// Copyright (C) 2012-2013 ChaosForge / Kornel Kisielewicz
// http://chaosforge.org/
//
// This file is part of NV Libraries.
// For conditions of distribution and use, see copyright notice in nv.hh

#include "nv/formats/md5_loader.hh"

#include <glm/gtc/constants.hpp>
#include <glm/gtx/string_cast.hpp>
#include "nv/logging.hh"
#include "nv/io/std_stream.hh"
#include <cstring>

using namespace nv;

static void next_line( std::istream& stream )
{
	stream.ignore( std::numeric_limits<std::streamsize>::max(), '\n' );
}

static inline void discard( std::istream& stream, const std::string& token )
{
	std::string discarded;
	stream >> discarded;
	assert( discarded == token );
}


static void remove_quotes( std::string& str )
{
	size_t n;
	while ( ( n = str.find('\"') ) != std::string::npos ) str.erase(n,1);
}

void unit_quat_w( glm::quat& quat )
{
	float t = 1.0f - ( quat.x * quat.x ) - ( quat.y * quat.y ) - ( quat.z * quat.z );
	quat.w = ( t < 0.0f ? 0.0f : -sqrtf(t) );
}

bool md5_loader::load( stream& source )
{
	std_stream sstream( &source );
	std::string command;

	sstream >> command;
	while ( !sstream.eof() )
	{
		if ( command == "MD5Version" )
		{
			sstream >> m_md5_version;
			assert( m_md5_version == 10 );
		}
		else if ( command == "commandline" )
		{
			next_line( sstream ); 
		}
		else if ( command == "numJoints" )
		{
			sstream >> m_num_joints;
			m_joints.reserve( m_num_joints );
		}
		else if ( command == "numMeshes" )
		{
			sstream >> m_num_meshes;
			m_meshes.reserve( m_num_meshes );
		}
		else if ( command == "joints" )
		{
			discard( sstream, "{" );
			md5_joint joint;
			for ( int i = 0; i < m_num_joints; ++i )
			{
				sstream >> joint.name >> joint.parent_id;
				discard( sstream, "(" );
				sstream >> joint.pos.x >> joint.pos.y >> joint.pos.z;
				discard( sstream, ")" );
				discard( sstream, "(" );
				sstream >> joint.orient.x >> joint.orient.y >> joint.orient.z;
				remove_quotes( joint.name );
				unit_quat_w( joint.orient );
				m_joints.push_back( joint );
				next_line( sstream );
			}
			discard( sstream, "}" );
		}
		else if ( command == "mesh" )
		{
			// TODO : efficiency dammit
			md5_mesh mesh;
			int num_verts, num_tris, num_weights;

			discard( sstream, "{" );
			sstream >> command;
			while ( command != "}" ) 
			{
				if ( command == "shader" )
				{
					sstream >> mesh.shader;
					remove_quotes( mesh.shader );
					// texturePath.replace_extension( ".tga" );
					next_line( sstream );
				}
				else if ( command == "numverts")
				{
					sstream >> num_verts; 
					next_line( sstream );
					for ( int i = 0; i < num_verts; ++i )
					{
						md5_vertex vert;
						std::string ignore;
						discard( sstream, "vert" );
						sstream >> ignore;
						discard( sstream, "(" );
						sstream >> vert.texcoord.x >> vert.texcoord.y;
						discard( sstream, ")" );
						sstream >> vert.start_weight >> vert.weight_count;
						next_line( sstream );

						mesh.verts.push_back(vert);
						mesh.texcoord_buffer.push_back( vert.texcoord );
					}  
				}
				else if ( command == "numtris" )
				{
					sstream >> num_tris;
					next_line( sstream );
					for ( int i = 0; i < num_tris; ++i )
					{
						md5_triangle tri;
						std::string ignore;
						discard( sstream, "tri" );
						sstream >> ignore >> tri.indices[0] >> tri.indices[1] >> tri.indices[2];
						next_line( sstream );

						mesh.tris.push_back( tri );
						mesh.index_buffer.push_back( (uint32)tri.indices[0] );
						mesh.index_buffer.push_back( (uint32)tri.indices[1] );
						mesh.index_buffer.push_back( (uint32)tri.indices[2] );
					}              
				}
				else if ( command == "numweights" )
				{
					sstream >> num_weights;
					next_line( sstream );
					for ( int i = 0; i < num_weights; ++i )
					{
						md5_weight weight;
						std::string ignore;
						discard( sstream, "weight" );
						sstream >> ignore >> weight.joint_id >> weight.bias;
						discard( sstream, "(" );
						sstream >> weight.pos.x >> weight.pos.y >> weight.pos.z;
						discard( sstream, ")" );
						next_line( sstream );
						mesh.weights.push_back(weight);
					}
				}
				else
				{
					next_line( sstream );
				}

				sstream >> command;
			}

			prepare_mesh( mesh );
			prepare_normals( mesh );

			m_meshes.push_back(mesh);
		}
		sstream >> command;
	}

	assert( m_joints.size() == m_num_joints );
	assert( m_meshes.size() == m_num_meshes );
	return true;
}

bool md5_loader::prepare_mesh( md5_mesh& mesh )
{
	mesh.position_buffer.clear();
	mesh.texcoord_buffer.clear();

	for ( uint32 i = 0; i < mesh.verts.size(); ++i )
	{
		md5_vertex& vert = mesh.verts[i];

		vert.position = glm::vec3(0);
		vert.normal   = glm::vec3(0);
		vert.tangent  = glm::vec3(0);

		for ( int j = 0; j < vert.weight_count; ++j )
		{
			md5_weight& weight = mesh.weights[vert.start_weight + j];
			md5_joint&  joint  = m_joints[weight.joint_id];

			glm::vec3 rot_pos = joint.orient * weight.pos;

			vert.position += ( joint.pos + rot_pos ) * weight.bias;
		}

		mesh.position_buffer.push_back(vert.position);
		mesh.texcoord_buffer.push_back(vert.texcoord);
	}

	return true;
}

bool md5_loader::prepare_normals( md5_mesh& mesh )
{
	mesh.normal_buffer.clear();

	for ( unsigned int i = 0; i < mesh.tris.size(); ++i )
	{
		const md5_triangle& tri = mesh.tris[i];
		glm::vec3 v1 = mesh.verts[ tri.indices[0] ].position;
		glm::vec3 v2 = mesh.verts[ tri.indices[1] ].position;
		glm::vec3 v3 = mesh.verts[ tri.indices[2] ].position;
		glm::vec3 xyz1 = v3 - v1;
		glm::vec3 xyz2 = v2 - v1;

		glm::vec3 normal = glm::cross( xyz1, xyz2 );

		mesh.verts[ tri.indices[0] ].normal += normal;
		mesh.verts[ tri.indices[1] ].normal += normal;
		mesh.verts[ tri.indices[2] ].normal += normal;

		const vec2& w1 = mesh.verts[ tri.indices[0] ].texcoord;
		const vec2& w2 = mesh.verts[ tri.indices[1] ].texcoord;
		const vec2& w3 = mesh.verts[ tri.indices[2] ].texcoord;

		vec2 st1 = w3 - w1;
		vec2 st2 = w2 - w1;

		float coef = 1.0f / (st1.x * st2.y - st2.x * st1.y);

		vec3 tangent = (( xyz1 * st2.y ) - ( xyz2 * st1.y )) * coef;

		mesh.verts[ tri.indices[0] ].tangent += tangent;
		mesh.verts[ tri.indices[1] ].tangent += tangent;
		mesh.verts[ tri.indices[2] ].tangent += tangent;
	}

	for ( unsigned int i = 0; i < mesh.verts.size(); ++i )
	{
		md5_vertex& vert = mesh.verts[i];

		glm::vec3 normal  = glm::normalize( vert.normal );
		glm::vec3 tangent = glm::normalize( vert.tangent );
		mesh.normal_buffer.push_back( normal );
		mesh.tangent_buffer.push_back( tangent );

		vert.normal  = glm::vec3(0);
		vert.tangent = glm::vec3(0);

		for ( int j = 0; j < vert.weight_count; ++j )
		{
			const md5_weight& weight = mesh.weights[vert.start_weight + j];
			const md5_joint&  joint  = m_joints[weight.joint_id];
			vert.normal  += ( normal  * joint.orient ) * weight.bias;
			vert.tangent += ( tangent * joint.orient ) * weight.bias;
		}
	}

	return true;
}

mesh* md5_loader::release_mesh()
{
	mesh* m = new mesh();
	auto position = m->add_attribute< vec3 >( "nv_position" );
	auto normal   = m->add_attribute< vec3 >( "nv_normal" );
	auto texcoord = m->add_attribute< vec2 >( "nv_texcoord" );
	auto tangent  = m->add_attribute< vec2 >( "nv_tangent" );
	auto indices  = m->add_indices< uint32 >();

	position->get().assign( m_meshes[0].position_buffer.begin(), m_meshes[0].position_buffer.end() );
	normal  ->get().assign( m_meshes[0].normal_buffer.begin(),   m_meshes[0].normal_buffer.end() );
	texcoord->get().assign( m_meshes[0].texcoord_buffer.begin(), m_meshes[0].texcoord_buffer.end() );
	tangent ->get().assign( m_meshes[0].tangent_buffer.begin(),  m_meshes[0].tangent_buffer.end() );
	indices ->get().assign( m_meshes[0].index_buffer.begin(),    m_meshes[0].index_buffer.end() );

	m_size = m_meshes[0].index_buffer.size();
	return m;
}