engine/lib/tags.php

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<?php
function calculate_tag_size($min, $max, $number_of_tags, $buckets = 6) {
    $delta = (($max - $min) / $buckets);
    $thresholds = array();

    for ($n = 1; $n <= $buckets; $n++) {
        $thresholds[$n - 1] = ($min + $n) * $delta;
    }

    // Correction
    if ($thresholds[$buckets - 1] > $max) {
        $thresholds[$buckets - 1] = $max;
    }

    $size = 0;
    for ($n = 0; $n < count($thresholds); $n++) {
        if ($number_of_tags >= $thresholds[$n]) {
            $size = $n;
        }
    }

    return $size;
}

function generate_tag_cloud(array $tags, $buckets = 6) {
    $cloud = array();

    $min = 65535;
    $max = 0;

    foreach ($tags as $tag) {
        $cloud[$tag]++;

        if ($cloud[$tag] > $max) {
            $max = $cloud[$tag];
        }

        if ($cloud[$tag] < $min) {
            $min = $cloud[$tag];
        }
    }

    foreach ($cloud as $k => $v) {
        $cloud[$k] = calculate_tag_size($min, $max, $v, $buckets);
    }

    return $cloud;
}

function elgg_get_tags(array $options = array()) {
    global $CONFIG;

    $defaults = array(
        'threshold'             =>  1,
        'tag_names'             =>  array(),
        'limit'                 =>  10,

        'types'                 =>  ELGG_ENTITIES_ANY_VALUE,
        'subtypes'              =>  ELGG_ENTITIES_ANY_VALUE,
        'type_subtype_pairs'    =>  ELGG_ENTITIES_ANY_VALUE,

        'owner_guids'           =>  ELGG_ENTITIES_ANY_VALUE,
        'container_guids'       =>  ELGG_ENTITIES_ANY_VALUE,
        'site_guids'            =>  $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,

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


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

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

    $registered_tags = elgg_get_registered_tag_metadata_names();

    if (!is_array($options['tag_names'])) {
        return false;
    }

    // empty array so use all registered tag names
    if (count($options['tag_names']) == 0) {
        $options['tag_names'] = $registered_tags;
    }

    $diff = array_diff($options['tag_names'], $registered_tags);
    if (count($diff) > 0) {
        elgg_deprecated_notice('Tag metadata names must be registered by elgg_register_tag_metadata_name()', 1.7);
        // return false;
    }


    $wheres = $options['wheres'];

    // catch for tags that were spaces
    $wheres[] = "msv.string != ''";

    $sanitised_tags = array();
    foreach ($options['tag_names'] as $tag) {
        $sanitised_tags[] = '"' . sanitise_string($tag) . '"';
    }
    $tags_in = implode(',', $sanitised_tags);
    $wheres[] = "(msn.string IN ($tags_in))";

    $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.site_guid', $options['site_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_entity_time_where_sql('e', $options['created_time_upper'],
        $options['created_time_lower'], $options['modified_time_upper'], $options['modified_time_lower']);

    // 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]);
        }
    }

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

    $joins = $options['joins'];

    $joins[] = "JOIN {$CONFIG->dbprefix}metadata md on md.entity_guid = e.guid";
    $joins[] = "JOIN {$CONFIG->dbprefix}metastrings msv on msv.id = md.value_id";
    $joins[] = "JOIN {$CONFIG->dbprefix}metastrings msn on md.name_id = msn.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]);
        }
    }


    $query  = "SELECT msv.string as tag, count(msv.id) as total ";
    $query .= "FROM {$CONFIG->dbprefix}entities e ";

    // 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');

    $threshold = sanitise_int($options['threshold']);
    $query .= " GROUP BY msv.string HAVING total >= {$threshold} ";
    $query .= " ORDER BY total DESC ";

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

    return get_data($query);
}

function elgg_view_tagcloud(array $options = array()) {

    $type = $subtype = '';
    if (isset($options['type'])) {
        $type = $options['type'];
    }
    if (isset($options['subtype'])) {
        $subtype = $options['subtype'];
    }

    $tag_data = elgg_get_tags($options);
    return elgg_view("output/tagcloud", array(
        'value' => $tag_data,
        'type' => $type,
        'subtype' => $subtype,
    ));
}

function elgg_register_tag_metadata_name($name) {
    global $CONFIG;

    if (!isset($CONFIG->registered_tag_metadata_names)) {
        $CONFIG->registered_tag_metadata_names = array();
    }

    if (!in_array($name, $CONFIG->registered_tag_metadata_names)) {
        $CONFIG->registered_tag_metadata_names[] = $name;
    }

    return TRUE;
}

function elgg_get_registered_tag_metadata_names() {
    global $CONFIG;

    $names = (isset($CONFIG->registered_tag_metadata_names))
        ? $CONFIG->registered_tag_metadata_names : array();

    return $names;
}

function elgg_tagcloud_page_handler($page) {

    $title = elgg_view_title(elgg_echo('tags:site_cloud'));
    $options = array(
        'threshold' => 0,
        'limit' => 100,
        'tag_name' => 'tags',
    );
    $tags = elgg_view_tagcloud($options);
    $content = $title . $tags;
    $body = elgg_view_layout('one_sidebar', array('content' => $content));

    echo elgg_view_page(elgg_echo('tags:site_cloud'), $body);
    return true;
}

function elgg_tags_init() {
    // register the standard tags metadata name
    elgg_register_tag_metadata_name('tags');
    
    elgg_register_page_handler('tags', 'elgg_tagcloud_page_handler');
}

elgg_register_event_handler('init', 'system', 'elgg_tags_init');

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