/**
 * 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 "Configuration.h"
#include "AwkException.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;
	std::vector<writer::AttributeMetadata> currentWriterMetadata;
	std::map<string_t, string_t> currenVariablesMapping;
	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 AwkException(L"Unable to create a pipe.");
	}

	void redirectFD(int oldfd, int newfd) {
		int result = dup2(oldfd, newfd);
		if (result < 0) throw AwkException(L"Unable redirect FD.");
	}

	void closeOrThrow(int fd) {
		int error = close(fd);
		if (error) throw AwkException(L"Unable to close FD: " + to_wstring(fd) + L" from PID: " + to_wstring(getpid()));
	}

	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 AwkException(L"Unable to do execvp().");
	}

	/* TODO: move to lib-cli when stable and used in other modules */
	void setEnv(const char * name, const string_t& value) {
		setenv(name, convertor.to_bytes(value).c_str(), true);
	}

	/* TODO: move to lib-cli when stable and used in other modules */
	void setEnv(const char * name, std::string& value) {
		setenv(name, value.c_str(), true);
	}

	/* TODO: move to lib-cli when stable and used in other modules */
	void setEnv(const char * name, const integer_t& value) {
		setenv(name, to_string(value).c_str(), true);
	}

	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);
			int error1;
			int error2;
			__pid_t waitPID1 = wait(&error1);
			__pid_t waitPID2 = wait(&error2);
			if (error1 || error2) throw AwkException(L"The child process returned an error exit code.");
			awkInputWriterFD = -1;
		}

		currentAttributeIndex = 0;
		currentReaderMetadata.clear();
		currentWriterMetadata.clear();
		currenVariablesMapping.clear();
		currentRelationConfiguration = nullptr;
	}

	void generateVariableMappings() {
		for (AttributeMetadata m : currentReaderMetadata) currenVariablesMapping[m.getAttributeName()] = L"";
		for (writer::AttributeMetadata m : currentWriterMetadata) currenVariablesMapping[m.attributeName] = L"";
		for (DefinitionRecipe d : configuration.definitions) currenVariablesMapping[d.name] = L"";
		for (DefinitionRecipe d : currentRelationConfiguration->definitions) currenVariablesMapping[d.name] = L"";

		for (std::pair<string_t, string_t> m : currenVariablesMapping) {
			currenVariablesMapping[m.first] = escapeAwkVariableName(m.first);
		}
	}

	string_t a2v(const string_t& attributeName) {
		if (currenVariablesMapping.find(attributeName) != currenVariablesMapping.end()) return currenVariablesMapping[attributeName];
		else throw AwkException(L"Unable to find value in currenVariablesMapping");
	}

	template <typename K, typename V> bool containsValue(std::map<K, V> map, V value) {
		for (std::pair<K, V> p : map) if (p.second == value) return true;
		return false;
	}

	string_t escapeAwkVariableName(const string_t& attributeName) {
		// cat awkgram.y | awk -v FS='\\{"|",' -v ORS='|' '/static const struct token tokentab/, /\};/ { if (/^\{/) { print $2} }'
		// cat AwkHandler.h | awk -v FS=' |\\(' -v ORS='|' '/awkScript.*"function/ { print $4; }'
		std::wregex awkReservedNames(L"FS|OFS|NR|NF|" L"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");
		std::wregex trReservedNames(L"_escape|_unescape|_readVariables|_writeVariables|record");
		std::wregex badCharacters(L"[^a-zA-Z0-9_]|^([0-9])");

		const string_t& name = std::regex_replace(attributeName, badCharacters, L"_$1");

		bool badName = false;
		badName |= regex_match(name, awkReservedNames);
		badName |= regex_match(name, trReservedNames);
		badName |= containsValue(currenVariablesMapping, name);

		if (badName) return escapeAwkVariableName(L"_" + name);
		else return name;
	}

	string_t escapeAwkValue(const string_t& value) {
		std::wstringstream escaped;
		for (wchar_t ch : value) {
			if (ch == '\t') escaped << L"\\t";
			else if (ch == '\n') escaped << L"\\n";
			else if (ch == '\\') escaped << L"\\\\";
			else escaped << ch;
		}
		return escaped.str();
	}

	void processAwkOutput(int awkOutputReaderFD) {
		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);

		if (currentRelationConfiguration->drop) {
			for (wchar_t ch; awkOutputReader.read(&ch, 1).good();); // just eat the lines from the AWK
		} else {
			std::wstringstream currentValue;
			for (wchar_t ch; awkOutputReader.read(&ch, 1).good();) {
				if (ch == '\t' || ch == '\n') {
					relationalWriter->writeAttribute(currentValue.str());
					currentValue.str(L"");
					currentValue.clear();
				} else if (ch == '\\') {
					ch = awkOutputReader.get();
					if (ch == 't') currentValue << L'\t';
					else if (ch == 'n') currentValue << L'\n';
					else if (ch == '\\') currentValue << L'\\';
					else throw AwkException(L"Unknown escape sequence. Only \\t, \\n and \\\\ are supported.");
				} else {
					currentValue << ch;
				}
			}
		}

		closeOrThrow(awkOutputReaderFD);
	}

	void debugVariableMapping(const string_t& relationName) {
		relationalWriter->startRelation(relationName + L".variableMapping",{
			{L"attribute", writer::TypeId::STRING},
			{L"variable", writer::TypeId::STRING},
		}, true);

		for (std::pair<string_t, string_t> m : currenVariablesMapping) {
			relationalWriter->writeAttribute(m.first);
			relationalWriter->writeAttribute(m.second);
		}
	}

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();

		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
			}
		}

		currentReaderMetadata = attributes;
		// TODO: move to a reusable method (or use same metadata on both reader and writer side?)		
		if (currentRelationConfiguration && currentRelationConfiguration->writerMetadata.size()) {
			if (currentRelationConfiguration->inputAttributesPrepend) add(currentReaderMetadata, currentWriterMetadata);
			currentWriterMetadata.insert(currentWriterMetadata.end(), currentRelationConfiguration->writerMetadata.begin(), currentRelationConfiguration->writerMetadata.end());
			if (currentRelationConfiguration->inputAttributesAppend) add(currentReaderMetadata, currentWriterMetadata);
		} else {
			add(currentReaderMetadata, currentWriterMetadata);
		}

		if (currentRelationConfiguration) {
			generateVariableMappings();

			int awkInputReaderFD;
			int awkOutputReaderFD;
			int awkOutputWriterFD;

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

			relationalWriterFlush();
			__pid_t awkPid = fork();

			if (awkPid < 0) {
				throw AwkException(L"Unable to fork AWK process.");
			} else if (awkPid == 0) {
				// AWK child process
				closeOrThrow(awkInputWriterFD);
				closeOrThrow(awkOutputReaderFD);

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

				// Environment variables:
				setEnv("relationName", name);
				setEnv("inputAttributeCount", currentReaderMetadata.size());
				setEnv("outputAttributeCount", currentWriterMetadata.size());
				// TODO: better names? ENV vs. AWK variables?
				for (int i = 0; i < currentReaderMetadata.size(); i++) {
					setEnv((std::string("inputAttributeName") + std::to_string(i)).c_str(), currentReaderMetadata[i].getAttributeName());
					setEnv("inputAttributeType" + i, currentReaderMetadata[i].getTypeName());
				}
				for (int i = 0; i < currentWriterMetadata.size(); i++) {
					setEnv("outputAttributeName" + i, currentWriterMetadata[i].attributeName);
					// setEnv("outputAttributeType" + i, currentWriterMetadata[i].typeId); // TODO: type?
				}

				// AWK script:
				std::wstringstream awkScript;
				awkScript << L"BEGIN {" << std::endl;
				awkScript << L"FS=\"\\t\";" << std::endl;
				awkScript << L"OFS=\"\\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 << LR"AWK(
function _escape(value,    i) {
	result = "";
	split(value, chars, "");
	for (i = 1; i <= length(chars); i++) {
		ch = chars[i];
		if (ch == "\\")      { ch = "\\\\"; }
		else if (ch == "\t") { ch = "\\t"; }
		else if (ch == "\n") { ch = "\\n"; }
		result = result ch;
	}
	return result;
};
						
function _unescape(value,    i) {
	result = "";
	split(value, chars, "");
	for (i = 1; i <= length(chars); i++) {
		ch = chars[i];
		if (ch == "\\") {
			ch = chars[++i];
			if (ch == "\\")     { ch = "\\"; }
			else if (ch == "t") { ch = "\t"; }
			else if (ch == "n") { ch = "\n"; }
			else {
				printf("Unsupported escape sequence: %s\n", ch) > "/dev/stderr";
				exit 70;
			}
		}
		result = result ch;
	}
	return result;
};
)AWK";

				awkScript << std::endl;

				awkScript << L"function _readVariables() {" << std::endl;
				for (int i = 0; i < currentReaderMetadata.size(); i++) {
					AttributeMetadata& a = currentReaderMetadata[i];
					awkScript << a2v(a.getAttributeName());
					if (a.getTypeId() == TypeId::INTEGER) awkScript << L"=$" << (i + 1) << L";";
					else if (a.getTypeId() == TypeId::BOOLEAN) awkScript << L"= $" << (i + 1) << L" == \"true\";";
					else awkScript << L"=_unescape($" << (i + 1) << L");";
					awkScript << std::endl;
				}
				awkScript << L"};" << std::endl;
				awkScript << std::endl;

				awkScript << L"function _writeVariables() {" << std::endl;
				awkScript << L"NF=" << currentWriterMetadata.size() << ";" << std::endl;
				for (int i = 0; i < currentWriterMetadata.size(); i++) {
					writer::AttributeMetadata& a = currentWriterMetadata[i];
					awkScript << L"$" << (i + 1);
					if (a.typeId == writer::TypeId::INTEGER) awkScript << L"=" << a2v(a.attributeName) << L";";
					else if (a.typeId == writer::TypeId::BOOLEAN) awkScript << L"= " << a2v(a.attributeName) << L" ? \"true\" : \"false\" ;";
					else awkScript << L"=_escape(" << a2v(a.attributeName) << L");";
					awkScript << std::endl;
				}
				awkScript << L"};" << std::endl;
				awkScript << std::endl;

				awkScript << L"function record() {" << std::endl;
				awkScript << L"_writeVariables();" << std::endl;
				awkScript << L"print;" << std::endl;
				awkScript << L"};" << std::endl;
				awkScript << std::endl;

				awkScript << L"{ _readVariables();  }" << std::endl; // read line (input attributes) into AWK variables
				awkScript << L"{ _writeVariables(); }" << std::endl; // write AWK variables to the line (so it matches the output attributes and can be implicitly printed without explicit record() call)
				awkScript << std::endl;

				awkScript << currentRelationConfiguration->awkForEach << std::endl; // user's code – can modify variables, filter results or explicitly call record() (can generate additional records or duplicate them)

				// 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 AwkException(L"Unable to fork Writer process.");
				} else if (writerPid == 0) {
					// Writer child process
					closeOrThrow(awkInputWriterFD);

					if (currentRelationConfiguration->debugVariableMapping) debugVariableMapping(name);

					if (currentRelationConfiguration->drop) {
						// TODO: omit whole this process and pipe AWK output to /dev/null?
					} else {
						relationalWriter->startRelation(name, currentWriterMetadata, true);
					}

					processAwkOutput(awkOutputReaderFD);
					exit(0);
				} else {
					// Parent process
					closeOrThrow(awkOutputReaderFD);
				}
			}
		} else {
			relationalWriter->startRelation(name, currentWriterMetadata, true);
		}

	}

	void attribute(const string_t& value) override {
		if (currentRelationConfiguration) {
			currentAttributeIndex++;
			currentAttributeIndex = currentAttributeIndex % currentReaderMetadata.size();

			std::string awkValue = convertor.to_bytes(escapeAwkValue(value));
			if (currentAttributeIndex == 0) awkValue += "\n";
			else awkValue += "\t";

			write(awkInputWriterFD, awkValue.c_str(), awkValue.length());
		} else {
			relationalWriter->writeAttribute(value);
		}
	}

	void endOfPipe() {
		cleanUp();
	}

};

}
}
}