using UnityEngine;
using System.Collections.Generic;

public class ParticleTrailAlpha : ParticleCleaner
{
    private static int? colorId;
    private float? _fadeStartTime;
    private readonly List<TrailMaterialRecord> _trailAlphaList = new List<TrailMaterialRecord>();

    protected override void Awake()
    {
        base.Awake();
        if (colorId == null)
            colorId = Shader.PropertyToID("_Alpha");
        for (var i = 0; i < trailRendererList.Count; i++)
        {
            var materials = trailRendererList[i].materials;
            for (var j = 0; j < materials.Length; j++)
            {
                var material = materials[j];
                _trailAlphaList.Add(new TrailMaterialRecord(material));
            }
        }
    }

    protected override void EnableComponents(bool isEnable)
    {
        base.EnableComponents(isEnable);
        _fadeStartTime = null;
        if (isEnable)
            for (var i = 0; i < _trailAlphaList.Count; i++)
                _trailAlphaList[i].SetRatio(1f);
    }

    public override void StartDelayRecovery()
    {
        base.StartDelayRecovery();
        _fadeStartTime = Time.unscaledTime;
    }

    private void Update()
    {
        if (_fadeStartTime != null && DelayRecoveryTime > 0f)
        {
            var ratio = Mathf.Clamp01((Time.unscaledTime - _fadeStartTime.Value) / DelayRecoveryTime);
            for (var i = 0; i < _trailAlphaList.Count; i++)
                _trailAlphaList[i].SetRatio(1f - ratio);
        }
    }
    
    private class TrailMaterialRecord
    {
        private readonly Material _material;
        private readonly float _baseAlpha;
        
        public TrailMaterialRecord(Material material)
        {
            _material = material;
            _baseAlpha = material.GetFloat(colorId.Value);
        }

        public void SetRatio(float ratio)
        {
            _material.SetFloat(colorId.Value, ratio * _baseAlpha);
        }
    }
}