<?php
/**
 * webtrees: online genealogy
 * Copyright (C) 2017 webtrees development team
 * 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
 * MERCHANTASET NAMES 'utf8' COLLATE 'utf8_unicode_ci'LITY 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/>.
 */
namespace Fisharebest\Webtrees;

use Exception;
use Fisharebest\Webtrees\Schema\MigrationInterface;
use PDO;
use PDOException;

/**
 * Extend PHP's native PDO class.
 */
class Database {
	/** @var Database Implement the singleton pattern */
	private static $instance;

	/** @var PDO Native PHP database driver */
	private static $pdo;

	/** @var Statement[] Cache of prepared statements */
	private static $prepared = [];

	/** @var string Prefix allows multiple instances in one database */
	private static $table_prefix = '';

	/**
	 * Begin a transaction.
	 *
	 * @return bool
	 */
	public static function beginTransaction() {
		return self::$pdo->beginTransaction();
	}

	/**
	 * Commit this transaction.
	 *
	 * @return bool
	 */
	public static function commit() {
		return self::$pdo->commit();
	}

	/**
	 * Disconnect from the server, so we can connect to another one
	 */
	public static function disconnect() {
		self::$pdo = null;
	}

	/**
	 * Implement the singleton pattern, using a static accessor.
	 *
	 * @param string[] $config
	 *
	 * @throws Exception
	 */
	public static function createInstance(array $config) {
		if (self::$pdo instanceof PDO) {
			throw new Exception('Database::createInstance() can only be called once.');
		}

		self::$table_prefix = $config['tblpfx'];

		// Create the underlying PDO object
		self::$pdo = new PDO(
			(substr($config['dbhost'], 0, 1) === '/' ?
				"mysql:unix_socket={$config['dbhost']};dbname={$config['dbname']}" :
				"mysql:host={$config['dbhost']};dbname={$config['dbname']};port={$config['dbport']}"
			),
			$config['dbuser'], $config['dbpass'],
			[
				PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
				PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_OBJ,
				PDO::ATTR_CASE               => PDO::CASE_LOWER,
				PDO::ATTR_AUTOCOMMIT         => true,
			]
		);

		self::$pdo = DebugBar::initPDO(self::$pdo);

		self::$pdo->exec("SET NAMES 'utf8' COLLATE 'utf8_unicode_ci'");
		self::$pdo->prepare("SET time_zone = :time_zone")->execute(['time_zone' => date('P')]);

		self::$instance = new self;
	}

	/**
	 * We don't access $instance directly, only via query(), exec() and prepare()
	 *
	 * @throws Exception
	 *
	 * @return Database
	 */
	public static function getInstance() {
		if (self::$pdo instanceof PDO) {
			return self::$instance;
		} else {
			throw new Exception('createInstance() must be called before getInstance().');
		}
	}

	/**
	 * Are we currently connected to a database?
	 *
	 * @return bool
	 */
	public static function isConnected() {
		return self::$pdo instanceof PDO;
	}

	/**
	 * Determine the most recently created value of an AUTO_INCREMENT field.
	 *
	 * @return string
	 */
	public static function lastInsertId() {
		return self::$pdo->lastInsertId();
	}

	/**
	 * Quote a string for embedding in a MySQL statement.
	 *
	 * The native quote() function does not convert PHP nulls to DB nulls
	 *
	 * @param  string $string
	 *
	 * @return string
	 *
	 * @deprecated We should use bind-variables instead.
	 */
	public static function quote($string) {
		if (is_null($string)) {
			return 'NULL';
		} else {
			return self::$pdo->quote($string, PDO::PARAM_STR);
		}
	}

	/**
	 * Execute an SQL statement, and log the result.
	 *
	 * @param string $sql The SQL statement to execute
	 *
	 * @return int The number of rows affected by this SQL query
	 */
	public static function exec($sql) {
		$sql = str_replace('##', self::$table_prefix, $sql);

		return self::$pdo->exec($sql);
	}

	/**
	 * Prepare an SQL statement for execution.
	 *
	 * @param $sql
	 *
	 * @throws Exception
	 *
	 * @return Statement
	 */
	public static function prepare($sql) {
		if (!self::$pdo instanceof PDO) {
			throw new Exception('No Connection Established');
		}
		$sql = str_replace('##', self::$table_prefix, $sql);

		$hash = md5($sql);
		if (!array_key_exists($hash, self::$prepared)) {
			self::$prepared[$hash] = new Statement(self::$pdo->prepare($sql));
		}

		return self::$prepared[$hash];
	}

	/**
	 * Roll back this transaction.
	 *
	 * @return bool
	 */
	public static function rollBack() {
		return self::$pdo->rollBack();
	}

	/**
	 * Run a series of scripts to bring the database schema up to date.
	 *
	 * @param string $namespace      Where to find our MigrationXXX classes
	 * @param string $schema_name    Where to find our MigrationXXX classes
	 * @param int    $target_version updade/downgrade to this version
	 *
	 * @throws PDOException
	 *
	 * @return bool  Were any updates applied
	 */
	public static function updateSchema($namespace, $schema_name, $target_version) {
		try {
			$current_version = (int) Site::getPreference($schema_name);
		} catch (PDOException $ex) {
			DebugBar::addThrowable($ex);

			// During initial installation, the site_preference table won’t exist.
			$current_version = 0;
		}

		$updates_applied = false;

		// Update the schema, one version at a time.
		while ($current_version < $target_version) {
			$class = $namespace . '\\Migration' . $current_version;
			/** @var MigrationInterface $migration */
			$migration = new $class;
			$migration->upgrade();
			$current_version++;
			Site::setPreference($schema_name, (string) $current_version);
			$updates_applied = true;
		}

		return $updates_applied;
	}

	/**
	 * Escape a string for use in a SQL "LIKE" clause
	 *
	 * @param string $string
	 *
	 * @return string
	 */
	public static function escapeLike($string) {
		return strtr(
			$string,
			[
				'\\' => '\\\\',
				'%'  => '\%',
				'_'  => '\_',
			]
		);
	}
}
