/**
 * Relational pipes
 * Copyright © 2019 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, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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 <string>
#include <vector>
#include <iostream>
#include <sstream>
#include <locale>
#include <codecvt>
#include <regex>

#include <unistd.h>
#include <wait.h>
#include <ext/stdio_filebuf.h>

#include <relpipe/reader/typedefs.h>
#include <relpipe/reader/TypeId.h>
#include <relpipe/reader/handlers/RelationalReaderStringHandler.h>
#include <relpipe/reader/handlers/AttributeMetadata.h>

#include <relpipe/writer/Factory.h>

#include <relpipe/cli/RelpipeCLIException.h>

#include "Configuration.h"

namespace relpipe {
namespace tr {
namespace awk {

using namespace std;
using namespace relpipe;
using namespace relpipe::reader;
using namespace relpipe::reader::handlers;

/**
 * This transformation consists of three processes connected together using pipes.
 * 
 * Processes:
 *	- Parent: process RelationalReaderStringHandler events (read relational data, usually from STDIN) and pass them in the special text format to the pipe1
 *  - AWK: external program (/usr/bin/awk), read from the pipe1, writes to the pipe2
 *  - Writer: reads from the pipe2 and writes to relationalWriter (relational data, usually to STDOUT)
 */
class AwkHandler : public RelationalReaderStringHandler {
private:
	Configuration configuration;
	writer::RelationalWriter* relationalWriter;
	std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings

	int awkInputWriterFD = -1;
	std::vector<AttributeMetadata> currentReaderMetadata;
	integer_t currentAttributeIndex = 0;

	void createPipe(int& readerFD, int& writerFD) {
		int fds[2];
		int result = pipe(fds);
		readerFD = fds[0];
		writerFD = fds[1];
		if (result < 0) throw cli::RelpipeCLIException(L"Unable to create a pipe.", cli::CLI::EXIT_CODE_UNEXPECTED_ERROR); // TODO: better exceptions?
	}

	void redirectFD(int oldfd, int newfd) {
		int result = dup2(oldfd, newfd);
		if (result < 0) throw cli::RelpipeCLIException(L"Unable redirect FD.", cli::CLI::EXIT_CODE_UNEXPECTED_ERROR); // TODO: better exceptions?
	}

	void closeOrThrow(int fd) {
		int error = close(fd);
		if (error) throw cli::RelpipeCLIException(L"Unable to close FD: " + to_wstring(fd) + L" from PID: " + to_wstring(getpid()), cli::CLI::EXIT_CODE_UNEXPECTED_ERROR); // TODO: better exceptions?
	}

	void execp(const std::vector<std::string>& args) {
		const char** a = new const char*[args.size() + 1];
		for (size_t i = 0; i < args.size(); i++) a[i] = args[i].c_str();
		a[args.size()] = nullptr;

		execvp(a[0], (char*const*) a);

		delete[] a;
		throw cli::RelpipeCLIException(L"Unable to do execvp().", cli::CLI::EXIT_CODE_UNEXPECTED_ERROR); // TODO: better exceptions?
	}

	void cleanUp() {
		if (awkInputWriterFD >= 0) {
			closeOrThrow(awkInputWriterFD);
			// TODO: check exit codes
			__pid_t waitResult1 = wait(NULL);
			__pid_t waitResult2 = wait(NULL);
			awkInputWriterFD = -1;
		}

		currentAttributeIndex = 0;
		currentReaderMetadata.clear();
	}

	string_t a2v(const string_t& attributeName) {
		// FIXME: escape reserved names; prefix with _ ?
		// cat awkgram.y | awk -v FS='\\{"|",' -v ORS='|' '/static const struct token tokentab/, /\};/ { if (/^\{/) { print $2} }'
		// BEGIN|BEGINFILE|END|ENDFILE|adump|and|asort|asorti|atan2|bindtextdomain|break|case|close|compl|continue|cos|dcgettext|dcngettext|default|delete|do|else|eval|exit|exp|fflush|for|func|function|gensub|getline|gsub|if|in|include|index|int|intdiv0|isarray|length|load|log|lshift|match|mktime|namespace|next|nextfile|or|patsplit|print|printf|rand|return|rshift|sin|split|sprintf|sqrt|srand|stopme|strftime|strtonum|sub|substr|switch|system|systime|tolower|toupper|typeof|while|xor
		return attributeName;
	}

	string_t escapeAwkValue(const string_t& value) {
		// FIXME: escape field and record separators
		return value;
	}

public:

	AwkHandler(writer::RelationalWriter* relationalWriter, Configuration& configuration) : relationalWriter(relationalWriter), configuration(configuration) {
	}

	void startRelation(string_t name, vector<AttributeMetadata> attributes) override {
		cleanUp();

		currentReaderMetadata = attributes;

		int awkInputReaderFD;
		int awkOutputReaderFD;
		int awkOutputWriterFD;

		createPipe(awkInputReaderFD, awkInputWriterFD);
		createPipe(awkOutputReaderFD, awkOutputWriterFD);

		__pid_t awkPid = fork();

		if (awkPid < 0) {
			throw cli::RelpipeCLIException(L"Unable to fork AWK process.", cli::CLI::EXIT_CODE_UNEXPECTED_ERROR); // TODO: better exceptions?
		} else if (awkPid == 0) {
			// AWK child process
			closeOrThrow(awkInputWriterFD);
			closeOrThrow(awkOutputReaderFD);

			redirectFD(awkInputReaderFD, STDIN_FILENO);
			redirectFD(awkOutputWriterFD, STDOUT_FILENO);

			std::wstringstream awkScript;
			awkScript << L"BEGIN {" << std::endl;
			awkScript << L"FS=\"\\t\";" << std::endl;
			awkScript << L"};" << std::endl;

			awkScript << L"END {" << std::endl;
			// awkScript << … << std::endl;
			awkScript << L"};" << std::endl;

			awkScript << L"{print \"AWK says: line \" NR \" '\" $0 \"' has \" NF \" fields; first field is '\" $1 \"'\";}" << std::endl;

			std::vector<std::string> args;
			args.push_back("awk");
			args.push_back(convertor.to_bytes(awkScript.str()));

			// Runs AWK program found on $PATH → user can plug-in a custom implementation or a wrapper, but this can be also bit dangerous (however AWK itself is dangerous).
			execp(args);
		} else {
			// Parent process
			closeOrThrow(awkInputReaderFD);
			closeOrThrow(awkOutputWriterFD);

			__pid_t writerPid = fork();

			if (writerPid < 0) {
				throw cli::RelpipeCLIException(L"Unable to fork Writer process.", cli::CLI::EXIT_CODE_UNEXPECTED_ERROR); // TODO: better exceptions?
			} else if (writerPid == 0) {
				// Writer child process
				closeOrThrow(awkInputWriterFD);

				locale::global(locale("")); // needed for processing unicode texts, otherwise getline() stopped working on first line with non-ascii characters; TODO: move somewhere else?

				__gnu_cxx::stdio_filebuf<wchar_t> awkOutputReaderBuffer(awkOutputReaderFD, std::ios::in);
				std::wistream awkOutputReader(&awkOutputReaderBuffer);

				relationalWriter->startRelation(L"writer_debug",{
					{L"message", writer::TypeId::STRING},
				}, true);

				for (string_t line; getline(awkOutputReader, line).good();) {
					relationalWriter->writeAttribute(line);
				}

				closeOrThrow(awkOutputReaderFD);
				exit(0);
			} else {
				// Parent process
				closeOrThrow(awkOutputReaderFD);
			}
		}

	}

	void attribute(const string_t& value) override {
		string_t variableName = a2v(currentReaderMetadata[currentAttributeIndex].getAttributeName());
		string_t variableValue = escapeAwkValue(value);

		currentAttributeIndex++;
		currentAttributeIndex = currentAttributeIndex % currentReaderMetadata.size();

		// TODO: just the value – move name to the AWK function
		std::string variablePair = convertor.to_bytes(variableName + L"=" + variableValue);

		if (currentAttributeIndex == 0) variablePair += "\n";
		else variablePair += "\t";

		write(awkInputWriterFD, variablePair.c_str(), variablePair.length());

	}

	void endOfPipe() {
		cleanUp();
	}

};

}
}
}