/**

 * 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<functional>

#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::function<void() > relationalWriterFlush;

	std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings

	int awkInputWriterFD = -1;

	RelationConfiguration* currentRelationConfiguration = nullptr;

	std::vector<AttributeMetadata> currentReaderMetadata;

	vector<writer::AttributeMetadata> currentWriterMetadata;

	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 addDefinition(std::vector<std::string>& awkCliArgs, DefinitionRecipe& d) {

		awkCliArgs.push_back("-v");

		awkCliArgs.push_back(convertor.to_bytes(a2v(d.name) + L"=" + d.value));

	}

	void add(vector<AttributeMetadata>& readerAttributes, vector<writer::AttributeMetadata>& writerAttributes) {

		for (AttributeMetadata readerAttributes : readerAttributes)

			writerAttributes.push_back({

				readerAttributes.getAttributeName(),

				relationalWriter->toTypeId(readerAttributes.getTypeName())

			});

	}

	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();

		currentWriterMetadata.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:

	/**

	 * @param relationalWriter

	 * @param relationalWriterFlush the writer must be flushed before fork() in order to 

	 * avoid duplicate output (otherwise single relation might be written from two processes); 

	 * This is a little hack – if it stops working, we should reconnect the pipes 

	 * and use the writer only from a single process and avoid its effective duplication,

	 * or use different writers for each relation (or process).

	 * @param configuration

	 */

	AwkHandler(writer::RelationalWriter* relationalWriter, std::function<void() > relationalWriterFlush, Configuration& configuration) : relationalWriter(relationalWriter), relationalWriterFlush(relationalWriterFlush), configuration(configuration) {

	}

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

		cleanUp();

		currentReaderMetadata = attributes;

		currentRelationConfiguration = nullptr;

		for (int i = 0; i < configuration.relationConfigurations.size(); i++) {

			if (regex_match(name, wregex(configuration.relationConfigurations[i].relation))) {

				currentRelationConfiguration = &configuration.relationConfigurations[i];

				break; // it there are multiple matches, only the first configuration is used

			}

		}

		if (currentRelationConfiguration) {

			int awkInputReaderFD;

			int awkOutputReaderFD;

			int awkOutputWriterFD;

			createPipe(awkInputReaderFD, awkInputWriterFD);

			createPipe(awkOutputReaderFD, awkOutputWriterFD);

			relationalWriterFlush();

			__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);

				// AWK script:

				std::wstringstream awkScript;

				awkScript << L"BEGIN {" << std::endl;

				awkScript << L"FS=\"\\t\";" << std::endl;

				awkScript << currentRelationConfiguration->awkBeforeRecords << std::endl;

				awkScript << L"};" << std::endl;

				awkScript << std::endl;

				awkScript << L"END {" << std::endl;

				awkScript << currentRelationConfiguration->awkAfterRecords << std::endl;

				awkScript << L"};" << std::endl;

				awkScript << std::endl;

				awkScript << currentRelationConfiguration->awkForEach << std::endl;

				// CLI arguments:

				std::vector<std::string> args;

				args.push_back("awk");

				for (auto d : configuration.definitions) addDefinition(args, d);

				for (auto d : currentRelationConfiguration->definitions) addDefinition(args, d);

				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);

					// FIXME: currentWriterMetadata

					relationalWriter->startRelation(name,{

						{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);

				}

			}

		} else {

			add(currentReaderMetadata, currentWriterMetadata);

			relationalWriter->startRelation(name, currentWriterMetadata, true);

		}

	}

	void attribute(const string_t& value) override {

		if (currentRelationConfiguration) {

			currentAttributeIndex++;

			currentAttributeIndex = currentAttributeIndex % currentReaderMetadata.size();

		} else {

			relationalWriter->writeAttribute(value);

		}

	}

	void endOfPipe() {

		cleanUp();

	}

};

}

}

}