using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Serialization;

namespace DamageVolumeSystem
{
    [Icon("Assets/Scripts/DamageVolumeSystem/Icon/DamageGenerator.png")]
    [RequireComponent(typeof(BoxCollider))]
    [ExecuteAlways]
    public class DamageGenerator : MonoBehaviour
    {
        [HideInInspector] public DamageHost binding;

        // 伤害
        public int damage = 2500;
        
        // 衰减曲线
        public AnimationCurve falloffCurveByDistance =  AnimationCurve.Linear(0, 1, 1, 0);
        public AnimationCurve falloffCurveBySpeed =  AnimationCurve.Linear(0, 1, 1, 0);

        // 碰撞体
        private BoxCollider _collider;
        
        // 碰撞时发生伤害
        public bool emitOnCollide = true;
        
        // 扫描到的碰撞体
        private readonly HashSet<DamageHost> _scannedHosts = new();
        
        // 速度缩放
        private float _speedScale;
        
        // 上一帧的位置
        private Vector3 _lastPosition;
        
        private void Start()
        { 
            _collider = GetComponent<BoxCollider>(); 
        }

        private void FixedUpdate()
        {
            var p = transform.position;
            var distanceToLast = Vector3.Distance(p, _lastPosition);
            var next = falloffCurveBySpeed.Evaluate(1 - Mathf.Clamp01(distanceToLast / 1.5f));
            _speedScale = 0.5f + next * 2;
            
            _lastPosition = p;
        }

        public void Update()
        {
#if UNITY_EDITOR
            _collider.isTrigger = true;
            _collider.center = Vector3.zero;
            _collider.size = transform.lossyScale;
#endif
        }

        private void OnTriggerEnter(Collider other)
        {
            var damageHost = other.GetComponent<DamageHost>();
            if (damageHost != null && _scannedHosts.Add(damageHost))
            {
                // 碰撞时立刻产生伤害
                if (emitOnCollide)
                    Emit();
            }
        }

        private void OnTriggerExit(Collider other)
        {
            var damageHost = other.GetComponent<DamageHost>();
            if (damageHost != null && _scannedHosts.Contains(damageHost))
            {
                _scannedHosts.Remove(damageHost);
            }
        }

        public void Emit()
        {
            var pos = transform.position;
            
            foreach (var scannedHost in _scannedHosts)
            {
                var selfGroup = binding?.group ?? 12;
                if (selfGroup == scannedHost.group)
                    continue;
                
                var posTarget = scannedHost.transform.position;
                var distance = Vector3.Distance(pos, posTarget);
                var percent = Mathf.Clamp01(distance / 2);

                var direction = (posTarget - pos).normalized;
                
                // 用衰减曲线重新映射百分比
                var rePercent = falloffCurveByDistance.Evaluate(1 - percent);
                var calcDamage = Mathf.RoundToInt(rePercent * damage * _speedScale);
                
                Debug.Log($"[伤害生成器: {gameObject.name}] 对 {scannedHost.name} 造成 {calcDamage} 点伤害 (距离衰减 {percent} -> {rePercent}, 速度增益 {_speedScale})");
                scannedHost.onDamageReceived.Invoke(new Damage
                {
                    Group = binding?.group ?? 12,
                    Force = calcDamage,
                    Direction = direction,
                });
            }
        }

        # region Display
        
        private void OnDrawGizmos()
        {
            var t = transform;
            Gizmos.color = GetColorByGroupId(binding?.group?? 12);
            
            // 画指向线
            foreach (var scannedHost in _scannedHosts)
            {
                Gizmos.DrawLine(scannedHost.transform.position, t.position);
            }
            
            // 画生成框
            Gizmos.matrix = t.localToWorldMatrix;
            DrawSpecialCube(Vector3.zero, t.lossyScale);
        }

        private void DrawSpecialCube(Vector3 center, Vector3 size)
        {
            var color = Gizmos.color;
            Gizmos.DrawWireCube(center, size);
            Gizmos.color = new Color(color.r, color.g, color.b, 0.5f);
            Gizmos.DrawCube(center, size);
        }

        private Color GetColorByGroupId(int group)
        {
            switch (group)
            {
                case 0:  return Color.red;
                case 1:  return Color.blue;
                case 2:  return Color.green;
                case 3:  return Color.yellow;
                case 4:  return Color.magenta;
                case 5:  return Color.cyan;
                case 6:  return new Color(1f, 0.5f, 0f);
                case 7:  return new Color(0.4f, 0.01f, 0.5f);
                case 8:  return new Color(0.63f, 0.87f, 0f);
                case 9:  return new Color(0.98f, 0.67f, 0.91f);
                case 10: return new Color(0.49f, 0.93f, 0.67f);
                case 11: return new Color(0.11f, 0.55f, 0.8f);
                default: return Color.white;
            }
        }
        
        #endregion
    }
}