using UnityEngine;
using UnityEngine.UI;

using System;
using System.Collections;

public class UIPartical : Image 
{
    #region 变量

    public Animator Animator
    {
        get
        {
            if (_Animator == null)
            {
                _Animator = GetComponentInParent<Animator>();
            }

            return _Animator;
        }
        set { _Animator = value; }
    }
    public ParticleSystem ParticleSystem
    {
        get
        {
            if (_ParticleSystem == null)
            {
                _ParticleSystem = GetComponent<ParticleSystem>();
            }

            return _ParticleSystem;
        }
        set { _ParticleSystem = value; }
    }

    private Animator _Animator;
    private ParticleSystem _ParticleSystem;

    #endregion

    private void Update()
    {
        SetAllDirty();
    }

    public void Begin()
    {
        if (Animator == null || ParticleSystem == null)
        {
            return;
        }

        if (Animator.isInitialized)
        {
            Animator.SetTrigger("Play");
        }
        
        ParticleSystem.Play();
    }


    protected override void OnPopulateMesh(VertexHelper toFill)
    {
        if (ParticleSystem == null)
        {
            Debug.Log("There is no ParticalSystem");

            return;
        }

        toFill.Clear();

        ParticleSystem.Particle[] particles = new ParticleSystem.Particle[ParticleSystem.particleCount];

        ParticleSystem.GetParticles(particles);

        for (int i = 0; i < particles.Length; i++)
        {
            DrawParticle(toFill, particles[i]);
        }
    }

    protected void DrawParticle(VertexHelper toFill, ParticleSystem.Particle particle)
    {
        UIVertex[] vertices = new UIVertex[4];

        Vector3 upAxis = new Vector3(0, 1, 0);
        Vector3 rightAxis = new Vector3(1, 0, 0);

        if (Math.Abs(particle.rotation) > 0.0005f)
        {
            particle.rotation *= Mathf.Deg2Rad;

            upAxis = new Vector3(-Mathf.Sin(particle.rotation), Mathf.Cos(particle.rotation), 0);
            rightAxis = new Vector3(Mathf.Cos(particle.rotation), Mathf.Sin(particle.rotation), 0);
        }

        vertices[0].position = particle.position + upAxis * sprite.rect.height / 50 - rightAxis * sprite.rect.width / 50;
        vertices[1].position = particle.position + upAxis * sprite.rect.height / 50 + rightAxis * sprite.rect.width / 50;
        vertices[2].position = particle.position - upAxis * sprite.rect.height / 50 + rightAxis * sprite.rect.width / 50;
        vertices[3].position = particle.position - upAxis * sprite.rect.height / 50 - rightAxis * sprite.rect.width / 50;

        vertices[0].color = particle.GetCurrentColor(ParticleSystem);
        vertices[1].color = particle.GetCurrentColor(ParticleSystem);
        vertices[2].color = particle.GetCurrentColor(ParticleSystem);
        vertices[3].color = particle.GetCurrentColor(ParticleSystem);

        vertices[0].uv0 = new Vector2(0, 1);
        vertices[1].uv0 = new Vector2(1, 1);
        vertices[2].uv0 = new Vector2(1, 0);
        vertices[3].uv0 = new Vector2(0, 0);

        toFill.AddUIVertexQuad(vertices);
    }
}