using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Rendering;

// https://docs.unity3d.com/Manual/GraphicsCommandBuffers.html
// https://docs.unity3d.com/ScriptReference/Rendering.CameraEvent.html

// 前向渲染的camera events
// * DepthTexture
// * DepthNormalTexture
// * ForwardOpaque
// * ImageEffectsOpaque
// * Skybox
// * ForwardAlpha
// * ImageEffects
// * Everything

[Flags]
public enum ERenderingEvent
{
    None = 0,
    BeforeDepthTexture = 1,
    BeforeDepthNormalsTexture = 1 << 1,
    BeforeForwardOpaque = 1 << 2,
    BeforeImageEffectsOpaque = 1 << 3,
    BeforeSkybox = 1 << 4,
    BeforeForwardAlpha = 1 << 5,
    BeforeImageEffects = 1 << 6,
    //BeforeEverything         = 1 << 7,
    AfterDepthTexture = 1 << 8,
    AfterDepthNormalsTexture = 1 << 9,
    AfterForwardOpaque = 1 << 10,
    AfterImageEffectsOpaque = 1 << 11,
    AfterSkybox = 1 << 12,
    AfterForwardAlpha = 1 << 13,
    AfterImageEffects = 1 << 14,
    AfterEverything = 1 << 15,
}

public static class RenderingUtility
{
    public static Dictionary<ERenderingEvent, CameraEvent> renderingEventToCameraEventDic = new Dictionary<ERenderingEvent, CameraEvent> {
        {ERenderingEvent.BeforeDepthTexture, CameraEvent.BeforeDepthTexture },
        {ERenderingEvent.BeforeDepthNormalsTexture, CameraEvent.BeforeDepthNormalsTexture },
        {ERenderingEvent.BeforeForwardOpaque, CameraEvent.BeforeForwardOpaque },
        {ERenderingEvent.BeforeImageEffectsOpaque, CameraEvent.BeforeImageEffectsOpaque },
        {ERenderingEvent.BeforeSkybox, CameraEvent.BeforeSkybox },
        {ERenderingEvent.BeforeForwardAlpha, CameraEvent.BeforeForwardAlpha },
        {ERenderingEvent.BeforeImageEffects, CameraEvent.BeforeImageEffects },
        {ERenderingEvent.AfterDepthTexture, CameraEvent.AfterDepthTexture },
        {ERenderingEvent.AfterDepthNormalsTexture, CameraEvent.AfterDepthNormalsTexture },
        {ERenderingEvent.AfterForwardOpaque, CameraEvent.AfterForwardOpaque },
        {ERenderingEvent.AfterImageEffectsOpaque, CameraEvent.AfterImageEffectsOpaque },
        {ERenderingEvent.AfterSkybox, CameraEvent.AfterSkybox },
        {ERenderingEvent.AfterForwardAlpha, CameraEvent.AfterForwardAlpha },
        {ERenderingEvent.AfterImageEffects, CameraEvent.AfterImageEffects },
        {ERenderingEvent.AfterEverything, CameraEvent.AfterEverything },
    };

    public static CameraEvent ToCameraEvent(this ERenderingEvent e)
    {
        return renderingEventToCameraEventDic[e];
    }

    /// <summary>
    /// 计算在rt里面的区域
    /// </summary>
    /// <param name="camera">相机</param>
    /// <param name="worldPos">世界空间坐标</param>
    /// <param name="size">异体矩形(billboard)的相机空间大小</param>
    /// <returns></returns>
    public static Vector4 GetTillingOffset(Camera camera, Vector3 worldPos, float size)
    {
        Vector4 tileOffset = new Vector4(1,1,0,0);
        Vector3 camPos = camera.WorldToCameraSpace(worldPos);

        Vector3 bottomLeft = new Vector3(camPos.x - size / 2, camPos.y - size / 2, camPos.z);
        Vector3 topRight = new Vector3(camPos.x + size / 2, camPos.y + size / 2, camPos.z);
        Vector2 blViewPos = camera.CameraToViewportSpace(bottomLeft);
        Vector2 trViewPos = camera.CameraToViewportSpace(topRight);
        float width = trViewPos.x - blViewPos.x;
        float height = trViewPos.y - blViewPos.y;

        tileOffset.x = width;
        tileOffset.y = height;
        tileOffset.z = blViewPos.x;
        tileOffset.w = blViewPos.y;
        return tileOffset;
    }

}