (_pad == null && !Open(sdl)) return null;

            var buttons = PadButtons.None;
            foreach (var (sdlButton, pad) in ButtonMap)
                if (sdl.GameControllerGetButton(_pad, sdlButton) != 0) buttons |= pad;
            return new GamepadState(
                new Vector2(Axis(sdl, GameControllerAxis.Leftx), Axis(sdl, GameControllerAxis.Lefty)),
                new Vector2(Axis(sdl, GameControllerAxis.Rightx), Axis(sdl, GameControllerAxis.Righty)),
                Math.Max(0f, Axis(sdl, GameControllerAxis.Triggerleft)),
                Math.Max(0f, Axis(sdl, GameControllerAxis.Triggerright)),
                buttons);
        }
        catch (Exception ex)
        {
            if (EngineDebug.Input) EngineDebug.Write("input", $"gamepad disabled: {ex.Message}");
            _failed = true;
            return null;
        }
    }

    private static readonly (GameControllerButton Sdl, PadButtons Pad)[] ButtonMap =
    {
        (GameControllerButton.A, PadButtons.A), (GameControllerButton.B, PadButtons.B),
        (GameControllerButton.X, PadButtons.X), (GameControllerButton.Y, PadButtons.Y),
        (GameControllerButton.Back, PadButtons.Back), (GameControllerButton.Start, PadButtons.Start),
        (GameControllerButton.Leftshoulder, PadButtons.LeftShoulder), (GameControllerButton.Rightshoulder, PadButtons.RightShoulder),
        (GameControllerButton.DpadUp, PadButtons.DpadUp), (GameControllerButton.DpadDown, PadButtons.DpadDown),
        (GameControllerButton.DpadLeft, PadButtons.DpadLeft), (GameControllerButton.DpadRight, PadButtons.DpadRight),
    };

    private bool Init()
    {
        var sdl = Sdl.GetApi();
        sdl.SetHint(Sdl.HintJoystickAllowBackgroundEvents, "1"); // the Avalonia window has focus, not SDL
        sdl.SetHint(Sdl.HintNoSignalHandlers, "1");
        if (sdl.InitSubSystem(Sdl.InitGamecontroller) != 0)
        {
            if (EngineDebug.Input) EngineDebug.Write("input", $"gamepad disabled: {sdl.GetErrorS()}");
            _failed = true;
            return false;
        }
        sdl.JoystickEventState(0); // SDL_IGNORE: state is polled; nothing drains SDL's event queue
        sdl.GameControllerEventState(0);
        _sdl = sdl;
        return true;
    }

    private bool Open(Sdl sdl)
    {
        int count = sdl.NumJoysticks();
        for (int i = 0; i < count; i++)
        {
            if (sdl.IsGameController(i) != SdlBool.True) continue;
            _pad = sdl.GameControllerOpen(i);
            if (_pad == null) continue;
            if (EngineDebug.Input) EngineDebug.Write("input", $"gamepad attached: {sdl.GameControllerNameS(_pad)}");
            return true;
        }
        return false;
    }

    private float Axis(Sdl sdl, GameControllerAxis axis) =>
        Math.Clamp(sdl.GameControllerGetAxis(_pad, axis) / 32767f, -1f, 1f);

    public void Dispose()
    {
        if (_sdl is null) return;
        if (_pad != null) _sdl.GameControllerClose(_pad);
        _pad = null;
        _sdl.QuitSubSystem(Sdl.InitGamecontroller);
        _sdl = null;
    }
}