using System.Collections.Generic;
using UnityEngine;

// Enemy Prefabを一定間隔で生成する
public class EnemySpawner : MonoBehaviour
{
    [Tooltip("生成するEnemy Prefab")]
    [SerializeField] private Enemy enemyPrefab;

    [Tooltip("生成位置の候補")]
    [SerializeField] private Transform[] spawnPoints;

    [Tooltip("生成間隔")]
    [SerializeField] private float spawnInterval = 1.5f;

    [Tooltip("同時に存在できるEnemyの最大数")]
    [SerializeField] private int maxAliveCount = 5;

    private readonly List<Enemy> _aliveEnemies = new();
    private float _spawnTimer;

    private void Update()
    {
        CleanupDestroyedEnemies();

        _spawnTimer += Time.deltaTime;
        if (_spawnTimer < spawnInterval)
            return;

        _spawnTimer = 0f;
        Spawn();
    }

    private void Spawn()
    {
        if (_aliveEnemies.Count >= maxAliveCount)
            return;

        var spawnPoint =
            spawnPoints[Random.Range(0, spawnPoints.Length)];
        var enemy = Instantiate(
            enemyPrefab,
            spawnPoint.position,
            spawnPoint.rotation);

        _aliveEnemies.Add(enemy);
    }

    private void CleanupDestroyedEnemies()
    {
        _aliveEnemies.RemoveAll(enemy => enemy == null);
    }
}