#include "externals.hh"
#include "c-shaders.hh"


namespace {

const std::map< std::string , E_ShaderInput > InputTypes_( ([] {
	std::map< std::string , E_ShaderInput > t;
	t.emplace( "chunk" , E_ShaderInput::CHUNK );
	t.emplace( "library" , E_ShaderInput::LIBRARY );
	t.emplace( "lib" , E_ShaderInput::LIBRARY );
	t.emplace( "vertex" , E_ShaderInput::VERTEX );
	t.emplace( "fragment" , E_ShaderInput::FRAGMENT );
	t.emplace( "compute" , E_ShaderInput::COMPUTE );
	t.emplace( "geo" , E_ShaderInput::GEOMETRY );
	t.emplace( "geometry" , E_ShaderInput::GEOMETRY );
	return t;
})());

const std::regex PreprocDirective_( "^\\s*//!\\s*([a-z]+(\\s+([^\\s]+))*)\\s*$" );

} // namespace <anon>


/*============================================================================*/
namespace {

// Input reader state and functions, used when loading a source file
struct T_InputReader_
{
	using T_Tokens_ = std::vector< std::string >;

	FILE* const file;
	T_ShaderInput& input;
	uint32_t line{ 0 };

	char* buffer{ nullptr };
	ssize_t readCount;

	std::string accumulator{ };
	uint32_t accumLines{ 0 };

	T_InputReader_( FILE* const file ,
			T_ShaderInput& input )
		: file( file ) , input( input )
	{ }
	~T_InputReader_( );

	void read( );

	void handleDirective( T_Tokens_ const& tokens );

	void error( T_String const& err );
	void nl( );
	void addAccumulated( );
};

/*----------------------------------------------------------------------------*/

T_InputReader_::~T_InputReader_( )
{
	if ( buffer ) {
		free( buffer );
	}
	fclose( file );
}

void T_InputReader_::read( )
{
	size_t bsz( 0 );
	while ( ( readCount = getline( &buffer , &bsz , file ) ) != -1 ) {
		line ++;
		std::cmatch match;
		if ( std::regex_match( buffer , match , PreprocDirective_ ) ) {
			const T_Tokens_ tokens( ([](std::string const& a) {
				using stri = std::istream_iterator< std::string >;
				std::istringstream iss( a );
				return T_Tokens_{ stri( iss ) , stri( ) };
			})( match[ 1 ].str( ) ) );
			assert( tokens.size( ) >= 1 );
			handleDirective( tokens );
		} else {
			accumulator += buffer;
			accumLines ++;
		}
	}
	addAccumulated( );
}

/*----------------------------------------------------------------------------*/

void T_InputReader_::handleDirective(
		T_Tokens_ const& tokens )
{
	auto const& directive( tokens[ 0 ] );

	if ( directive == "include" ) {
		if ( tokens.size( ) != 2 ) {
			nl( );
			error( "invalid arguments" );
			return;
		}
		addAccumulated( );
		auto& ck( input.chunks );
		ck.addNew( E_ShaderInputChunk::INCLUDE , tokens[ 1 ].c_str( ) , 1 );

	} else if ( directive == "type" ) {
		nl( );
		if ( tokens.size( ) != 2 ) {
			error( "invalid arguments" );
			return;
		}
		auto pos( InputTypes_.find( tokens[ 1 ] ) );
		if ( pos == InputTypes_.end( ) ) {
			error( "unknown type" );
		} else {
			input.type = pos->second;
		}

	} else {
		nl( );
		error( "unknown directive" );
	}
}

/*----------------------------------------------------------------------------*/

void T_InputReader_::error(
		T_String const& err )
{
	input.errors.addNew( line , err );
}

void T_InputReader_::nl( )
{
	accumLines ++;
	accumulator += '\n';
}

void T_InputReader_::addAccumulated( )
{
	if ( accumLines ) {
		auto& ck( input.chunks );
		ck.addNew( E_ShaderInputChunk::CODE ,
				accumulator.c_str( ) , accumLines );
		accumulator = {};
		accumLines = 0;
	}
}

} // namespace <anon>


/*= T_ShaderInput ============================================================*/

bool T_ShaderInput::load(
		T_String const& path )
{
	type = E_ShaderInput::CHUNK;
	chunks.clear( );
	errors.clear( );

	FILE* const file{ fopen( (char const*) path.toOSString( ).data( ) , "r" ) };
	if ( !file ) {
		return false;
	}

	T_InputReader_ reader( file , *this );
	reader.read( );

	return true;
}