/**

 * 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 <memory>

#include <vector>

#include <array>

#include <sstream>

#include "ASN1Reader.h"

namespace relpipe {

namespace in {

namespace asn1 {

namespace lib {

/**

 * Reads ASN.1 data encoded as BER (DER, CER).

 */

class BasicASN1Reader : public ASN1Reader {

private:

	bool started = false;

	enum class TagClass : uint8_t {

		Universal = 0,

		Application = 1,

		ContextSpecific = 2,

		Private = 3

	};

	enum class PC : uint8_t {

		Primitive = 0,

		Constructed = 1

	};

	class Header {

	public:

		TagClass tagClass;

		PC pc;

		uint64_t tag;

		bool definiteLength;

		size_t length;

	};

	class LevelMetadata {

	public:

		bool definiteLength;

		size_t length;

		size_t start;

	};

	std::vector<LevelMetadata> level;

	void checkRemainingItems() {

		if (level.size()) {

			LevelMetadata& l = level.back();

			if (l.definiteLength && l.length == getBytesRead() - l.start) {

				level.pop_back();

				handlers.writeCollectionEnd();

				checkRemainingItems(); // multiple collections may end at the same point

			}

		}

	}

	Header readHeader() {

		Header h;

		memset(&h, 0, sizeof (h)); // TODO: remove, not needed

		uint8_t tagByte;

		read(&tagByte, 1);

		h.tagClass = (TagClass) (tagByte >> 6);

		h.pc = (PC) ((tagByte >> 5) & 1);

		h.tag = tagByte & (0xFF >> 3);

		if (h.tag == 31) { // all five tag bits are set → tag number (greater than 30) is encoded in following octets

			h.tag = 0;

			uint8_t moreTag = 0;

			do {

				read(&moreTag, 1);

				h.tag = h.tag << 7 | (moreTag & (0xFF >> 1));

			} while (moreTag & (1 << 7));

		}

		uint8_t lengthByte;

		read(&lengthByte, 1);

		if (lengthByte >> 7 == 0) {

			// definite short

			h.definiteLength = true;

			h.length = lengthByte;

		} else if (lengthByte == 0b10000000) {

			// indefinite

			h.definiteLength = false;

			h.length = 0;

		} else if (lengthByte == 0xFF) {

			throw relpipe::writer::RelpipeWriterException(L"ASN.1 lengthByte == 0xFF (reserved value)"); // TODO: better exception

		} else {

			// definite long

			h.definiteLength = true;

			h.length = 0;

			std::vector<uint8_t> lengthBytes(lengthByte & 0b01111111, 0);

			read(lengthBytes.data(), lengthBytes.size());

			for (uint8_t l : lengthBytes) h.length = (h.length << 8) + l;

		}

		return h;

	}

	void readNext() {

		checkRemainingItems();

		Header typeHeader = readHeader();

		// commit(); // TODO: commit here and recover later instead of rollback?

		if (!started) {

			handlers.writeStreamStart();

			started = true;

		}

		// TODO: check tagClass and pc

		// TODO: constants, more types

		if (typeHeader.tag == 0 && typeHeader.tagClass == TagClass::Universal && typeHeader.pc == PC::Primitive) {

			handlers.writeCollectionEnd();

		} else if (typeHeader.tag == 16) {

			level.push_back({typeHeader.definiteLength, typeHeader.length, getBytesRead()}); // TODO: transaction

			handlers.writeCollectionStart(ASN1ContentHandler::CollectionType::Sequence);

		} else if (typeHeader.tag == 17) {

			level.push_back({typeHeader.definiteLength, typeHeader.length, getBytesRead()}); // TODO: transaction

			handlers.writeCollectionStart(ASN1ContentHandler::CollectionType::Set);

		} else if (typeHeader.pc == PC::Constructed) {

			level.push_back({typeHeader.definiteLength, typeHeader.length, getBytesRead()}); // TODO: transaction

			handlers.writeCollectionStart(ASN1ContentHandler::CollectionType::Constructed);

		} else if (typeHeader.tag == 5 && typeHeader.length == 0) {

			handlers.writeNull();

		} else if (typeHeader.tag == 1) {

			bool value;

			read((uint8_t*) & value, 1);

			handlers.writeBoolean(value);

		} else if (typeHeader.tag == 2 && typeHeader.tagClass == TagClass::Universal && typeHeader.definiteLength) {

			// TODO: check available bytes before allocating buffer

			std::vector<uint8_t> value(typeHeader.length, 0x00);

			read(value.data(), typeHeader.length);

			handlers.writeInteger(ASN1ContentHandler::Integer(value));

		} else if (typeHeader.tag == 12 && typeHeader.tagClass == TagClass::Universal && typeHeader.definiteLength) {

			// TODO: check available bytes before allocating buffer

			std::string s;

			s.resize(typeHeader.length);

			read((uint8_t*) s.data(), typeHeader.length);

			handlers.writeString(ASN1ContentHandler::StringType::UTF8String, s);

		} else if (typeHeader.tag == 19 && typeHeader.tagClass == TagClass::Universal && typeHeader.definiteLength) {

			// TODO: check encoding

			// TODO: check available bytes before allocating buffer

			std::string s;

			s.resize(typeHeader.length);

			read((uint8_t*) s.data(), typeHeader.length);

			handlers.writeString(ASN1ContentHandler::StringType::PrintableString, s);

		} else {

			// TODO: do not skip, parse

			std::vector<uint8_t> temp(typeHeader.length, 0);

			read(temp.data(), typeHeader.length);

			// TODO: recover transaction?

			std::stringstream description;

			description << "value:"

					<< " tag = " << typeHeader.tag

					<< " tagClass = " << (int) typeHeader.tagClass

					<< " pc = " << (int) typeHeader.pc

					<< " length = " << typeHeader.length

					<< " definite = " << (typeHeader.definiteLength ? "true" : "false");

			handlers.writeString(ASN1ContentHandler::StringType::UTF8String, description.str());

		}

		commit();

	}

protected:

	void update() override {

		while (true) readNext();

	}

public:

	void close() override {

		checkRemainingItems();

		// TODO: check the bytes remaining in the buffer

		if (started) handlers.writeStreamEnd();

	}

};

}

}

}

}