/**

 * Relational pipes

 * Copyright © 2022 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 <memory>

#include <string>

#include <vector>

#include <iostream>

#include <sstream>

#include <locale>

#include <codecvt>

#include <relpipe/reader/typedefs.h>

#include <relpipe/reader/TypeId.h>

#include <relpipe/reader/handlers/RelationalReaderStringHandler.h>

#include <relpipe/reader/handlers/AttributeMetadata.h>

#include "Configuration.h"

#include "RelpipeSQLWriterException.h"

namespace relpipe {

namespace out {

namespace sql {

using namespace relpipe;

using namespace relpipe::reader;

using namespace relpipe::reader::handlers;

class SQLHandler : public RelationalReaderStringHandler {

private:

	std::ostream& output;

	Configuration& configuration;

	const char QUOTE = '"';

	std::wstring_convert<std::codecvt_utf8<wchar_t>> convertor; // generate SQL always in UTF-8

	std::vector<AttributeMetadata> firstAttributes;

	integer_t valueCount = 0;

	/**

	 * @param a

	 * @param b

	 * @return true if relations have same number and types of attributes (names may differ)

	 */

	bool matches(const std::vector<AttributeMetadata>& a, const std::vector<AttributeMetadata>& b) {

		if (a.size() != b.size()) return false;

		for (int i = 0, limit = a.size(); i < limit; i++) if (a[i].getTypeId() != b[i].getTypeId()) return false;

		return true;

	}

public:

	SQLHandler(std::ostream& output, Configuration& configuration) : output(output), configuration(configuration) {

	}

	void startRelation(string_t name, std::vector<AttributeMetadata> attributes) override {

		// TODO: CREATE TABLE

		// TODO: escape identifiers

		// TODO: ALTER TABLE / add columns on duplicate relation name

		// TODO: custom data type mapping

		// TODO: custom name transformation

		// TODO: custom SQL script before/after stream/relation/record

		// TODO: comments and/or custom comments

		// TODO: optional transactions: BEGIN/COMMIT/ROLLBACK for stream/relation/record

		output << "CREATE TABLE " << convertor.to_bytes(name) << " ( ... );" << std::endl;

		if (firstAttributes.empty()) {

			firstAttributes = attributes;

			if (configuration.writeHeader) for (auto attr : attributes) attribute(configuration.writeTypes ? attr.getAttributeName() + L"::" + attr.getTypeName() : attr.getAttributeName());

		} else if (matches(firstAttributes, attributes)) {

			// do UNION ALL – just append the records

		} else {

			// throw RelpipeSQLWriterException(L"To the SQL format we can convert only one relation or multiple relations that have same number of attributes of same types (relation and attribute names may differ – result is named after the first one).");

		}

	}

	void attribute(const string_t& value) override {

		valueCount++;

		if (value.size() > 0) {

			output << QUOTE;

			for (auto ch : convertor.to_bytes(value)) {

				if (ch == QUOTE) output << QUOTE << QUOTE;

				else output << ch;

			}

			output << QUOTE;

		}

		if (valueCount % firstAttributes.size()) {

			output << ",";

		} else {

			// TODO: INSERT INTO ...

			// TODO: escape identifiers and values

			// TODO: optional use of function/procedure instead of INSERT

			// TODO: optional INSERT of multiple records

			output << std::endl << "INSERT INTO ... VALUES ... ;" << std::endl;;

			valueCount = 0;

		}

	}

	void endOfPipe() {

		output.flush();

	}

};

}

}

}