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

namespace UnityEngine.Experimental.Rendering
{
    public class TexturePadding
    {
        static readonly int _RectOffset = Shader.PropertyToID("_RectOffset");
        static readonly int _Source = Shader.PropertyToID("_Source");

        ComputeShader m_CS;
        int m_KMainTopRight;
        int m_KMainTop;
        int m_KMainRight;

        public TexturePadding(ComputeShader cs)
        {
            m_CS = cs;
            m_KMainTopRight     = m_CS.FindKernel("KMainTopRight");
            m_KMainTop          = m_CS.FindKernel("KMainTop");
            m_KMainRight        = m_CS.FindKernel("KMainRight");
        }
        public void Pad(CommandBuffer cmd, RenderTexture source, RectInt from, RectInt to)
        {
            if (from.width < to.width)
            {
                cmd.SetComputeIntParams(m_CS, _RectOffset, from.width, 0);
                cmd.SetComputeTextureParam(m_CS, m_KMainRight, _Source, source);
                cmd.DispatchCompute(m_CS, m_KMainRight, to.width - from.width, from.height, 1);
            }
            if (from.height < to.height)
            {
                cmd.SetComputeIntParams(m_CS, _RectOffset, 0, from.height);
                cmd.SetComputeTextureParam(m_CS, m_KMainTop, _Source, source);
                cmd.DispatchCompute(m_CS, m_KMainTop, from.width, to.height - from.height, 1);
            }
            if (from.width < to.width && from.height < to.height)
            {
                cmd.SetComputeIntParams(m_CS, _RectOffset, from.width, from.height);
                cmd.SetComputeTextureParam(m_CS, m_KMainTopRight, _Source, source);
                cmd.DispatchCompute(m_CS, m_KMainTopRight, to.width - from.width, to.height - from.height, 1);
            }
        }
    }
}