/******************************************************************************
 * The MIT License (MIT)
 * 
 * Copyright (c) 2015-2018 Baldur Karlsson
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 ******************************************************************************/

struct meshV2F
{
	float4 pos : SV_Position;
	float3 norm : Normal;
	float4 secondary : Secondary;
};

struct meshA2V
{
	float4 pos : pos;
	float4 secondary : sec;
};

meshV2F RENDERDOC_MeshVS(meshA2V IN, uint vid : SV_VertexID)
{
	meshV2F OUT = (meshV2F)0;
  
	float2 psprite[4] =
	{
		float2(-1.0f, -1.0f),
		float2(-1.0f,  1.0f),
		float2( 1.0f, -1.0f),
		float2( 1.0f,  1.0f)
	};

	OUT.pos = mul(IN.pos, ModelViewProj);
	OUT.pos.xy += SpriteSize.xy*0.01f*psprite[vid%4]*OUT.pos.w;
	OUT.norm = float3(0, 0, 1);
	OUT.secondary = IN.secondary;

	return OUT;
}

struct triSizeV2F
{
	float4 pos : SV_Position;
	float pixarea : PixArea;
};

cbuffer viewportCBuf : register(b0)
{
	float4 viewport;
};

[maxvertexcount(3)]
void RENDERDOC_TriangleSizeGS(triangle meshV2F input[3], inout TriangleStream<triSizeV2F> TriStream)
{
	triSizeV2F output;

	float2 a = input[0].pos.xy / input[0].pos.w;
	float2 b = input[1].pos.xy / input[1].pos.w;
	float2 c = input[2].pos.xy / input[2].pos.w;

	a = (a * 0.5f + 0.5f) * viewport.xy;
	b = (b * 0.5f + 0.5f) * viewport.xy;
	c = (c * 0.5f + 0.5f) * viewport.xy;

	float ab = length(a - b);
	float bc = length(b - c);
	float ca = length(c - a);

	float s = (ab + bc + ca) / 2.0f;

	float area = sqrt( s * (s - ab) * (s - bc) * (s - ca) );

	for(int i=0; i<3; i++)
	{
		output.pos = input[i].pos;
		output.pixarea = area;
		TriStream.Append(output);
	}
	TriStream.RestartStrip();
}

float4 RENDERDOC_TriangleSizePS(triSizeV2F IN) : SV_Target0
{
	return float4(max(IN.pixarea, 0.001f).xxx, 1.0f);
}

[maxvertexcount(3)]
void RENDERDOC_MeshGS(triangle meshV2F input[3], inout TriangleStream<meshV2F> TriStream)
{
    meshV2F output;

    float4 faceEdgeA = mul(input[1].pos, InvProj) - mul(input[0].pos, InvProj);
    float4 faceEdgeB = mul(input[2].pos, InvProj) - mul(input[0].pos, InvProj);
    float3 faceNormal = normalize( cross(faceEdgeA.xyz, faceEdgeB.xyz) );

    for(int i=0; i<3; i++)
    {
        output.pos = input[i].pos;
        output.norm = faceNormal;
        output.secondary = input[i].secondary;
        TriStream.Append(output);
    }
    TriStream.RestartStrip();
}

cbuffer MeshColourPush : register(b2)
{
  float4 MeshColour;
}

float4 RENDERDOC_MeshPS(meshV2F IN) : SV_Target0
{
	uint type = OutputDisplayFormat;

	if(type == MESHDISPLAY_SECONDARY)
		return float4(IN.secondary.xyz, 1);
	else if(type == MESHDISPLAY_SECONDARY_ALPHA)
		return float4(IN.secondary.www, 1);
	else if(type == MESHDISPLAY_FACELIT)
	{
		float3 lightDir = normalize(float3(0, -0.3f, -1));

		return float4(MeshColour.xyz*abs(dot(lightDir, IN.norm)), 1);
	}
	else //if(type == MESHDISPLAY_SOLID)
		return float4(MeshColour.xyz, 1);
}

Buffer<uint> index : register(t0);
Buffer<float4> vertex : register(t1);
AppendStructuredBuffer<uint4> pickresult : register(u0);

cbuffer MeshPickData : register(b0)
{
	float3 PickRayPos;
	uint PickIdx;

	float3 PickRayDir;
	uint PickNumVerts;

	float2 PickCoords;
	float2 PickViewport;

	uint PickMeshMode;
	uint PickUnproject;
	float2 Padding;

	row_major float4x4 PickMVP;
};


bool TriangleRayIntersect(float3 A, float3 B, float3 C, 
	float3 RayPosition, float3 RayDirection, out float3 HitPosition)
{
	bool Result = false;

	float3 v0v1 = B - A;
	float3 v0v2 = C - A;
	float3 pvec = cross(RayDirection, v0v2);
	float det = dot(v0v1, pvec);

	// if the determinant is negative the triangle is backfacing, but we still take those!
	// if the determinant is close to 0, the ray misses the triangle
	if (abs(det) > 0)
	{
		float invDet = 1 / det;

		float3 tvec = RayPosition - A;
		float3 qvec = cross(tvec, v0v1);
		float u = dot(tvec, pvec) * invDet;
		float v = dot(RayDirection, qvec) * invDet;

		if (u >= 0 && u <= 1 &&
			v >= 0 && u + v <= 1)
		{
			float t = dot(v0v2, qvec) * invDet;
			if (t > 0)
			{
				HitPosition = RayPosition + (RayDirection * t);
				Result = true;
			}

		}
	}

	return Result;
}


void trianglePath(uint threadID)
{
	uint vertid = uint(fmod(float(threadID), float(PickNumVerts)));
	
	uint vertid0 = 0;
	uint vertid1 = 0;
	uint vertid2 = 0;
	switch (PickMeshMode)
	{
		case MESH_TRIANGLE_LIST:
		{
			vertid *= 3;
			vertid0 = vertid;
			vertid1 = vertid+1;
			vertid2 = vertid+2;
			break;
		}
		case MESH_TRIANGLE_STRIP:
		{
			vertid0 = vertid;
			vertid1 = vertid+1;
			vertid2 = vertid+2;
			break;
		}
		case MESH_TRIANGLE_LIST_ADJ:
		{
			vertid *= 6;
			vertid0 = vertid;
			vertid1 = vertid+2;
			vertid2 = vertid+4;
			break;
		}
		case MESH_TRIANGLE_STRIP_ADJ:
		{
			vertid *= 2;
			vertid0 = vertid;
			vertid1 = vertid+2;
			vertid2 = vertid+4;
			break;
		}
	}

	float4 pos0 = PickIdx ? vertex[index[vertid0]] : vertex[vertid0];
	float4 pos1 = PickIdx ? vertex[index[vertid1]] : vertex[vertid1];
	float4 pos2 = PickIdx ? vertex[index[vertid2]] : vertex[vertid2];
	

	float3 hitPosition;
	bool hit;
	if (PickUnproject == 1)
	{
		hit = TriangleRayIntersect(pos0.xyz / pos0.w, pos1.xyz / pos1.w, pos2.xyz / pos2.w,
			PickRayPos, PickRayDir,
			/*out*/ hitPosition);
	}
	else
	{
		hit = TriangleRayIntersect(pos0.xyz, pos1.xyz, pos2.xyz,
			PickRayPos, PickRayDir,
			/*out*/ hitPosition);
	}
	
	// ray hit a triangle, so return the vertex that was closest 
	// to the triangle/ray intersection point
	if (hit)
	{
		float dist0 = distance(pos0.xyz/pos0.w, hitPosition);
		float dist1 = distance(pos1.xyz/pos1.w, hitPosition);
		float dist2 = distance(pos2.xyz/pos2.w, hitPosition);

		uint meshVert = vertid0;
		if (dist1 < dist0 && dist1 < dist2)
		{
			meshVert = vertid1;
		}
		else if (dist2 < dist0 && dist2 < dist1)
		{
			meshVert = vertid2;
		}
		pickresult.Append(uint4(meshVert, 
						  asuint(hitPosition.x), asuint(hitPosition.y), asuint(hitPosition.z)));
	}

}

void defaultPath(uint threadID)
{
	uint vertid = threadID;

	if(vertid >= PickNumVerts)
		return;

	uint idx = PickIdx ? index[vertid] : vertid;

	float4 pos = vertex[idx];

	float4 wpos = mul(pos, PickMVP);

	if (PickUnproject == 1)
		wpos.xyz /= wpos.www;
	
	wpos.xy *= float2(1.0f, -1.0f);

	float2 scr = (wpos.xy + 1.0f) * 0.5f * PickViewport;

	// close to target co-ords? add to list
	float len = length(scr - PickCoords);
	if(len < 35.0f)
	{
		pickresult.Append(uint4(vertid, idx, asuint(len), asuint(wpos.z)));
	}
}

[numthreads(1024, 1, 1)]
void RENDERDOC_MeshPickCS(uint3 tid : SV_DispatchThreadID)
{
	if (PickMeshMode == MESH_OTHER)
	{
		defaultPath(tid.x);
	}
	else
	{
		trianglePath(tid.x);
	}
}
