/**
 * 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 <unistd.h>

#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);
		if (result != SQLITE_OK) {
			sqlite3_close(db);
			throw SqlException(L"Unable to open SQLite database.");
		}
	}

	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;
		// TODO: support also other data types
		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) {
		std::string file = configuration.file.size() ? convertor.to_bytes(configuration.file) : ":memory:";
		connection.reset(new Connection(file.c_str()));
	}

	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);
		
		if (configuration.file.size() && !configuration.keepFile) {
			int result = unlink(convertor.to_bytes(configuration.file).c_str());
			if (result) throw SqlException(L"Unable to delete SQLite file.");
		}
	}

};

}
}
}