using System;
using UnityEngine;

// ゲーム全体の開始、勝敗、撃破数を管理する
public class GameManager : MonoBehaviour
{
    [SerializeField] private DamageReceiver playerDamageReceiver;
    [SerializeField] private PlayerController playerController;
    [SerializeField] private EnemySpawner enemySpawner;
    [SerializeField] private int clearDefeatCount = 10;

    public event Action<GameState> StateChanged;
    public event Action<int, int> DefeatCountChanged;

    public GameState State { get; private set; } = GameState.Ready;
    public int DefeatCount { get; private set; }
    public int ClearDefeatCount => clearDefeatCount;

    private void OnEnable()
    {
        // Enemyクラスの撃破通知を購読する
        Enemy.Defeated += OnEnemyDefeated;
        playerDamageReceiver.Died += OnPlayerDied;
    }

    private void OnDisable()
    {
        // GameManagerが無効になる際は購読を解除する
        Enemy.Defeated -= OnEnemyDefeated;
        playerDamageReceiver.Died -= OnPlayerDied;
    }

    private void Start()
    {
        ChangeState(GameState.Playing);
        DefeatCountChanged?.Invoke(DefeatCount, clearDefeatCount);
    }

    private void OnEnemyDefeated(Enemy enemy)
    {
        if (State != GameState.Playing)
            return;

        DefeatCount++;
        DefeatCountChanged?.Invoke(DefeatCount, clearDefeatCount);

        if (DefeatCount >= clearDefeatCount)
            Finish(GameState.GameClear);
    }

    private void OnPlayerDied()
    {
        Finish(GameState.GameOver);
    }

    private void Finish(GameState result)
    {
        if (State != GameState.Playing)
            return;

        playerController.SetControlEnabled(false);
        enemySpawner.StopGameplay();
        ChangeState(result);
    }

    private void ChangeState(GameState nextState)
    {
        if (State == nextState)
            return;

        if (!CanTransition(State, nextState))
        {
            Debug.LogWarning(
                $"許可されていない状態遷移です: {State} -> {nextState}");
            return;
        }

        State = nextState;
        StateChanged?.Invoke(State);
    }

    private static bool CanTransition(
        GameState currentState,
        GameState nextState)
    {
        return (currentState, nextState) switch
        {
            (GameState.Ready, GameState.Playing) => true,
            (GameState.Playing, GameState.GameClear) => true,
            (GameState.Playing, GameState.GameOver) => true,
            _ => false
        };
    }
}