/**

 * Relational pipes

 * Copyright © 2020 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 <cstdlib>

#include <iostream>

#include <memory>

#include <vector>

#include <yaml.h>

#include <relpipe/writer/RelationalWriter.h>

#include <relpipe/writer/typedefs.h>

namespace relpipe {

namespace in {

namespace yaml {

class YAMLCommand {

private:

	std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // YAML strings are in UTF-8

	class YAMLEvent {

	private:

		yaml_event_t event;

	public:

		YAMLEvent(yaml_event_t event) : event(event) {

		}

		virtual ~YAMLEvent() {

			yaml_event_delete(&event);

		}

		const yaml_event_type_t getType() const {

			return event.type;

		}

		const relpipe::writer::string_t getTypeName() const {

			return findTypeName(event.type);

		}

		/** Just for debugging and error handling */

		static const relpipe::writer::string_t findTypeName(const yaml_event_type_t eventType) {

			if (eventType == YAML_NO_EVENT) return L"NO";

			else if (eventType == YAML_STREAM_START_EVENT) return L"STREAM_START";

			else if (eventType == YAML_STREAM_END_EVENT) return L"STREAM_END";

			else if (eventType == YAML_DOCUMENT_START_EVENT) return L"DOCUMENT_START";

			else if (eventType == YAML_DOCUMENT_END_EVENT) return L"DOCUMENT_END";

			else if (eventType == YAML_ALIAS_EVENT) return L"ALIAS";

			else if (eventType == YAML_SCALAR_EVENT) return L"SCALAR";

			else if (eventType == YAML_SEQUENCE_START_EVENT) return L"SEQUENCE_START";

			else if (eventType == YAML_SEQUENCE_END_EVENT) return L"SEQUENCE_END";

			else if (eventType == YAML_MAPPING_START_EVENT) return L"MAPPING_START";

			else if (eventType == YAML_MAPPING_END_EVENT) return L"MAPPING_END";

			else return L"UNKNOWN";

		}

		const yaml_event_t* getEvent() const {

			return &event;

		}

		YAMLEvent(const YAMLEvent&) = delete;

		YAMLEvent& operator=(const YAMLEvent&) = delete;

	};

	class YAMLParser {

	private:

		yaml_parser_t yamlParser;

		std::istream* input = nullptr;

		static int readFromInput(void* instance, unsigned char* buffer, size_t size, size_t* length) {

			std::istream* input = ((YAMLParser*) instance)->input;

			input->read((char*) buffer, size);

			*length = input->gcount();

			return (input->good() || input->eof()) ? 1 : 0;

		}

	public:

		YAMLParser() {

			yaml_parser_initialize(&yamlParser);

		}

		virtual ~YAMLParser() {

			yaml_parser_delete(&yamlParser);

		}

		YAMLParser(const YAMLParser&) = delete;

		YAMLParser& operator=(const YAMLParser&) = delete;

		void setInput(std::istream* input) {

			this->input = input;

			yaml_parser_set_input(&yamlParser, readFromInput, (void*) this);

		}

		YAMLEvent* next() {

			yaml_event_t event;

			int result = yaml_parser_parse(&yamlParser, &event);

			return result == 1 && event.type != yaml_event_type_e::YAML_NO_EVENT ? new YAMLEvent(event) : nullptr; // 1 = OK in yaml.h; YAML_NO_EVENT = end

		}

	};

	using YAMLEvent_p = std::shared_ptr<YAMLEvent>;

	YAMLParser parser;

	std::shared_ptr<relpipe::writer::RelationalWriter> writer;

	relpipe::writer::string_t relationName;

	std::vector<relpipe::writer::string_t> record;

	std::vector<relpipe::writer::AttributeMetadata> attributesMetadata;

	relpipe::writer::string_t y2s(const yaml_char_t* value) {

		return value ? convertor.from_bytes((const char*) value) : L"";

	}

	relpipe::writer::string_t fetchScalarValue(YAMLEvent_p event) {

		if (event->getType() == YAML_SCALAR_EVENT) return y2s(event->getEvent()->data.scalar.value);

		else throw relpipe::writer::RelpipeWriterException(L"Invalid YAML structure: expected SCALAR but got: " + event->getTypeName());

	}

	void consumeEvent(const yaml_event_type_t expectedEventType, relpipe::writer::string_t expectedScalarValue = L"") {

		YAMLEvent_p event = YAMLEvent_p(parser.next());

		if (!event) throw relpipe::writer::RelpipeWriterException(L"Invalid YAML structure: missing event: " + YAMLEvent::findTypeName(expectedEventType));

		if (event->getType() != expectedEventType) throw relpipe::writer::RelpipeWriterException(L"Invalid YAML structure: expected event: " + YAMLEvent::findTypeName(expectedEventType) + L", but got: " + event->getTypeName());

		if (expectedEventType == YAML_SCALAR_EVENT && expectedScalarValue.size() && expectedScalarValue != fetchScalarValue(event)) throw relpipe::writer::RelpipeWriterException(L"Invalid YAML structure: expected scalar value: " + expectedScalarValue + L", but got " + fetchScalarValue(event));

	}

	relpipe::writer::string_t consumeScalarEvent() {

		YAMLEvent_p event = YAMLEvent_p(parser.next());

		if (event && event->getType() == YAML_SCALAR_EVENT) return fetchScalarValue(event);

		else throw relpipe::writer::RelpipeWriterException(L"Invalid YAML structure: expected SCALAR, but got: " + event->getTypeName());

	}

	void processRelation() {

		YAMLEvent_p event = YAMLEvent_p(parser.next());

		if (event->getType() == YAML_MAPPING_START_EVENT) processRelationWithMetadata();

		else if (event->getType() == YAML_SEQUENCE_START_EVENT)processRelationWithoutMetadata();

		else throw relpipe::writer::RelpipeWriterException(L"Invalid YAML structure: expected MAPPING or SEQUENCE, but got: " + event->getTypeName());

	}

	void processRelationWithMetadata() {

		consumeEvent(YAML_SCALAR_EVENT, L"attribute-metadata");

		consumeEvent(YAML_SEQUENCE_START_EVENT);

			if (event->getType() != YAML_MAPPING_START_EVENT) throw relpipe::writer::RelpipeWriterException(L"Invalid YAML structure: expected MAPPING (attribute-metadata), but got: " + event->getTypeName());

			relpipe::writer::string_t name;

			relpipe::writer::string_t type = L"string";

				auto key = fetchScalarValue(event);

				auto value = consumeScalarEvent();

				if (key == L"name") name = value;

				else if (key == L"type") type = value;

				else; // unsupported metadata, later there might be something useful

			}

			attributesMetadata.push_back({name, writer->toTypeId(type)});

		}

		writer->startRelation(relationName, attributesMetadata, true);

		YAMLEvent_p event = YAMLEvent_p(parser.next());

		if (event->getType() == YAML_SCALAR_EVENT && fetchScalarValue(event) == L"record") {

			consumeEvent(YAML_SEQUENCE_START_EVENT);

			processRecords();

			consumeEvent(YAML_MAPPING_END_EVENT);

		} else if (event->getType() == YAML_MAPPING_END_EVENT) {

			// empty relation, no records

		} else {

			relpipe::writer::RelpipeWriterException(L"Invalid YAML structure: expected 'record' or MAPPING_END, but got: " + event->getTypeName());

		}

	}

	void processRelationWithoutMetadata() {

		// First record:

		consumeEvent(YAML_MAPPING_START_EVENT);

		record.clear();

			auto name = fetchScalarValue(event);

			auto value = consumeScalarEvent();

			attributesMetadata.push_back({name, relpipe::writer::TypeId::STRING});

			record.push_back(value);

		}

		writer->startRelation(relationName, attributesMetadata, true);

		for (auto value : record) writer->writeAttribute(value);

		// Following records:

		processRecords();

	}

	void processRecords() {

			if (event->getType() != YAML_MAPPING_START_EVENT) throw relpipe::writer::RelpipeWriterException(L"Invalid YAML structure: expected MAPPING (record), but got: " + event->getTypeName());

			record.clear();

			record.resize(attributesMetadata.size());

				auto name = fetchScalarValue(event);

				auto value = consumeScalarEvent();

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

					if (name == attributesMetadata[i].attributeName) {

						record[i] = value;

						break;

					}

				}

			}

			for (auto value : record) writer->writeAttribute(value);

		}

	}

public:

	YAMLCommand() {

	}

	virtual ~YAMLCommand() {

	}

	void process(std::istream& input, std::shared_ptr<relpipe::writer::RelationalWriter> writer) {

		parser.setInput(&input);

		this->writer = writer;

		consumeEvent(YAML_STREAM_START_EVENT);

		consumeEvent(YAML_DOCUMENT_START_EVENT);

		consumeEvent(YAML_MAPPING_START_EVENT);

			relationName = fetchScalarValue(event);

			attributesMetadata.clear();

			processRelation();

		}

		consumeEvent(YAML_DOCUMENT_END_EVENT);

		consumeEvent(YAML_STREAM_END_EVENT);

	}

};

}

}

}