<?php
/**
 * Elgg metastrngs
 * Functions to manage object metastrings.
 *
 * @package Elgg.Core
 * @subpackage DataModel.MetaStrings
 */

/** Cache metastrings for a page */
global $METASTRINGS_CACHE;
$METASTRINGS_CACHE = array();

/** Keep a record of strings we know don't exist */
global $METASTRINGS_DEADNAME_CACHE;
$METASTRINGS_DEADNAME_CACHE = array();

/**
 * Return the meta string id for a given tag, or false.
 *
 * @param string $string         The value to store
 * @param bool   $case_sensitive Do we want to make the query case sensitive?
 *                               If not there may be more than one result
 *
 * @return int|array|false meta   string id, array of ids or false if none found
 */
function get_metastring_id($string, $case_sensitive = TRUE) {
	global $CONFIG, $METASTRINGS_CACHE, $METASTRINGS_DEADNAME_CACHE;

	$string = sanitise_string($string);

	// caching doesn't work for case insensitive searches
	if ($case_sensitive) {
		$result = array_search($string, $METASTRINGS_CACHE, true);

		if ($result !== false) {
			elgg_log("** Returning id for string:$string from cache.");
			return $result;
		}

		// See if we have previously looked for this and found nothing
		if (in_array($string, $METASTRINGS_DEADNAME_CACHE, true)) {
			return false;
		}

		// Experimental memcache
		$msfc = null;
		static $metastrings_memcache;
		if ((!$metastrings_memcache) && (is_memcache_available())) {
			$metastrings_memcache = new ElggMemcache('metastrings_memcache');
		}
		if ($metastrings_memcache) {
			$msfc = $metastrings_memcache->load($string);
		}
		if ($msfc) {
			return $msfc;
		}
	}

	// Case sensitive
	if ($case_sensitive) {
		$query = "SELECT * from {$CONFIG->dbprefix}metastrings where string= BINARY '$string' limit 1";
	} else {
		$query = "SELECT * from {$CONFIG->dbprefix}metastrings where string = '$string'";
	}

	$row = FALSE;
	$metaStrings = get_data($query, "entity_row_to_elggstar");
	if (is_array($metaStrings)) {
		if (sizeof($metaStrings) > 1) {
			$ids = array();
			foreach ($metaStrings as $metaString) {
				$ids[] = $metaString->id;
			}
			return $ids;
		} else {
			$row = $metaStrings[0];
		}
	}

	if ($row) {
		$METASTRINGS_CACHE[$row->id] = $row->string; // Cache it

		// Attempt to memcache it if memcache is available
		if ($metastrings_memcache) {
			$metastrings_memcache->save($row->string, $row->id);
		}

		elgg_log("** Cacheing string '{$row->string}'");

		return $row->id;
	} else {
		$METASTRINGS_DEADNAME_CACHE[$string] = $string;
	}

	return false;
}

/**
 * When given an ID, returns the corresponding metastring
 *
 * @param int $id Metastring ID
 *
 * @return string Metastring
 */
function get_metastring($id) {
	global $CONFIG, $METASTRINGS_CACHE;

	$id = (int) $id;

	if (isset($METASTRINGS_CACHE[$id])) {
		elgg_log("** Returning string for id:$id from cache.");

		return $METASTRINGS_CACHE[$id];
	}

	$row = get_data_row("SELECT * from {$CONFIG->dbprefix}metastrings where id='$id' limit 1");
	if ($row) {
		$METASTRINGS_CACHE[$id] = $row->string; // Cache it
		elgg_log("** Cacheing string '{$row->string}'");

		return $row->string;
	}

	return false;
}

/**
 * Add a metastring.
 * It returns the id of the tag, whether by creating it or updating it.
 *
 * @param string $string         The value (whatever that is) to be stored
 * @param bool   $case_sensitive Do we want to make the query case sensitive?
 *
 * @return mixed Integer tag or false.
 */
function add_metastring($string, $case_sensitive = true) {
	global $CONFIG, $METASTRINGS_CACHE, $METASTRINGS_DEADNAME_CACHE;

	$sanstring = sanitise_string($string);

	$id = get_metastring_id($string, $case_sensitive);
	if ($id) {
		return $id;
	}

	$result = insert_data("INSERT into {$CONFIG->dbprefix}metastrings (string) values ('$sanstring')");
	if ($result) {
		$METASTRINGS_CACHE[$result] = $string;
		if (isset($METASTRINGS_DEADNAME_CACHE[$string])) {
			unset($METASTRINGS_DEADNAME_CACHE[$string]);
		}
	}

	return $result;
}

/**
 * Delete any orphaned entries in metastrings. This is run by the garbage collector.
 *
 * @return bool
 */
function delete_orphaned_metastrings() {
	global $CONFIG;

	// If memcache is enabled then we need to flush it of deleted values
	if (is_memcache_available()) {
		$select_query = "
		SELECT *
		from {$CONFIG->dbprefix}metastrings where
		(
			(id not in (select name_id from {$CONFIG->dbprefix}metadata)) AND
			(id not in (select value_id from {$CONFIG->dbprefix}metadata)) AND
			(id not in (select name_id from {$CONFIG->dbprefix}annotations)) AND
			(id not in (select value_id from {$CONFIG->dbprefix}annotations))
		)";

		$dead = get_data($select_query);
		if ($dead) {
			static $metastrings_memcache;
			if (!$metastrings_memcache) {
				$metastrings_memcache = new ElggMemcache('metastrings_memcache');
			}

			foreach ($dead as $d) {
				$metastrings_memcache->delete($d->string);
			}
		}
	}

	$query = "
		DELETE
		from {$CONFIG->dbprefix}metastrings where
		(
			(id not in (select name_id from {$CONFIG->dbprefix}metadata)) AND
			(id not in (select value_id from {$CONFIG->dbprefix}metadata)) AND
			(id not in (select name_id from {$CONFIG->dbprefix}annotations)) AND
			(id not in (select value_id from {$CONFIG->dbprefix}annotations))
		)";

	return delete_data($query);
}


/**
 * Returns an array of either ElggAnnotation or ElggMetadata objects.
 * Accepts all elgg_get_entities() options for entity restraints.
 *
 * @see elgg_get_entities
 *
 * @param array  $options Array in format:
 *
 * 	metastring_names => NULL|ARR metastring names
 *
 * 	metastring_values => NULL|ARR metastring values
 *
 * 	metastring_case_sensitive => BOOL Overall Case sensitive
 *
 *  metastring_owner_guids => NULL|ARR guids for metadata owners
 *
 *  metastring_created_time_lower => INT Lower limit for created time.
 *
 *  metastring_created_time_upper => INT Upper limit for created time.
 *
 *  metastring_calculation => STR Perform the MySQL function on the metastring values returned.
 *
 * @param string $type    Either metadata or annotations
 * @return mixed
 * @access private
 */
function elgg_get_metastring_based_objects($options, $type = 'metadata') {

	if ($type != 'metadata' && $type != 'annotations') {
		return false;
	}

	$defaults = array(
		// entities
		'types'					=>	ELGG_ENTITIES_ANY_VALUE,
		'subtypes'				=>	ELGG_ENTITIES_ANY_VALUE,
		'type_subtype_pairs'	=>	ELGG_ENTITIES_ANY_VALUE,

		'guids'					=>	ELGG_ENTITIES_ANY_VALUE,
		'owner_guids'			=>	ELGG_ENTITIES_ANY_VALUE,
		'container_guids'		=>	ELGG_ENTITIES_ANY_VALUE,
		'site_guids'			=>	get_config('site_guid'),

		'modified_time_lower'	=>	ELGG_ENTITIES_ANY_VALUE,
		'modified_time_upper'	=>	ELGG_ENTITIES_ANY_VALUE,
		'created_time_lower'	=>	ELGG_ENTITIES_ANY_VALUE,
		'created_time_upper'	=>	ELGG_ENTITIES_ANY_VALUE,

		// options are normalized to the plural in case we ever add support for them.
		'metastring_names'							=>	ELGG_ENTITIES_ANY_VALUE,
		'metastring_values'							=>	ELGG_ENTITIES_ANY_VALUE,
		//'metastring_name_value_pairs'				=>	ELGG_ENTITIES_ANY_VALUE,
		//'metastring_name_value_pairs_operator'	=>	'AND',

		'metastring_case_sensitive' 				=>	TRUE,
		//'order_by_metastring'						=>	array(),
		'metastring_calculation'					=>	ELGG_ENTITIES_NO_VALUE,

		'metastring_created_time_lower'				=>	ELGG_ENTITIES_ANY_VALUE,
		'metastring_created_time_upper'				=>	ELGG_ENTITIES_ANY_VALUE,

		'metastring_owner_guids'					=>	ELGG_ENTITIES_ANY_VALUE,

		// sql
		'order_by'	=>	'n_table.time_created asc',
		'limit'		=>	10,
		'offset'	=>	0,
		'count'		=>	FALSE,
		'selects'	=>	array(),
		'wheres'	=>	array(),
		'joins'		=>	array(),

		'callback'	=> ($type == 'annotations') ? 'row_to_elggannotation' : 'row_to_elggmetadata'
	);

	$options = array_merge($defaults, $options);

	// can't use helper function with type_subtype_pair because
	// it's already an array...just need to merge it
	if (isset($options['type_subtype_pair'])) {
		if (isset($options['type_subtype_pairs'])) {
			$options['type_subtype_pairs'] = array_merge($options['type_subtype_pairs'],
				$options['type_subtype_pair']);
		} else {
			$options['type_subtype_pairs'] = $options['type_subtype_pair'];
		}
	}

	$singulars = array('type', 'subtype', 'guid', 'owner_guid', 'container_guid', 'site_guid',
						'metastring_name', 'metastring_value'
					);
	$options = elgg_normalise_plural_options_array($options, $singulars);

	if (!$options) {
		return false;
	}

	$db_prefix = elgg_get_config('dbprefix');

	// evaluate where clauses
	if (!is_array($options['wheres'])) {
		$options['wheres'] = array($options['wheres']);
	}

	$wheres = $options['wheres'];

	// entities
	$wheres[] = elgg_get_entity_type_subtype_where_sql('e', $options['types'],
		$options['subtypes'], $options['type_subtype_pairs']);

	$wheres[] = elgg_get_guid_based_where_sql('e.guid', $options['guids']);
	$wheres[] = elgg_get_guid_based_where_sql('e.owner_guid', $options['owner_guids']);
	$wheres[] = elgg_get_guid_based_where_sql('e.container_guid', $options['container_guids']);
	$wheres[] = elgg_get_guid_based_where_sql('e.site_guid', $options['site_guids']);

	$wheres[] = elgg_get_entity_time_where_sql('e', $options['created_time_upper'],
		$options['created_time_lower'], $options['modified_time_upper'], $options['modified_time_lower']);


	$wheres[] = elgg_get_entity_time_where_sql('n_table', $options['metastring_created_time_upper'],
		$options['metastring_created_time_lower'], null, null);

	$wheres[] = elgg_get_guid_based_where_sql('n_table.owner_guid', $options['metastring_owner_guids']);

	// remove identical where clauses
	$wheres = array_unique($wheres);

	// see if any functions failed
	// remove empty strings on successful functions
	foreach ($wheres as $i => $where) {
		if ($where === FALSE) {
			return FALSE;
		} elseif (empty($where)) {
			unset($wheres[$i]);
		}
	}

	// evaluate join clauses
	if (!is_array($options['joins'])) {
		$options['joins'] = array($options['joins']);
	}

	$joins = $options['joins'];

	$joins[] = "JOIN {$db_prefix}entities e ON n_table.entity_guid = e.guid";
	$joins[] = "JOIN {$db_prefix}metastrings n on n_table.name_id = n.id";
	$joins[] = "JOIN {$db_prefix}metastrings v on n_table.value_id = v.id";


	// remove identical join clauses
	$joins = array_unique($joins);

	foreach ($joins as $i => $join) {
		if ($join === FALSE) {
			return FALSE;
		} elseif (empty($join)) {
			unset($joins[$i]);
		}
	}

	// metastrings
	$metastring_clauses = elgg_get_metastring_sql('n_table', $options['metastring_names'],
		$options['metastring_values'], $options['metastring_case_sensitive']);

	if ($metastring_clauses) {
		$wheres = array_merge($wheres, $metastring_clauses['wheres']);
		$joins = array_merge($joins, $metastring_clauses['joins']);
	}

	// check for calculations
	if ($options['count']) {
		$options['metastring_calculation'] = 'count';
	}

	if ($options['metastring_calculation'] === ELGG_ENTITIES_NO_VALUE) {
		$query = "SELECT DISTINCT n_table.*, n.string as name, v.string as value FROM {$db_prefix}$type n_table";
	} else {
		$query = "SELECT DISTINCT v.string as value, {$options['metastring_calculation']}(v.string) as calculation FROM {$db_prefix}$type n_table";
	}

	// add joins
	foreach ($joins as $j) {
		$query .= " $j ";
	}

	// add wheres
	$query .= ' WHERE ';

	foreach ($wheres as $w) {
		$query .= " $w AND ";
	}

	// Add access controls
	$query .= get_access_sql_suffix('e');
	if ($options['metastring_calculation'] === ELGG_ENTITIES_NO_VALUE) {
		if ($options['group_by'] = sanitise_string($options['group_by'])) {
			$query .= " GROUP BY {$options['group_by']}";
		}

		if ($options['order_by'] = sanitise_string($options['order_by'])) {
			$query .= " ORDER BY {$options['order_by']}, n_table.id";
		}

		if ($options['limit']) {
			$limit = sanitise_int($options['limit']);
			$offset = sanitise_int($options['offset']);
			$query .= " LIMIT $offset, $limit";
		}

		$dt = get_data($query, $options['callback']);
		return $dt;
	} else {
		$result = get_data_row($query);
		return $result->calculation;
	}
}


/**
 * Returns an array of joins and wheres for use in metastrings.
 *
 * @note The $pairs is reserved for name/value pairs if we want to implement those.
 *
 * @param string $table          The annotation or metadata table name or alias
 * @param array  $names          An array of names
 * @param array  $values         An array of values
 * @param array  $pairs          Name / value pairs. Not currently used.
 * @param bool   $case_sensitive Should name and values be case sensitive?
 *
 * @return array
 */
function elgg_get_metastring_sql($table, $names = null, $values = null,
	$pairs = null, $case_sensitive = false) {

	if ((!$names && $names !== 0)
		&& (!$values && $values !== 0)
		&& (!$pairs && $pairs !== 0)) {

		return '';
	}

	$db_prefix = elgg_get_config('dbprefix');

	// join counter for incremental joins.
	$i = 1;

	// binary forces byte-to-byte comparision of strings, making
	// it case- and diacritical-mark- sensitive.
	// only supported on values.
	$binary = ($case_sensitive) ? ' BINARY ' : '';

	$access = get_access_sql_suffix($table);

	$return = array (
		'joins' => array (),
		'wheres' => array()
	);

	$wheres = array();

	// get names wheres and joins
	$names_where = '';
	if ($names !== NULL) {
		if (!is_array($names)) {
			$names = array($names);
		}

		$sanitised_names = array();
		foreach ($names as $name) {
			// normalise to 0.
			if (!$name) {
				$name = '0';
			}
			$sanitised_names[] = '\'' . sanitise_string($name) . '\'';
		}

		if ($names_str = implode(',', $sanitised_names)) {
			$return['joins'][] = "JOIN {$db_prefix}metastrings msn on $table.name_id = msn.id";
			$names_where = "(msn.string IN ($names_str))";
		}
	}

	// get values wheres and joins
	$values_where = '';
	if ($values !== NULL) {
		if (!is_array($values)) {
			$values = array($values);
		}

		$sanitised_values = array();
		foreach ($values as $value) {
			// normalize to 0
			if (!$value) {
				$value = 0;
			}
			$sanitised_values[] = '\'' . sanitise_string($value) . '\'';
		}

		if ($values_str = implode(',', $sanitised_values)) {
			$return['joins'][] = "JOIN {$db_prefix}metastrings msv on $table.value_id = msv.id";
			$values_where = "({$binary}msv.string IN ($values_str))";
		}
	}

	if ($names_where && $values_where) {
		$wheres[] = "($names_where AND $values_where AND $access)";
	} elseif ($names_where) {
		$wheres[] = "($names_where AND $access)";
	} elseif ($values_where) {
		$wheres[] = "($values_where AND $access)";
	}

	if ($where = implode(' AND ', $wheres)) {
		$return['wheres'][] = "($where)";
	}

	return $return;
}