/**

 * Relational pipes

 * Copyright © 2021 František Kučera (Frantovo.cz, GlobalCode.info)

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, version 3 of the License.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program. If not, see <http://www.gnu.org/licenses/>.

 */

#pragma once

#include <cstring>

#include <cstdint>

namespace relpipe {

namespace in {

namespace asn1 {

namespace lib {

class AbstractParserImpl;

/**

 * Event-driven parser that consumes sequence of byte buffers (chunked stream)

 * and produces some output (implementation specific).

 * 

 * The flow is controlled from outside: incomming data pieces are passed to the parser through the write() method as they come.

 * 

 * From the child class perspective (implementation of particular parser)

 * data pieces are obtained through the read() method from the internal buffer maintained by AbstractParser.

 */

class AbstractParser {

private:

	friend AbstractParserImpl;

	AbstractParserImpl* implementation;

	void rollback();

public:

	virtual ~AbstractParser();

	/**

	 * Submit a part of incomming data to the parser.

	 * When possible, such data are usually processed synchronously during this method call.

	 * If not (incomplete TLV/AVP/PDU/token/etc.) this part is appended to the internal buffer maintained by AbstractParser

	 * and processed in some next cycle or – in worst case – during the close() call.

	 * 

	 * @param buffer readable memory

	 * @param length size of the buffer

	 */

	void write(const uint8_t* buffer, const size_t length);

	/**

	 * Finalize the parsing process.

	 * After calling this method, all data from AbstractParser buffers should be consumed, parsed and results published.

	 * No write() call is expected after close() and would fail.

	 * However the parser object remains valid and may be used to get some auxiliary information (if supperted by given implementation).

	 */

	virtual void close();

protected:

	AbstractParser();

	/**

	 * May be thrown from the update() method in order to cancel currenty cycle and do explicit rollback.

	 * Same data will be processed in the next cycle.

	 */

	class ExplicitRollbackException {

		// TODO: common super-class for exceptions, hidden implementation

	};

	/**

	 * May be called from the update() method in order to explicitly confirm that read data was successfully processed.

	 * Such data will not be processed again during the next cycle (even if ReadBufferUnderflowException occurs later in this cycle).

	 * Explicit commit() call is useful when we did some demanding work (so we are not willing to do it again in case of ReadBufferUnderflowException);

	 * and is necessary when we already published some outputs or did other non-idempotent operation or caused some other significant side effects.

	 * If there is no commit() called and update() just finishes, commit() is called implicitly.

	 * 

	 * Note: There is no accessible rollback() method – throw ExplicitRollbackException instead.

	 */

	void commit();

	/**

	 * Fill the buffer with incomming data of given length (exactly).

	 * 

	 * If there are not enough data available, ReadBufferUnderflowException is thrown.

	 * This exception should not be caught in the child class – it should propagate back to the AbstractParser

	 * where it causes rollback(). In such case, the same data will be available during next update() cycle.

	 * 

	 * @param buffer writable memory

	 * @param length size of the buffer

	 */

	void read(uint8_t* buffer, const size_t length);

	/**

	 * Like read(), but does not update the marks (buffer positions), so it can be called again and again with same result.

	 * 

	 * @param buffer writable memory

	 * @param length size of the buffer

	 */

	void peek(uint8_t* buffer, const size_t length);

	/**

	 * @return total number of bytes that were successfully read

	 */

	size_t getBytesRead();

	/**

	 * Reads input from buffers using read(), parses data and usually emits the result (e.g. to a handler/listener).

	 * Is specific for particular format/parser.

	 * 

	 * This method is called at least once at the end of the stream (with whole stream content in read buffers).

	 * Usually it is called more often, by default: after each write (with just already received data part in read buffers).

	 */

	virtual void update() = 0;

};

}

}

}

}