/**

 * 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, 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 <vector>

#include <filesystem>

#include <regex>

#include <memory>

#include <sstream>

#include <relpipe/writer/typedefs.h>

#include <relpipe/writer/AttributeMetadata.h>

#include <relpipe/writer/RelationalWriter.h>

#include "RequestedField.h"

#include "SubProcess.h"

#include "AttributeFinder.h"

#include "StreamletMsg.h"

namespace relpipe {

namespace in {

namespace filesystem {

namespace fs = std::filesystem;

using namespace relpipe::writer;

class StreamletAttributeFinder : public AttributeFinder {

private:

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

	std::map<int, std::shared_ptr<SubProcess>> subProcesses;

	std::map<int, std::vector<AttributeMetadata>> cachedMetadata;

	string_t getStreamletCommand(const RequestedField& field) {

		const char* streamletPathChars = getenv("RELPIPE_IN_FILESYSTEM_STREAMLET_PATH");

		if (streamletPathChars) {

			std::wstringstream current;

			string_t streamletPath = convertor.from_bytes(streamletPathChars);

			for (int i = 0, streamletPathSize = streamletPath.size(); i < streamletPathSize; i++) {

				if (streamletPath[i] == ':' || i == streamletPathSize - 1) { // FIXME: support \: and \\ escaping

					current << L"/" << field.name;

					fs::path streamletFile(current.str());

						return current.str();

					} else {

						current.str(L"");

						current.clear();

					}

				} else {

					current.put(streamletPath[i]);

				}

			}

			throw RelpipeWriterException(L"Streamlet „" + field.name + L"“ was not found at $RELPIPE_IN_FILESYSTEM_STREAMLET_PATH");

		} else {

			throw RelpipeWriterException(L"Missing environment variable RELPIPE_IN_FILESYSTEM_STREAMLET_PATH → unable to find streamlet.");

		}

	}

protected:

	void startFile(const fs::path& file, const string& fileRaw, bool exists) override {

		AttributeFinder::startFile(file, fileRaw, exists);

		if (exists) {

			for (auto subProcess : subProcesses) {

				subProcess.second->write({StreamletMsg::INPUT_ATTRIBUTE, L"0", convertor.from_bytes(currentFileRaw), L"false"}); // index, value, isNull

				subProcess.second->write({StreamletMsg::WAITING_FOR_OUTPUT_ATTRIBUTES});

			}

		}

	}

	virtual void writeFieldOfExistingFile(RelationalWriter* writer, const string_t& relationName, const RequestedField & field) override {

		// TODO: paralelize also over records → fork multiple processes and distribute records across them; then collect results (with a lock)

		if (field.group == RequestedField::GROUP_STREAMLET) {

			for (auto metadata : cachedMetadata[field.id]) {

				SubProcess::Message m = subProcesses[field.id]->read();

				if (m.code == StreamletMsg::OUTPUT_ATTRIBUTE) writer->writeAttribute(m.parameters[0]);

				else throw RelpipeWriterException(L"Protocol violation from exec sub-process while reading: „" + metadata.attributeName + L"“. Expected OUTPUT_ATTRIBUTE but got: " + m.toString());

			}

			SubProcess::Message m = subProcesses[field.id]->read();

			if (m.code != StreamletMsg::WAITING_FOR_INPUT_ATTRIBUTES) throw RelpipeWriterException(L"Protocol violation from exec sub-process. Expected WAITING_FOR_INPUT_ATTRIBUTES but got: " + m.toString());

			// TODO: generic protocol violation error messages / method for checking responses

		}

	}

public:

	static const string_t SCRIPT_PREFIX;

	virtual vector<AttributeMetadata> toMetadata(RelationalWriter* writer, const string_t& relationName, const RequestedField& field) override {

		if (field.group == RequestedField::GROUP_STREAMLET) {

			if (cachedMetadata.count(field.id)) {

				return cachedMetadata[field.id];

			} else {

				std::vector<string_t> commandLine = {getStreamletCommand(field)};

				std::map<string_t, string_t> environment;

				for (auto mn : StreamletMsg::getMessageNames()) {

					environment[L"EXEC_MSG_" + mn.second] = std::to_wstring(mn.first);

					environment[L"EXEC_MSG_" + std::to_wstring(mn.first)] = mn.second;

				}

				shared_ptr<SubProcess> subProcess(SubProcess::create(commandLine, environment));

				subProcesses[field.id] = subProcess;

				string_t version = L"1";

				subProcess->write({StreamletMsg::VERSION_SUPPORTED, version});

				subProcess->write({StreamletMsg::WAITING_FOR_VERSION});

				SubProcess::Message versionMessage = subProcess->read();

				if (versionMessage.code == StreamletMsg::VERSION_ACCEPTED && versionMessage.parameters[0] == version) {

					subProcess->write({StreamletMsg::RELATION_START, relationName});

					subProcess->write({StreamletMsg::INPUT_ATTRIBUTE_METADATA, L"path", L"string"});

					for (string_t alias : field.getAliases()) subProcess->write({StreamletMsg::OUTPUT_ATTRIBUTE_ALIAS, alias});

					for (int i = 0; i < field.options.size();) subProcess->write({StreamletMsg::OPTION, field.options[i++], field.options[i++]});

					subProcess->write({StreamletMsg::WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA});

					vector<AttributeMetadata> metadata;

					while (true) {

						SubProcess::Message m = subProcess->read();

						if (m.code == StreamletMsg::OUTPUT_ATTRIBUTE_METADATA) metadata.push_back({m.parameters[0], writer->toTypeId(m.parameters[1])});

						else if (m.code == StreamletMsg::WAITING_FOR_INPUT_ATTRIBUTES) break;

					}

					cachedMetadata[field.id] = metadata;

					return metadata;

				} else {

					throw RelpipeWriterException(L"Incompatible exec sub-process version or message: " + versionMessage.toString());

				}

			}

		} else {

			return {};

		}

	}

	virtual ~StreamletAttributeFinder() override {

		for (auto s : subProcesses) {

			try {

				s.second->write({StreamletMsg::RELATION_END});

				s.second->wait();

			} catch (...) {

				std::wcerr << L"Exception caught during closing sub-process #" + std::to_wstring(s.first) + L" and waiting for its end." << std::endl;

			}

		}

	}

};

const relpipe::writer::string_t StreamletAttributeFinder::SCRIPT_PREFIX = L"__relpipe_in_filesystem_script_";

}

}

}