/**

 * 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

 *

 * 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 <iostream>

#include <string>

#include <sstream>

#include <vector>

#include <set>

#include <relpipe/writer/typedefs.h>

#include <relpipe/writer/RelationalWriter.h>

#include <relpipe/writer/AttributeMetadata.h>

namespace relpipe {

namespace in {

namespace recfile {

using namespace relpipe::writer;

class RecfileCommand {

private:

	enum class RecfileLineType {

		METADATA,

		DATA,

		SEPARATOR,

		COMMENT,

		END,

	};

	class RecfileHandler {

	private:

		RelationalWriter* writer;

		string_t currentRelationName;

		std::vector<AttributeMetadata> currentAttributeMetadata;

		std::vector<string_t> currentRecord;

		std::vector<std::vector<string_t>> currentRecords;

		size_t prefetchCount = 1;

		bool headerWritten = false;

		void writeHeader() {

			if (headerWritten) return;

			if (currentRelationName.size() == 0) currentRelationName = L"recfile";

			std::set<string_t> uniqueAttributeNames;

			// TODO: add also attribute names from type hints from recfile metadata

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

				std::vector<string_t> record = currentRecords[i];

				for (int j = 0; j < record.size(); j += 2) {

					if (uniqueAttributeNames.insert(record[j]).second) {

						currentAttributeMetadata.push_back({record[j], TypeId::STRING}); // TODO: type from type hints

					}

				}

			}

			writer->startRelation(currentRelationName, currentAttributeMetadata, true);

			headerWritten = true;

		}

		string_t findValue(std::vector<string_t>& record, TypeId type, string_t& name) {

			for (int j = 0; j < record.size(); j += 2) if (record[j] == name) return record[j + 1];

			return L""; // TODO: proper empty/null value for given type

		}

		void writeRecords() {

			for (std::vector<string_t> record : currentRecords) {

				for (AttributeMetadata a : currentAttributeMetadata) {

					writer->writeAttribute(findValue(record, a.typeId, a.attributeName));

				}

			}

			currentRecords.clear();

		}

		void metadata(const string_t& name, const string_t& value) {

			if (name == L"rec") {

				currentRelationName = value;

				currentAttributeMetadata.clear();

				currentRecord.clear();

				currentRecords.clear();

				headerWritten = false;

			} else if (name == L"type") {

				// TODO: save type hint

			} else {

				// ignore – other recfile metadata like keys or auto-increments

			}

		}

		void data(const string_t& name, const string_t& value) {

			currentRecord.push_back(name);

			currentRecord.push_back(value);

		}

		void comment(const string_t& value) {

			// ignore comments

		}

		void separator() {

			if (currentRecord.size()) {

				currentRecords.push_back(currentRecord);

				currentRecord.clear();

			}

			if (prefetchCount > 0 && currentRecords.size() >= prefetchCount) {

				writeHeader();

				writeRecords();

			}

		}

		void end() {

			if (currentRecord.size()) currentRecords.push_back(currentRecord);

			writeHeader();

			writeRecords();

		}

	public:

		RecfileHandler(RelationalWriter* writer) : writer(writer) {

		}

		virtual ~RecfileHandler() {

		}

		void logicalLine(RecfileLineType type, const string_t& name = L"", const string_t& value = L"") {

			switch (type) {

				case RecfileLineType::METADATA: return metadata(name, value);

				case RecfileLineType::DATA: return data(name, value);

				case RecfileLineType::COMMENT: return comment(value);

				case RecfileLineType::SEPARATOR: return separator();

				case RecfileLineType::END: return end();

			}

		}

	};

	enum class ParserState {

		START,

		NAME,

		VALUE,

		VALUE_CONTINUATION,

		COMMENT,

		END,

	};

	class RecfileParser {

	private:

		wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings or are recfiles always in UTF-8?

		RecfileHandler& handler;

		void emitLogicalLine(RecfileLineType& type, std::stringstream& name, std::stringstream& value) {

			handler.logicalLine(type, convertor.from_bytes(name.str()), convertor.from_bytes(value.str()));

			name.str("");

			name.clear();

			value.str("");

			value.clear();

			type = RecfileLineType::DATA;

		}

	public:

		RecfileParser(RecfileHandler& handler) : handler(handler) {

		}

		virtual ~RecfileParser() {

		}

		void parse(std::istream& input) {

			ParserState state = ParserState::START;

			RecfileLineType type = RecfileLineType::DATA;

			std::stringstream name;

			std::stringstream value;

			char ch;

			while (state != ParserState::END && input.good()) {

				ch = input.get();

				if (input.eof()) continue;

				switch (state) {

					case ParserState::START:

						if (ch == '%') {

							type = RecfileLineType::METADATA;

							break;

						} else if (ch == ' ') {

							break;

						} else if (ch == '\n') {

							handler.logicalLine(RecfileLineType::SEPARATOR);

							break;

						} else if (ch == '#') {

							type = RecfileLineType::COMMENT;

							state = ParserState::COMMENT;

							if (input.get() != ' ') input.unget();

							break;

						} // else → name

					case ParserState::NAME:

						if (ch == ':') {

							state = ParserState::VALUE;

							if (input.get() != ' ') input.unget();

						} else {

							name << ch;

						}

						break;

					case ParserState::VALUE:

						if (ch == '\n') state = ParserState::VALUE_CONTINUATION;

						else value << ch;

						break;

					case ParserState::VALUE_CONTINUATION:

						if (ch == '+') {

							state = ParserState::VALUE;

							if (value.tellp()) value << '\n';

							if (input.get() != ' ') input.unget();

						} else {

							input.unget();

							state = ParserState::START;

							emitLogicalLine(type, name, value);

						}

						break;

					case ParserState::COMMENT:

						if (ch == '\n') {

							state = ParserState::START;

							emitLogicalLine(type, name, value);

						} else {

							value << ch;

						}

						break;

					default:

						throw RelpipeWriterException(L"Unknown ParserState: " + std::to_wstring((int) state) + L" in RecfileParser."); // TODO: better exception

				}

			}

			if (name.tellp()) emitLogicalLine(type, name, value);

			handler.logicalLine(RecfileLineType::END);

		}

	};

public:

	void process(std::istream& input, std::ostream& output) {

		unique_ptr<RelationalWriter> writer(Factory::create(output));

		RecfileHandler handler(writer.get());

		RecfileParser parser(handler);

		parser.parse(input);

	}

};

}

}

}