<?php
/**
 * DynamicPageList3
 * DPL Variables Class
 *
 * @author		IlyaHaykinson, Unendlich, Dangerville, Algorithmix, Theaitetos, Alexia E. Smith, Universal Omega
 * @license		GPL-2.0-or-later
 * @package		DynamicPageList3
 *
 **/
namespace DPL;

class Query {
	/**
	 * Parameters Object
	 *
	 * @var		object
	 */
	private $parameters;

	/**
	 * Mediawiki DB Object
	 *
	 * @var		object
	 */
	private $DB;

	/**
	 * Array of prefixed and escaped table names.
	 *
	 * @var		array
	 */
	private $tableNames = [];

	/**
	 * Parameters that have already been processed.
	 *
	 * @var		array
	 */
	private $parametersProcessed = [];

	/**
	 * Select Fields
	 *
	 * @var		array
	 */
	private $select = [];

	/**
	 * The generated SQL Query.
	 *
	 * @var     string
	 */
	private $sqlQuery = '';

	/**
	 * Selected Fields - An array to look up keys against for speed optimization.
	 *
	 * @var		array
	 */
	private $selectedFields = [];

	/**
	 * Prefixed and escaped table names.
	 *
	 * @var		array
	 */
	private $tables = [];

	/**
	 * Where Clauses
	 *
	 * @var		array
	 */
	private $where = [];

	/**
	 * Group By Clauses
	 *
	 * @var		array
	 */
	private $groupBy = [];

	/**
	 * Order By Clauses
	 *
	 * @var		array
	 */
	private $orderBy = [];

	/**
	 * Join Clauses
	 *
	 * @var		array
	 */
	private $join = [];

	/**
	 * Limit
	 *
	 * @var		integer
	 */
	private $limit = false;

	/**
	 * Offset
	 *
	 * @var		integer
	 */
	private $offset = false;

	/**
	 * Order By Direction
	 *
	 * @var		string
	 */
	private $direction = 'ASC';

	/**
	 * Distinct Results
	 *
	 * @var		boolean
	 */
	private $distinct = true;

	/**
	 * Character Set Collation
	 *
	 * @var		string
	 */
	private $collation = false;

	/**
	 * Number of Rows Found
	 *
	 * @var		integer
	 */
	private $foundRows = 0;

	/**
	 * Was the revision auxiliary table select added for firstedit and lastedit?
	 *
	 * @var		boolean
	 */
	private $revisionAuxWhereAdded = false;

	/**
	 * Main Constructor
	 *
	 * @access	public
	 * @param	\DPL\Parameters	$parameters
	 * @return	void
	 */
	public function __construct(Parameters $parameters) {
		$this->parameters = $parameters;

		$this->tableNames = self::getTableNames();

		$this->DB = wfGetDB(DB_REPLICA, 'dpl');
	}

	/**
	 * Start a query build.
	 *
	 * @access	public
	 * @param	boolean	Calculate Found Rows
	 * @return	mixed	Mediawiki Result Object or False
	 */
	public function buildAndSelect($calcRows = false) {
		global $wgNonincludableNamespaces;

		$options = [];

		$parameters = $this->parameters->getAllParameters();
		foreach ($parameters as $parameter => $option) {
			$function = "_" . $parameter;
			//Some parameters do not modifiy the query so we check if the function to modify the query exists first.
			$success = true;
			if (method_exists($this, $function)) {
				$success = $this->$function($option);
			}
			if ($success === false) {
				throw new \MWException(__METHOD__ . ": SQL Build Error returned from {$function} for " . serialize($option) . ".");
			}
			$this->parametersProcessed[$parameter] = true;
		}

		if (!$this->parameters->getParameter('openreferences')) {
			//Add things that are always part of the query.
			$this->addTable('page', $this->tableNames['page']);
			$this->addSelect(
				[
					'page_namespace'	=> $this->tableNames['page'] . '.page_namespace',
					'page_id'			=> $this->tableNames['page'] . '.page_id',
					'page_title'		=> $this->tableNames['page'] . '.page_title'
				]
			);
		}
		//Always add nonincludeable namespaces.
		if (is_array($wgNonincludableNamespaces) && count($wgNonincludableNamespaces)) {
			$this->addNotWhere(
				[
					$this->tableNames['page'] . '.page_namespace' => $wgNonincludableNamespaces
				]
			);
		}

		if ($this->offset !== false) {
			$options['OFFSET'] = $this->offset;
		}
		if ($this->limit !== false) {
			$options['LIMIT'] = $this->limit;
		} elseif ($this->offset !== false && $this->limit === false) {
			$options['LIMIT'] = $this->parameters->getData('count')['default'];
		}

		if ($this->parameters->getParameter('openreferences')) {
			if (count($this->parameters->getParameter('imagecontainer')) > 0) {
				//$sSqlSelectFrom = $sSqlCl_to.'ic.il_to, '.$sSqlSelPage."ic.il_to AS sortkey".' FROM '.$this->tableNames['imagelinks'].' AS ic';
				$tables = [
					'ic'	=> 'imagelinks'
				];
			} else {
				//$sSqlSelectFrom = "SELECT $sSqlCalcFoundRows $sSqlDistinct ".$sSqlCl_to.'pl_namespace, pl_title'.$sSqlSelPage.$sSqlSortkey.' FROM '.$this->tableNames['pagelinks'];
				$this->addSelect(
					[
						'pl_namespace',
						'pl_title'
					]
				);
				$tables = [
					'pagelinks'
				];
			}
		} else {
			$tables = $this->tables;
			if (count($this->groupBy)) {
				$options['GROUP BY'] = $this->groupBy;
			}
			if (count($this->orderBy)) {
				$options['ORDER BY'] = $this->orderBy;
				foreach ($options['ORDER BY'] as $key => $value) {
					$options['ORDER BY'][$key] .= " " . $this->direction;
				}
			}
		}
		if ($this->parameters->getParameter('goal') == 'categories') {
			$categoriesGoal = true;
			$select = [
				$this->tableNames['page'] . '.page_id'
			];
			$options[] = 'DISTINCT';
		} else {
			if ($calcRows) {
				$options[] = 'SQL_CALC_FOUND_ROWS';
			}
			if ($this->distinct) {
				$options[] = 'DISTINCT';
			}
			$categoriesGoal = false;
			$select = $this->select;
		}

		$queryError = false;
		try {
			if ($categoriesGoal) {
				$result = $this->DB->select(
					$tables,
					$select,
					$this->where,
					__METHOD__,
					$options,
					$this->join
				);

				while ($row = $result->fetchRow()) {
					$pageIds[] = $row['page_id'];
				}
				$sql = $this->DB->selectSQLText(
					[
						'clgoal'	=> 'categorylinks'
					],
					[
						'clgoal.cl_to'
					],
					[
						'clgoal.cl_from'	=> $pageIds
					],
					__METHOD__,
					[
						'ORDER BY'	=> 'clgoal.cl_to ' . $this->direction
					]
				);
			} else {
				$sql = $this->DB->selectSQLText(
					$tables,
					$select,
					$this->where,
					__METHOD__,
					$options,
					$this->join
				);
			}

			$this->sqlQuery = $sql;
			$result = $this->DB->query($sql, __METHOD__);

			if ($calcRows) {
				$calcRowsResult = $this->DB->query('SELECT FOUND_ROWS() AS rowcount', __METHOD__);
				$total = $this->DB->fetchRow($calcRowsResult);
				$this->foundRows = intval($total['rowcount']);
				$this->DB->freeResult($calcRowsResult);
			}
		} catch (Exception $e) {
			$queryError = true;
		}
		if ($queryError == true || $result === false) {
			throw new \MWException(__METHOD__ . ": " . wfMessage('dpl_query_error', DPL_VERSION, $this->DB->lastError())->text());
		}

		return $result;
	}

	/**
	 * Return the number of found rows.
	 *
	 * @access	public
	 * @return	integer	Number of Found Rows
	 */
	public function getFoundRows() {
		return $this->foundRows;
	}

	/**
	 * Returns the generated SQL Query
	 *
	 * @access	public
	 * @return	string	SQL Query
	 */
	public function getSqlQuery() {
		return $this->sqlQuery;
	}

	/**
	 * Return prefixed and quoted tables that are needed.
	 *
	 * @access	public
	 * @return	array	Prepared table names.
	 */
	public static function getTableNames() {
		$DB = wfGetDB(DB_REPLICA, 'dpl');
		$tables = [
			'categorylinks',
			'dpl_clview',
			'externallinks',
			'flaggedpages',
			'imagelinks',
			'page',
			'pagelinks',
			'recentchanges',
			'revision',
			'revision_actor_temp',
			'templatelinks'
		];

		$tableNames = [];
		foreach ($tables as $table) {
			$tableNames[$table] = $DB->tableName($table);
		}
		return $tableNames;
	}

	/**
	 * Add a table to the output.
	 *
	 * @access	public
	 * @param	string	Raw Table Name - Will be ran through tableName().
	 * @param	string	Table Alias
	 * @return	boolean	Success - Added, false if the table alias already exists.
	 */
	public function addTable($table, $alias) {
		if (empty($table)) {
			throw new \MWException(__METHOD__ . ': An empty table name was passed.');
		}
		if (empty($alias) || is_numeric($alias)) {
			throw new \MWException(__METHOD__ . ': An empty or numeric table alias was passed.');
		}
		if (!isset($this->tables[$alias])) {
			$this->tables[$alias] = $this->DB->tableName($table);
			return true;
		} else {
			return false;
		}
	}

	/**
	 * Add a where clause to the output.
	 * Where clauses get imploded together with AND at the end.	 Any custom where clauses should be preformed before placed into here.
	 *
	 * @access	public
	 * @param	string	Where clause
	 * @return	boolean	Success
	 */
	public function addWhere($where) {
		if (empty($where)) {
			throw new \MWException(__METHOD__ . ': An empty where clause was passed.');
		}
		if (is_string($where)) {
			$this->where[] = $where;
		} elseif (is_array($where)) {
			$this->where = array_merge($this->where, $where);
		} else {
			throw new \MWException(__METHOD__ . ': An invalid where clause was passed.');
			return false;
		}
		return true;
	}

	/**
	 * Add a where clause to the output that uses NOT IN or !=.
	 *
	 * @access	public
	 * @param	array	Field => Value(s)
	 * @return	boolean	Success
	 */
	public function addNotWhere($where) {
		if (empty($where)) {
			throw new \MWException(__METHOD__ . ': An empty not where clause was passed.');
			return false;
		}
		if (is_array($where)) {
			foreach ($where as $field => $values) {
				$this->where[] = $field . (count($values) > 1 ? ' NOT IN(' . $this->DB->makeList($values) . ')' : ' != ' . $this->DB->addQuotes(current($values)));
			}
		} else {
			throw new \MWException(__METHOD__ . ': An invalid not where clause was passed.');
			return false;
		}
		return true;
	}

	/**
	 * Add a field to select.
	 * Will ignore duplicate values if the exact same alias and exact same field are passed.
	 *
	 * @access	public
	 * @param	array	Array of fields with the array key being the field alias.  Leave the array key as a numeric index to not specify an alias.
	 * @return	boolean	Success
	 */
	public function addSelect($fields) {
		if (!is_array($fields)) {
			throw new \MWException(__METHOD__ . ': A non-array was passed.');
		}
		foreach ($fields as $alias => $field) {
			if (!is_numeric($alias) && array_key_exists($alias, $this->select) && $this->select[$alias] != $field) {
				//In case of a code bug that is overwriting an existing field alias throw an exception.
				throw new \MWException(__METHOD__ . ": Attempted to overwrite existing field alias `{$this->select[$alias]}` AS `{$alias}` with `{$field}` AS `{$alias}`.");
			}
			//String alias and does not exist already.
			if (!is_numeric($alias) && !array_key_exists($alias, $this->select)) {
				$this->select[$alias] = $field;
			}

			//Speed up by not using in_array() or array_key_exists().  Toss the field names into their own array as keys => true to exploit a speedy look up with isset().
			if (is_numeric($alias) && !isset($this->selectedFields[$field])) {
				$this->select[] = $field;
				$this->selectedFields[$field] = true;
			}
		}
		return true;
	}

	/**
	 * Add a GROUP BY clause to the output.
	 *
	 * @access	public
	 * @param	string	Group By Clause
	 * @return	boolean	Success
	 */
	public function addGroupBy($groupBy) {
		if (empty($groupBy)) {
			throw new \MWException(__METHOD__ . ': An empty group by clause was passed.');
		}
		$this->groupBy[] = $groupBy;
		return true;
	}

	/**
	 * Add a ORDER BY clause to the output.
	 *
	 * @access	public
	 * @param	string	Order By Clause
	 * @return	boolean	Success
	 */
	public function addOrderBy($orderBy) {
		if (empty($orderBy)) {
			throw new \MWException(__METHOD__ . ': An empty order by clause was passed.');
		}
		$this->orderBy[] = $orderBy;
		return true;
	}

	/**
	 * Add a JOIN clause to the output.
	 *
	 * @access	public
	 * @param	string	Table Alias
	 * @param	array	Join Conditions in the format of the join type to the on where condition.  Example: ['JOIN TYPE' => 'this = that']
	 * @return	boolean	Success
	 */
	public function addJoin($tableAlias, $joinConditions) {
		if (empty($tableAlias) || empty($joinConditions)) {
			throw new \MWException(__METHOD__ . ': An empty join clause was passed.');
		}
		if (isset($this->join[$tableAlias])) {
			throw new \MWException(__METHOD__ . ': Attempted to overwrite existing join clause.');
		}
		$this->join[$tableAlias] = $joinConditions;
		return true;
	}

	/**
	 * Set the limit.
	 *
	 * @access	public
	 * @param	mixed	Integer limit or false to unset.
	 * @return	boolean	Success
	 */
	public function setLimit($limit) {
		if (is_numeric($limit)) {
			$this->limit = intval($limit);
		} else {
			$this->limit = false;
		}
		return true;
	}

	/**
	 * Set the offset.
	 *
	 * @access	public
	 * @param	mixed	Integer offset or false to unset.
	 * @return	boolean	Success
	 */
	public function setOffset($offset) {
		if (is_numeric($offset)) {
			$this->offset = intval($offset);
		} else {
			$this->offset = false;
		}
		return true;
	}

	/**
	 * Set the ORDER BY direction
	 *
	 * @access	public
	 * @param	string	SQL direction key word.
	 * @return	boolean	Success
	 */
	public function setOrderDir($direction) {
		$this->direction = $direction;
		return true;
	}

	/**
	 * Set the character set collation.
	 *
	 * @access	public
	 * @param	string	Collation
	 * @return	void
	 */
	public function setCollation($collation) {
		$this->collation = $collation;
	}

	/**
	 * Return SQL prefixed collation.
	 *
	 * @access	public
	 * @return	string	SQL Collation
	 */
	public function getCollateSQL() {
		return ($this->collation !== false ? 'COLLATE ' . $this->collation : null);
	}

	/**
	 * Recursively get and return an array of subcategories.
	 *
	 * @access	public
	 * @param	string	Category Name
	 * @param	integer	[Optional] Maximum Depth
	 * @return	array	Subcategories
	 */
	public static function getSubcategories($categoryName, $depth = 1) {
		$DB = wfGetDB(DB_REPLICA, 'dpl');

		if ($depth > 2) {
			//Hard constrain depth because lots of recursion is bad.
			$depth = 2;
		}
		$categories = [];
		$result = $DB->select(
			['page', 'categorylinks'],
			['page_title'],
			[
				'page_namespace'		=> intval(NS_CATEGORY),
				'categorylinks.cl_to'	=> str_replace(' ', '_', $categoryName)
			],
			__METHOD__,
			['DISTINCT'],
			[
				'categorylinks' => [
					'INNER JOIN',
					'page.page_id = categorylinks.cl_from'
				]
			]
		);
		while ($row = $result->fetchRow()) {
			$categories[] = $row['page_title'];
			if ($depth > 1) {
				$categories = array_merge($categories, self::getSubcategories($row['page_title'], $depth - 1));
			}
		}
		$categories = array_unique($categories);
		$DB->freeResult($result);
		return $categories;
	}

	/**
	 * Helper method to handle relative timestamps.
	 *
	 * @access	private
	 * @param	mixed	Integer or string
	 * @return	integer
	 */
	private function convertTimestamp($inputDate) {
		$timestamp = $inputDate;
		switch ($inputDate) {
			case 'today':
				$timestamp = date('YmdHis');
				break;
			case 'last hour':
				$date = new \DateTime();
				$date->sub(new \DateInterval('P1H'));
				$timestamp = $date->format('YmdHis');
				break;
			case 'last day':
				$date = new \DateTime();
				$date->sub(new \DateInterval('P1D'));
				$timestamp = $date->format('YmdHis');
				break;
			case 'last week':
				$date = new \DateTime();
				$date->sub(new \DateInterval('P7D'));
				$timestamp = $date->format('YmdHis');
				break;
			case 'last month':
				$date = new \DateTime();
				$date->sub(new \DateInterval('P1M'));
				$timestamp = $date->format('YmdHis');
				break;
			case 'last year':
				$date = new \DateTime();
				$date->sub(new \DateInterval('P1Y'));
				$timestamp = $date->format('YmdHis');
				break;
		}

		if (is_numeric($timestamp)) {
			return $this->DB->addQuotes($timestamp);
		}
		return 0;
	}

	/**
	 * Set SQL for 'addauthor' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _addauthor($option) {
		//Addauthor can not be used with addlasteditor.
		if (!isset($this->parametersProcessed['addlasteditor']) || !$this->parametersProcessed['addlasteditor']) {
			$this->addTable('revision_actor_temp', 'rev');
			$this->addWhere(
				[
					$this->tableNames['page'] . '.page_id = rev.revactor_page',
					'rev.revactor_timestamp = (SELECT MIN(rev_aux_min.revactor_timestamp) FROM ' . $this->tableNames['revision_actor_temp'] . ' AS rev_aux_min WHERE rev_aux_min.revactor_page = rev.revactor_page)'
				]
			);
			$this->_adduser(null, 'rev');
		}
	}

	/**
	 * Set SQL for 'addcategories' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _addcategories($option) {
		$this->addTable('categorylinks', 'cl_gc');
		$this->addSelect(
			[
				'cats' => "GROUP_CONCAT(DISTINCT cl_gc.cl_to ORDER BY cl_gc.cl_to ASC SEPARATOR ' | ')"
			]
		);
		$this->addJoin(
			'cl_gc',
			[
				'LEFT OUTER JOIN',
				'page_id = cl_gc.cl_from'
			]
		);
		$this->addGroupBy($this->tableNames['page'] . '.page_id');
	}

	/**
	 * Set SQL for 'addcontribution' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _addcontribution($option) {
		$this->addTable('recentchanges', 'rc');

		$field = 'rc.rc_actor';

		$this->addSelect(
			[
				'contribution'	=> 'SUM(ABS(rc.rc_new_len - rc.rc_old_len))',
				'contributor'	=> $field
			]
		);
		$this->addWhere(
			[
				$this->tableNames['page'] . '.page_id = rc.rc_cur_id'
			]
		);
		$this->addGroupBy('rc.rc_cur_id');
	}

	/**
	 * Set SQL for 'addeditdate' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _addeditdate($option) {
		$this->addTable('revision_actor_temp', 'rev');
		$this->addSelect(['rev.revactor_timestamp']);
		$this->addWhere(
			[
				$this->tableNames['page'] . '.page_id = rev.revactor_page',
			]
		);
	}

	/**
	 * Set SQL for 'addfirstcategorydate' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _addfirstcategorydate($option) {
		//@TODO: This should be programmatically determining which categorylink table to use instead of assuming the first one.
		$this->addSelect(
			[
				'cl_timestamp'	=> "DATE_FORMAT(cl1.cl_timestamp, '%Y%m%d%H%i%s')"
			]
		);
	}

	/**
	 * Set SQL for 'addlasteditor' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _addlasteditor($option) {
		//Addlasteditor can not be used with addauthor.
		if (!isset($this->parametersProcessed['addauthor']) || !$this->parametersProcessed['addauthor']) {
			$this->addTable('revision_actor_temp', 'rev');
			$this->addWhere(
				[
					$this->tableNames['page'] . '.page_id = rev.revactor_page',
					'rev.revactor_timestamp = (SELECT MAX(rev_aux_max.revactor_timestamp) FROM ' . $this->tableNames['revision_actor_temp'] . ' AS rev_aux_max WHERE rev_aux_max.revactor_page = rev.revactor_page)'
				]
			);
			$this->_adduser(null, 'rev');
		}
	}

	/**
	 * Set SQL for 'addpagecounter' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _addpagecounter($option) {
		if (class_exists("\\HitCounters\\Hooks")) {
			$this->addTable('hit_counter', 'hit_counter');
			$this->addSelect(
				[
					"page_counter"	=> "hit_counter.page_counter"
				]
			);
			if (!isset($this->join['hit_counter'])) {
				$this->addJoin(
					'hit_counter',
					[
						"LEFT JOIN",
						"hit_counter.page_id = " . $this->tableNames['page'] . '.page_id'
					]
				);
			}
		}
	}

	/**
	 * Set SQL for 'addpagesize' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _addpagesize($option) {
		$this->addSelect(
			[
				"page_len"	=> "{$this->tableNames['page']}.page_len"
			]
		);
	}

	/**
	 * Set SQL for 'addpagetoucheddate' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _addpagetoucheddate($option) {
		$this->addSelect(
			[
				"page_touched"	=> "{$this->tableNames['page']}.page_touched"
			]
		);
	}

	/**
	 * Set SQL for 'adduser' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @param	string	[Optional] Table Alias
	 * @return	void
	 */
	private function _adduser($option, $tableAlias = '') {
		$tableAlias = (!empty($tableAlias) ? $tableAlias . '.' : '');
		$this->addSelect(
			[
				$tableAlias . 'revactor_actor',
			]
		);
	}

	/**
	 * Set SQL for 'allrevisionsbefore' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _allrevisionsbefore($option) {
		$this->addTable('revision_actor_temp', 'rev');
		$this->addSelect(
			[
				'rev.revactor_rev',
				'rev.revactor_timestamp'
			]
		);
		$this->addOrderBy('rev.revactor_rev');
		$this->setOrderDir('DESC');
		$this->addWhere(
			[
				$this->tableNames['page'] . '.page_id = rev.revactor_page',
				'rev.revactor_timestamp < ' . $this->convertTimestamp($option)
			]
		);
	}

	/**
	 * Set SQL for 'allrevisionssince' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _allrevisionssince($option) {
		$this->addTable('revision_actor_temp', 'rev');
		$this->addSelect(
			[
				'rev.rev_rev',
				'rev.revactor_timestamp'
			]
		);
		$this->addOrderBy('rev.revactor_rev');
		$this->setOrderDir('DESC');
		$this->addWhere(
			[
				$this->tableNames['page'] . '.page_id = rev.revactor_page',
				'rev.revactor_timestamp >= ' . $this->convertTimestamp($option)
			]
		);
	}

	/**
	 * Set SQL for 'articlecategory' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _articlecategory($option) {
		$this->addWhere("{$this->tableNames['page']}.page_title IN (SELECT p2.page_title FROM {$this->tableNames['page']} p2 INNER JOIN {$this->tableNames['categorylinks']} clstc ON (clstc.cl_from = p2.page_id AND clstc.cl_to = " . $this->DB->addQuotes($option) . ") WHERE p2.page_namespace = 0)");
	}

	/**
	 * Set SQL for 'categoriesminmax' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _categoriesminmax($option) {
		if (is_numeric($option[0])) {
			$this->addWhere(intval($option[0]) . ' <= (SELECT count(*) FROM ' . $this->tableNames['categorylinks'] . ' WHERE ' . $this->tableNames['categorylinks'] . '.cl_from=page_id)');
		}
		if (is_numeric($option[1])) {
			$this->addWhere(intval($option[1]) . ' >= (SELECT count(*) FROM ' . $this->tableNames['categorylinks'] . ' WHERE ' . $this->tableNames['categorylinks'] . '.cl_from=page_id)');
		}
	}

	/**
	 * Set SQL for 'category' parameter.  This includes 'category', 'categorymatch', and 'categoryregexp'.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _category($option) {
		$i = 0;
		foreach ($option as $comparisonType => $operatorTypes) {
			foreach ($operatorTypes as $operatorType => $categoryGroups) {
				foreach ($categoryGroups as $categories) {
					if (!is_array($categories)) {
						continue;
					}
					$tableName = (in_array('', $categories) ? 'dpl_clview' : 'categorylinks');
					if ($operatorType == 'AND') {
						foreach ($categories as $category) {
							$i++;
							$tableAlias = "cl{$i}";
							$this->addTable($tableName, $tableAlias);
							$this->addJoin(
								$tableAlias,
								[
									'INNER JOIN',
									"{$this->tableNames['page']}.page_id = {$tableAlias}.cl_from AND $tableAlias.cl_to {$comparisonType} " . $this->DB->addQuotes(str_replace(' ', '_', $category))
								]
							);
						}
					} elseif ($operatorType == 'OR') {
						$i++;
						$tableAlias = "cl{$i}";
						$this->addTable($tableName, $tableAlias);

						$joinOn = "{$this->tableNames['page']}.page_id = {$tableAlias}.cl_from AND (";
						$ors = [];
						foreach ($categories as $category) {
							$ors[] = "{$tableAlias}.cl_to {$comparisonType} " . $this->DB->addQuotes(str_replace(' ', '_', $category));
						}
						$joinOn .= implode(" {$operatorType} ", $ors);
						$joinOn .= ')';

						$this->addJoin(
							$tableAlias,
							[
								'INNER JOIN',
								$joinOn
							]
						);
					}
				}
			}
		}
	}

	/**
	 * Set SQL for 'notcategory' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _notcategory($option) {
		$i = 0;
		foreach ($option as $operatorType => $categories) {
			foreach ($categories as $category) {
				$i++;

				$tableAlias = "ecl{$i}";
				$this->addTable('categorylinks', $tableAlias);

				$this->addJoin(
					$tableAlias,
					[
						'LEFT OUTER JOIN',
						"{$this->tableNames['page']}.page_id = {$tableAlias}.cl_from AND {$tableAlias}.cl_to {$operatorType}" . $this->DB->addQuotes(str_replace(' ', '_', $category))
					]
				);
				$this->addWhere(
					[
						"{$tableAlias}.cl_to"	=> null
					]
				);
			}
		}
	}

	/**
	 * Set SQL for 'createdby' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _createdby($option) {
		$this->addTable('revision', 'creation_rev');
		$this->addTable('revision_actor_temp', 'creation_rev_actor');
		$this->_adduser(null, 'creation_rev_actor');
		$user = new \User;

		$this->addWhere(
			[
				$this->DB->addQuotes(  $user->newFromName( $option )->getActorId() ) . ' = creation_rev_actor.revactor_actor',
				'creation_rev_actor.revactor_page = page_id',
				'creation_rev.rev_parent_id = 0'
			]
		);
	}

	/**
	 * Set SQL for 'distinct' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _distinct($option) {
		if ($option == 'strict' || $option === true) {
			$this->distinct = true;
		} else {
			$this->distinct = false;
		}
	}

	/**
	 * Set SQL for 'firstrevisionsince' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _firstrevisionsince($option) {
		$this->addTable('revision_actor_temp', 'rev');
		$this->addSelect(
			[
				'rev.revactor_rev',
				'rev.revactor_timestamp'
			]
		);
		// tell the query optimizer not to look at rows that the following subquery will filter out anyway
		$this->addWhere(
			[
				$this->tableNames['page'] . '.page_id = rev.revactor_page',
				'rev.revactor_timestamp >= ' . $this->DB->addQuotes($option)
			]
		);
		$this->addWhere(
			[
				$this->tableNames['page'] . '.page_id = rev.revactor_page',
				'rev.revactor_timestamp = (SELECT MIN(rev_aux_snc.revactor_timestamp) FROM ' . $this->tableNames['revision_actor_temp'] . ' AS rev_aux_snc WHERE rev_aux_snc.revactor_page=rev.revactor_page AND rev_aux_snc.revactor_timestamp >= ' . $this->convertTimestamp($option) . ')'
			]
		);
	}

	/**
	 * Set SQL for 'goal' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _goal($option) {
		if ($option == 'categories') {
			$this->setLimit(false);
			$this->setOffset(false);
		}
	}

	/**
	 * Set SQL for 'hiddencategories' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _hiddencategories($option) {
		//@TODO: Unfinished functionality!  Never implemented by original author.
	}

	/**
	 * Set SQL for 'imagecontainer' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _imagecontainer($option) {
		$this->addTable('imagelinks', 'ic');
		$this->addSelect(
			[
				'sortkey'	=> 'ic.il_to'
			]
		);
		if (!$this->parameters->getParameter('openreferences')) {
			$where = [
				"{$this->tableNames['page']}.page_namespace = " . intval(NS_FILE),
				"{$this->tableNames['page']}.page_title = ic.il_to"
			];
		}
		$ors = [];
		foreach ($option as $linkGroup) {
			foreach ($linkGroup as $link) {
				if ($this->parameters->getParameter('ignorecase')) {
					$ors[] = "LOWER(CAST(ic.il_from AS char) = LOWER(" . $this->DB->addQuotes($link->getArticleID()) . ')';
				} else {
					$ors[] = "ic.il_from = " . $this->DB->addQuotes($link->getArticleID());
				}
			}
		}
		$where[] = '(' . implode(' OR ', $ors) . ')';
		$this->addWhere($where);
	}

	/**
	 * Set SQL for 'imageused' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _imageused($option) {
		if ($this->parameters->getParameter('distinct') == 'strict') {
			$this->addGroupBy('page_title');
		}
		$this->addTable('imagelinks', 'il');
		$this->addSelect(
			[
				'image_sel_title'	=> 'il.il_to'
			]
		);
		$where[] = $this->tableNames['page'] . '.page_id = il.il_from';
		$ors = [];
		foreach ($option as $linkGroup) {
			foreach ($linkGroup as $link) {
				if ($this->parameters->getParameter('ignorecase')) {
					$ors[] = "LOWER(CAST(il.il_to AS char))=LOWER(" . $this->DB->addQuotes($link->getDbKey()) . ')';
				} else {
					$ors[] = "il.il_to=" . $this->DB->addQuotes($link->getDbKey());
				}
			}
		}
		$where[] = '(' . implode(' OR ', $ors) . ')';
		$this->addWhere($where);
	}

	/**
	 * Set SQL for 'lastmodifiedby' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _lastmodifiedby($option) {
	   $user = new \User;
	   
	   $this->addWhere($this->DB->addQuotes( $user->newFromName( $option )->getActorId() ) . ' = (SELECT revactor_actor FROM ' . $this->tableNames['revision_actor_temp'] . ' WHERE ' . $this->tableNames['revision_actor_temp'] . '.revactor_page=page_id ORDER BY ' . $this->tableNames['revision_actor_temp'] . '.revactor_timestamp DESC LIMIT 1)');
	}

	/**
	 * Set SQL for 'lastrevisionbefore' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _lastrevisionbefore($option) {
		$this->addTable('revision_actor_temp', 'rev');
		$this->addSelect(['rev.revactor_rev', 'rev.revactor_timestamp']);
		// tell the query optimizer not to look at rows that the following subquery will filter out anyway
		$this->addWhere(
			[
				$this->tableNames['page'] . '.page_id = rev.revactor_page',
				'rev.revactor_timestamp < ' . $this->convertTimestamp($option)
			]
		);
		$this->addWhere(
			[
				$this->tableNames['page'] . '.page_id = rev.revactor_page',
				'rev.revactor_timestamp = (SELECT MAX(rev_aux_bef.revactor_timestamp) FROM ' . $this->tableNames['revision_actor_temp'] . ' AS rev_aux_bef WHERE rev_aux_bef.revactor_page=rev.revacor_page AND rev_aux_bef.revactor_timestamp < ' . $this->convertTimestamp($option) . ')'
			]
		);
	}

	/**
	 * Set SQL for 'linksfrom' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _linksfrom($option) {
		if ($this->parameters->getParameter('distinct') == 'strict') {
			$this->addGroupBy('page_title');
		}
		if ($this->parameters->getParameter('openreferences')) {
			$ors = [];
			foreach ($option as $linkGroup) {
				foreach ($linkGroup as $link) {
					$ors[] = '(pl_from = ' . $link->getArticleID() . ')';
				}
			}
			$where[] = '(' . implode(' OR ', $ors) . ')';
		} else {
			$this->addTable('pagelinks', 'plf');
			$this->addTable('page', 'pagesrc');
			$this->addSelect(
				[
					'sel_title' => 'pagesrc.page_title',
					'sel_ns' => 'pagesrc.page_namespace'
				]
			);
			$where = [
				$this->tableNames['page'] . '.page_namespace = plf.pl_namespace',
				$this->tableNames['page'] . '.page_title = plf.pl_title',
				'pagesrc.page_id = plf.pl_from'
			];
			$ors = [];
			foreach ($option as $linkGroup) {
				foreach ($linkGroup as $link) {
					$ors[] = 'plf.pl_from = ' . $link->getArticleID();
				}
			}
			$where[] = '(' . implode(' OR ', $ors) . ')';
		}
		$this->addWhere($where);
	}

	/**
	 * Set SQL for 'linksto' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _linksto($option) {
		if ($this->parameters->getParameter('distinct') == 'strict') {
			$this->addGroupBy('page_title');
		}
		if (count($option) > 0) {
			$this->addTable('pagelinks', 'pl');
			$this->addSelect(['sel_title' => 'pl.pl_title', 'sel_ns' => 'pl.pl_namespace']);
			foreach ($option as $index => $linkGroup) {
				if ($index == 0) {
					$where = $this->tableNames['page'] . '.page_id=pl.pl_from AND ';
					$ors = [];
					foreach ($linkGroup as $link) {
						$_or = '(pl.pl_namespace=' . intval($link->getNamespace());
						if (strpos($link->getDbKey(), '%') >= 0) {
							$operator = 'LIKE';
						} else {
							$operator = '=';
						}
						if ($this->parameters->getParameter('ignorecase')) {
							$_or .= ' AND LOWER(CAST(pl.pl_title AS char)) ' . $operator . ' LOWER(' . $this->DB->addQuotes($link->getDbKey()) . ')';
						} else {
							$_or .= ' AND pl.pl_title ' . $operator . ' ' . $this->DB->addQuotes($link->getDbKey());
						}
						$_or .= ')';
						$ors[] = $_or;
					}
					$where .= '(' . implode(' OR ', $ors) . ')';
				} else {
					$where = 'EXISTS(select pl_from FROM ' . $this->tableNames['pagelinks'] . ' WHERE (' . $this->tableNames['pagelinks'] . '.pl_from=page_id AND ';
					$ors = [];
					foreach ($linkGroup as $link) {
						$_or = '(' . $this->tableNames['pagelinks'] . '.pl_namespace=' . intval($link->getNamespace());
						if (strpos($link->getDbKey(), '%') >= 0) {
							$operator = 'LIKE';
						} else {
							$operator = '=';
						}
						if ($this->parameters->getParameter('ignorecase')) {
							$_or .= ' AND LOWER(CAST(' . $this->tableNames['pagelinks'] . '.pl_title AS char)) ' . $operator . ' LOWER(' . $this->DB->addQuotes($link->getDbKey()) . ')';
						} else {
							$_or .= ' AND ' . $this->tableNames['pagelinks'] . '.pl_title ' . $operator . ' ' . $this->DB->addQuotes($link->getDbKey());
						}
						$_or .= ')';
						$ors[] = $_or;
					}
					$where .= '(' . implode(' OR ', $ors) . ')';
					$where .= '))';
				}
				$this->addWhere($where);
			}
		}
	}

	/**
	 * Set SQL for 'notlinksfrom' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _notlinksfrom($option) {
		if ($this->parameters->getParameter('distinct') == 'strict') {
			$this->addGroupBy('page_title');
		}
		if ($this->parameters->getParameter('openreferences')) {
			$ands = [];
			foreach ($option as $linkGroup) {
				foreach ($linkGroup as $link) {
					$ands[] = 'pl_from <> ' . intval($link->getArticleID()) . ' ';
				}
			}
			$where = '(' . implode(' AND ', $ands) . ')';
		} else {
			$where = 'CONCAT(page_namespace,page_title) NOT IN (SELECT CONCAT(' . $this->tableNames['pagelinks'] . '.pl_namespace,' . $this->tableNames['pagelinks'] . '.pl_title) FROM ' . $this->tableNames['pagelinks'] . ' WHERE ';
			$ors = [];
			foreach ($option as $linkGroup) {
				foreach ($linkGroup as $link) {
					$ors[] = $this->tableNames['pagelinks'] . '.pl_from = ' . intval($link->getArticleID());
				}
			}
			$where .= implode(' OR ', $ors) . ')';
		}
		$this->addWhere($where);
	}

	/**
	 * Set SQL for 'notlinksto' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _notlinksto($option) {
		if ($this->parameters->getParameter('distinct') == 'strict') {
			$this->addGroupBy('page_title');
		}
		if (count($option)) {
			$where = $this->tableNames['page'] . '.page_id NOT IN (SELECT ' . $this->tableNames['pagelinks'] . '.pl_from FROM ' . $this->tableNames['pagelinks'] . ' WHERE ';
			$ors = [];
			foreach ($option as $linkGroup) {
				foreach ($linkGroup as $link) {
					$_or = '(' . $this->tableNames['pagelinks'] . '.pl_namespace=' . intval($link->getNamespace());
					if (strpos($link->getDbKey(), '%') >= 0) {
						$operator = 'LIKE';
					} else {
						$operator = '=';
					}
					if ($this->parameters->getParameter('ignorecase')) {
						$_or .= ' AND LOWER(CAST(' . $this->tableNames['pagelinks'] . '.pl_title AS char)) ' . $operator . ' LOWER(' . $this->DB->addQuotes($link->getDbKey()) . '))';
					} else {
						$_or .= ' AND ' . $this->tableNames['pagelinks'] . '.pl_title ' . $operator . ' ' . $this->DB->addQuotes($link->getDbKey()) . ')';
					}
					$ors[] = $_or;
				}
			}
			$where .= '(' . implode(' OR ', $ors) . '))';
		}
		$this->addWhere($where);
	}

	/**
	 * Set SQL for 'linkstoexternal' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _linkstoexternal($option) {
		if ($this->parameters->getParameter('distinct') == 'strict') {
			$this->addGroupBy('page_title');
		}
		if (count($option) > 0) {
			$this->addTable('externallinks', 'el');
			$this->addSelect(['el_to' => 'el.el_to']);
			foreach ($option as $index => $linkGroup) {
				if ($index == 0) {
					$where = $this->tableNames['page'] . '.page_id=el.el_from AND ';
					$ors = [];
					foreach ($linkGroup as $link) {
						$ors[] = 'el.el_to LIKE ' . $this->DB->addQuotes($link);
					}
					$where .= '(' . implode(' OR ', $ors) . ')';
				} else {
					$where = 'EXISTS(SELECT el_from FROM ' . $this->tableNames['externallinks'] . ' WHERE (' . $this->tableNames['externallinks'] . '.el_from=page_id AND ';
					$ors = [];
					foreach ($linkGroup as $link) {
						$ors[] = $this->tableNames['externallinks'] . '.el_to LIKE ' . $this->DB->addQuotes($link);
					}
					$where .= '(' . implode(' OR ', $ors) . ')';
					$where .= '))';
				}
				$this->addWhere($where);
			}
		}
	}

	/**
	 * Set SQL for 'maxrevisions' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _maxrevisions($option) {
		$this->addWhere("((SELECT count(rev_aux3.revactor_page) FROM {$this->tableNames['revision_actor_temp']} AS rev_aux3 WHERE rev_aux3.revactor_page = {$this->tableNames['page']}.page_id) <= {$option})");
	}

	/**
	 * Set SQL for 'minoredits' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _minoredits($option) {
		if (isset($option) && $option == 'exclude') {
			$this->addTable('revision', 'revision');
			$this->addWhere('revision.rev_minor_edit = 0');
		}
	}

	/**
	 * Set SQL for 'minrevisions' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _minrevisions($option) {
		$this->addWhere("((SELECT count(rev_aux2.revactor_page) FROM {$this->tableNames['revision_actor_temp']} AS rev_aux2 WHERE rev_aux2.revactor_page = {$this->tableNames['page']}.page_id) >= {$option})");
	}

	/**
	 * Set SQL for 'modifiedby' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _modifiedby($option) {
		$this->addTable('revision_actor_temp', 'change_rev');
		$user = new \User;

		$this->addWhere($this->DB->addQuotes( $user->newFromName( $option )->getActorId() ) . ' = change_rev.revactor_actor AND change_rev.revactor_page = page_id');
	}

	/**
	 * Set SQL for 'namespace' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _namespace($option) {
	    $option === 0 ?? $option = '0';
		if (is_array($option) && count($option)) {
			if ($this->parameters->getParameter('openreferences')) {
				$this->addWhere(
					[
						"{$this->tableNames['pagelinks']}.pl_namespace"	=> $option
					]
				);
			} else {
				$this->addWhere(
					[
						"{$this->tableNames['page']}.page_namespace"	=> $option
					]
				);
			}
		}
	}

	/**
	 * Set SQL for 'notcreatedby' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _notcreatedby($option) {
		$this->addTable('revision', 'no_creation_rev');
		$this->addTable('revision_actor_temp', 'no_creation_rev_actor');
		$user = new \User;

		$this->addWhere($this->DB->addQuotes( $user->newFromName( $option )->getActorId() ) . ' != no_creation_rev_actor.revactor_actor AND no_creation_rev_actor.revactor_page = page_id AND no_creation_rev.rev_parent_id = 0');
	}

	/**
	 * Set SQL for 'notlastmodifiedby' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _notlastmodifiedby($option) {
	    $user = new \User;
		$this->addWhere($this->DB->addQuotes( $user->newFromName( $option )->getActorId() ) . ' != (SELECT revactor_actor FROM ' . $this->tableNames['revision_actor_temp'] . ' WHERE ' . $this->tableNames['revision_actor_temp'] . '.revactor_page=page_id ORDER BY ' . $this->tableNames['revision_actor_temp'] . '.revactor_timestamp DESC LIMIT 1)');
	}

	/**
	 * Set SQL for 'notmodifiedby' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _notmodifiedby($option) {
	    $user = new \User;
		$this->addWhere('NOT EXISTS (SELECT 1 FROM ' . $this->tableNames['revision_actor_temp'] . ' WHERE ' . $this->tableNames['revision_actor_temp'] . '.revactor_page=page_id AND ' . $this->tableNames['revision_actor_temp'] . '.revactor_actor = ' . $this->DB->addQuotes( $user->newFromName( $option )->getActorId() ) . ' LIMIT 1)');
	}

	/**
	 * Set SQL for 'notnamespace' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _notnamespace($option) {
		if (is_array($option) && count($option)) {
			if ($this->parameters->getParameter('openreferences')) {
				$this->addNotWhere(
					[
						"{$this->tableNames['pagelinks']}.pl_namespace" => $option
					]
				);
			} else {
				$this->addNotWhere(
					[
						"{$this->tableNames['page']}.page_namespace" => $option
					]
				);
			}
		}
	}

	/**
	 * Set SQL for 'count' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _count($option) {
		$this->setLimit($option);
	}

	/**
	 * Set SQL for 'offset' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _offset($option) {
		$this->setOffset($option);
	}

	/**
	 * Set SQL for 'order' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _order($option) {
		$orderMethod = $this->parameters->getParameter('ordermethod');
		if (!empty($orderMethod) && is_array($orderMethod) && $orderMethod[0] !== 'none') {
			if ($option === 'descending' || $option === 'desc') {
				$this->setOrderDir('DESC');
			} else {
				$this->setOrderDir('ASC');
			}
		}
	}

	/**
	 * Set SQL for 'ordercollation' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _ordercollation($option) {
		$option = mb_strtolower($option);

		$results = $this->DB->query('SHOW CHARACTER SET');
		if (!$results) {
			return false;
		}

		while ($row = $results->fetchRow()) {
			if ($option == $row['Default collation']) {
				$this->setCollation($option);
				break;
			}
		}
		return true;
	}

	/**
	 * Set SQL for 'ordermethod' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _ordermethod($option) {
		global $wgContLang;

		if ($this->parameters->getParameter('goal') == 'categories') {
			//No order methods for returning categories.
			return true;
		}

		$namespaces = $wgContLang->getNamespaces();
		//$aStrictNs = array_slice((array) Config::getSetting('allowedNamespaces'), 1, count(Config::getSetting('allowedNamespaces')), true);
		$namespaces = array_slice($namespaces, 3, count($namespaces), true);
		$_namespaceIdToText = "CASE {$this->tableNames['page']}.page_namespace";
		foreach ($namespaces as $id => $name) {
			$_namespaceIdToText .= ' WHEN ' . intval($id) . " THEN " . $this->DB->addQuotes($name . ':');
		}
		$_namespaceIdToText .= ' END';

		$option = (array)$option;
		foreach ($option as $orderMethod) {
			switch ($orderMethod) {
				case 'category':
					$this->addOrderBy('cl_head.cl_to');
					$this->addSelect(['cl_head.cl_to']); //Gives category headings in the result.
					if ((is_array($this->parameters->getParameter('catheadings')) && in_array('', $this->parameters->getParameter('catheadings'))) || (is_array($this->parameters->getParameter('catnotheadings')) && in_array('', $this->parameters->getParameter('catnotheadings')))) {
						$_clTableName = 'dpl_clview';
						$_clTableAlias = $_clTableName;
					} else {
						$_clTableName = 'categorylinks';
						$_clTableAlias = 'cl_head';
					}
					$this->addTable($_clTableName, $_clTableAlias);
					$this->addJoin(
						$_clTableAlias,
						[
							"LEFT OUTER JOIN",
							"page_id = cl_head.cl_from"
						]
					);
					if (is_array($this->parameters->getParameter('catheadings')) && count($this->parameters->getParameter('catheadings'))) {
						$this->addWhere(
							[
								"cl_head.cl_to"	=> $this->parameters->getParameter('catheadings')
							]
						);
					}
					if (is_array($this->parameters->getParameter('catnotheadings')) && count($this->parameters->getParameter('catnotheadings'))) {
						$this->addNotWhere(
							[
								'cl_head.cl_to' => $this->parameters->getParameter('catnotheadings')
							]
						);
					}
					break;
				case 'categoryadd':
					//@TODO: See TODO in __addfirstcategorydate().
					$this->addOrderBy('cl1.cl_timestamp');
					break;
				case 'counter':
					if (class_exists("\\HitCounters\\Hooks")) {
						//If the "addpagecounter" parameter was not used the table and join need to be added now.
						if (!array_key_exists('hit_counter', $this->tables)) {
							$this->addTable('hit_counter', 'hit_counter');

							if (!isset($this->join['hit_counter'])) {
								$this->addJoin(
									'hit_counter',
									[
										"LEFT JOIN",
										"hit_counter.page_id = " . $this->tableNames['page'] . '.page_id'
									]
								);
							}
						}
						$this->addOrderBy('hit_counter.page_counter');
					}
					break;
				case 'firstedit':
					$this->addOrderBy('rev.revactor_timestamp');
					$this->addTable('revision_actor_temp', 'rev');
					$this->addSelect(
						[
							'rev.revactor_timestamp'
						]
					);
					if (!$this->revisionAuxWhereAdded) {
						$this->addWhere(
							[
								"{$this->tableNames['page']}.page_id = rev.revactor_page",
								"rev.revactor_timestamp = (SELECT MIN(rev_aux.revactor_timestamp) FROM {$this->tableNames['revision_actor_temp']} AS rev_aux WHERE rev_aux.revactor_page=rev.revactor_page)"
							]
						);
					}
					$this->revisionAuxWhereAdded = true;
					break;
				case 'lastedit':
					if (\DynamicPageListHooks::isLikeIntersection()) {
						$this->addOrderBy('page_touched');
						$this->addSelect(
							[
								"page_touched" => "{$this->tableNames['page']}.page_touched"
							]
						);
					} else {
						$this->addOrderBy('rev.revactor_timestamp');
						$this->addTable('revision_actor_temp', 'rev');
						$this->addSelect(['rev.revactor_timestamp']);
						if (!$this->revisionAuxWhereAdded) {
							$this->addWhere(
								[
									"{$this->tableNames['page']}.page_id = rev.revactor_page",
									"rev.revactor_timestamp = (SELECT MAX(rev_aux.revactor_timestamp) FROM {$this->tableNames['revision_actor_temp']} AS rev_aux WHERE rev_aux.revactor_page = rev.revactor_page)"
								]
							);
						}
						$this->revisionAuxWhereAdded = true;
					}
					break;
				case 'pagesel':
					$this->addOrderBy('sortkey');
					$this->addSelect(
						[
							'sortkey' => 'CONCAT(pl.pl_namespace, pl.pl_title) ' . $this->getCollateSQL()
						]
					);
					break;
				case 'pagetouched':
					$this->addOrderBy('page_touched');
					$this->addSelect(
						[
							"page_touched" => "{$this->tableNames['page']}.page_touched"
						]
					);
					break;
				case 'size':
					$this->addOrderBy('page_len');
					break;
				case 'sortkey':
					$this->addOrderBy('sortkey');
					// If cl_sortkey is null (uncategorized page), generate a sortkey in the usual way (full page name, underscores replaced with spaces).
					// UTF-8 created problems with non-utf-8 MySQL databases
					$replaceConcat = "REPLACE(CONCAT({$_namespaceIdToText}, " . $this->tableNames['page'] . ".page_title), '_', ' ')";

					$category = (array)$this->parameters->getParameter('category');
					$notCategory = (array)$this->parameters->getParameter('notcategory');
					if (count($category) + count($notCategory) > 0) {
						if (in_array('category', $this->parameters->getParameter('ordermethod'))) {
							$this->addSelect(
								[
									'sortkey' => "IFNULL(cl_head.cl_sortkey, {$replaceConcat}) " . $this->getCollateSQL()
								]
							);
						} else {
							//This runs on the assumption that at least one category parameter was used and that numbering starts at 1.
							$this->addSelect(
								[
									'sortkey' => "IFNULL(cl1.cl_sortkey, {$replaceConcat}) " . $this->getCollateSQL()
								]
							);
						}
					} else {
						$this->addSelect(
							[
								'sortkey' => $replaceConcat . $this->getCollateSQL()
							]
						);
					}
					break;
				case 'titlewithoutnamespace':
					if ($this->parameters->getParameter('openreferences')) {
						$this->addOrderBy("pl_title");
					} else {
						$this->addOrderBy("page_title");
					}
					$this->addSelect(
						[
							'sortkey' => "{$this->tableNames['page']}.page_title " . $this->getCollateSQL()
						]
					);
					break;
				case 'title':
					$this->addOrderBy('sortkey');
					if ($this->parameters->getParameter('openreferences')) {
						$this->addSelect(
							[
								'sortkey' => "REPLACE(CONCAT(IF(pl_namespace  =0, '', CONCAT(" . $_namespaceIdToText . ", ':')), pl_title), '_', ' ') " . $this->getCollateSQL()
							]
						);
					} else {
						//Generate sortkey like for category links. UTF-8 created problems with non-utf-8 MySQL databases.
						$this->addSelect(
							[
								'sortkey' => "REPLACE(CONCAT(IF(" . $this->tableNames['page'] . ".page_namespace = 0, '', CONCAT(" . $_namespaceIdToText . ", ':')), " . $this->tableNames['page'] . ".page_title), '_', ' ') " . $this->getCollateSQL()
							]
						);
					}
					break;
				case 'user':
				    $user = new \User;
					$this->addOrderBy( $user->newFromName( 'rev.revactor_actor' )->getActorId() );
					$this->addTable('revision_actor_temp', 'rev');
					$this->_adduser(null, 'rev');
					break;
				case 'none':
					break;
			}
		}
	}

	/**
	 * Set SQL for 'redirects' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _redirects($option) {
		if (!$this->parameters->getParameter('openreferences')) {
			switch ($option) {
				case 'only':
					$this->addWhere(
						[
							$this->tableNames['page'] . ".page_is_redirect"	=> 1
						]
					);
					break;
				case 'exclude':
					$this->addWhere(
						[
							$this->tableNames['page'] . ".page_is_redirect"	=> 0
						]
					);
					break;
			}
		}
	}

	/**
	 * Set SQL for 'stablepages' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _stablepages($option) {
		if (function_exists('efLoadFlaggedRevs')) {
			//Do not add this again if 'qualitypages' has already added it.
			if (!$this->parametersProcessed['qualitypages']) {
				$this->addJoin(
					'flaggedpages',
					[
						"LEFT JOIN",
						"page_id = fp_page_id"
					]
				);
			}
			switch ($option) {
				case 'only':
					$this->addWhere(
						[
							'fp_stable IS NOT NULL'
						]
					);
					break;
				case 'exclude':
					$this->addWhere(
						[
							'fp_stable'	=> null
						]
					);
					break;
			}
		}
	}

	/**
	 * Set SQL for 'qualitypages' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _qualitypages($option) {
		if (function_exists('efLoadFlaggedRevs')) {
			//Do not add this again if 'stablepages' has already added it.
			if (!$this->parametersProcessed['stablepages']) {
				$this->addJoin(
					'flaggedpages',
					[
						"LEFT JOIN",
						"page_id = fp_page_id"
					]
				);
			}
			switch ($option) {
				case 'only':
					$this->addWhere('fp_quality >= 1');
					break;
				case 'exclude':
					$this->addWhere('fp_quality = 0');
					break;
			}
		}
	}

	/**
	 * Set SQL for 'title' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _title($option) {
		$ors = [];
		foreach ($option as $comparisonType => $titles) {
			foreach ($titles as $title) {
				if ($this->parameters->getParameter('openreferences')) {
					if ($this->parameters->getParameter('ignorecase')) {
						$_or = "LOWER(CAST(pl_title AS char)) {$comparisonType}" . strtolower($this->DB->addQuotes($title));
					} else {
						$_or = "pl_title {$comparisonType} " . $this->DB->addQuotes($title);
					}
				} else {
					if ($this->parameters->getParameter('ignorecase')) {
						$_or = "LOWER(CAST({$this->tableNames['page']}.page_title AS char)) {$comparisonType}" . strtolower($this->DB->addQuotes($title));
					} else {
						$_or = "{$this->tableNames['page']}.page_title {$comparisonType}" . $this->DB->addQuotes($title);
					}
				}
				$ors[] = $_or;
			}
		}
		$where = '(' . implode(' OR ', $ors) . ')';
		$this->addWhere($where);
	}

	/**
	 * Set SQL for 'nottitle' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _nottitle($option) {
		$ors = [];
		foreach ($option as $comparisonType => $titles) {
			foreach ($titles as $title) {
				if ($this->parameters->getParameter('openreferences')) {
					if ($this->parameters->getParameter('ignorecase')) {
						$_or = "LOWER(CAST(pl_title AS char)) {$comparisonType}" . strtolower($this->DB->addQuotes($title));
					} else {
						$_or = "pl_title {$comparisonType} " . $this->DB->addQuotes($title);
					}
				} else {
					if ($this->parameters->getParameter('ignorecase')) {
						$_or = "LOWER(CAST({$this->tableNames['page']}.page_title AS char)) {$comparisonType}" . strtolower($this->DB->addQuotes($title));
					} else {
						$_or = "{$this->tableNames['page']}.page_title {$comparisonType}" . $this->DB->addQuotes($title);
					}
				}
				$ors[] = $_or;
			}
		}
		$where = 'NOT (' . implode(' OR ', $ors) . ')';
		$this->addWhere($where);
	}

	/**
	 * Set SQL for 'titlegt' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _titlegt($option) {
		$where = '(';
		if (substr($option, 0, 2) == '=_') {
			if ($this->parameters->getParameter('openreferences')) {
				$where .= 'pl_title >= ' . $this->DB->addQuotes(substr($sTitleGE, 2));
			} else {
				$where .= $this->tableNames['page'] . '.page_title >= ' . $this->DB->addQuotes(substr($option, 2));
			}
		} else {
			if ($this->parameters->getParameter('openreferences')) {
				$where .= 'pl_title > ' . $this->DB->addQuotes($option);
			} else {
				$where .= $this->tableNames['page'] . '.page_title > ' . $this->DB->addQuotes($option);
			}
		}
		$where .= ')';
		$this->addWhere($where);
	}

	/**
	 * Set SQL for 'titlelt' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _titlelt($option) {
		$where = '(';
		if (substr($option, 0, 2) == '=_') {
			if ($this->parameters->getParameter('openreferences')) {
				$where .= 'pl_title <= ' . $this->DB->addQuotes(substr($option, 2));
			} else {
				$where .= $this->tableNames['page'] . '.page_title <= ' . $this->DB->addQuotes(substr($option, 2));
			}
		} else {
			if ($this->parameters->getParameter('openreferences')) {
				$where .= 'pl_title < ' . $this->DB->addQuotes($option);
			} else {
				$where .= $this->tableNames['page'] . '.page_title < ' . $this->DB->addQuotes($option);
			}
		}
		$where .= ')';
		$this->addWhere($where);
	}

	/**
	 * Set SQL for 'usedby' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _usedby($option) {
		if ($this->parameters->getParameter('openreferences')) {
			$ors = [];
			foreach ($option as $linkGroup) {
				foreach ($linkGroup as $link) {
					$ors[] = 'tpl_from = ' . intval($link->getArticleID());
				}
			}
			$where = '(' . implode(' OR ', $ors) . ')';
		} else {
			$this->addTable('templatelinks', 'tpl');
			$this->addTable('page', 'tplsrc');
			$this->addSelect(['tpl_sel_title' => 'tplsrc.page_title', 'tpl_sel_ns' => 'tplsrc.page_namespace']);
			$where = $this->tableNames['page'] . '.page_namespace = tpl.tl_namespace AND ' .
					 $this->tableNames['page'] . '.page_title = tpl.tl_title AND tplsrc.page_id = tpl.tl_from AND ';
			$ors = [];
			foreach ($option as $linkGroup) {
				foreach ($linkGroup as $link) {
					$ors[] = 'tpl.tl_from = ' . intval($link->getArticleID());
				}
			}
			$where .= '(' . implode(' OR ', $ors) . ')';
		}
		$this->addWhere($where);
	}

	/**
	 * Set SQL for 'uses' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _uses($option) {
		$this->addTable('templatelinks', 'tl');
		$where = $this->tableNames['page'] . '.page_id=tl.tl_from AND (';
		$ors = [];
		foreach ($option as $linkGroup) {
			foreach ($linkGroup as $link) {
				$_or = '(tl.tl_namespace=' . intval($link->getNamespace());
				if ($this->parameters->getParameter('ignorecase')) {
					$_or .= " AND LOWER(CAST(tl.tl_title AS char))=LOWER(" . $this->DB->addQuotes($link->getDbKey()) . '))';
				} else {
					$_or .= " AND tl.tl_title=" . $this->DB->addQuotes($link->getDbKey()) . ')';
				}
				$ors[] = $_or;
			}
		}
		$where .= implode(' OR ', $ors) . ')';
		$this->addWhere($where);
	}

	/**
	 * Set SQL for 'notuses' parameter.
	 *
	 * @access	private
	 * @param	mixed	Parameter Option
	 * @return	void
	 */
	private function _notuses($option) {
		if (count($option) > 0) {
			$where = $this->tableNames['page'] . '.page_id NOT IN (SELECT ' . $this->tableNames['templatelinks'] . '.tl_from FROM ' . $this->tableNames['templatelinks'] . ' WHERE (';
			$ors = [];
			foreach ($option as $linkGroup) {
				foreach ($linkGroup as $link) {
					$_or = '(' . $this->tableNames['templatelinks'] . '.tl_namespace=' . intval($link->getNamespace());
					if ($this->parameters->getParameter('ignorecase')) {
						$_or .= ' AND LOWER(CAST(' . $this->tableNames['templatelinks'] . '.tl_title AS char))=LOWER(' . $this->DB->addQuotes($link->getDbKey()) . '))';
					} else {
						$_or .= ' AND ' . $this->tableNames['templatelinks'] . '.tl_title=' . $this->DB->addQuotes($link->getDbKey()) . ')';
					}
					$ors[] = $_or;
				}
			}
			$where .= implode(' OR ', $ors) . '))';
		}
		$this->addWhere($where);
	}
}