/**
 * 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();
	}

};

}
}
}