using UnityEngine;

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。
    /// </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;

        private HealthSystem _healthSystem;
        private int _lastHealth = -1;
        private int _maxHealth;

        private void Start()
        {
            _healthSystem = GetComponent<HealthSystem>();
            if (_healthSystem == null)
            {
                enabled = false;
                return;
            }

            // 获取 maxHealth（通过反射读取私有字段）
            var field = typeof(HealthSystem).GetField("maxHealth",
                System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
            if (field != null)
                _maxHealth = (int)field.GetValue(_healthSystem);
            else
                _maxHealth = 3;

            UpdateBar();
        }

        private void LateUpdate()
        {
            UpdateBar();
        }

        /// <summary>
        /// 根据当前血量更新血条显示。
        /// </summary>
        private void UpdateBar()
        {
            if (_healthSystem == null || fillRenderer == null || bgRenderer == null) return;

            // 获取当前血量（反射）
            var healthField = typeof(HealthSystem).GetField("health",
                System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
            int currentHealth = healthField != null ? (int)healthField.GetValue(_healthSystem) : _maxHealth;

            // 血量没变化则跳过（性能优化）
            if (currentHealth == _lastHealth) return;
            _lastHealth = currentHealth;

            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;
        }
    }
}