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

namespace LeTai.Asset.TranslucentImage
{
public static class Blitter
{
    static Mesh fullscreenTriangle;

    /// <summary>
    /// A fullscreen triangle mesh.
    /// </summary>
    static Mesh FullscreenTriangle
    {
        get
        {
            if (fullscreenTriangle != null)
                return fullscreenTriangle;

            fullscreenTriangle = new Mesh { name = "Fullscreen Triangle" };
            fullscreenTriangle.SetVertices(
                new List<Vector3> {
                    new Vector3(-1f, -1f, 0f),
                    new Vector3(-1f, 3f,  0f),
                    new Vector3(3f,  -1f, 0f)
                }
            );
            fullscreenTriangle.SetIndices(new[] { 0, 1, 2 }, MeshTopology.Triangles, 0, false);
            fullscreenTriangle.UploadMeshData(false);

            return fullscreenTriangle;
        }
    }

    public static void Blit(
        CommandBuffer          cmd,
        RenderTargetIdentifier source,
        RenderTargetIdentifier destination,
        Material               material,
        int                    passIndex,
        MaterialPropertyBlock  propertyBlock = null,
        Rect                   viewport      = default
    )
    {
        cmd.SetGlobalTexture(ShaderID.MAIN_TEX, source);
        cmd.SetRenderTarget(new RenderTargetIdentifier(destination, 0, CubemapFace.Unknown, -1),
                            RenderBufferLoadAction.DontCare,
                            RenderBufferStoreAction.Store,
                            RenderBufferLoadAction.DontCare,
                            RenderBufferStoreAction.DontCare);
        if (viewport.width != 0)
            cmd.SetViewport(viewport);

        if (SystemInfo.graphicsShaderLevel >= 30
#if !UNITY_2023_1_OR_NEWER
         && SystemInfo.graphicsDeviceType != GraphicsDeviceType.OpenGLES2
#endif
           )
            cmd.DrawProcedural(Matrix4x4.identity, material, passIndex, MeshTopology.Triangles, 3, 1, propertyBlock);
        else
            cmd.DrawMesh(FullscreenTriangle, Matrix4x4.identity, material, 0, passIndex, propertyBlock);
    }
}
}