/** Implementation of the BVH loader */
/*
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Open Asset Import Library (ASSIMP)
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Copyright (c) 2006-2008, ASSIMP Development Team

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*/

#include "AssimpPCH.h"
#include "BVHLoader.h"
#include "fast_atof.h"

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
BVHLoader::BVHLoader()
{
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
BVHLoader::~BVHLoader()
{
}

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file. 
bool BVHLoader::CanRead( const std::string& pFile, IOSystem* pIOHandler) const
{
	// check file extension 
	std::string::size_type pos = pFile.find_last_of('.');
	// no file extension - can't read
	if( pos == std::string::npos)
		return false;
	std::string extension = pFile.substr( pos);
	for( std::string::iterator it = extension.begin(); it != extension.end(); ++it)
		*it = tolower( *it);

	if( extension == ".bvh")
		return true;

	return false;
}

// ------------------------------------------------------------------------------------------------
// Imports the given file into the given scene structure. 
void BVHLoader::InternReadFile( const std::string& pFile, aiScene* pScene, IOSystem* pIOHandler)
{
	mFileName = pFile;

	// read file into memory
	boost::scoped_ptr<IOStream> file( pIOHandler->Open( pFile));
	if( file.get() == NULL)
		throw new ImportErrorException( "Failed to open file " + pFile + ".");

	size_t fileSize = file->FileSize();
	if( fileSize == 0)
		throw new ImportErrorException( "File is too small.");

	mBuffer.resize( fileSize);
	file->Read( &mBuffer.front(), 1, fileSize);

	// start reading
	mReader = mBuffer.begin();
	mLine = 1;
	ReadStructure( pScene);
}

// ------------------------------------------------------------------------------------------------
// Reads the file
void BVHLoader::ReadStructure( aiScene* pScene)
{
	// first comes hierarchy
	std::string header = GetNextToken();
	if( header != "HIERARCHY")
		ThrowException( "Expected header string \"HIERARCHY\".");
	ReadHierarchy( pScene);

	// then comes the motion data
	std::string motion = GetNextToken();
	if( motion != "MOTION")
		ThrowException( "Expected beginning of motion data \"MOTION\".");
	ReadMotion( pScene);
}

// ------------------------------------------------------------------------------------------------
// Reads the hierarchy
void BVHLoader::ReadHierarchy( aiScene* pScene)
{
	std::string root = GetNextToken();
	if( root != "ROOT")
		ThrowException( "Expected root node \"ROOT\".");

	// Go read the hierarchy from here
	pScene->mRootNode = ReadNode();
}

// ------------------------------------------------------------------------------------------------
// Reads a node and recursively its childs and returns the created node;
aiNode* BVHLoader::ReadNode()
{
	// first token is name
	std::string nodeName = GetNextToken();
	if( nodeName.empty() || nodeName == "{")
		ThrowException( boost::str( boost::format( "Expected node name, but found \"%s\".") % nodeName));

	// HACK: (thom) end nodes are called "End Site". If the name of the node is "Site", we know it's going to be an end node
	if( nodeName == "Site")
		nodeName = "End Site";

	// then an opening brace should follow
	std::string openBrace = GetNextToken();
	if( openBrace != "{")
		ThrowException( boost::str( boost::format( "Expected opening brace \"{\", but found \"%s\".") % openBrace));

	// Create a node
	aiNode* node = new aiNode( nodeName);
	std::vector<aiNode*> childNodes;

	// now read the node's contents
	while( 1)
	{
		std::string token = GetNextToken();
		
		// node offset to parent node
		if( token == "OFFSET")
			ReadNodeOffset( node);
		else if( token == "CHANNELS")
			ReadNodeChannels( node);
		else if( token == "JOINT")
		{
			// child node follows
			aiNode* child = ReadNode();
			childNodes.push_back( child);
		} else 
		if( token == "End")
		{
			// HACK: (thom) end child node follows. Full token is "End Site", then no name, then a node.
			// But I don't want to write another function for this, so I simply leave the "Site" for ReadNode() as a node name
			aiNode* child = ReadNode();
			childNodes.push_back( child);
		} else
		if( token == "}")
		{
			// we're done with that part of the hierarchy
			break;
		} else
		{
			// everything else is a parse error
			ThrowException( boost::str( boost::format( "Unknown keyword \"%s\".") % token));
		}
	}

	// add the child nodes if there are any
	if( childNodes.size() > 0)
	{
		node->mNumChildren = childNodes.size();
		node->mChildren = new aiNode*[node->mNumChildren];
		std::copy( childNodes.begin(), childNodes.end(), node->mChildren);
	}

	// and return the sub-hierarchy we built here
	return node;
}

// ------------------------------------------------------------------------------------------------
// Reads a node offset for the given node
void BVHLoader::ReadNodeOffset( aiNode* pNode)
{
	// Offset consists of three floats to read
	aiVector3D offset;
	offset.x = GetNextTokenAsFloat();
	offset.y = GetNextTokenAsFloat();
	offset.z = GetNextTokenAsFloat();

	// build a transformation matrix from it
	pNode->mTransformation = aiMatrix4x4( 1.0f, 0.0f, 0.0f, offset.x, 0.0f, 1.0f, 0.0f, offset.y,
		0.0f, 0.0f, 1.0f, offset.z, 0.0f, 0.0f, 0.0f, 1.0f);
}

// ------------------------------------------------------------------------------------------------
// Reads the animation channels for the given node
void BVHLoader::ReadNodeChannels( aiNode* pNode)
{
	// number of channels. Use the float reader because we're lazy
	float numChannelsFloat = GetNextTokenAsFloat();
	unsigned int numChannels = (unsigned int) numChannelsFloat;

	// TODO: (thom) proper channel parsing. For the moment I just skip the number of tokens
	for( unsigned int a = 0; a < numChannels; a++)
		GetNextToken();
}

// ------------------------------------------------------------------------------------------------
// Reads the motion data
void BVHLoader::ReadMotion( aiScene* pScene)
{
	// Read number of frames
	std::string tokenFrames = GetNextToken();
	if( tokenFrames != "Frames:")
		ThrowException( boost::str( boost::format( "Expected frame count \"Frames:\", but found \"%s\".") % tokenFrames));

	float numFramesFloat = GetNextTokenAsFloat();
	unsigned int numFrames = (unsigned int) numFramesFloat;

	// Read frame duration
	std::string tokenDuration1 = GetNextToken();
	std::string tokenDuration2 = GetNextToken();
	if( tokenDuration1 != "Frame" || tokenDuration2 != "Time:")
		ThrowException( boost::str( boost::format( "Expected frame duration \"Frame Time:\", but found \"%s %s\".") % tokenDuration1 % tokenDuration2));

	float frameDuration = GetNextTokenAsFloat();

	// resize value array accordingly
	// ************* Continue here ********
	//mMotionValues.resize( boost::extents[numFrames][numChannels]);
}

// ------------------------------------------------------------------------------------------------
// Retrieves the next token
std::string BVHLoader::GetNextToken()
{
	// skip any preceeding whitespace
	while( mReader != mBuffer.end())
	{
		if( !isspace( *mReader))
			break;

		// count lines
		if( *mReader == '\n')
			mLine++;

		++mReader;
	}

	// collect all chars till the next whitespace. BVH is easy in respect to that.
	std::string token;
	while( mReader != mBuffer.end())
	{
		if( isspace( *mReader))
			break;

		token.push_back( *mReader);
		++mReader;

		// little extra logic to make sure braces are counted correctly
		if( token == "{" || token == "}")
			break;
	}

	// empty token means end of file, which is just fine
	return token;
}

// ------------------------------------------------------------------------------------------------
// Reads the next token as a float
float BVHLoader::GetNextTokenAsFloat()
{
	std::string token = GetNextToken();
	if( token.empty())
		ThrowException( "Unexpected end of file while trying to read a float");

	// check if the float is valid by testing if the atof() function consumed every char of the token
	const char* ctoken = token.c_str();
	float result = 0.0f;
	ctoken = fast_atof_move( ctoken, result);

	if( ctoken != token.c_str() + token.length())
		ThrowException( boost::str( boost::format( "Expected a floating point number, but found \"%s\".") % token));

	return result;
}

// ------------------------------------------------------------------------------------------------
// Aborts the file reading with an exception
void BVHLoader::ThrowException( const std::string& pError)
{
	throw new ImportErrorException( boost::str( boost::format( "%s:%d - %s") % mFileName % mLine % pError));
}