<?php
/**
 * Elgg search plugin
 *
 */

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

/**
 * Initialize search plugin
 */
function search_init() {
	global $CONFIG;
	require_once 'search_hooks.php';

	// page handler for search actions and results
	elgg_register_page_handler('search', 'search_page_handler');

	// register some default search hooks
	elgg_register_plugin_hook_handler('search', 'object', 'search_objects_hook');
	elgg_register_plugin_hook_handler('search', 'user', 'search_users_hook');
	elgg_register_plugin_hook_handler('search', 'group', 'search_groups_hook');

	// tags and comments are a bit different.
	// register a search types and a hooks for them.
	elgg_register_plugin_hook_handler('search_types', 'get_types', 'search_custom_types_tags_hook');
	elgg_register_plugin_hook_handler('search', 'tags', 'search_tags_hook');

	// get server min and max allowed chars for ft searching
	$CONFIG->search_info = array();

	$ft_min_max = search_get_ft_min_max();
	$CONFIG->search_info['min_chars'] = $ft_min_max->min;
	$CONFIG->search_info['max_chars'] = $ft_min_max->max;

	// add in CSS for search elements
	elgg_extend_view('elgg.css', 'search/css');

	// extend view for elgg topbar search box
	elgg_extend_view('page/elements/header', 'search/header');

	elgg_register_plugin_hook_handler('robots.txt', 'site', 'search_exclude_robots');
}

/**
 * Page handler for search
 *
 * @param array $page Page elements from core page handler
 * @return bool
 */
function search_page_handler($page) {

	// if there is no q set, we're being called from a legacy installation
	// it expects a search by tags.
	// actually it doesn't, but maybe it should.
	// maintain backward compatibility
	if(!get_input('q', get_input('tag', NULL))) {
		set_input('q', $page[0]);
		//set_input('search_type', 'tags');
	}

	echo elgg_view_resource('search/index');
	return true;
}

/**
 * Return a string with highlighted matched queries and relevant context
 * Determines context based upon occurance and distance of words with each other.
 *
 * @param string $haystack
 * @param string $query
 * @param int $min_match_context = 30
 * @param int $max_length = 300
 * @param bool $tag_match Search is for tags. Don't ignore words.
 * @return string
 */
function search_get_highlighted_relevant_substrings($haystack, $query, $min_match_context = 30, $max_length = 300, $tag_match = false) {

	$haystack = strip_tags($haystack);
	$haystack_length = elgg_strlen($haystack);
	$haystack_lc = elgg_strtolower($haystack);

	if (!$tag_match) {
		$words = search_remove_ignored_words($query, 'array');
	} else {
		$words = array();
	}

	// if haystack < $max_length return the entire haystack w/formatting immediately
	if ($haystack_length <= $max_length) {
		$return = search_highlight_words($words, $haystack);

		return $return;
	}

	// get the starting positions and lengths for all matching words
	$starts = array();
	$lengths = array();
	foreach ($words as $word) {
		$word = elgg_strtolower($word);
		$count = elgg_substr_count($haystack_lc, $word);
		$word_len = elgg_strlen($word);
		$haystack_len = elgg_strlen($haystack_lc);

		// find the start positions for the words
		if ($count > 1) {
			$offset = 0;
			while (FALSE !== $pos = elgg_strpos($haystack_lc, $word, $offset)) {
				$start = ($pos - $min_match_context > 0) ? $pos - $min_match_context : 0;
				$starts[] = $start;
				$stop = $pos + $word_len + $min_match_context;
				$lengths[] = $stop - $start;
				$offset += $pos + $word_len;

				if ($offset >= $haystack_len) {
					break;
				}
			}
		} else {
			$pos = elgg_strpos($haystack_lc, $word);
			$start = ($pos - $min_match_context > 0) ? $pos - $min_match_context : 0;
			$starts[] = $start;
			$stop = $pos + $word_len + $min_match_context;
			$lengths[] = $stop - $start;
		}
	}

	$offsets = search_consolidate_substrings($starts, $lengths);

	// figure out if we can adjust the offsets and lengths
	// in order to return more context
	$total_length = array_sum($offsets);

	$add_length = 0;
	if ($total_length < $max_length && $offsets) {
		$add_length = floor((($max_length - $total_length) / count($offsets)) / 2);

		$starts = array();
		$lengths = array();
		foreach ($offsets as $offset => $length) {
			$start = ($offset - $add_length > 0) ? $offset - $add_length : 0;
			$length = $length + $add_length;
			$starts[] = $start;
			$lengths[] = $length;
		}

		$offsets = search_consolidate_substrings($starts, $lengths);
	}

	// sort by order of string size descending (which is roughly
	// the proximity of matched terms) so we can keep the
	// substrings with terms closest together and discard
	// the others as needed to fit within $max_length.
	arsort($offsets);

	$return_strs = array();
	$total_length = 0;
	foreach ($offsets as $start => $length) {
		$string = trim(elgg_substr($haystack, $start, $length));

		// continue past if adding this substring exceeds max length
		if ($total_length + $length > $max_length) {
			continue;
		}

		$total_length += $length;
		$return_strs[$start] = $string;
	}

	// put the strings in order of occurence
	ksort($return_strs);

	// add ...s where needed
	$return = implode('...', $return_strs);
	if (!array_key_exists(0, $return_strs)) {
		$return = "...$return";
	}

	// add to end of string if last substring doesn't hit the end.
	$starts = array_keys($return_strs);
	$last_pos = $starts[count($starts)-1];
	if ($last_pos + elgg_strlen($return_strs[$last_pos]) < $haystack_length) {
		$return .= '...';
	}

	$return = search_highlight_words($words, $return);

	return $return;
}


/**
 * Takes an array of offsets and lengths and consolidates any
 * overlapping entries, returning an array of new offsets and lengths
 *
 * Offsets and lengths are specified in separate arrays because of possible
 * index collisions with the offsets.
 *
 * @param array $offsets
 * @param array $lengths
 * @return array
 */
function search_consolidate_substrings($offsets, $lengths) {
	// sort offsets by occurence
	asort($offsets, SORT_NUMERIC);

	// reset the indexes maintaining association with the original offsets.
	$offsets = array_merge($offsets);

	$new_lengths = array();
	foreach ($offsets as $i => $offset) {
		$new_lengths[] = $lengths[$i];
	}

	$lengths = $new_lengths;

	$return = array();
	$count = count($offsets);
	for ($i=0; $i<$count; $i++) {
		$offset = $offsets[$i];
		$length = $lengths[$i];
		$end_pos = $offset + $length;

		// find the next entry that doesn't overlap
		while (array_key_exists($i+1, $offsets) && $end_pos > $offsets[$i+1]) {
			$i++;
			if (!array_key_exists($i, $offsets)) {
				break;
			}
			$end_pos = $lengths[$i] + $offsets[$i];
		}

		$length = $end_pos - $offset;

		// will never have a colliding offset, so can return as a single array
		$return[$offset] = $length;
	}

	return $return;
}

/**
 * Safely highlights the words in $words found in $string avoiding recursion
 *
 * @param array $words
 * @param string $string
 * @return string
 */
function search_highlight_words($words, $string) {
	$i = 1;
	$replace_html = array(
		'strong' => rand(10000, 99999),
		'class' => rand(10000, 99999),
		'search-highlight' => rand(10000, 99999),
		'search-highlight-color' => rand(10000, 99999)
	);

	foreach ($words as $word) {
		// remove any boolean mode operators
		$word = preg_replace("/([\-\+~])([\w]+)/i", '$2', $word);
		
		// escape the delimiter and any other regexp special chars
		$word = preg_quote($word, '/');
		
		$search = "/($word)/i";

		// @todo
		// must replace with placeholders in case one of the search terms is
		// in the html string.
		// later, will replace the placeholders with the actual html.
		// Yeah this is hacky.  I'm tired.
		$strong = $replace_html['strong'];
		$class = $replace_html['class'];
		$highlight = $replace_html['search-highlight'];
		$color = $replace_html['search-highlight-color'];

		$replace = "<$strong $class=\"$highlight $color{$i}\">$1</$strong>";
		$string = preg_replace($search, $replace, $string);
		$i++;
	}

	foreach ($replace_html as $replace => $search) {
		$string = str_replace($search, $replace, $string);
	}

	return $string;
}

/**
 * Returns a query with stop and too short words removed.
 * (Unless the entire query is < ft_min_word_chars, in which case
 * it's taken literally.)
 *
 * @param array $query
 * @param str $format Return as an array or a string
 * @return mixed
 */
function search_remove_ignored_words($query, $format = 'array') {
	global $CONFIG;

	// don't worry about "s or boolean operators
	//$query = str_replace(array('"', '-', '+', '~'), '', stripslashes(strip_tags($query)));
	$query = stripslashes(strip_tags($query));
	$query = trim($query);
	
	$words = preg_split('/\s+/', $query);

	$min_chars = $CONFIG->search_info['min_chars'];
	// if > ft_min_word we're not running in literal mode.
	if (elgg_strlen($query) >= $min_chars) {
		// clean out any words that are ignored by mysql
		foreach ($words as $i => $word) {
			if (elgg_strlen($word) < $min_chars) {
				unset ($words[$i]);
			}
		}
	}

	if ($format == 'string') {
		return implode(' ', $words);
	}

	return $words;
}


/**
 * Passes results, and original params to the view functions for
 * search type.
 *
 * @param array $results
 * @param array $params
 * @param string $view_type = list, entity or layout
 * @return string
 */
function search_get_search_view($params, $view_type) {
	switch ($view_type) {
		case 'list':
		case 'entity':
		case 'layout':
			break;

		default:
			return FALSE;
	}

	$view_order = array();

	// check if there's a special search list view for this type:subtype
	if (isset($params['type']) && $params['type'] && isset($params['subtype']) && $params['subtype']) {
		$view_order[] = "search/{$params['type']}/{$params['subtype']}/$view_type";
	}

	// also check for the default type
	if (isset($params['type']) && $params['type']) {
		$view_order[] = "search/{$params['type']}/$view_type";
	}

	// check search types
	if (isset($params['search_type']) && $params['search_type']) {
		$view_order[] = "search/{$params['search_type']}/$view_type";
	}

	// finally default to a search list default
	$view_order[] = "search/$view_type";

	foreach ($view_order as $view) {
		if (elgg_view_exists($view)) {
			return $view;
		}
	}

	return FALSE;
}

/**
 * Returns a where clause for a search query.
 *
 * @param str $table Prefix for table to search on
 * @param array $fields Fields to match against
 * @param array $params Original search params
 * @return str
 */
function search_get_where_sql($table, $fields, $params, $use_fulltext = TRUE) {
	global $CONFIG;
	$query = $params['query'];

	// add the table prefix to the fields
	foreach ($fields as $i => $field) {
		if ($table) {
			$fields[$i] = "$table.$field";
		}
	}
	
	$where = '';

	// if query is shorter than the min for fts words
	// it's likely a single acronym or similar
	// switch to literal mode
	if (elgg_strlen($query) < $CONFIG->search_info['min_chars']) {
		$likes = array();
		$query = sanitise_string($query);
		foreach ($fields as $field) {
			$likes[] = "$field LIKE '%$query%'";
		}
		$likes_str = implode(' OR ', $likes);
		$where = "($likes_str)";
	} else {
		// if we're not using full text, rewrite the query for bool mode.
		// exploiting a feature(ish) of bool mode where +-word is the same as -word
		if (!$use_fulltext) {
			$query = '+' . str_replace(' ', ' +', $query);
		}
		
		// if using advanced, boolean operators, or paired "s, switch into boolean mode
		$booleans_used = preg_match("/([\-\+~])([\w]+)/i", $query);
		$advanced_search = (isset($params['advanced_search']) && $params['advanced_search']);
		$quotes_used = (elgg_substr_count($query, '"') >= 2); 
		
		if (!$use_fulltext || $booleans_used || $advanced_search || $quotes_used) {
			$options = 'IN BOOLEAN MODE';
		} else {
			// natural language mode is default and this keyword isn't supported in < 5.1
			//$options = 'IN NATURAL LANGUAGE MODE';
			$options = '';
		}
		
		// if short query, use query expansion.
		// @todo doesn't seem to be working well.
//		if (elgg_strlen($query) < 5) {
//			$options .= ' WITH QUERY EXPANSION';
//		}
		$query = sanitise_string($query);

		$fields_str = implode(',', $fields);
		$where = "(MATCH ($fields_str) AGAINST ('$query' $options))";
	}

	return $where;
}


/**
 * Returns ORDER BY sql for insertion into elgg_get_entities().
 *
 * @param str $entities_table Prefix for entities table.
 * @param str $type_table Prefix for the type table.
 * @param str $sort ORDER BY part
 * @param str $order ASC or DESC
 * @return str
 */
function search_get_order_by_sql($entities_table, $type_table, $sort, $order) {

	$on = NULL;

	switch ($sort) {
		default:
		case 'relevance':
			// default is relevance descending.
			// ascending relevancy is silly and complicated.
			$on = '';
			break;
		case 'created':
			$on = "$entities_table.time_created";
			break;
		case 'updated':
			$on = "$entities_table.time_updated";
			break;
		case 'action_on':
			// @todo not supported yet in core
			$on = '';
			break;
		case 'alpha':
			// @todo not support yet because both title
			// and name columns are used for this depending
			// on the entity, which we don't always know.  >:O
			break;
	}
	$order = strtolower($order);
	if ($order != 'asc' && $order != 'desc') {
		$order = 'DESC';
	}

	if ($on) {
		$order_by = "$on $order";
	} else {
		$order_by = '';
	}

	return $order_by;
}

/**
 * Exclude robots from indexing search pages
 *
 * This is good for performance since search is slow and there are many pages all
 * with the same content.
 *
 * @param string $hook Hook name
 * @param string $type Hook type
 * @param string $text robots.txt content for plugins
 * @return string
 */
function search_exclude_robots($hook, $type, $text) {
	$text .= <<<TEXT
User-agent: *
Disallow: /search/

TEXT;

	return $text;
}

/**
 * Returns minimum and maximum lengths of words for MySQL search
 * This function looks for stored config values, and, if none set,
 * queries the DB and saves them
 * @return stdClass An object with min and max properties
 */
function search_get_ft_min_max() {

	$min = (int) elgg_get_config('search_ft_min_word_len');
	$max = (int) elgg_get_config('search_ft_max_word_len');

	if (!$min || !$max) {
		// defaults from MySQL on Ubuntu Linux
		$min = 4;
		$max = 90;
		try {
			$result = get_data_row('SELECT @@ft_min_word_len as min, @@ft_max_word_len as max');
			$min = $result->min;
			$max = $result->max;
		} catch (DatabaseException $e) {
			// some servers don't have these values set which leads to exception
			// we ignore the exception
		}
		elgg_save_config('search_ft_min_word_len', $min);
		elgg_save_config('search_ft_max_word_len', $max);
	}

	$ft = new stdClass();
	$ft->min = $min;
	$ft->max = $max;

	return $ft;
}
