/**

 * 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 <codecvt>

#include <vector>

#include <libxml++-2.6/libxml++/libxml++.h>

#include <yaml.h>

#include "XMLNameCodec.h"

namespace relpipe {

namespace in {

namespace xmltable {

class XMLDocumentConstructor {

private:

	std::istream* input = nullptr;

	xmlpp::DomParser* parser = nullptr;

	yaml_parser_t yamlParser;

	XMLNameCodec nameCodec;

	enum class Mode {

		ROOT,

		SEQUENCE,

		MAPPING,

		MAP_KEY

	};

	xmlpp::Element* current;

	std::vector<Mode> mode;

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

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

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

		*length = input->gcount();

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

	}

	/**

	 * Both YAML and XML strings are in UTF-8.

	 */

	const char* y2x(yaml_char_t* value) {

		return value ? (const char*) value : "";

	}

	const Glib::ustring y2xname(yaml_char_t* value) {

		return nameCodec.encode(y2x(value));

	}

	xmlpp::Element* parentOrSelf(xmlpp::Element* current) {

		return current->get_parent() == nullptr ? current : current->get_parent();

	}

public:

	XMLDocumentConstructor(std::istream* input, xmlpp::DomParser* parser) : input(input), parser(parser) {

		yaml_parser_initialize(&yamlParser);

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

	}

	virtual ~XMLDocumentConstructor() {

		yaml_parser_delete(&yamlParser);

	}

	void setOption(const std::string& uri, const std::string& value) {

	}

	void process() {

		mode.push_back(Mode::ROOT);

		std::string itemName;

		while (true) {

			yaml_event_t event;

			if (!yaml_parser_parse(&yamlParser, &event)) {

				// FIXME: throw exception

				return;

			}

			if (event.type == YAML_STREAM_END_EVENT) {

				yaml_event_delete(&event);

				break;

			} else if (event.type == YAML_STREAM_START_EVENT) {

			} else if (event.type == YAML_NO_EVENT) {

				current->add_child("null"); // TODO: null?

			} else if (event.type == YAML_DOCUMENT_START_EVENT) {

			} else if (event.type == YAML_DOCUMENT_END_EVENT) {

			} else if (event.type == YAML_ALIAS_EVENT) {

				// TODO: alias?

			} else if (event.type == YAML_SCALAR_EVENT) {

				if (mode.back() == Mode::SEQUENCE) {

					current->add_child(itemName)->add_child_text(y2x(event.data.scalar.value));

				} else if (mode.back() == Mode::MAPPING) {

					current = current->add_child(y2xname(event.data.scalar.value));

					mode.push_back(Mode::MAP_KEY);

				} else if (mode.back() == Mode::MAP_KEY) {

					current->add_child_text(y2x(event.data.scalar.value));

					current = parentOrSelf(current);

					mode.pop_back();

				} else if (mode.back() == Mode::ROOT) {

					current->add_child_text(y2x(event.data.scalar.value));

				} else {

					// TODO: process YAML_SCALAR_EVENT

				}

			} else if (event.type == YAML_SEQUENCE_START_EVENT) {

				xmlpp::Element* parent = current->get_parent();

				if (parent) {

					itemName = current->get_name();

					parent->remove_child(current);

					current = parent;

				} else {

					itemName = "item";

				}

				if (mode.back() == Mode::MAP_KEY) mode.pop_back();

				mode.push_back(Mode::SEQUENCE);

			} else if (event.type == YAML_SEQUENCE_END_EVENT) {

				mode.pop_back(); // TODO: assert sequence?

			} else if (event.type == YAML_MAPPING_START_EVENT) {

				if (mode.back() == Mode::ROOT) {

				} else if (mode.back() == Mode::SEQUENCE) {

					current = current->add_child(itemName);

				} else if (mode.back() == Mode::MAP_KEY) {

					mode.pop_back();

				} else {

					// TODO: map might be a key of another map → wrap/nest

				}

				mode.push_back(Mode::MAPPING);

			} else if (event.type == YAML_MAPPING_END_EVENT) {

				current = parentOrSelf(current);

				mode.pop_back(); // TODO: assert map?

			} else {

				// TODO: unsupported type?

			}

			yaml_event_delete(&event);

		}

	}

};

}

}

}