using System.Collections.Generic;

using Engine.Core;
using Engine.Systems.Input;

using SDL3;

namespace Engine.Integration.SDL3;

public class Sdl3KeyboardInputs : Behaviour, ISdl3EventProcessor, IButtonInputs<SDL.Keycode>
{
    public IButtonInputs<SDL.Keycode>.InputEvent OnAnyButtonPressed { get; } = new();
    public IButtonInputs<SDL.Keycode>.InputEvent OnAnyButtonReleased { get; } = new();

    private readonly Dictionary<SDL.Keycode, IButtonInputs<SDL.Keycode>.InputEvent> OnPressed = new(256);
    private readonly Dictionary<SDL.Keycode, IButtonInputs<SDL.Keycode>.InputEvent> OnReleased = new(256);

    private readonly FastList<SDL.Keycode> currentlyPressedKeys = [];

    public void RegisterOnPress(SDL.Keycode key, IButtonInputs<SDL.Keycode>.InputEvent.EventHandler callback)
    {
        if (!OnPressed.TryGetValue(key, out IButtonInputs<SDL.Keycode>.InputEvent? delegateCallback))
        {
            delegateCallback = new();
            OnPressed.Add(key, delegateCallback);
        }

        delegateCallback.AddListener(callback);
    }

    public void UnregisterOnPress(SDL.Keycode key, IButtonInputs<SDL.Keycode>.InputEvent.EventHandler callback)
    {
        if (OnPressed.TryGetValue(key, out IButtonInputs<SDL.Keycode>.InputEvent? delegateCallback))
            delegateCallback.RemoveListener(callback);
    }

    public void RegisterOnRelease(SDL.Keycode key, IButtonInputs<SDL.Keycode>.InputEvent.EventHandler callback)
    {
        if (!OnReleased.TryGetValue(key, out IButtonInputs<SDL.Keycode>.InputEvent? delegateCallback))
        {
            delegateCallback = new();
            OnReleased.Add(key, delegateCallback);
        }

        delegateCallback.AddListener(callback);
    }

    public void UnregisterOnRelease(SDL.Keycode key, IButtonInputs<SDL.Keycode>.InputEvent.EventHandler callback)
    {
        if (OnReleased.TryGetValue(key, out IButtonInputs<SDL.Keycode>.InputEvent? delegateCallback))
            delegateCallback.RemoveListener(callback);
    }

    public bool IsPressed(SDL.Keycode button) => currentlyPressedKeys.Contains(button);

    public void Process(SDL.Event sdlEvent)
    {
        switch ((SDL.EventType)sdlEvent.Type)
        {
            case SDL.EventType.KeyDown:
                SDL.Keycode currentlyPressedKey = sdlEvent.Key.Key;
                if (IsPressed(currentlyPressedKey))
                    return;

                currentlyPressedKeys.Add(currentlyPressedKey);

                if (OnPressed.TryGetValue(currentlyPressedKey, out IButtonInputs<SDL.Keycode>.InputEvent? pressCallback))
                    pressCallback?.Invoke(this, new(currentlyPressedKey));

                OnAnyButtonPressed?.Invoke(this, new(currentlyPressedKey));
                return;

            case SDL.EventType.KeyUp:
                SDL.Keycode previouslyPressedKey = sdlEvent.Key.Key;
                if (!IsPressed(previouslyPressedKey))
                    return;

                currentlyPressedKeys.Remove(previouslyPressedKey);

                if (OnReleased.TryGetValue(previouslyPressedKey, out IButtonInputs<SDL.Keycode>.InputEvent? releaseCallback))
                    releaseCallback?.Invoke(this, new(previouslyPressedKey));

                OnAnyButtonReleased?.Invoke(this, new(previouslyPressedKey));
                return;
        }
    }
}