/**
 * Relational pipes
 * Copyright © 2020 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 <sstream>
#include <codecvt>
#include <arpa/inet.h>

#include "UnescapingProcessor.h"

using namespace std;
using namespace relpipe::writer;

namespace relpipe {
namespace in {
namespace ini {
namespace lib {

/**
 * Should work according to <https://docs.oracle.com/javase/specs/jls/se15/html/jls-3.html#jls-3.3> 3.3. Unicode Escapes 
 */
class JavaPropertiesUnescapingProcessor : public UnescapingProcessor {
private:
	wstring_convert < codecvt_utf8<wchar_t>> convertor; // INI parser works with UTF-8

	bool readHex(const char* hexadecimal, size_t hexLength, uint8_t* resultBuffer, size_t binLength) {
		if (hexLength != binLength * 2) return false;

		for (size_t i = 0; i < binLength; i++) {
			uint8_t value = 0;
			char a = hexadecimal[i * 2];
			char b = hexadecimal[i * 2 + 1];

			if (a >= '0' && a <= '9') value += (a - '0')*16;
			else if (a >= 'a' && a <= 'f') value += (a - 'a' + 10)*16;
			else if (a >= 'A' && a <= 'F') value += (a - 'A' + 10)*16;
			else return false;

			if (b >= '0' && b <= '9') value += b - '0';
			else if (b >= 'a' && b <= 'f') value += b - 'a' + 10;
			else if (b >= 'A' && b <= 'F') value += b - 'A' + 10;
			else return false;

			if (resultBuffer) resultBuffer[i] = value;
		}
		return true;
	}

public:
	
	std::string unescape(const std::string& s, const TextType type) override {
		std::stringstream result;
		for (int i = 0, length = s.size(); i < length; i++) {
			char ch = s[i];
			if (i + 1 < length && ch == ESC) {
				ch = s[i + 1];
				if (ch == 'u') {
					// TODO: simplify, clean-up, verify (but seems working)
					i++;
					int hexLength = 4;
					if (i + hexLength < length) {
						uint16_t u16;
						bool hexOK = readHex(s.c_str() + i + 1, hexLength, (uint8_t*) & u16, sizeof (u16));
						if (hexOK) result << convertor.to_bytes(ntohs(u16));
						else throw std::logic_error(std::string("Invalid unicode escape sequence: invalid HEX"));
						i += hexLength;
					} else {
						throw std::logic_error(std::string("Invalid unicode escape sequence: missing characters"));
					}

				} else if (ch == ESC) put(result, ESC, i).put(ESC); // copy and skip even the second \ to avoid its misinterpretation in the next cycle
				else result.put(ESC); // keep the escape sequence for later unescaping phase
			} else if (ch == ESC) {
				throw std::logic_error(std::string("Missing escape sequence")); // this should not happen
			} else {
				result.put(ch);
			}
		}
		return result.str();
	}

};

}
}
}
}