#include "externals.hh"
#include "shaders.hh"
#include "globals.hh"

#include <ebcl/Sets.hh>


namespace {

const std::regex PreprocDirective_( "^\\s*//!\\s*([a-z]+(\\s+([^\\s]+))*)\\s*$" );
const std::regex GLSLErrorNv_( "^[0-9]*\\(([0-9]+).*$" );

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 GLenum ProgramTypes_[] = {
	GL_VERTEX_SHADER ,
	GL_FRAGMENT_SHADER ,
	GL_GEOMETRY_SHADER ,
	GL_COMPUTE_SHADER
};

const GLbitfield PipelineStages_[] = {
	GL_VERTEX_SHADER_BIT ,
	GL_FRAGMENT_SHADER_BIT ,
	GL_GEOMETRY_SHADER_BIT ,
	GL_COMPUTE_SHADER_BIT
};

static_assert( sizeof( PipelineStages_ ) / sizeof( GLbitfield ) == size_t( E_ShaderType::__COUNT__ ) ,
		"missing pipeline stage constants" );


/*============================================================================*/

// 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


/*= 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;
}


/*= T_ShaderPogram ===========================================================*/

T_ShaderProgram::T_ShaderProgram( )
	: T_ShaderProgram( 0 )
{ }

T_ShaderProgram::T_ShaderProgram(
		T_ShaderProgram const& other )
	: T_ShaderProgram( other.id_ )
{ }

T_ShaderProgram::T_ShaderProgram(
		T_ShaderProgram&& other ) noexcept
	: T_ShaderProgram( )
{
	swap( other.id_ , id_ );
}

T_ShaderProgram::T_ShaderProgram(
		const uint32_t id ) noexcept
	: id_( id )
{
	if ( id_ ) {
		Globals::Shaders( ).programs_[ id_ - 1 ].saReferences ++;
	}
}

T_ShaderProgram::~T_ShaderProgram( )
{
	if ( id_ ) {
		Globals::Shaders( ).dereferenceProgram( id_ - 1 );
	}
}

T_ShaderProgram& T_ShaderProgram::operator=(
		T_ShaderProgram const& other )
{
	if ( this != &other ) {
		if ( id_ ) {
			Globals::Shaders( ).dereferenceProgram( id_ - 1 );
		}
		id_ = other.id_;
		if ( id_ ) {
			Globals::Shaders( ).programs_[ id_ - 1 ].saReferences ++;
		}
	}
	return *this;
}

T_ShaderProgram& T_ShaderProgram::operator=(
		T_ShaderProgram&& other ) noexcept
{
	if ( this != &other ) {
		if ( id_ ) {
			Globals::Shaders( ).dereferenceProgram( id_ - 1 );
		}
		id_ = other.id_;
		other.id_ = T_String{};
	}
	return *this;
}

bool T_ShaderProgram::valid( ) const noexcept
{
	return id_ && Globals::Shaders( ).programs_[ id_ - 1 ].id != 0;
}

void T_ShaderProgram::enable( ) const
{
	if ( !id_ ) {
		return;
	}

	auto const& p( Globals::Shaders( ).programs_[ id_ - 1 ] );
	if ( p.id ) {
		glBindProgramPipeline( 0 );
		glUseProgram( p.id );
	}
}

GLuint T_ShaderProgram::id( ) const
{
	if ( id_ ) {
		return Globals::Shaders( ).programs_[ id_ - 1 ].id;
	} else {
		return 0;
	}
}

T_Optional< E_ShaderType > T_ShaderProgram::type( ) const
{
	if ( id_ ) {
		return Globals::Shaders( ).programs_[ id_ - 1 ].code.type;
	} else {
		return {};
	}
}

T_String T_ShaderProgram::name( ) const
{
	if ( id_ ) {
		return Globals::Shaders( ).programs_[ id_ - 1 ].name;
	} else {
		return {};
	}
}


/*= T_ShaderPipeline =========================================================*/

T_ShaderPipeline::T_ShaderPipeline( )
	: T_ShaderPipeline( T_String{} )
{ }

T_ShaderPipeline::T_ShaderPipeline(
		T_ShaderPipeline const& other )
	: T_ShaderPipeline( other.id_ )
{ }

T_ShaderPipeline::T_ShaderPipeline(
		T_ShaderPipeline&& other ) noexcept
	: T_ShaderPipeline( )
{
	swap( other.id_ , id_ );
}

T_ShaderPipeline::T_ShaderPipeline( T_String id ) noexcept
	: id_( std::move( id ) )
{
	if ( id_ ) {
		Globals::Shaders( ).pipelines_.get( id_ )->references ++;
	}
}

T_ShaderPipeline::~T_ShaderPipeline( )
{
	if ( id_ ) {
		Globals::Shaders( ).dereferencePipeline( id_ );
	}
}

T_ShaderPipeline& T_ShaderPipeline::operator=(
		T_ShaderPipeline const& other )
{
	if ( this != &other ) {
		if ( id_ ) {
			Globals::Shaders( ).dereferencePipeline( id_ );
		}
		id_ = other.id_;
		if ( id_ ) {
			Globals::Shaders( ).pipelines_.get( id_ )->references ++;
		}
	}
	return *this;
}

T_ShaderPipeline& T_ShaderPipeline::operator=(
		T_ShaderPipeline&& other ) noexcept
{
	if ( this != &other ) {
		if ( id_ ) {
			Globals::Shaders( ).dereferencePipeline( id_ );
		}
		id_ = other.id_;
		other.id_ = T_String{};
	}
	return *this;
}

bool T_ShaderPipeline::valid( ) const noexcept
{
	return id_
		&& Globals::Shaders( ).pipelines_.get( id_ )->id != 0;
}

void T_ShaderPipeline::enable( ) const
{
	if ( !id_ ) {
		return;
	}

	auto const* pl( Globals::Shaders( ).pipelines_.get( id_ ) );
	if ( pl && pl->id ) {
		glUseProgram( 0 );
		glBindProgramPipeline( pl->id );
	}
}

GLuint T_ShaderPipeline::id( ) const
{
	if ( id_ ) {
		return Globals::Shaders( ).pipelines_.get( id_ )->id;
	} else {
		return 0;
	}
}

GLuint T_ShaderPipeline::program(
		const E_ShaderType program ) const
{
	if ( !valid( ) ) {
		return 0;
	}

	auto const& sm( Globals::Shaders( ) );
	auto const& pl( *sm.pipelines_.get( id_ ) );
	for ( auto const& pn : pl.programs ) {
		auto const* pos( sm.programIndex_.get( pn ) );
		if ( !pos ) {
			continue;
		}
		auto& p( sm.programs_[ *pos ] );
		if ( p.code.type == program ) {
			return p.id;
		}
	}
	return 0;
}


/*= T_CodeBuilder_ ===========================================================*/

namespace {

using F_GetInput_ = std::function< T_ShaderInput const*( T_String const& ) >;
using T_Code_ = T_ShaderManager::T_ShaderCode;

// Code builder, state and functions
struct T_CodeBuilder_
{
	struct T_StackEntry_ {
		T_String name;
		T_ShaderInput const* input;
		uint32_t pos;
	};

	F_GetInput_ loader;
	const T_String name;
	T_Code_& code;

	T_ShaderInput const* main;
	T_KeyValueTable< T_String , uint32_t > pos;
	std::vector< T_StackEntry_ > stack;
	T_Array< T_String > libraries;
	T_ShaderInput const* current;
	uint32_t cpos{ 0 };
	T_String cname;

	T_CodeBuilder_( F_GetInput_ loader ,
			T_String const& name ,
			T_Code_& code )
		: loader( loader ) , name( name ) , code( code ) ,
			main( loader( name ) )
	{ }

	bool buildCode( );
	void appendChunk( T_ShaderInputChunk const& chunk );
	void include( T_String const& name ,
			const uint32_t lines );
	void next( );

	void addInputLoaderErrors(
			T_ShaderInput const* input ,
			T_String const& name );
};

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

bool T_CodeBuilder_::buildCode( )
{
	code = T_Code_{ };
	code.files.add( name , main != nullptr );
	if ( !main ) {
		return false;
	}
	if ( main->type == E_ShaderInput::CHUNK
			|| main->type == E_ShaderInput::LIBRARY ) {
		code.errors.addNew( name , 0 , "invalid type" );
	} else {
		code.type = E_ShaderType( int( main->type ) - 2 );
	}
	addInputLoaderErrors( main , name );
	cname = name;
	current = main;

	while ( cpos < current->chunks.size( ) ) {
		auto& chunk( current->chunks[ cpos ] );
		if ( chunk.type == E_ShaderInputChunk::CODE ) {
			appendChunk( chunk );
		} else {
			include( chunk.text , chunk.lines );
		}

		next( );
	}

	code.code << '\0';
	return true;
}

void T_CodeBuilder_::appendChunk(
		T_ShaderInputChunk const& chunk )
{
	auto* p( pos.get( cname ) );
	if ( !p ) {
		pos.add( cname , 0u );
		p = pos.get( cname );
	}
	code.sources.addNew( cname );
	code.counts.add( chunk.lines );
	code.starts.add( *p );
	code.code << chunk.text;
	*p += chunk.lines;
}

void T_CodeBuilder_::include(
		T_String const& nname ,
		const uint32_t lines )
{
	auto* const p( pos.get( cname ) );
	const auto prevPos( *p );
	*p += lines;

	// Avoid recursion
	if ( nname == cname || 0 != count_if( stack.begin( ) , stack.end( ) ,
				[nname] ( T_StackEntry_ const& e ) {
					return nname == e.name;
				} ) ) {
		T_StringBuilder sb;
		code.errors.addNew( cname , prevPos ,
				sb << "recursive inclusion of '"
					<< nname << "'" );
		return;
	}

	// Avoid including libraries more than once
	if ( libraries.contains( nname ) ) {
		return;
	}

	T_ShaderInput const* const isi( loader( nname ) );
	code.files.add( nname , isi != nullptr );

	// Check for problems
	if ( !isi ) {
		// Not found
		code.errors.addNew( cname , prevPos , "file not found" );
		return;
	}
	if ( isi->type != E_ShaderInput::CHUNK && isi->type != E_ShaderInput::LIBRARY ) {
		// Trying to load a top-level shader
		code.errors.addNew( cname , prevPos , "trying to include a top-level file" );
		return;
	}

	// Add input loader errors
	if ( !libraries.contains( nname ) ) {
		addInputLoaderErrors( isi , nname );
	}
	libraries.add( nname );

	// Enter the new file
	stack.push_back( T_StackEntry_{ cname , current , cpos } );
	cname = nname;
	current = isi;
	cpos = UINT32_MAX;
	pos.set( cname , 0u );
}

void T_CodeBuilder_::next( )
{
	cpos ++;
	while ( cpos == current->chunks.size( ) && !stack.empty( ) ) {
		T_StackEntry_ const& se( stack[ stack.size( ) - 1 ] );
		pos.remove( cname );
		cpos = se.pos + 1;
		current = se.input;
		cname = se.name;
		stack.pop_back( );
	}
}

void T_CodeBuilder_::addInputLoaderErrors(
		T_ShaderInput const* input ,
		T_String const& name )
{
	for ( auto const& errs : input->errors ) {
		code.errors.addNew( name , errs.line , (char*) errs.error.toOSString( ).data( ) );
	}
}


} // namespace

/*============================================================================*/

T_ShaderManager::T_ShaderManager( ) noexcept
	: pipelines_( []( T_Pipeline_ const& p ) -> T_String {
			return p.idString;
		} )
{ }

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

T_ShaderProgram T_ShaderManager::program(
		T_String const& name )
{
	loadProgram( name );
	assert( programIndex_.contains( name ) );
	assert( programs_[ *programIndex_.get( name ) ].name == name );
	return T_ShaderProgram( *programIndex_.get( name ) + 1 );
}

T_ShaderPipeline T_ShaderManager::pipeline(
		std::initializer_list< T_String > shaders )
{
	if ( shaders.size( ) < 1 || shaders.size( ) > 5 ) {
		return {};
	}

	const T_String id( ([&shaders] () {
		T_StringBuilder sb;
		for ( auto const& s : shaders ) {
			sb << s << '|';
		}
		sb << '\0';
		return T_String{ std::move( sb.data( ) ) };
	} )() );

	auto const* existing( pipelines_.get( id ) );
	if ( existing ) {
		return T_ShaderPipeline{ existing->idString };
	}

	pipelines_.add( T_Pipeline_{ id , shaders } );
	auto& p( *pipelines_.get( id ) );
	for ( auto const& pName : shaders ) {
		loadProgram( p.idString , pName );
	}
	initPipeline( p );

	return T_ShaderPipeline{ p.idString };
}

T_ShaderPipeline T_ShaderManager::pipeline(
		T_String const* shaderNames ,
		uint32_t count )
{
	if ( count < 1 || count > 5 ) {
		return {};
	}

	const T_String id( ([shaderNames,count] () {
		T_StringBuilder sb;
		for ( auto i = 0u ; i < count ; i ++ ) {
			sb << shaderNames[ i ] << '|';
		}
		sb << '\0';
		return T_String{ std::move( sb.data( ) ) };
	} )() );

	auto const* existing( pipelines_.get( id ) );
	if ( existing ) {
		return T_ShaderPipeline{ existing->idString };
	}

	pipelines_.add( T_Pipeline_{ id , shaderNames , count } );
	auto& p( *pipelines_.get( id ) );
	for ( auto i = 0u ; i < count ; i ++ ) {
		loadProgram( p.idString , shaderNames[ i ] );
	}
	initPipeline( p );

	return T_ShaderPipeline{ p.idString };
}

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

void T_ShaderManager::update( )
{
	using namespace ebcl;
	T_Set< T_String > temp{ UseTag< ArrayBacked< 64 > >( ) };
	T_StringBuilder sb;
	inputs_.clear( );

	// Check for missing files
	for ( auto it = missing_.keys( ).cbegin( ) ; it.valid( ) ; ++it ) {
		const bool exists( ([&sb] ( T_String const& name ) -> bool {
			struct stat buffer;
			sb.clear( );
			sb << "shaders/" << name << '\0';
			return ( stat( sb.data( ) , &buffer ) == 0 );
		})( *it ) );
		if ( !exists ) {
			continue;
		}
		auto& set( missing_.values( )[ it.pos( ) ] );
		for ( auto& s : set ) {
			if ( !updates_.contains( s ) ) {
				updates_.add( std::move( s ) );
			}
		}
		temp.add( *it );
	}

	// Remove all marked entries
	for ( auto i = 0u ; i < temp.size( ) ; i ++ ) {
		missing_.remove( temp[ i ] );
	}
	temp.clear( );

	// Reset programs that need to be updated
	for ( auto it = updates_.begin( ) ; it.valid( ) ; ) {
		auto const* p( programIndex_.get( *it ) );
		if ( p ) {
			auto& pr( programs_[ *p ] );
			for ( auto const& ref : pr.plReferences ) {
				if ( !temp.contains( ref ) ) {
					temp.add( ref );
				}
			}
			resetProgram( pr );
			++it;
		} else {
			updates_.removeSwap( it.pos( ) );
		}
	}
	if ( updates_.empty( ) ) {
		return;
	}

	// Reset pipelines affected by the programs above
	for ( auto i = 0u ; i < temp.size( ) ; i ++ ) {
		auto& pipeline( *pipelines_.get( temp[ i ] ) );
		if ( pipeline.id != 0 ) {
			glDeleteProgramPipelines( 1 , &pipeline.id );
			pipeline.id = 0;
		}
	}

	// Try to load all updated programs
	sb.clear( );
	for ( auto const& name : updates_ ) {
		auto& pr( programs_[ *programIndex_.get( name ) ] );
		initProgram( pr );
		for ( auto const& e : pr.code.errors ) {
			sb << e.source << ':' << e.line << ": "
				<< e.error << '\n';
		}
	}
	sb << '\0';
	printf( "%s" , sb.data( ) );

	// Try to initialise all affected pipelines
	for ( auto i = 0u ; i < temp.size( ) ; i ++ ) {
		initPipeline( *pipelines_.get( temp[ i ] ) );
	}

	updates_.clear( );
}


void T_ShaderManager::loadProgram(
		T_String const& pipeline ,
		T_String const& name )
{
	if ( !useExistingProgram( pipeline , name ) ) {
		initProgramRecord( name ).plReferences.add( pipeline );
	}
}

bool T_ShaderManager::useExistingProgram(
		T_String const& pipeline ,
		T_String const& name )
{
	auto const* pos( programIndex_.get( name ) );
	if ( !pos ) {
		return false;
	}
	auto& refs( programs_[ *pos ].plReferences );
	assert( !refs.contains( pipeline ) );
	refs.add( pipeline );
	return true;
}

void T_ShaderManager::loadProgram(
		T_String const& name )
{
	if ( !useExistingProgram( name ) ) {
		initProgramRecord( name );
	}
}

bool T_ShaderManager::useExistingProgram(
		T_String const& name )
{
	auto const* pos( programIndex_.get( name ) );
	if ( !pos ) {
		return false;
	}
	programs_[ *pos ].saReferences ++;
	return true;
}


uint32_t T_ShaderManager::newProgramRecord( )
{
	uint32_t i = 0;
	while ( i < programs_.size( ) ) {
		if ( programs_[ i ].plReferences.empty( )
				&& !programs_[ i ].saReferences ) {
			return i;
		}
		i ++;
	}
	programs_.addNew( );
	return i;
}

T_ShaderManager::T_Program_& T_ShaderManager::initProgramRecord(
		T_String const& name )
{
	const uint32_t index( newProgramRecord( ) );
	auto& program( programs_[ index ] );
	programIndex_.add( name , index );
	program.name = name;
	program.id = 0;
	initProgram( program );

	T_StringBuilder sb;
	for ( auto const& e : program.code.errors ) {
		sb << e.source << ':' << e.line << ": "
			<< e.error << '\n';
	}
	sb << '\0';
	printf( "%s" , sb.data( ) );

	return program;
}


T_ShaderInput const* T_ShaderManager::getInput(
		T_String const& name )
{
	auto const* const existing( inputs_.get( name ) );
	if ( existing ) {
		return existing->get( );
	}

	T_ShaderInput ni;
	T_StringBuilder sb;
	sb << "shaders/" << name;
	if ( !ni.load( sb ) ) {
		return nullptr;
	}
	inputs_.add( name , NewOwned< T_ShaderInput >( std::move( ni ) ) );
	return inputs_.get( name )->get( );
}


void T_ShaderManager::dereferencePipeline(
		T_String const& id )
{
	auto& pipeline( *pipelines_.get( id ) );
	assert( pipeline.references > 0 );
	pipeline.references --;
	if ( pipeline.references > 0 ) {
		return;
	}

	if ( pipeline.id != 0 ) {
		glDeleteProgramPipelines( 1 , &pipeline.id );
		pipeline.id = 0;
	}

	for ( auto const& pName : pipeline.programs ) {
		auto const* pos( programIndex_.get( pName ) );
		assert( pos );
		dereferenceProgram( *pos , id );
	}

	pipelines_.remove( pipeline.idString );
}


void T_ShaderManager::dereferenceProgram(
		const uint32_t index ,
		T_String const& pipeline )
{
	auto& program( programs_[ index ] );
	auto& refs( program.plReferences );
	const auto plidx( refs.indexOf( pipeline ) );
	assert( plidx >= 0 );
	refs.remove( plidx );
	if ( !refs.empty( ) || program.saReferences ) {
		return;
	}
	resetProgram( program );
	programIndex_.remove( program.name );
}


void T_ShaderManager::dereferenceProgram(
		const uint32_t index )
{
	auto& program( programs_[ index ] );
	assert( program.saReferences > 0 );
	program.saReferences --;
	if ( program.saReferences || !program.plReferences.empty( ) ) {
		return;
	}
	resetProgram( program );
	programIndex_.remove( program.name );
}


void T_ShaderManager::initPipeline(
		T_Pipeline_& pipeline ) const
{
	assert( pipeline.id == 0 );

	printf( "init pipeline %s\n" , pipeline.idString.toOSString( ).data( ) );
	constexpr auto nst{ size_t( E_ShaderType::__COUNT__ ) };
	int32_t programs[ nst ];
	for ( auto i = 0u ; i < nst ; i ++ ) {
		programs[ i ] = -1;
	}

	for ( auto const& pName : pipeline.programs ) {
		const uint32_t pid( *programIndex_.get( pName ) );
		auto const& program( programs_[ pid ] );
		if ( programs[ int( program.code.type ) ] != -1
				|| program.id == 0 ) {
			printf( "... failed\n" );
			return;
		}
		programs[ int( program.code.type ) ] = pid;
	}

	GLuint id( 0 );
	GL_CHECK( {} );
	glGenProgramPipelines( 1 , &id );
	GL_CHECK( return );
	for ( auto i = 0u ; i < nst ; i ++ ) {
		const auto pid( programs[ i ] );
		if ( pid == -1 ) {
			continue;
		}
		auto& program( programs_[ pid ] );
		const GLbitfield type( PipelineStages_[ int( program.code.type ) ] );
		glUseProgramStages( id , type , program.id );
	}
	GL_CHECK({
		glDeleteProgramPipelines( 1 , &id );
		printf( "... failed\n" );
		return;
	});

	pipeline.id = id;
	printf( "... success\n" );
}


void T_ShaderManager::initProgram(
		T_Program_& program )
{
	assert( program.id == 0 );

	// Build the code
	auto name( program.name );
	printf( "init program %s\n" , program.name.toOSString( ).data( ) );
	auto& code( program.code );
	T_CodeBuilder_ cb( [this]( T_String const& n ) { return getInput( n ); } ,
			name , code );
	const bool built(
			T_CodeBuilder_{
				[this]( T_String const& n ) { return getInput( n ); } ,
				program.name , code
			}.buildCode( ) );

	// Initialise file watcher + missing files
	program.watch = T_WatchedFiles{ Globals::Watcher( ) ,
			[this,name]() {
				programUpdated( name );
			} };
	const auto nf( code.files.size( ) );
	auto& w( *( program.watch.target( ) ) );
	for ( auto i = 0u ; i < nf ; i ++ ) {
		T_String const& fn( code.files.keys( )[ i ] );
		if ( code.files.values( )[ i ] ) {
			T_StringBuilder sb;
			sb << "shaders/" << fn;
			w.watch( std::move( sb ) );
		} else {
			auto& mset( missing_.getOrCreate( fn ) );
			if ( !mset.contains( name ) ) {
				mset.add( name );
			}
		}
	}

	if ( !( built && code.errors.empty( ) ) ) {
		return;
	}

	// Try to compile the program
	char const* const list[] = {
		program.code.code.data( )
	};
	const GLenum sid = glCreateShaderProgramv(
			ProgramTypes_[ int( code.type ) ] ,
			1 , &list[ 0 ] );
	if ( sid == 0 ) {
		code.errors.addNew( name , 0 , "failed to create GL program" );
		return;
	}

	// Read and convert the log
	int infoLogLength( 0 );
	glGetProgramiv( sid , GL_INFO_LOG_LENGTH , &infoLogLength );
	if ( infoLogLength ) {
		char buffer[ infoLogLength + 1 ];
		glGetProgramInfoLog( sid , infoLogLength , nullptr , buffer );
		char* start( buffer );
		char* found( strchr( buffer , '\n' ) );
		while ( found ) {
			*found = 0;
			parseGLSLError( code , start );
			start = found + 1;
			found = strchr( start , '\n' );
		}
		if ( start < &buffer[ infoLogLength - 1 ] ) {
			parseGLSLError( code , start );
		}
	}

	// Did it link?
	GLint lnk( 0 );
	glGetProgramiv( sid , GL_LINK_STATUS , &lnk );
	if ( lnk ) {
		program.id = sid;
		printf( "... success\n" );
	} else {
		glDeleteProgram( sid );
	}
}

void T_ShaderManager::parseGLSLError(
		T_ShaderCode& code ,
		char const* errorLine )
{
	assert( !code.sources.empty( ) );

	std::cmatch m;
	uint32_t rawLine;
	if ( std::regex_match( errorLine , m , GLSLErrorNv_ ) ) {
		rawLine = atoi( m[ 1 ].str( ).c_str( ) );
	} else {
		rawLine = 0;
	}

	uint32_t check = 0 , pos = 0;
	while ( pos < code.starts.size( ) && check < rawLine ) {
		check += code.counts[ pos ];
		pos ++;
	}

	code.errors.addNew(
			pos == 0 ? "*unknown*" : ((char*)code.sources[ pos - 1 ].toOSString( ).data( ) ) ,
			pos == 0 ? 0 : ( rawLine + code.counts[ pos - 1 ] - check + code.starts[ pos - 1 ] ) ,
			errorLine );
}

void T_ShaderManager::programUpdated(
		T_String const& name )
{
	if ( !updates_.contains( name ) ) {
		updates_.add( name );
	}
}

void T_ShaderManager::resetProgram(
		T_Program_& program )
{
	if ( program.watch ) {
		program.watch->clear( );
	}
	if ( program.id != 0 ) {
		glDeleteProgram( program.id );
		program.id = 0;
		return;
	}

	auto const& files( program.code.files );
	const auto nf( files.size( ) );
	for ( auto i = 0u ; i < nf ; i ++ ) {
		T_String const& k{ files.keys( )[ i ] };
		bool v{ files[ i ] };
		auto* const ptr( missing_.get( k ) );
		if ( v || !ptr ) {
			continue;
		}
		auto& set( *ptr );
		const auto index( set.indexOf( program.name ) );
		if ( index != -1 ) {
			set.removeSwap( index );
			if ( set.empty( ) ) {
				missing_.remove( k );
			}
		}
	}
}

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

void T_ShaderManager::makeUI( )
{
	if ( !uiEnabled_ ) {
		return;
	}

	using namespace ImGui;
	auto const& dspSize( GetIO( ).DisplaySize );
	SetNextWindowSize( ImVec2( dspSize.x , 150 ) , ImGuiSetCond_Appearing );
	SetNextWindowPos( ImVec2( 0 , dspSize.y - 150 ) , ImGuiSetCond_Appearing );
	Begin( "Shaders" , &uiEnabled_ , ImGuiWindowFlags_NoCollapse );

	const auto n( std::count_if( programs_.begin( ) , programs_.end( ) ,
			[]( auto const& p ) {
				return !p.plReferences.empty( ) || p.saReferences != 0;
			} ) );

	std::vector< size_t > indices;
	const auto rn = programs_.size( );
	for ( auto i = 0u ; i < rn ; i ++ ) {
		auto const& p( programs_[ i ] );
		if ( !p.plReferences.empty( ) || p.saReferences ) {
			indices.push_back( i );
		}
	}
	std::sort( indices.begin( ) , indices.end( ) ,
		[this]( size_t a , size_t b ) {
			auto const& pa( programs_[ a ] );
			auto const& pb( programs_[ b ] );
			if ( pa.code.errors.size( ) != pb.code.errors.size( ) ) {
				return pa.code.errors.size( ) > pb.code.errors.size( );
			}
			if ( pa.plReferences.size( ) != pb.plReferences.size( ) ) {
				return pa.plReferences.size( ) > pb.plReferences.size( );
			}
			return programs_[ a ].name < programs_[ b ].name;
		} );

	for ( auto i = 0u ; i < n ; i ++ ) {
		auto const& program( programs_[ indices[ i ] ] );
		const auto nErrors( program.code.errors.size( ) );

		const bool open( nErrors
				? TreeNodeEx( &program , ImGuiTreeNodeFlags_OpenOnArrow
						| ImGuiTreeNodeFlags_OpenOnDoubleClick , "%s" ,
					program.name.toOSString( ).data( ) )
				: false );

		if ( !nErrors ) {
			Text( "%s" , program.name.toOSString( ).data( ) );
		}

		SameLine( 400 );
		Text( "Usage: %u" , program.plReferences.size( ) + program.saReferences );
		SameLine( 550 );
		if ( program.code.errors.empty( ) ) {
			PushStyleColor( ImGuiCol_Text , ImVec4( .6 , 1 , .6 , 1 ) );
			Text( "No errors" );
		} else {
			PushStyleColor( ImGuiCol_Text , ImVec4( 1 , .6 , .6 , 1 ) );
			Text( "%u error%s" , nErrors , nErrors > 1 ? "s" : "" );
		}
		PopStyleColor( );

		if ( open ) {
			for ( auto const& err : program.code.errors ) {
				NewLine( );
				SameLine( 50 );
				Text( "%s" , err.source.toOSString( ).data( ) );
				SameLine( 250 );
				Text( "line %d" , err.line );
				SameLine( 370 );
				Text( "%s" , err.error.toOSString( ).data( ) );
			}
			TreePop( );
		}
	}

	End( );
}