using System.Collections.Generic;
using UnityEngine;
#if ENABLE_INPUT_SYSTEM
using UnityEngine.InputSystem;
#endif

/// <summary>
/// Switches the game between high-level modes (Player Control, Paint). The switch
/// key (Tab) cycles to the next registered mode. Register additional modes in
/// <see cref="BuildModes"/>. Attach to a single, persistent scene GameObject.
/// </summary>
[DisallowMultipleComponent]
public class GameModeManager : MonoBehaviour
{
    [Header("Controlled Systems")]
    [Tooltip("Player movement controller. Empty = found automatically.")]
    public PlayerCharacterController player;

    [Tooltip("Third-person orbit camera input. Empty = found automatically.")]
    public ThirdPersonOrbitInput cameraInput;

    [Tooltip("Mesh painter. Empty = found automatically.")]
    public MeshPainter painter;

    [Header("Switching")]
    [Tooltip("Key that cycles to the next mode.")]
#if ENABLE_INPUT_SYSTEM
    public Key switchKey = Key.Tab;
#else
    public KeyCode switchKey = KeyCode.Tab;
#endif

    [Tooltip("Mode active at startup (0 = Player Control).")]
    public int startModeIndex = 0;

    public PlayerCharacterController Player => player;
    public ThirdPersonOrbitInput CameraInput => cameraInput;
    public MeshPainter Painter => painter;

    private readonly List<GameMode> _modes = new List<GameMode>();
    private int _activeIndex = -1;

    /// <summary>The currently active mode (null before startup).</summary>
    public GameMode ActiveMode =>
        (_activeIndex >= 0 && _activeIndex < _modes.Count) ? _modes[_activeIndex] : null;

    private void Awake()
    {
        if (!player) player = FindFirstObjectByType<PlayerCharacterController>();
        if (!cameraInput) cameraInput = FindFirstObjectByType<ThirdPersonOrbitInput>();
        if (!painter) painter = FindFirstObjectByType<MeshPainter>();

        BuildModes();
    }

    private void Start()
    {
        if (_modes.Count > 0)
            SwitchTo(Mathf.Clamp(startModeIndex, 0, _modes.Count - 1));
    }

    /// <summary>Registers all available modes. Add new modes here.</summary>
    private void BuildModes()
    {
        _modes.Clear();
        _modes.Add(new PlayerControlMode());
        _modes.Add(new PaintMode());

        foreach (var m in _modes)
            m.Bind(this);
    }

    private void Update()
    {
        if (_modes.Count == 0) return;

        if (WasSwitchPressed())
            SwitchTo((_activeIndex + 1) % _modes.Count);

        ActiveMode?.Tick();
    }

    /// <summary>Activates the mode at <paramref name="index"/> (Exit old, Enter new).</summary>
    public void SwitchTo(int index)
    {
        if (index < 0 || index >= _modes.Count || index == _activeIndex) return;

        ActiveMode?.Exit();
        _activeIndex = index;
        ActiveMode.Enter();

        Debug.Log($"[GameModeManager] Mode -> {ActiveMode.DisplayName}", this);
    }

    private bool WasSwitchPressed()
    {
#if ENABLE_INPUT_SYSTEM
        return Keyboard.current != null && Keyboard.current[switchKey].wasPressedThisFrame;
#else
        return Input.GetKeyDown(switchKey);
#endif
    }
}