<?php
/**
 * @package     Joomla.Platform
 * @subpackage  Database
 *
 * @copyright   Copyright (C) 2005 - 2017 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE
 */

defined('JPATH_PLATFORM') or die;

/**
 * MySQL database driver supporting PDO based connections
 *
 * @link   https://secure.php.net/manual/en/ref.pdo-mysql.php
 * @since  3.4
 */
class JDatabaseDriverPdomysql extends JDatabaseDriverPdo
{
	/**
	 * The name of the database driver.
	 *
	 * @var    string
	 * @since  3.4
	 */
	public $name = 'pdomysql';

	/**
	 * The type of the database server family supported by this driver.
	 *
	 * @var    string
	 * @since  CMS 3.5.0
	 */
	public $serverType = 'mysql';

	/**
	 * The character(s) used to quote SQL statement names such as table names or field names,
	 * etc. The child classes should define this as necessary.  If a single character string the
	 * same character is used for both sides of the quoted name, else the first character will be
	 * used for the opening quote and the second for the closing quote.
	 *
	 * @var    string
	 * @since  3.4
	 */
	protected $nameQuote = '`';

	/**
	 * The null or zero representation of a timestamp for the database driver.  This should be
	 * defined in child classes to hold the appropriate value for the engine.
	 *
	 * @var    string
	 * @since  3.4
	 */
	protected $nullDate = '0000-00-00 00:00:00';

	/**
	 * The minimum supported database version.
	 *
	 * @var    string
	 * @since  3.4
	 */
	protected static $dbMinimum = '5.0.4';

	/**
	 * Constructor.
	 *
	 * @param   array  $options  Array of database options with keys: host, user, password, database, select.
	 *
	 * @since   3.4
	 */
	public function __construct($options)
	{
		// Get some basic values from the options.
		$options['driver']  = 'mysql';

		if (!isset($options['charset']) || $options['charset'] == 'utf8')
		{
			$options['charset'] = 'utf8mb4';
		}

		/**
		 * Pre-populate the UTF-8 Multibyte compatibility flag. Unfortunately PDO won't report the server version
		 * unless we're connected to it, and we cannot connect to it unless we know if it supports utf8mb4, which requires
		 * us knowing the server version. Because of this chicken and egg issue, we _assume_ it's supported and we'll just
		 * catch any problems at connection time.
		 */
		$this->utf8mb4 = ($options['charset'] == 'utf8mb4');

		// Finalize initialisation.
		parent::__construct($options);
	}

	/**
	 * Connects to the database if needed.
	 *
	 * @return  void  Returns void if the database connected successfully.
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function connect()
	{
		if ($this->connection)
		{
			return;
		}

		try
		{
			// Try to connect to MySQL
			parent::connect();
		}
		catch (\RuntimeException $e)
		{
			// If the connection failed, but not because of the wrong character set, then bubble up the exception.
			if (!$this->utf8mb4)
			{
				throw $e;
			}

			/*
			 * Otherwise, try connecting again without using
			 * utf8mb4 and see if maybe that was the problem. If the
			 * connection succeeds, then we will have learned that the
			 * client end of the connection does not support utf8mb4.
  			 */
			$this->utf8mb4 = false;
			$this->options['charset'] = 'utf8';

			parent::connect();
		}

		if ($this->utf8mb4)
		{
			/*
 			 * At this point we know the client supports utf8mb4.  Now
 			 * we must check if the server supports utf8mb4 as well.
 			 */
			$serverVersion = $this->connection->getAttribute(PDO::ATTR_SERVER_VERSION);
			$this->utf8mb4 = version_compare($serverVersion, '5.5.3', '>=');

			if (!$this->utf8mb4)
			{
				// Reconnect with the utf8 character set.
				parent::disconnect();
				$this->options['charset'] = 'utf8';
				parent::connect();
			}
		}

		$this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
		$this->connection->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);

		// Set sql_mode to non_strict mode
		$this->connection->query("SET @@SESSION.sql_mode = '';");
	}

	/**
	 * Test to see if the MySQL connector is available.
	 *
	 * @return  boolean  True on success, false otherwise.
	 *
	 * @since   3.4
	 */
	public static function isSupported()
	{
		return class_exists('PDO') && in_array('mysql', PDO::getAvailableDrivers());
	}

	/**
	 * Drops a table from the database.
	 *
	 * @param   string   $tableName  The name of the database table to drop.
	 * @param   boolean  $ifExists   Optionally specify that the table must exist before it is dropped.
	 *
	 * @return  JDatabaseDriverPdomysql  Returns this object to support chaining.
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function dropTable($tableName, $ifExists = true)
	{
		$this->connect();

		$query = $this->getQuery(true);

		$query->setQuery('DROP TABLE ' . ($ifExists ? 'IF EXISTS ' : '') . $this->quoteName($tableName));

		$this->setQuery($query);

		$this->execute();

		return $this;
	}

	/**
	 * Select a database for use.
	 *
	 * @param   string  $database  The name of the database to select for use.
	 *
	 * @return  boolean  True if the database was successfully selected.
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function select($database)
	{
		$this->connect();

		$this->setQuery('USE ' . $this->quoteName($database));

		$this->execute();

		return $this;
	}

	/**
	 * Method to get the database collation in use by sampling a text field of a table in the database.
	 *
	 * @return  mixed  The collation in use by the database (string) or boolean false if not supported.
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function getCollation()
	{
		$this->connect();

		// Attempt to get the database collation by accessing the server system variable.
		$this->setQuery('SHOW VARIABLES LIKE "collation_database"');
		$result = $this->loadObject();

		if (property_exists($result, 'Value'))
		{
			return $result->Value;
		}
		else
		{
			return false;
		}
	}

	/**
	 * Method to get the database connection collation, as reported by the driver. If the connector doesn't support
	 * reporting this value please return an empty string.
	 *
	 * @return  string
	 */
	public function getConnectionCollation()
	{
		$this->connect();

		// Attempt to get the database collation by accessing the server system variable.
		$this->setQuery('SHOW VARIABLES LIKE "collation_connection"');
		$result = $this->loadObject();

		if (property_exists($result, 'Value'))
		{
			return $result->Value;
		}
		else
		{
			return false;
		}
	}

	/**
	 * Shows the table CREATE statement that creates the given tables.
	 *
	 * @param   mixed  $tables  A table name or a list of table names.
	 *
	 * @return  array  A list of the create SQL for the tables.
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function getTableCreate($tables)
	{
		$this->connect();

		// Initialise variables.
		$result = array();

		// Sanitize input to an array and iterate over the list.
		settype($tables, 'array');

		foreach ($tables as $table)
		{
			$this->setQuery('SHOW CREATE TABLE ' . $this->quoteName($table));

			$row = $this->loadRow();

			// Populate the result array based on the create statements.
			$result[$table] = $row[1];
		}

		return $result;
	}

	/**
	 * Retrieves field information about a given table.
	 *
	 * @param   string   $table     The name of the database table.
	 * @param   boolean  $typeOnly  True to only return field types.
	 *
	 * @return  array  An array of fields for the database table.
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function getTableColumns($table, $typeOnly = true)
	{
		$this->connect();

		$result = array();

		// Set the query to get the table fields statement.
		$this->setQuery('SHOW FULL COLUMNS FROM ' . $this->quoteName($table));

		$fields = $this->loadObjectList();

		// If we only want the type as the value add just that to the list.
		if ($typeOnly)
		{
			foreach ($fields as $field)
			{
				$result[$field->Field] = preg_replace('/[(0-9)]/', '', $field->Type);
			}
		}
		// If we want the whole field data object add that to the list.
		else
		{
			foreach ($fields as $field)
			{
				$result[$field->Field] = $field;
			}
		}

		return $result;
	}

	/**
	 * Get the details list of keys for a table.
	 *
	 * @param   string  $table  The name of the table.
	 *
	 * @return  array  An array of the column specification for the table.
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function getTableKeys($table)
	{
		$this->connect();

		// Get the details columns information.
		$this->setQuery('SHOW KEYS FROM ' . $this->quoteName($table));

		$keys = $this->loadObjectList();

		return $keys;
	}

	/**
	 * Method to get an array of all tables in the database.
	 *
	 * @return  array  An array of all the tables in the database.
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function getTableList()
	{
		$this->connect();

		// Set the query to get the tables statement.
		$this->setQuery('SHOW TABLES');
		$tables = $this->loadColumn();

		return $tables;
	}

	/**
	 * Get the version of the database connector.
	 *
	 * @return  string  The database connector version.
	 *
	 * @since   3.4
	 */
	public function getVersion()
	{
		$this->connect();

		return $this->getOption(PDO::ATTR_SERVER_VERSION);
	}

	/**
	 * Locks a table in the database.
	 *
	 * @param   string  $table  The name of the table to unlock.
	 *
	 * @return  JDatabaseDriverPdomysql  Returns this object to support chaining.
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function lockTable($table)
	{
		$this->setQuery('LOCK TABLES ' . $this->quoteName($table) . ' WRITE')->execute();

		return $this;
	}

	/**
	 * Renames a table in the database.
	 *
	 * @param   string  $oldTable  The name of the table to be renamed
	 * @param   string  $newTable  The new name for the table.
	 * @param   string  $backup    Not used by MySQL.
	 * @param   string  $prefix    Not used by MySQL.
	 *
	 * @return  JDatabaseDriverPdomysql  Returns this object to support chaining.
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function renameTable($oldTable, $newTable, $backup = null, $prefix = null)
	{
		$this->setQuery('RENAME TABLE ' . $this->quoteName($oldTable) . ' TO ' . $this->quoteName($newTable));

		$this->execute();

		return $this;
	}

	/**
	 * Method to escape a string for usage in an SQL statement.
	 *
	 * Oracle escaping reference:
	 * http://www.orafaq.com/wiki/SQL_FAQ#How_does_one_escape_special_characters_when_writing_SQL_queries.3F
	 *
	 * SQLite escaping notes:
	 * http://www.sqlite.org/faq.html#q14
	 *
	 * Method body is as implemented by the Zend Framework
	 *
	 * Note: Using query objects with bound variables is
	 * preferable to the below.
	 *
	 * @param   string   $text   The string to be escaped.
	 * @param   boolean  $extra  Unused optional parameter to provide extra escaping.
	 *
	 * @return  string  The escaped string.
	 *
	 * @since   3.4
	 */
	public function escape($text, $extra = false)
	{
		$this->connect();

		if (is_int($text) || is_float($text))
		{
			return $text;
		}

		$result = substr($this->connection->quote($text), 1, -1);

		if ($extra)
		{
			$result = addcslashes($result, '%_');
		}

		return $result;
	}

	/**
	 * Unlocks tables in the database.
	 *
	 * @return  JDatabaseDriverPdomysql  Returns this object to support chaining.
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function unlockTables()
	{
		$this->setQuery('UNLOCK TABLES')->execute();

		return $this;
	}

	/**
	 * Method to commit a transaction.
	 *
	 * @param   boolean  $toSavepoint  If true, commit to the last savepoint.
	 *
	 * @return  void
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function transactionCommit($toSavepoint = false)
	{
		$this->connect();

		if (!$toSavepoint || $this->transactionDepth <= 1)
		{
			parent::transactionCommit($toSavepoint);
		}
		else
		{
			$this->transactionDepth--;
		}
	}

	/**
	 * Method to roll back a transaction.
	 *
	 * @param   boolean  $toSavepoint  If true, rollback to the last savepoint.
	 *
	 * @return  void
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function transactionRollback($toSavepoint = false)
	{
		$this->connect();

		if (!$toSavepoint || $this->transactionDepth <= 1)
		{
			parent::transactionRollback($toSavepoint);
		}
		else
		{
			$savepoint = 'SP_' . ($this->transactionDepth - 1);
			$this->setQuery('ROLLBACK TO SAVEPOINT ' . $this->quoteName($savepoint));

			if ($this->execute())
			{
				$this->transactionDepth--;
			}
		}
	}

	/**
	 * Method to initialize a transaction.
	 *
	 * @param   boolean  $asSavepoint  If true and a transaction is already active, a savepoint will be created.
	 *
	 * @return  void
	 *
	 * @since   3.4
	 * @throws  RuntimeException
	 */
	public function transactionStart($asSavepoint = false)
	{
		$this->connect();

		if (!$asSavepoint || !$this->transactionDepth)
		{
			parent::transactionStart($asSavepoint);
		}
		else
		{
			$savepoint = 'SP_' . $this->transactionDepth;
			$this->setQuery('SAVEPOINT ' . $this->quoteName($savepoint));

			if ($this->execute())
			{
				$this->transactionDepth++;
			}
		}
	}
}
