#include "ConfigFile.h"

#include <iostream>
#include <algorithm>

namespace Config::Hydrogen  ::detail::  ConfigFile_m
{
	namespace
	{
		struct EoF {};

		std::string
		readLine( std::istream &input )
		{
			std::string rv;
			std::getline( input, rv );
			if( not input ) throw EoF{};

			// SStrip trailing '#' comments...
			const auto endComment= std::find( begin( rv ), end( rv ), '#' );
			rv.erase( endComment, end( rv ) );
			return rv;
		}

		std::string
		trimWhitespace( std::string s )
		{
			// Trim from the front
			std::reverse( begin( s ), end( s ) );
			while( not s.empty() and s.back() == ' ' ) s.pop_back();

			// Trim from the back
			std::reverse( begin( s ), end( s ) );
			while( not s.empty() and s.back() == ' ' ) s.pop_back();

			return s;
		}

		auto
		parseLine( const std::string &line )
		{
			const auto split= std::find( begin( line ), end( line ), '=' );
			if( split == end( line ) ) throw std::runtime_error{ "Unable to parse configuration line: `" + line + "`" };
			const auto key= trimWhitespace( { begin( line ), split } );
			const auto value= trimWhitespace( { split + 1, end( line ) } );

			return std::tuple{ key, value };
		}
	}

	ConfigFile::ConfigFile( std::istream &&input, const std::map< std::string, std::string > &schema )
		: config( schema )
	{
		while( input )
		try
		{
			const std::string line= trimWhitespace( readLine( input ) );
			if( line.empty() ) continue; // Skip blank lines.
			
			const auto [ key, value ]= parseLine( line );

			if( not schema.contains( key ) )
			{
				std::cerr << "Unrecognized key in config file: `" << key << "`" << std::endl;
				continue;
			}

			config.at( key )= value;
		}
		catch( const EoF & ) { break; }

		std::cerr << "Configuration parsed:" << std::endl;
		for( const auto &[ key, value ]: config )
		{
			std::cerr << key << " = " << value << std::endl;
		}
	}

	std::string
	ConfigFile::get( const std::string &name ) const
	{
		return config.at( name );
	}
}