/**
 * 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 <string>
#include <exception>
#include <cstring>

#include "AbstractParser.h"

namespace relpipe {
namespace in {
namespace asn1 {
namespace lib {

class TransactionalBuffer {
private:
	uint8_t* buffer;
	size_t bufferSize;
	bool hasData = false;
	size_t writePosition = 0;
	// size_t writePositionCommited = 0; // TODO: transactions also on the writing side?
	size_t readPosition = 0;
	size_t readPositionCommited = 0;

	size_t bytesRead = 0;
	size_t bytesReadCommited = 0;

	size_t availableForReading() {
		if (readPosition < writePosition) return writePosition - readPosition;
		else if (readPosition > writePosition) return bufferSize - readPosition + writePosition;
		else if (hasData) return bufferSize;
		else return 0;
	}

	size_t availableForWriting() {
		if (readPositionCommited < writePosition) return bufferSize - writePosition + readPositionCommited;
		else if (readPositionCommited > writePosition) return readPositionCommited - writePosition;
		else if (hasData) return 0;
		else return bufferSize;
	}

public:

	/**
	 * Is thrown from read() and peak() methods if there are not enough data.
	 * Interrupts current update() cycle and causes rollback.
	 */
	class ReadBufferUnderflowException {
		// TODO: common super-class for exceptions, hidden implementation
	};

	/**
	 * Is thrown from write() method of the buffer when there is not enough space.
	 * Interrupts whole process.
	 */
	class WriteBufferOverflowException {
	};

	TransactionalBuffer(size_t initialSize = 4096) : bufferSize(initialSize) {
		// TODO: initial size + resize + hard upper limit
		buffer = (uint8_t*) malloc(bufferSize);
	}

	virtual ~TransactionalBuffer() {
		free(buffer);
	}

	void write(const uint8_t* inputBuffer, const size_t length) {
		if (length == 0) return;
		if (length > availableForWriting()) throw WriteBufferOverflowException(); // TODO: optional resize

		hasData = true;

		const size_t a = std::min(length, bufferSize - writePosition);
		const size_t b = length - a;

		// TODO: map buffer twice in the memory in order to create a continuous area and avoid the second memcpy()?
		memcpy(buffer + writePosition, inputBuffer, a);
		memcpy(buffer, inputBuffer + a, b);

		writePosition = (writePosition + length) % bufferSize;
	}

	void read(uint8_t* outputBuffer, const size_t length) {
		if (length == 0) return;

		peek(outputBuffer, length);
		readPosition = (readPosition + length) % bufferSize;
		hasData = readPosition != writePosition;
		bytesRead += length;
	}

	void peek(uint8_t* outputBuffer, const size_t length) {
		if (length == 0) return;
		if (length > availableForReading()) throw ReadBufferUnderflowException();

		const size_t a = std::min(length, bufferSize - readPosition);
		const size_t b = length - a;

		memcpy(outputBuffer, buffer + readPosition, a);
		memcpy(outputBuffer + a, buffer, b);
	}

	void commitRead() {
		readPositionCommited = readPosition;
		bytesReadCommited = bytesRead;
	}

	void rollbackRead() {
		readPosition = readPositionCommited;
		bytesRead = bytesReadCommited;
	}

	size_t getBytesRead() {
		return bytesRead;
	}

};


}
}
}
}