using UnityEngine;
using UnityEngine.UI;

public class EnemyHealthBar : MonoBehaviour
{
    [Header("UI設定")]
    [SerializeField] private Slider hpSlider;
    [SerializeField] private EnemyHealth targetEnemyHealth;

    [Header("追従設定")]
    [Tooltip("敵の原点から頭上へどれだけ浮かせるか（メートル）")]
    [SerializeField] private Vector3 offset = new Vector3(0, 2.0f, 0);

    private Transform targetTransform;
    private Transform mainCameraTransform;

    private void Start()
    {
        // ターゲットのEnemyHealthを自動検索
        if (targetEnemyHealth == null)
        {
            targetEnemyHealth = GetComponentInParent<EnemyHealth>();
        }

        if (targetEnemyHealth != null)
        {
            targetTransform = targetEnemyHealth.transform;
            targetEnemyHealth.OnHealthChanged += UpdateHp;
            targetEnemyHealth.OnDeath += HandleDeath;

            UpdateHp(targetEnemyHealth.CurrentHealth, targetEnemyHealth.MaxHealth);
        }

        if (Camera.main != null)
        {
            mainCameraTransform = Camera.main.transform;
        }
    }

    private void OnDestroy()
    {
        if (targetEnemyHealth != null)
        {
            targetEnemyHealth.OnHealthChanged -= UpdateHp;
            targetEnemyHealth.OnDeath -= HandleDeath;
        }
    }

    private void LateUpdate()
    {
        if (targetTransform == null || mainCameraTransform == null) return;

        // 1. 敵の頭上に位置を追従
        transform.position = targetTransform.position + offset;

        // 2. 常にカメラの向きへ正対（ビルボード処理：鏡像反転を防ぐためカメラの向きと平行にする）
        transform.forward = mainCameraTransform.forward;
    }

    private void UpdateHp(float current, float max)
    {
        if (hpSlider != null)
        {
            hpSlider.maxValue = max;
            hpSlider.value = current;
        }
    }

    private void HandleDeath()
    {
        // 敵が死んだらバーを即座に非表示
        gameObject.SetActive(false);
    }
}