<?php
/**
 * Joomla! Content Management System
 *
 * @copyright  Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
 * @license    GNU General Public License version 2 or later; see LICENSE.txt
 */

namespace Joomla\CMS\Schema;

defined('JPATH_PLATFORM') or die;

/**
 * Each object represents one query, which is one line from a DDL SQL query.
 * This class is used to check the site's database to see if the DDL query has been run.
 * If not, it provides the ability to fix the database by re-running the DDL query.
 * The queries are parsed from the update files in the folder
 * `administrator/components/com_admin/sql/updates/<database>`.
 * These updates are run automatically if the site was updated using com_installer.
 * However, it is possible that the program files could be updated without udpating
 * the database (for example, if a user just copies the new files over the top of an
 * existing installation).
 *
 * This is an abstract class. We need to extend it for each database and add a
 * buildCheckQuery() method that creates the query to check that a DDL query has been run.
 *
 * @since  2.5
 */
abstract class ChangeItem
{
	/**
	 * Update file: full path file name where query was found
	 *
	 * @var    string
	 * @since  2.5
	 */
	public $file = null;

	/**
	 * Update query: query used to change the db schema (one line from the file)
	 *
	 * @var    string
	 * @since  2.5
	 */
	public $updateQuery = null;

	/**
	 * Check query: query used to check the db schema
	 *
	 * @var    string
	 * @since  2.5
	 */
	public $checkQuery = null;

	/**
	 * Check query result: expected result of check query if database is up to date
	 *
	 * @var    string
	 * @since  2.5
	 */
	public $checkQueryExpected = 1;

	/**
	 * \JDatabaseDriver object
	 *
	 * @var    \JDatabaseDriver
	 * @since  2.5
	 */
	public $db = null;

	/**
	 * Query type: To be used in building a language key for a
	 * message to tell user what was checked / changed
	 * Possible values: ADD_TABLE, ADD_COLUMN, CHANGE_COLUMN_TYPE, ADD_INDEX
	 *
	 * @var    string
	 * @since  2.5
	 */
	public $queryType = null;

	/**
	 * Array with values for use in a \JText::sprintf statment indicating what was checked
	 *
	 * Tells you what the message should be, based on which elements are defined, as follows:
	 *     For ADD_TABLE: table
	 *     For ADD_COLUMN: table, column
	 *     For CHANGE_COLUMN_TYPE: table, column, type
	 *     For ADD_INDEX: table, index
	 *
	 * @var    array
	 * @since  2.5
	 */
	public $msgElements = array();

	/**
	 * Checked status
	 *
	 * @var    integer   0=not checked, -1=skipped, -2=failed, 1=succeeded
	 * @since  2.5
	 */
	public $checkStatus = 0;

	/**
	 * Rerun status
	 *
	 * @var    int   0=not rerun, -1=skipped, -2=failed, 1=succeeded
	 * @since  2.5
	 */
	public $rerunStatus = 0;

	/**
	 * Constructor: builds check query and message from $updateQuery
	 *
	 * @param   \JDatabaseDriver  $db     Database connector object
	 * @param   string            $file   Full path name of the sql file
	 * @param   string            $query  Text of the sql query (one line of the file)
	 *
	 * @since   2.5
	 */
	public function __construct($db, $file, $query)
	{
		$this->updateQuery = $query;
		$this->file = $file;
		$this->db = $db;
		$this->buildCheckQuery();
	}

	/**
	 * Returns a reference to the ChangeItem object.
	 *
	 * @param   \JDatabaseDriver  $db     Database connector object
	 * @param   string            $file   Full path name of the sql file
	 * @param   string            $query  Text of the sql query (one line of the file)
	 *
	 * @return  ChangeItem  instance based on the database driver
	 *
	 * @since   2.5
	 * @throws  \RuntimeException if class for database driver not found
	 */
	public static function getInstance($db, $file, $query)
	{
		// Get the class name
		$serverType = $db->getServerType();

		// For `mssql` server types, convert the type to `sqlsrv`
		if ($serverType === 'mssql')
		{
			$serverType = 'sqlsrv';
		}

		$class = '\\Joomla\\CMS\\Schema\\ChangeItem\\' . ucfirst($serverType) . 'ChangeItem';

		// If the class exists, return it.
		if (class_exists($class))
		{
			return new $class($db, $file, $query);
		}

		throw new \RuntimeException(sprintf('ChangeItem child class not found for the %s database driver', $serverType), 500);
	}

	/**
	 * Checks a DDL query to see if it is a known type
	 * If yes, build a check query to see if the DDL has been run on the database.
	 * If successful, the $msgElements, $queryType, $checkStatus and $checkQuery fields are populated.
	 * The $msgElements contains the text to create the user message.
	 * The $checkQuery contains the SQL query to check whether the schema change has
	 * been run against the current database. The $queryType contains the type of
	 * DDL query that was run (for example, CREATE_TABLE, ADD_COLUMN, CHANGE_COLUMN_TYPE, ADD_INDEX).
	 * The $checkStatus field is set to zero if the query is created
	 *
	 * If not successful, $checkQuery is empty and , and $checkStatus is -1.
	 * For example, this will happen if the current line is a non-DDL statement.
	 *
	 * @return void
	 *
	 * @since  2.5
	 */
	abstract protected function buildCheckQuery();

	/**
	 * Runs the check query and checks that 1 row is returned
	 * If yes, return true, otherwise return false
	 *
	 * @return  boolean  true on success, false otherwise
	 *
	 * @since  2.5
	 */
	public function check()
	{
		$this->checkStatus = -1;

		if ($this->checkQuery)
		{
			$this->db->setQuery($this->checkQuery);

			try
			{
				$rows = $this->db->loadRowList(0);
			}
			catch (\RuntimeException $e)
			{
				// Still render the error message from the Exception object
				\JFactory::getApplication()->enqueueMessage($e->getMessage(), 'error');
				$this->checkStatus = -2;

				return $this->checkStatus;
			}

			if (count($rows) === $this->checkQueryExpected)
			{
				$this->checkStatus = 1;

				return $this->checkStatus;
			}

			$this->checkStatus = -2;
		}

		return $this->checkStatus;
	}

	/**
	 * Runs the update query to apply the change to the database
	 *
	 * @return  void
	 *
	 * @since   2.5
	 */
	public function fix()
	{
		if ($this->checkStatus === -2)
		{
			// At this point we have a failed query
			$query = $this->db->convertUtf8mb4QueryToUtf8($this->updateQuery);
			$this->db->setQuery($query);

			if ($this->db->execute())
			{
				if ($this->check())
				{
					$this->checkStatus = 1;
					$this->rerunStatus = 1;
				}
				else
				{
					$this->rerunStatus = -2;
				}
			}
			else
			{
				$this->rerunStatus = -2;
			}
		}
	}
}