/**

 * 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, either version 3 of the License, or

 * (at your option) any later version.

 *

 * 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 <locale>

#include <codecvt>

#include <sqlite3.h>

#include <relpipe/reader/typedefs.h>

#include <relpipe/reader/TypeId.h>

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

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

#include <relpipe/writer/Factory.h>

#include "Configuration.h"

#include "SqlException.h"

namespace relpipe {

namespace tr {

namespace sql {

using namespace std;

using namespace relpipe;

using namespace relpipe::reader;

using namespace relpipe::reader::handlers;

class PreparedStatement {

private:

	sqlite3_stmt* stmt;

public:

	PreparedStatement(sqlite3_stmt* stmt) : stmt(stmt) {

	}

	virtual ~PreparedStatement() {

		sqlite3_finalize(stmt);

	}

	void setString(int parameterIndex, std::string value) {

		int result = sqlite3_bind_text(stmt, parameterIndex, value.c_str(), -1, SQLITE_TRANSIENT);

		if (result != SQLITE_OK) throw SqlException(L"Unable to set SQLite parameter.");

	}

	void setNull(int parameterIndex) {

		int result = sqlite3_bind_null(stmt, parameterIndex);

		if (result != SQLITE_OK) throw SqlException(L"Unable to set SQLite parameter.");

	}

	bool next() {

		int result = sqlite3_step(stmt);

		if (result == SQLITE_ROW) return true;

		else if (result == SQLITE_DONE) return false;

		else throw SqlException(L"Error while iterating over SQLite result.");

	}

	int getColumnCount() {

		return sqlite3_column_count(stmt);

	}

	std::string getColumName(int columnIndex) {

		const char* name = sqlite3_column_name(stmt, columnIndex);

		if (name) return name;

		else throw SqlException(L"Unable to get SQLite column name.");

	}

	// TODO: sqlite3_column_type

	std::string getString(int columnIndex) {

		const char* value = (const char*) sqlite3_column_text(stmt, columnIndex);

		return value ? value : ""; // TODO: support NULL values (when supported in relpipe format)

	}

};

class Connection {

private:

	sqlite3* db;

public:

	Connection(const char* filename) {

		int result = sqlite3_open(filename, &db);

	}

	virtual ~Connection() {

		sqlite3_close(db);

	}

	PreparedStatement prepareStatement(const char* sql) {

		const char* remaining;

		sqlite3_stmt *stmt;

		int result = sqlite3_prepare(db, sql, -1, &stmt, &remaining);

		if (result == SQLITE_OK) return PreparedStatement(stmt);

		else throw SqlException(L"Unable to prepare SQLite statement.");

	}

};

class SqlHandler : public RelationalReaderStringHandler {

private:

	Configuration configuration;

	writer::RelationalWriter* relationalWriter;

	std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings

	std::unique_ptr<Connection> connection;

	void processStatement(const Statement& statement) {

		PreparedStatement prepared = connection->prepareStatement(convertor.to_bytes(statement.sql).c_str());

		int columnCount = prepared.getColumnCount();

		int parameterCount = statement.parameters.size();

		for (int i = 0; i < parameterCount; i++) {

			prepared.setString(i + 1, convertor.to_bytes(statement.parameters[i].value));

		}

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

		for (int i = 0; i < columnCount; i++) metadata.push_back({convertor.from_bytes(prepared.getColumName(i).c_str()), relpipe::writer::TypeId::STRING});

		relationalWriter->startRelation(statement.relation, metadata, true);

		while (prepared.next()) {

			for (int i = 0; i < columnCount; i++) {

				relationalWriter->writeAttribute(convertor.from_bytes(prepared.getString(i)));

			}

		}

	}

public:

	SqlHandler(writer::RelationalWriter* relationalWriter, Configuration& configuration) : relationalWriter(relationalWriter), configuration(configuration) {

	}

	virtual ~SqlHandler() {

	}

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

	}

	void attribute(const string_t& value) override {

	}

	void endOfPipe() {

		for (const Statement& statement : configuration.statements) processStatement(statement);

	}

};

}

}

}