/*
Open Asset Import Library (ASSIMP)
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  following disclaimer.

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*/

/** @file GenUVCoords step */


#include "AssimpPCH.h"
#include "ComputeUVMappingProcess.h"
#include "ProcessHelper.h"

using namespace Assimp;

namespace {

	const static aiVector3D base_axis_y(0.f,1.f,0.f);
	const static aiVector3D base_axis_x(1.f,0.f,0.f);
	const static aiVector3D base_axis_z(0.f,0.f,1.f);
	const static float angle_epsilon = 0.95f;
}

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
ComputeUVMappingProcess::ComputeUVMappingProcess()
{
	// nothing to do here
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
ComputeUVMappingProcess::~ComputeUVMappingProcess()
{
	// nothing to do here
}

// ------------------------------------------------------------------------------------------------
// Returns whether the processing step is present in the given flag field.
bool ComputeUVMappingProcess::IsActive( unsigned int pFlags) const
{
	return	(pFlags & aiProcess_GenUVCoords) != 0;
}

// ------------------------------------------------------------------------------------------------
// Check whether a ray intersects a plane and find the intersection point
inline bool PlaneIntersect(const aiRay& ray, const aiVector3D& planePos,
	const aiVector3D& planeNormal, aiVector3D& pos)
{
	const float b = planeNormal * (planePos - ray.pos);
	float h = ray.dir * planeNormal;
    if ((h < 10e-5f && h > -10e-5f) || (h = b/h) < 0)
		return false;

    pos = ray.pos + (ray.dir * h);
    return true;
}

// ------------------------------------------------------------------------------------------------
// Find the first empty UV channel in a mesh
inline unsigned int FindEmptyUVChannel (aiMesh* mesh)
{
	for (unsigned int m = 0; m < AI_MAX_NUMBER_OF_TEXTURECOORDS;++m)
		if (!mesh->mTextureCoords[m])return m;
	
	DefaultLogger::get()->error("Unable to compute UV coordinates, no free UV slot found");
	return UINT_MAX;
}

// ------------------------------------------------------------------------------------------------
// Try to remove UV seams
void RemoveUVSeams (aiMesh* mesh, aiVector3D* out)
{
	// TODO: just a very rough algorithm. I think it could be done
	// much easier, but I don't know how and am currently too tired to 
	// to think about a better solution. 

	const static float LOWER_LIMIT = 0.1f;
	const static float UPPER_LIMIT = 0.9f;

	const static float LOWER_EPSILON = 10e-3f;
	const static float UPPER_EPSILON = 1.f-10e-3f;

	for (unsigned int fidx = 0; fidx < mesh->mNumFaces;++fidx)
	{
		const aiFace& face = mesh->mFaces[fidx];
		if (face.mNumIndices < 3) continue; // triangles and polygons only, please

		unsigned int small = face.mNumIndices, large = small;
		bool zero = false, one = false, round_to_zero = false;

		// Check whether this face lies on a UV seam. We can just guess,
		// but the assumption that a face with at least one very small
		// on the one side and one very large U coord on the other side 
		// lies on a UV seam should work for most cases.
		for (unsigned int n = 0; n < face.mNumIndices;++n)
		{
			if (out[face.mIndices[n]].x < LOWER_LIMIT)
			{
				small = n;

				// If we have a U value very close to 0 we can't
				// round the others to 0, too.
				if (out[face.mIndices[n]].x <= LOWER_EPSILON)
					zero = true;
				else round_to_zero = true;
			}
			if (out[face.mIndices[n]].x > UPPER_LIMIT)
			{
				large = n;

				// If we have a U value very close to 1 we can't
				// round the others to 1, too.
				if (out[face.mIndices[n]].x >= UPPER_EPSILON)
					one = true;
			}
		}
		if (small != face.mNumIndices && large != face.mNumIndices)
		{
			for (unsigned int n = 0; n < face.mNumIndices;++n)
			{
				// If the u value is over the upper limit and no other u 
				// value of that face is 0, round it to 0
				if (out[face.mIndices[n]].x > UPPER_LIMIT && !zero)
					out[face.mIndices[n]].x = 0.f;

				// If the u value is below the lower limit and no other u 
				// value of that face is 1, round it to 1
				else if (out[face.mIndices[n]].x < LOWER_LIMIT && !one)
					out[face.mIndices[n]].x = 1.f;

				// The face contains both 0 and 1 as UV coords. This can occur
				// for faces which have an edge that lies directly on the seam.
				// Due to numerical inaccuracies one U coord becomes 0, the
				// other 1. But we do still have a third UV coord to determine 
				// to which side we must round to.
				else if (one && zero)
				{
					if (round_to_zero && out[face.mIndices[n]].x >=  UPPER_EPSILON)
						out[face.mIndices[n]].x = 0.f;
					else if (!round_to_zero && out[face.mIndices[n]].x <= LOWER_EPSILON)
						out[face.mIndices[n]].x = 1.f;
				}
			}
		}
	}
}

// ------------------------------------------------------------------------------------------------
void ComputeUVMappingProcess::ComputeSphereMapping(aiMesh* mesh,const aiVector3D& axis, aiVector3D* out)
{
	aiVector3D center, min, max;
	FindMeshCenter(mesh, center, min, max);

	// If the axis is one of x,y,z run a faster code path. It's worth the extra effort ...
	// currently the mapping axis will always be one of x,y,z, except if the
	// PretransformVertices step is used (it transforms the meshes into worldspace, 
	// thus changing the mapping axis)
	if (axis * base_axis_x >= angle_epsilon)	{

		// For each point get a normalized projection vector in the sphere,
		// get its longitude and latitude and map them to their respective
		// UV axes. Problems occur around the poles ... unsolvable.
		//
		// The spherical coordinate system looks like this:
		// x = cos(lon)*cos(lat)
		// y = sin(lon)*cos(lat)
		// z = sin(lat)
		// 
		// Thus we can derive:
		// lat  = arcsin (z)
		// lon  = arctan (y/x)
		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)	{
			const aiVector3D diff = (mesh->mVertices[pnt]-center).Normalize();
			out[pnt] = aiVector3D((atan2 (diff.z, diff.y) + AI_MATH_PI_F ) / AI_MATH_TWO_PI_F,
				(asin  (diff.x) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.f);
		}
	}
	else if (axis * base_axis_y >= angle_epsilon)	{
		// ... just the same again
		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)	{
			const aiVector3D diff = (mesh->mVertices[pnt]-center).Normalize();
			out[pnt] = aiVector3D((atan2 (diff.x, diff.z) + AI_MATH_PI_F ) / AI_MATH_TWO_PI_F,
				(asin  (diff.y) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.f);
		}
	}
	else if (axis * base_axis_z >= angle_epsilon)	{
		// ... just the same again
		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)	{
			const aiVector3D diff = (mesh->mVertices[pnt]-center).Normalize();
			out[pnt] = aiVector3D((atan2 (diff.y, diff.x) + AI_MATH_PI_F ) / AI_MATH_TWO_PI_F,
				(asin  (diff.z) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.f);
		}
	}
	// slower code path in case the mapping axis is not one of the coordinate system axes
	else	{
		aiMatrix4x4 mTrafo;
		aiMatrix4x4::FromToMatrix(axis,base_axis_y,mTrafo);

		// again the same, except we're applying a transformation now
		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)	{
			const aiVector3D diff = ((mTrafo*mesh->mVertices[pnt])-center).Normalize();
			out[pnt] = aiVector3D((atan2 (diff.y, diff.x) + AI_MATH_PI_F ) / AI_MATH_TWO_PI_F,
				(asin  (diff.z) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.f);
		}
	}
	
	
	// Now find and remove UV seams. A seam occurs if a face has a tcoord
	// close to zero on the one side, and a tcoord close to one on the
	// other side.
	RemoveUVSeams(mesh,out);
}

// ------------------------------------------------------------------------------------------------
void ComputeUVMappingProcess::ComputeCylinderMapping(aiMesh* mesh,const aiVector3D& axis, aiVector3D* out)
{
	aiVector3D center, min, max;

	// If the axis is one of x,y,z run a faster code path. It's worth the extra effort ...
	// currently the mapping axis will always be one of x,y,z, except if the
	// PretransformVertices step is used (it transforms the meshes into worldspace, 
	// thus changing the mapping axis)
	if (axis * base_axis_x >= angle_epsilon)	{
		FindMeshCenter(mesh, center, min, max);
		const float diff = max.x - min.x;

		// If the main axis is 'z', the z coordinate of a point 'p' is mapped 
		// directly to the texture V axis. The other axis is derived from
		// the angle between ( p.x - c.x, p.y - c.y ) and (1,0), where
		// 'c' is the center point of the mesh.
		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)	{
			const aiVector3D& pos = mesh->mVertices[pnt];
			aiVector3D& uv  = out[pnt];

			uv.y = (pos.x - min.x) / diff;
			uv.x = (atan2 ( pos.z - center.z, pos.y - center.y) +(float)AI_MATH_PI ) / (float)AI_MATH_TWO_PI;
		}
	}
	else if (axis * base_axis_y >= angle_epsilon)	{
		FindMeshCenter(mesh, center, min, max);
		const float diff = max.y - min.y;

		// just the same ...
		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)	{
			const aiVector3D& pos = mesh->mVertices[pnt];
			aiVector3D& uv  = out[pnt];

			uv.y = (pos.y - min.y) / diff;
			uv.x = (atan2 ( pos.x - center.x, pos.z - center.z) +(float)AI_MATH_PI ) / (float)AI_MATH_TWO_PI;
		}
	}
	else if (axis * base_axis_z >= angle_epsilon)	{
		FindMeshCenter(mesh, center, min, max);
		const float diff = max.z - min.z;

		// just the same ...
		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)	{
			const aiVector3D& pos = mesh->mVertices[pnt];
			aiVector3D& uv  = out[pnt];

			uv.y = (pos.z - min.z) / diff;
			uv.x = (atan2 ( pos.y - center.y, pos.x - center.x) +(float)AI_MATH_PI ) / (float)AI_MATH_TWO_PI;
		}
	}
	// slower code path in case the mapping axis is not one of the coordinate system axes
	else {
		aiMatrix4x4 mTrafo;
		aiMatrix4x4::FromToMatrix(axis,base_axis_y,mTrafo);
		FindMeshCenterTransformed(mesh, center, min, max,mTrafo);
		const float diff = max.y - min.y;

		// again the same, except we're applying a transformation now
		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt){
			const aiVector3D pos = mTrafo* mesh->mVertices[pnt];
			aiVector3D& uv  = out[pnt];

			uv.y = (pos.y - min.y) / diff;
			uv.x = (atan2 ( pos.x - center.x, pos.z - center.z) +(float)AI_MATH_PI ) / (float)AI_MATH_TWO_PI;
		}
	}

	// Now find and remove UV seams. A seam occurs if a face has a tcoord
	// close to zero on the one side, and a tcoord close to one on the
	// other side.
	RemoveUVSeams(mesh,out);
}

// ------------------------------------------------------------------------------------------------
void ComputeUVMappingProcess::ComputePlaneMapping(aiMesh* mesh,const aiVector3D& axis, aiVector3D* out)
{
	float diffu,diffv;
	aiVector3D center, min, max;

	// If the axis is one of x,y,z run a faster code path. It's worth the extra effort ...
	// currently the mapping axis will always be one of x,y,z, except if the
	// PretransformVertices step is used (it transforms the meshes into worldspace, 
	// thus changing the mapping axis)
	if (axis * base_axis_x >= angle_epsilon)	{
		FindMeshCenter(mesh, center, min, max);
		diffu = max.z - min.z;
		diffv = max.y - min.y;

		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)	{
			const aiVector3D& pos = mesh->mVertices[pnt];
			out[pnt].Set((pos.z - min.z) / diffu,(pos.y - min.y) / diffv);
		}
	}
	else if (axis * base_axis_y >= angle_epsilon)	{
		FindMeshCenter(mesh, center, min, max);
		diffu = max.x - min.x;
		diffv = max.z - min.z;

		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)	{
			const aiVector3D& pos = mesh->mVertices[pnt];
			out[pnt].Set((pos.x - min.x) / diffu,(pos.z - min.z) / diffv);
		}
	}
	else if (axis * base_axis_z >= angle_epsilon)	{
		FindMeshCenter(mesh, center, min, max);
		diffu = max.y - min.y;
		diffv = max.z - min.z;

		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)	{
			const aiVector3D& pos = mesh->mVertices[pnt];
			out[pnt].Set((pos.y - min.y) / diffu,(pos.x - min.x) / diffv);
		}
	}
	// slower code path in case the mapping axis is not one of the coordinate system axes
	else
	{
		aiMatrix4x4 mTrafo;
		aiMatrix4x4::FromToMatrix(axis,base_axis_y,mTrafo);
		FindMeshCenterTransformed(mesh, center, min, max,mTrafo);
		diffu = max.x - min.x;
		diffv = max.z - min.z;

		// again the same, except we're applying a transformation now
		for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)	{
			const aiVector3D pos = mTrafo * mesh->mVertices[pnt];
			out[pnt].Set((pos.x - min.x) / diffu,(pos.z - min.z) / diffv);
		}
	}

	// shouldn't be necessary to remove UV seams ...
}

// ------------------------------------------------------------------------------------------------
void ComputeUVMappingProcess::ComputeBoxMapping(aiMesh* /*mesh*/, aiVector3D* /*out*/)
{
	DefaultLogger::get()->error("Mapping type currently not implemented");
}

// ------------------------------------------------------------------------------------------------
void ComputeUVMappingProcess::Execute( aiScene* pScene) 
{
	DefaultLogger::get()->debug("GenUVCoordsProcess begin");
	char buffer[1024];

	if (pScene->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT)
		throw DeadlyImportError("Post-processing order mismatch: expecting pseudo-indexed (\"verbose\") vertices here");

	std::list<MappingInfo> mappingStack;

	/*  Iterate through all materials and search for non-UV mapped textures
	 */
	for (unsigned int i = 0; i < pScene->mNumMaterials;++i)
	{
		mappingStack.clear();
		aiMaterial* mat = pScene->mMaterials[i];
		for (unsigned int a = 0; a < mat->mNumProperties;++a)
		{
			aiMaterialProperty* prop = mat->mProperties[a];
			if (!::strcmp( prop->mKey.data, "$tex.mapping"))
			{
				aiTextureMapping& mapping = *((aiTextureMapping*)prop->mData);
				if (aiTextureMapping_UV != mapping)
				{
					if (!DefaultLogger::isNullLogger())
					{
						sprintf(buffer, "Found non-UV mapped texture (%s,%i). Mapping type: %s",
							TextureTypeToString((aiTextureType)prop->mSemantic),prop->mIndex,
							MappingTypeToString(mapping));

						DefaultLogger::get()->info(buffer);
					}

					if (aiTextureMapping_OTHER == mapping)
						continue;

					MappingInfo info (mapping);

					// Get further properties - currently only the major axis
					for (unsigned int a2 = 0; a2 < mat->mNumProperties;++a2)
					{
						aiMaterialProperty* prop2 = mat->mProperties[a2];
						if (prop2->mSemantic != prop->mSemantic || prop2->mIndex != prop->mIndex)
							continue;

						if ( !::strcmp( prop2->mKey.data, "$tex.mapaxis"))	{
							info.axis = *((aiVector3D*)prop2->mData);
							break;
						}
					}

					unsigned int idx;

					// Check whether we have this mapping mode already
					std::list<MappingInfo>::iterator it = std::find (mappingStack.begin(),mappingStack.end(), info);
					if (mappingStack.end() != it)
					{
						idx = (*it).uv;
					}
					else
					{
						/*  We have found a non-UV mapped texture. Now
						*   we need to find all meshes using this material
						*   that we can compute UV channels for them.
						*/
						for (unsigned int m = 0; m < pScene->mNumMeshes;++m)
						{
							aiMesh* mesh = pScene->mMeshes[m];
							unsigned int outIdx;
							if ( mesh->mMaterialIndex != i || ( outIdx = FindEmptyUVChannel(mesh) ) == UINT_MAX ||
								!mesh->mNumVertices)
							{
								continue;
							}

							// Allocate output storage
							aiVector3D* p = mesh->mTextureCoords[outIdx] = new aiVector3D[mesh->mNumVertices];

							switch (mapping)
							{
							case aiTextureMapping_SPHERE:
								ComputeSphereMapping(mesh,info.axis,p);
								break;
							case aiTextureMapping_CYLINDER:
								ComputeCylinderMapping(mesh,info.axis,p);
								break;
							case aiTextureMapping_PLANE:
								ComputePlaneMapping(mesh,info.axis,p);
								break;
							case aiTextureMapping_BOX:
								ComputeBoxMapping(mesh,p);
								break;
							default:
								ai_assert(false);
							}
							if (m && idx != outIdx)
							{
								DefaultLogger::get()->warn("UV index mismatch. Not all meshes assigned to "
									"this material have equal numbers of UV channels. The UV index stored in  "
									"the material structure does therefore not apply for all meshes. ");
							}
							idx = outIdx;
						}
						info.uv = idx;
						mappingStack.push_back(info);
					}

					// Update the material property list
					mapping = aiTextureMapping_UV;
					((MaterialHelper*)mat)->AddProperty(&idx,1,AI_MATKEY_UVWSRC(prop->mSemantic,prop->mIndex));
				}
			}
		}
	}
	DefaultLogger::get()->debug("GenUVCoordsProcess finished");
}