using UnityEngine;
using IndianOceanAssets.Engine2_5D;

namespace IndianOceanAssets.Engine2_5D
{
    /// <summary>
    /// 敌人头顶血条 —— 挂在敌人 Prefab 上。
    /// 血条可视化物体（BG、Fill）已在 Prefab 中预建，运行时直接引用，无需动态创建。
    ///
    /// 解耦改造：直接引用同物体上的 HealthSystem（RequireComponent 保证存在），
    /// 订阅其 OnHealthChanged 事件刷新，彻底移除对私有字段的反射读取。
    /// 注意：不使用"全局共享 IntVariable"承载敌人血量——否则所有敌人血条会显示同一份血量，
    /// 正确的解法是"每个敌人读自己的 HealthSystem"（同物体组件引用，非 Find / 反射 / 跨对象）。
    /// </summary>
    [RequireComponent(typeof(HealthSystem))]
    public class EnemyHealthBar : MonoBehaviour
    {
        [Header("血条引用（Prefab 中预建）")]
        [SerializeField] private Transform barRoot;
        [SerializeField] private SpriteRenderer bgRenderer;
        [SerializeField] private SpriteRenderer fillRenderer;

        [Header("血条参数")]
        [Tooltip("血条宽度（世界单位）")]
        [SerializeField] private float barWidth = 1f;

        [Tooltip("血条高度（世界单位）")]
        [SerializeField] private float barHeight = 0.1f;

        [Header("颜色")]
        [SerializeField] private Color fillColor = new Color(0.8f, 0.1f, 0.1f, 0.9f);
        [SerializeField] private Color lowHealthColor = new Color(1f, 0.3f, 0f, 0.9f);

        [Tooltip("低于此比例时切换为低血量颜色")]
        [SerializeField] private float lowHealthThreshold = 0.3f;

        [Header("显示控制")]
        [Tooltip("满血时是否隐藏血条")]
        [SerializeField] private bool hideWhenFull = false;

        // 同物体上的 HealthSystem（RequireComponent 保证存在；非 Find / 反射 / 跨对象引用）
        private HealthSystem _healthSource;

        private void Start()
        {
            if (fillRenderer == null || bgRenderer == null)
            {
                enabled = false;
                return;
            }

            _healthSource = GetComponent<HealthSystem>();
            if (_healthSource != null)
            {
                _healthSource.OnHealthChanged += UpdateBar;
                UpdateBar(_healthSource.CurrentHealth, _healthSource.MaxHealth);
            }
            else
            {
                UpdateBar(1, 1);
            }
        }

        private void OnDestroy()
        {
            if (_healthSource != null)
                _healthSource.OnHealthChanged -= UpdateBar;
        }

        /// <summary>
        /// 根据当前血量更新血条显示（事件驱动，无反射、无每帧 LateUpdate）。
        /// </summary>
        private void UpdateBar(int currentHealth, int maxHealth)
        {
            if (fillRenderer == null || bgRenderer == null) return;

            if (maxHealth <= 0) maxHealth = 1;
            float ratio = Mathf.Clamp01((float)currentHealth / maxHealth);

            // 更新填充条缩放（居中对齐）
            fillRenderer.transform.localScale = new Vector3(barWidth * ratio, barHeight, 1f);
            fillRenderer.transform.localPosition = new Vector3(
                -(barWidth * (1f - ratio)) * 0.5f, 0f, 0f);

            // 低血量变色
            fillRenderer.color = ratio <= lowHealthThreshold ? lowHealthColor : fillColor;

            // 满血隐藏
            bool visible = !(hideWhenFull && ratio >= 1f);
            bgRenderer.enabled = visible;
            fillRenderer.enabled = visible;
        }
    }
}