int index( char c ) {
		for ( size_t ii = 0; ii < AVAILABLE_CHARS.size( ); ii++ ) {
			if ( AVAILABLE_CHARS [ ii ] == c ) {
				// std::cout << ii << " " << c << std::endl;
				return ii;
			}
		}
		return -1;
	}

	std::string extend_key( std::string& msg, std::string& key ) {
		//generating new key
		int msgLen = msg.size( );
		std::string newKey( msgLen, 'x' );
		int keyLen = key.size( ), i, j;
		for ( i = 0, j = 0; i < msgLen; ++i, ++j ) {
			if ( j == keyLen )
				j = 0;

			newKey [ i ] = key [ j ];
		}
		newKey [ i ] = '\0';
		return newKey;
	}

	std::string encrypt_vigenere( std::string& msg, std::string& key ) {
		int msgLen = msg.size( ), keyLen = key.size( ), i;
		std::string encryptedMsg( msgLen, 'x' );
		// char newKey[msgLen], encryptedMsg[msgLen], decryptedMsg[msgLen];

		std::string newKey = extend_key( msg, key );

		//encryption
		for ( i = 0; i < msgLen; ++i ) {
			// std::cout << msg[i] << " " << isalnum(msg[i]) << std::endl;
			if ( isalnum( msg [ i ] ) || msg [ i ] == ' ' ) {
				encryptedMsg [ i ] = AVAILABLE_CHARS [ ( ( index( msg [ i ] ) + index( newKey [ i ] ) ) % AVAILABLE_CHARS.size( ) ) ];
			}
			else {
				encryptedMsg [ i ] = msg [ i ];
			}
		}

		encryptedMsg [ i ] = '\0';
		return encryptedMsg;
	}

	std::string decrypt_vigenere( std::string& encryptedMsg, std::string& newKey ) {
		// decryption
		int msgLen = encryptedMsg.size( );
		std::string decryptedMsg( msgLen, 'x' );
		int i;
		for ( i = 0; i < msgLen; ++i ) {
			if ( isalnum( encryptedMsg [ i ] ) || encryptedMsg [ i ] == ' ' ) {
				decryptedMsg [ i ] = AVAILABLE_CHARS [ ( ( ( index( encryptedMsg [ i ] ) - index( newKey [ i ] ) ) + AVAILABLE_CHARS.size( ) ) % AVAILABLE_CHARS.size( ) ) ];
			}
			else {
				decryptedMsg [ i ] = encryptedMsg [ i ];
			}
		}
		decryptedMsg [ i ] = '\0';
		return decryptedMsg;
	}