// 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/obj_loader.hh"
#include "nv/io/std_stream.hh"
#include <sstream>

using namespace nv;

struct obj_vertex_vt
{
	vec3 position;
	vec2 texcoord;

	obj_vertex_vt( vec3 a_position, vec2 a_texcoord ) 
		: position( a_position ), texcoord( a_texcoord ) {}
};

struct obj_vertex_vtn
{
	vec3 position;
	vec2 texcoord;
	vec3 normal;

	obj_vertex_vtn( vec3 a_position, vec2 a_texcoord, vec3 a_normal ) 
		: position( a_position ), texcoord( a_texcoord ), normal( a_normal ) {}
};


struct obj_vertex_vtnt
{
	vec3 position;
	vec2 texcoord;
	vec3 normal;
	vec4 tangent;

	obj_vertex_vtnt( vec3 a_position, vec2 a_texcoord, vec3 a_normal ) 
		: position( a_position ), texcoord( a_texcoord ), normal( a_normal ) {}
};

struct obj_reader
{
	std::vector< vec3 > v;
	std::vector< vec3 > n;
	std::vector< vec2 > t;

	std::string line;
	std::string cmd;

	std::size_t size;

	obj_reader();
	bool read_stream( std::istream& stream );
	virtual size_t add_face( uint32* vi, uint32* ti, uint32* ni, size_t count ) = 0;
	virtual size_t raw_size() { return 0; }
	virtual const uint8* raw_pointer() { return nullptr; }
	virtual void calculate_tangents() {}

	virtual ~obj_reader(){}
};

obj_reader::obj_reader()
{
	// push in dummy 0-index objects for faster indexing
	v.push_back( vec3() );
	n.push_back( vec3() );
	t.push_back( vec2() );
	size = 0;
}

bool obj_reader::read_stream( std::istream& stream )
{
	f32 x, y, z;

	while ( std::getline( stream, line ) )
	{
		if ( line.length() < 3 || line[0] == '#' )
		{
			continue;
		}

		std::istringstream ss(line);
		ss >> cmd;

		if ( cmd == "v" )
		{
			ss >> x >> y >> z;
			v.push_back( vec3( x, y, z ) );
			continue;
		}

		if ( cmd == "vn" )
		{
			ss >> x >> y >> z;
			n.push_back( vec3( x, y, z ) );
			continue;
		}

		if ( cmd == "vt" )
		{
			ss >> x >> y;
			t.push_back( vec2( x, 1.0f - y ) );
			continue;
		}

		if ( cmd == "f" )
		{
			ss >> cmd;

			uint32 vis[8];
			uint32 tis[8];
			uint32 nis[8];
			bool   normals = false;
			uint32 count = 0;

			while ( !ss.fail() )
			{
				char ch;

				std::istringstream ss2( cmd );
				ss2 >> vis[count] >> ch;
				ss2 >> tis[count] >> ch;
				if ( ch == '/')
				{
					normals = true;
					ss2 >> nis[count];
				}

				ss >> cmd;
				count++;
			}

			size += add_face( vis, tis, normals ? nis : nullptr, count );
			continue;
		}

		if ( cmd == "g" || cmd == "s" )
		{
			// ignored
			continue;
		}

		// unknown command
	}

	return true;
}


struct mesh_obj_reader : public obj_reader
{
	mesh_obj_reader( mesh_data_creator* m ) : m_mesh( m ) {}
	virtual std::size_t add_face( uint32* vi, uint32* ti, uint32* ni, size_t count );
	virtual void calculate_tangents();

	mesh_data_creator* m_mesh;
};

size_t mesh_obj_reader::add_face( uint32* vi, uint32* ti, uint32* ni, size_t count )
{
	if ( count < 3 )
	{
		// TODO : report error?
		return 0;
	}

	// TODO : support if normals not present;

	std::vector< vec3 >& vp = m_mesh->get_positions();
	std::vector< vec3 >& vn = m_mesh->get_normals();
	std::vector< vec2 >& vt = m_mesh->get_texcoords();

	std::size_t result = 0;

	// Simple triangulation - obj's shouldn't have more than quads anyway
	for ( size_t i = 2; i < count; ++i )
	{
		result++;
		vp.push_back( v[ vi[ 0 ] ] );   vt.push_back( t[ ti[ 0 ] ] );   vn.push_back( n[ ni[ 0 ] ] );
		vp.push_back( v[ vi[ i-1 ] ] ); vt.push_back( t[ ti[ i-1 ] ] ); vn.push_back( n[ ni[ i-1 ] ] );
		vp.push_back( v[ vi[ i ] ] );   vt.push_back( t[ ti[ i ] ] );   vn.push_back( n[ ni[ i ] ] );
	}

	return result;
}

// based on http://www.terathon.com/code/tangent.html
void mesh_obj_reader::calculate_tangents()
{
	const std::vector< vec3 >& vp = m_mesh->get_positions();
	const std::vector< vec2 >& vt = m_mesh->get_texcoords();
	const std::vector< vec3 >& vn = m_mesh->get_normals();
	std::vector< vec3 >& tg = m_mesh->get_tangents();

	size_t count  = vp.size();
	size_t tcount = count / 3;

	std::vector< vec3 > tan1( count );
	std::vector< vec3 > tan2( count );
	tg.resize( count );

	for (size_t a = 0; a < tcount; ++a )
	{
		size_t i1 = a * 3;
		size_t i2 = a * 3 + 1;
		size_t i3 = a * 3 + 2;

		// TODO: simplify

		const vec3& v1 = vp[i1];
		const vec3& v2 = vp[i2];
		const vec3& v3 = vp[i3];

		const vec2& w1 = vt[i1];
		const vec2& w2 = vt[i2];
		const vec2& w3 = vt[i3];

		vec3 xyz1 = v2 - v1;
		vec3 xyz2 = v3 - v1;
		//vec2 st1  = w2 - w1;
		//vec2 st2  = w3 - w1;

		float s1 = w2.x - w1.x;
		float t1 = w2.y - w1.y;
		float s2 = w3.x - w1.x;
		float t2 = w3.y - w1.y;

		float stst = s1 * t2 - s2 * t1;
		float r = 0.0f;
		if (stst > 0.0f || stst < 0.0f) r = 1.0f / stst;

		vec3 sdir = ( t2 * xyz1 - t1 * xyz2 ) * r;
		vec3 tdir = ( s1 * xyz2 - s2 * xyz1 ) * r;

		// the += below obviously doesn't make sense in this case, but I'll
		// leave it here for when I move to indices
		tan1[i1] += sdir;
		tan1[i2] += sdir;
		tan1[i3] += sdir;

		// tan2 not needed anymore??
		tan2[i1] += tdir;
		tan2[i2] += tdir;
		tan2[i3] += tdir;
	}

	for (std::size_t a = 0; a < count; ++a )
	{
		const vec3& n = vn[a];
		const vec3& t = tan1[a];
		if ( ! (t.x == 0.0f && t.y == 0.0f && t.z == 0.0f) )
			tg[a] = vec3( glm::normalize(t - n * glm::dot( n, t )) ); 
			//tg[a][3] =    (glm::dot(glm::cross(n, t), tan2[a]) < 0.0f) ? -1.0f : 1.0f;
	}

}

nv::obj_loader::obj_loader( bool tangents )
	: m_mesh( nullptr ), m_tangents( tangents )
{

}

nv::obj_loader::~obj_loader()
{
	delete m_mesh;
}

bool nv::obj_loader::load( stream& source )
{
	if ( m_mesh != nullptr ) delete m_mesh;
	mesh_data_creator creator;
	mesh_obj_reader reader( &creator );
	std_stream sstream( &source );
	reader.read_stream( sstream );
	m_size = reader.size;
	if ( m_tangents )
	{
		reader.calculate_tangents();
	}
	m_mesh = creator.release();
	return true;
}

struct mesh_data_reader_vt : public obj_reader
{
	mesh_data_reader_vt()  {}
	virtual std::size_t add_face( uint32* vi, uint32* ti, uint32*, size_t count )
	{
		if ( count < 3 ) return 0; // TODO : report error?
		// TODO : support if normals not present;
		std::size_t result = 0;
		// Simple triangulation - obj's shouldn't have more than quads anyway
		for ( size_t i = 2; i < count; ++i )
		{
			result++;
			m_data.emplace_back( v[ vi[ 0 ]   ], t[ ti[ 0   ] ] );
			m_data.emplace_back( v[ vi[ i-1 ] ], t[ ti[ i-1 ] ] );
			m_data.emplace_back( v[ vi[ i ]   ], t[ ti[ i   ] ] );
		}
		return result;
	}
	std::vector< obj_vertex_vt > m_data;
	virtual size_t raw_size() { return m_data.size() * sizeof( obj_vertex_vt ); }
	virtual const uint8* raw_pointer() { return (const uint8*)m_data.data(); }
};

struct mesh_data_reader_vtn : public obj_reader
{
	mesh_data_reader_vtn()  {}
	virtual std::size_t add_face( uint32* vi, uint32* ti, uint32* ni, size_t count )
	{
		if ( count < 3 ) return 0; // TODO : report error?
		// TODO : support if normals not present;
		std::size_t result = 0;
		// Simple triangulation - obj's shouldn't have more than quads anyway
		for ( size_t i = 2; i < count; ++i )
		{
			result++;
			m_data.emplace_back( v[ vi[ 0 ]   ], t[ ti[ 0   ] ], n[ ni[ 0   ] ] );
			m_data.emplace_back( v[ vi[ i-1 ] ], t[ ti[ i-1 ] ], n[ ni[ i-1 ] ] );
			m_data.emplace_back( v[ vi[ i ]   ], t[ ti[ i   ] ], n[ ni[ i   ] ] );
		}
		return result;
	}
	std::vector< obj_vertex_vtn > m_data;
	virtual size_t raw_size() { return m_data.size() * sizeof( obj_vertex_vtn ); }
	virtual const uint8* raw_pointer() { return (const uint8*)m_data.data(); }
};

struct mesh_data_reader_vtnt : public obj_reader
{
	mesh_data_reader_vtnt()  {}
	virtual std::size_t add_face( uint32* vi, uint32* ti, uint32* ni, size_t count )
	{
		if ( count < 3 ) return 0; // TODO : report error?
		// TODO : support if normals not present;
		std::size_t result = 0;
		// Simple triangulation - obj's shouldn't have more than quads anyway
		for ( size_t i = 2; i < count; ++i )
		{
			result++;
			m_data.emplace_back( v[ vi[ 0 ]   ], t[ ti[ 0   ] ], n[ ni[ 0   ] ] );
			m_data.emplace_back( v[ vi[ i-1 ] ], t[ ti[ i-1 ] ], n[ ni[ i-1 ] ] );
			m_data.emplace_back( v[ vi[ i ]   ], t[ ti[ i   ] ], n[ ni[ i   ] ] );
		}
		return result;
	}
	std::vector< obj_vertex_vtnt > m_data;
	virtual size_t raw_size() { return m_data.size() * sizeof( obj_vertex_vtnt ); }
	virtual const uint8* raw_pointer() { return (const uint8*)m_data.data(); }

	// based on http://www.terathon.com/code/tangent.html
	void calculate_tangents()
	{
		//		const std::vector< vec3 >& vp = m_mesh->get_positions();
		//		const std::vector< vec2 >& vt = m_mesh->get_texcoords();
		//		const std::vector< vec3 >& vn = m_mesh->get_normals();
		//		std::vector< vec3 >& tg = m_mesh->get_tangents();

		size_t count  = m_data.size();
		size_t tcount = count / 3;

		std::vector< vec3 > tan1( count );
		std::vector< vec3 > tan2( count );

		for (size_t a = 0; a < tcount; ++a )
		{
			size_t i1 = a * 3;
			size_t i2 = a * 3 + 1;
			size_t i3 = a * 3 + 2;
			obj_vertex_vtnt& vtx1 = m_data[ i1 ];
			obj_vertex_vtnt& vtx2 = m_data[ i2 ];
			obj_vertex_vtnt& vtx3 = m_data[ i3 ];

			// TODO: simplify
			vec3 xyz1 = vtx2.position - vtx1.position;
			vec3 xyz2 = vtx3.position - vtx1.position;
			//vec2 st1  = w2 - w1;
			//vec2 st2  = w3 - w1;

			float s1 = vtx2.texcoord.x - vtx1.texcoord.x;
			float t1 = vtx2.texcoord.y - vtx1.texcoord.y;
			float s2 = vtx3.texcoord.x - vtx1.texcoord.x;
			float t2 = vtx3.texcoord.y - vtx1.texcoord.y;

			float stst = s1 * t2 - s2 * t1;
			float r = 0.0f;
			if (stst > 0.0f || stst < 0.0f) r = 1.0f / stst;

			vec3 sdir = ( t2 * xyz1 - t1 * xyz2 ) * r;
			vec3 tdir = ( s1 * xyz2 - s2 * xyz1 ) * r;

			// the += below obviously doesn't make sense in this case, but I'll
			// leave it here for when I move to indices
			tan1[i1] += sdir;
			tan1[i2] += sdir;
			tan1[i3] += sdir;

			// tan2 not needed anymore??
			tan2[i1] += tdir;
			tan2[i2] += tdir;
			tan2[i3] += tdir;
		}

		for (std::size_t a = 0; a < count; ++a )
		{
			const vec3& n = m_data[a].normal;
			const vec3& t = tan1[a];
			if ( ! (t.x == 0.0f && t.y == 0.0f && t.z == 0.0f) )
			{
				m_data[a].tangent    = vec4( glm::normalize(t - n * glm::dot( n, t )), 0.0f ); 
				m_data[a].tangent[3] = (glm::dot(glm::cross(n, t), tan2[a]) < 0.0f) ? -1.0f : 1.0f;
			}
		}

	}


};

nv::wavefront_loader::wavefront_loader( bool normals /*= true*/, bool tangents /*= false */ )
	: m_normals( normals ), m_tangents( tangents ), m_mesh( nullptr )
{
	if ( normals )
	{
		if ( tangents )
			m_descriptor.initialize<obj_vertex_vtnt>();
		else
			m_descriptor.initialize<obj_vertex_vtn>();
	}
	else
		m_descriptor.initialize<obj_vertex_vt>();
}

bool nv::wavefront_loader::load( stream& source )
{
	if ( m_mesh ) delete m_mesh;
	
	obj_reader* reader = nullptr;
	if ( m_normals )
	{
		if ( m_tangents )
			reader = new mesh_data_reader_vtnt();
		else
			reader = new mesh_data_reader_vtn();
	}
	else
		reader = new mesh_data_reader_vt();
	std_stream sstream( &source );
	reader->read_stream( sstream );

	if ( m_tangents )
	{
		reader->calculate_tangents();
	}
	

	mesh_raw_channel* channel = new mesh_raw_channel();
	nv::uint8* data = nullptr;
	if ( reader->raw_size() > 0 ) 
	{
		data = new uint8[ reader->raw_size() ];
		std::copy_n( reader->raw_pointer(), reader->raw_size(), data );
	}
	channel->data  = data;
	channel->desc  = m_descriptor;
	channel->count = reader->size * 3;
	channel->size  = reader->raw_size();
	delete reader;

	m_mesh = new mesh_data();
	m_mesh->add_channel( channel );
	return true;

}

mesh_data* nv::wavefront_loader::release_mesh_data()
{
	mesh_data* result = m_mesh;
	m_mesh = nullptr;
	return result;
}

nv::wavefront_loader::~wavefront_loader()
{
	if ( m_mesh ) delete m_mesh;
}