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Pepperminty-Wiki/modules/lib-search-engine.php

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<?php
register_module([
"name" => "Library: Search engine",
"version" => "0.13",
"author" => "Starbeamrainbowlabs",
"description" => "A library module that provides the backend to the search engine module.",
"id" => "lib-search-engine",
"depends" => [ "lib-storage-box" ],
"code" => function() {
}
]);
/*
███████ ███████ █████ ██████ ██████ ██ ██
██ ██ ██ ██ ██ ██ ██ ██ ██
███████ █████ ███████ ██████ ██ ███████
██ ██ ██ ██ ██ ██ ██ ██ ██
███████ ███████ ██ ██ ██ ██ ██████ ██ ██
*/
/**
* Holds a collection to methods to manipulate various types of search index.
* @package search
*/
class search
{
/**
* Words that we should exclude from the inverted index.
* @source http://xpo6.com/list-of-english-stop-words/
* @var string[]
*/
public static $stop_words = [
"a", "about", "above", "above", "across", "after", "afterwards", "again",
"against", "all", "almost", "alone", "along", "already", "also",
"although", "always", "am", "among", "amongst", "amoungst", "amount",
"an", "and", "another", "any", "anyhow", "anyone", "anything", "anyway",
"anywhere", "are", "around", "as", "at", "back", "be", "became",
"because", "become", "becomes", "becoming", "been", "before",
"beforehand", "behind", "being", "below", "beside", "besides",
"between", "beyond", "bill", "both", "bottom", "but", "by", "call",
"can", "can't", "cannot", "co", "con", "could", "couldnt", "cry", "de",
"describe", "detail", "do", "done", "down", "due", "during", "each",
"eg", "eight", "either", "eleven", "else", "elsewhere", "empty",
"enough", "etc", "even", "ever", "every", "everyone", "everything",
"everywhere", "except", "few", "fill", "find",
"fire", "first", "five", "for", "former", "formerly", "found",
"four", "from", "front", "full", "further", "get", "give", "go", "had",
"has", "hasnt", "have", "he", "hence", "her", "here", "hereafter",
"hereby", "herein", "hereupon", "hers", "herself", "him", "himself",
"his", "how", "however", "ie", "if", "in", "inc", "indeed",
"interest", "into", "is", "it", "its", "it's", "itself", "keep", "last",
"latter", "latterly", "least", "less", "ltd", "made", "many", "may",
"me", "meanwhile", "might", "mine", "more", "moreover", "most",
"mostly", "move", "much", "must", "my", "myself", "name", "namely",
"neither", "never", "nevertheless", "next", "nine", "no", "none",
"nor", "not", "nothing", "now", "nowhere", "of", "off", "often", "on",
"once", "one", "only", "onto", "or", "other", "others", "otherwise",
"our", "ours", "ourselves", "out", "over", "own", "part", "per",
"perhaps", "please", "put", "rather", "re", "same", "see", "seem",
"seemed", "seeming", "seems", "serious", "several", "she", "should",
"show", "side", "since", "sincere", "six", "sixty", "so", "some",
"somehow", "someone", "something", "sometime", "sometimes",
"somewhere", "still", "such", "system", "take", "ten", "than", "that",
"the", "their", "them", "themselves", "then", "thence", "there",
"thereafter", "thereby", "therefore", "therein", "thereupon", "these",
"they", "thickv", "thin", "third", "this", "those", "though", "three",
"through", "throughout", "thru", "thus", "to", "together", "too", "top",
"toward", "towards", "twelve", "twenty", "two", "un", "under", "until",
"up", "upon", "us", "very", "via", "was", "we", "well", "were", "what",
"whatever", "when", "whence", "whenever", "where", "whereafter",
"whereas", "whereby", "wherein", "whereupon", "wherever", "whether",
"which", "while", "whither", "who", "whoever", "whole", "whom", "whose",
"why", "will", "with", "within", "without", "would", "yet", "you",
"your", "yours", "yourself", "yourselves"
];
/**
* The StorageBox that contains the inverted index.
* @var StorageBox
*/
private static $invindex = null;
/**
* The transliterator that can be used to transliterate strings.
* Transliterated strings are more suitable for use with the search index.
* Note that this is no longer wrapped in a function as of v0.21 for
* performance reasons.
* @var Transliterator
*/
public static $literator = null;
/**
* Initialises the search system.
* Do not call this function! It is called automatically.
*/
public static function init() {
self::$literator = Transliterator::createFromRules(':: Any-Latin; :: Latin-ASCII; :: NFD; :: [:Nonspacing Mark:] Remove; :: Lower(); :: NFC;', Transliterator::FORWARD);
}
/**
* Converts a source string into an index of search terms that can be
* merged into an inverted index.
* Automatically transliterates the source string.
* @param string $source The source string to index.
* @return array An index represents the specified string.
*/
public static function index_generate(string $source) : array {
// We don't need to normalise or transliterate here because self::tokenize() does this for us
$source = html_entity_decode($source, ENT_QUOTES);
$source_length = mb_strlen($source);
$index = [];
$terms = self::tokenize($source, true);
foreach($terms as $term) {
// Skip over stop words (see https://en.wikipedia.org/wiki/Stop_words)
if(in_array($term[0], self::$stop_words)) continue;
if(!isset($index[$term[0]]))
$index[$term[0]] = [ "freq" => 0, "offsets" => [] ];
$index[$term[0]]["freq"]++;
$index[$term[0]]["offsets"][] = $term[1];
}
return $index;
}
/**
* Converts a source string into a series of raw tokens.
* @param string $source The source string to process.
* @param bool $capture_offsets Whether to capture & return the character offsets of the tokens detected. If true, then each token returned will be an array in the form [ token, char_offset ].
* @return array An array of raw tokens extracted from the specified source string.
*/
public static function tokenize(string $source, bool $capture_offsets = false) : array {
$flags = PREG_SPLIT_NO_EMPTY; // Don't return empty items
if($capture_offsets)
$flags |= PREG_SPLIT_OFFSET_CAPTURE;
// We don't need to normalise here because the transliterator handles
$source = self::$literator->transliterate($source);
$source = preg_replace('/[\[\]\|\{\}\/]/u', " ", $source);
return preg_split("/((^\p{P}+)|(\p{P}*\s+\p{P}*)|(\p{P}+$))|\|/u", $source, -1, $flags);
}
/**
* Removes (most) markdown markup from the specified string.
* Stripped strings are not suitable for indexing!
* @param string $source The source string to process.
* @return string The stripped string.
*/
public static function strip_markup(string $source) : string {
return preg_replace('/([\"*_\[\]]| - |`)/u', "", $source);
}
/**
* Rebuilds the master inverted index and clears the page id index.
* @param bool $output Whether to send progress information to the user's browser.
*/
public static function invindex_rebuild(bool $output = true) : void {
global $pageindex, $env, $paths, $settings;
$env->perfdata->invindex_rebuild = microtime(true);
if($output && !is_cli()) {
header("content-type: text/event-stream");
ob_end_flush();
}
// Clear the id index out
ids::clear();
// Clear the existing inverted index out
if(self::$invindex == null)
self::invindex_load($paths->searchindex);
self::$invindex->clear();
self::$invindex->set("|termlist|", []);
// Reindex each page in turn
$i = 0; $max = count(get_object_vars($pageindex));
$missing_files = 0;
foreach($pageindex as $pagename => $pagedetails)
{
$page_filename = $env->storage_prefix . $pagedetails->filename;
if(!file_exists($page_filename)) {
if(!is_cli()) echo("data: ");
echo("[" . ($i + 1) . " / $max] Error: Can't find $page_filename\n");
flush();
$i++; $missing_files++;
continue;
}
// We do not transliterate or normalise here because the indexer will take care of this for us
$index = self::index_generate(file_get_contents($page_filename));
$pageid = ids::getid($pagename);
self::invindex_merge($pageid, $index);
if($output) {
$message = "[" . ($i + 1) . " / $max] Added $pagename (id #$pageid) to the new search index.";
if(!is_cli()) $message = "data: $message\n\n";
else $message = "$message\r";
echo($message);
flush();
}
$i++;
}
$msg = "Syncing to disk....";
if(!is_cli()) $msg = "data: $msg\n\n";
else $msg = "$msg\r";
echo($msg);
self::invindex_close();
$env->perfdata->invindex_rebuild = round(microtime(true) - $env->perfdata->invindex_rebuild, 4);
if($output && !is_cli()) {
echo("data: Search index rebuilding complete in {$env->perfdata->invindex_rebuild}s.\n\n");
echo("data: Couldn't find $missing_files pages on disk. If $settings->sitename couldn't find some pages on disk, then you might need to manually correct $settings->sitename's page index (stored in pageindex.json).\n\n");
echo("data: Done! Saving new search index to '$paths->searchindex'.\n\n");
}
if(is_cli()) echo("\nSearch index rebuilding complete in {$env->perfdata->invindex_rebuild}s.\n");
// No need to save, it's an SQLite DB backend
}
/**
* Sorts an index alphabetically.
* This allows us to do a binary search instead of a regular
* sequential search.
* @param array $index The index to sort.
*/
public static function index_sort(&$index) {
$sorter = new Collator("");
uksort($index, function($a, $b) use($sorter) : int {
return $sorter->compare($a, $b);
});
}
/**
* Compares two *regular* indexes to find the differences between them.
* @param array $oldindex The old index.
* @param array $newindex The new index.
* @param array $changed An array to be filled with the nterms of all the changed entries.
* @param array $removed An array to be filled with the nterms of all the removed entries.
*/
public static function index_compare($oldindex, $newindex, &$changed, &$removed) {
foreach($oldindex as $nterm => $entry) {
if(!isset($newindex[$nterm]))
$removed[] = $nterm;
}
foreach($newindex as $nterm => $entry) {
if(!isset($oldindex[$nterm]) or // If this word is new
$newindex[$nterm] !== $oldindex[$nterm]) // If this word has changed
$changed[$nterm] = $newindex[$nterm];
}
}
/**
* Loads a connection to an inverted index.
* @param string $invindex_filename The path to the inverted index to load.
* @todo Remove this function and make everything streamable
*/
public static function invindex_load(string $invindex_filename) {
global $env, $paths;
$start_time = microtime(true);
self::$invindex = new StorageBox($invindex_filename);
$env->perfdata->searchindex_load_time = round((microtime(true) - $start_time)*1000, 3);
}
/**
* Closes the currently open inverted index.
*/
public static function invindex_close() {
global $env;
$start_time = microtime(true);
self::$invindex->close();
$env->perfdata->searchindex_close_time = round((microtime(true) - $start_time)*1000, 3);
}
/**
* Merge an index into an inverted index.
* @param int $pageid The id of the page to assign to the index that's being merged.
* @param array $index The regular index to merge.
* @param array $removals An array of index entries to remove from the inverted index. Useful for applying changes to an inverted index instead of deleting and remerging an entire page's index.
*/
public static function invindex_merge($pageid, &$index, &$removals = []) : void {
if(self::$invindex == null)
throw new Exception("Error: Can't merge into an inverted index that isn't loaded.");
if(!self::$invindex->has("|termlist|"))
self::$invindex->set("|termlist|", []);
$termlist = self::$invindex->get("|termlist|");
// Remove all the subentries that were removed since last time
foreach($removals as $nterm) {
// Delete the offsets
self::$invindex->delete("$nterm|$pageid");
// Delete the item from the list of pageids containing this term
$nterm_pageids = self::$invindex->get_arr_simple($nterm);
array_splice($nterm_pageids, array_search($pageid, $nterm_pageids), 1);
if(empty($nterm_pageids)) { // No need to keep the pageid list if there's nothing in it
self::$invindex->delete($nterm);
// Update the termlist if we're deleting the term completely
$termlist_loc = array_search($nterm, $termlist);
if($termlist_loc !== false) array_splice($termlist, $termlist_loc, 1);
}
else
self::$invindex->set_arr_simple($nterm, $nterm_pageids);
}
// Merge all the new / changed index entries into the inverted index
foreach($index as $nterm => $newentry) {
// if(!is_string($nterm)) $nterm = strval($nterm);
if(!self::$invindex->has($nterm)) {
self::$invindex->set_arr_simple($nterm, []);
$termlist[] = $nterm;
}
// Update the nterm pageid list
$nterm_pageids = self::$invindex->get_arr_simple($nterm);
if(array_search($pageid, $nterm_pageids) === false) {
$nterm_pageids[] = $pageid;
self::$invindex->set_arr_simple($nterm, $nterm_pageids);
}
// Store the offset list
self::$invindex->set("$nterm|$pageid", $newentry);
}
self::$invindex->set("|termlist|", $termlist);
}
/**
* Deletes the given pageid from the given pageindex.
* @param int $pageid The pageid to remove.
*/
public static function invindex_delete(int $pageid) {
$termlist = self::$invindex->get("|termlist|");
foreach($termlist as $nterm) {
$nterm_pageids = self::$invindex->get_arr_simple($nterm);
$nterm_loc = array_search($pageid, $nterm_pageids);
// If this nterm doesn't appear in the list, we're not interested
if($nterm_loc === false)
continue;
// Delete it from the ntemr list
array_splice($nterm_pageids, $nterm_loc, 1);
// Delete the offset list
self::$invindex->delete("$nterm|$pageid");
// If this term doesn't appear in any other documents, delete it
if(count($nterm_pageids) === 0) {
self::$invindex->delete($nterm);
array_splice($termlist, array_search($nterm, $termlist), 1);
}
else // Save the document id list back, since it still contains other pageids
self::$invindex->set_arr_simple($nterm, $nterm_pageids);
}
// Save the termlist back to the store
self::$invindex->set("|termlist|", $termlist);
}
/*
* ███████ ████████ █████ ███████
* ██ ██ ██ ██ ██
* ███████ ██ ███████ ███████
* ██ ██ ██ ██ ██
* ███████ ██ ██ ██ ███████
*/
/**
* Splits a query string into tokens. Does not require that the input string be transliterated.
* Was based on my earlier explode_adv: https://starbeamrainbowlabs.com/blog/article.php?article=posts/081-PHP-String-Splitting.html
* Now improved to be strtok-based, since it's much faster.
* Example I used when writing this: https://www.php.net/manual/en/function.strtok.php#94463
* @param string $query The query string to split.
*/
public function stas_split($query) {
$query = self::$literator->transliterate($query);
$terms = [];
$next_token = strtok($query, " \r\n\t");
while(true) {
if(strpos($next_token, '"') !== false)
$next_token .= " " . strtok('"') . '"';
if(strpos($next_token, "'") !== false)
$next_token .= " " . strtok("'") . "'";
$terms[] = $next_token;
$next_token = strtok(" \r\n\t");
if($next_token === false) break;
}
return $terms;
}
/**
* Parses an array of query tokens into an associative array of search directives.
* Supported syntax derived from these sources:
* https://help.duckduckgo.com/duckduckgo-help-pages/results/syntax/
* https://docs.microsoft.com/en-us/windows/win32/lwef/-search-2x-wds-aqsreference
* @param string[] $tokens The array of query tokens to parse.
*/
public function stas_parse($tokens) {
global $settings;
/* Supported Syntax *
*
* -term exclude a term
* +term double the weighting of a term
* terms !dest terms redirect entire query (minus the !bang) to interwiki with registered shortcut dest
* prefix:term apply prefix operator to term
*/
// var_dump($tokens);
$result = [
"terms" => [],
"exclude" => [],
"interwiki" => null
];
// foreach($operators as $op)
// $result[$op] = [];
$count = count($tokens);
for($i = count($tokens) - 1; $i >= 0; $i--) {
// Look for excludes
if($tokens[$i][0] == "-") {
if(in_array(substr($tokens[$i], 1), self::$stop_words)) {
$result["tokens"][] = [
"term" => substr($tokens[$i], 1),
"weight" => -1,
"location" => "all"
];
}
else
$result["exclude"][] = substr($tokens[$i], 1);
continue;
}
// Look for weighted terms
if($tokens[$i][0] == "+") {
if(in_array(substr($tokens[$i], 1), self::$stop_words)) {
$result["tokens"] = [ "term" => substr($tokens[$i], 1), "weight" => -1, "location" => "all" ];
}
else {
$result["terms"][] = [
"term" => substr($tokens[$i], 1),
"weight" => 2,
"location" => "all"
];
}
continue;
}
// Look for interwiki searches
if($tokens[$i][0] == "!" || substr($tokens[$i], -1) == "!") {
// You can only go to 1 interwiki destination at once, so we replace any previous finding with this one
$result["interwiki"] = trim($tokens[$i], "!");
}
// Look for colon directives in the form directive:term
// Also supports prefix:"quoted term with spaces", quotes stripped automatically
/*** Example directives *** (. = implemented, * = not implemented)
. intitle search only page titles for term
. intags search only tags for term
. inbody search page body only for term
* before search only pages that were last modified before term
* after search only pages that were last modified after term
* size search only pages that match the size spec term (e.g. 1k+ -> more than 1k bytes, 2k- -> less than 2k bytes, >5k -> more than 5k bytes, <10k -> less than 10k bytes)
**************************/
if(strpos($tokens[$i], ":") !== false) {
$parts = explode(":", $tokens[$i], 2);
if(!isset($result[$parts[0]]))
$result[$parts[0]] = [];
switch($parts[0]) {
case "intitle": // BUG: What if a normal word is found in a title?
$result["terms"][] = [
"term" => $parts[1],
"weight" => $settings->search_title_matches_weighting * mb_strlen($parts[1]),
"location" => "title"
];
break;
case "intags":
$result["terms"][] = [
"term" => $parts[1],
"weight" => $settings->search_tags_matches_weighting * mb_strlen($parts[1]),
"location" => "tags"
];
break;
case "inbody":
$result["terms"][] = [
"term" => $parts[1],
"weight" => 1,
"location" => "body"
];
break;
default:
$result[$parts[0]][] = trim($parts[1], '"');
break;
}
continue;
}
// Doesn't appear to be particularly special *shrugs*
// Set the weight to -1 if it's a stop word
$result["terms"][] = [
"term" => $tokens[$i],
"weight" => in_array($tokens[$i], self::$stop_words) ? -1 : 1,
"location" => "all"
];
}
return $result;
}
/**
* Searches the given inverted index for the specified search terms.
* @param string $query The search query.
* @return array An array of matching pages.
*/
public static function invindex_query($query)
{
global $settings, $pageindex;
$query_stas = self::stas_parse(
self::stas_split(self::$literator->transliterate($query))
);
/* Sub-array format:
* [
* nterms : [ nterm => frequency, nterm => frequency, .... ],
* offsets_body : int[],
* matches_title : int,
* matches_tags : int
* ]
*/
$matching_pages = [];
$match_template = [
"nterms" => [],
"offsets_body" => [],
"rank_title" => 0,
"rank_tags" => 0
];
// Query the inverted index
foreach($query_stas["terms"] as $term_def) {
if($term_def["weight"] == -1)
continue; // Skip stop words
if(!in_array($term_def["location"], ["all", "inbody"]))
continue; // Skip terms we shouldn't search the page body for
if(!self::$invindex->has($term_def["term"]))
continue; // Skip if it's not in the index
// For each page that contains this term.....
$term_pageids = self::$invindex->get_arr_simple($term_def["term"]);
foreach($term_pageids as $pageid) {
// Check to see if it contains any words we should exclude
$skip = false;
foreach($query_stas["exclude"] as $excl_term) {
if(self::$invindex->has("$excl_term|$pageid")) {
$skip = true;
break;
}
}
if($skip) continue;
// Get the list of offsets
$page_offsets = self::$invindex->get("{$term_def["term"]}|$pageid");
if(!isset($matching_pages[$pageid]))
$matching_pages[$pageid] = $match_template; // Arrays are assigned by copy in php
// Add it to the appropriate $matching_pages entry, not forgetting to apply the weighting
$matching_pages[$pageid]["offsets_body"] = array_merge(
$matching_pages[$pageid]["offsets_body"],
$page_offsets->offsets
);
$matching_pages[$pageid]["nterms"][$term_def["term"]] = $page_offsets->freq * $term_def["weight"];
}
}
// Query page titles & tags
foreach($query_stas["terms"] as $term_def) {
// No need to skip stop words here, since we're doing a normal
// sequential search anyway
if(!in_array($term_def["location"], ["all", "title", "tags"]))
continue; // Skip terms we shouldn't search the page body for
// Loop over the pageindex and search the titles / tags
reset($pageindex); // Reset array/object pointer
foreach($pageindex as $pagename => $pagedata) {
// Setup a variable to hold the current page's id
$pageid = null; // Cache the page id
$lit_title = self::$literator->transliterate($pagename);
$lit_tags = isset($pagedata->tags) ? self::$literator->transliterate(implode(" ", $pagedata->tags)) : null;
// Make sure that the title & tags don't contain a term we should exclude
$skip = false;
foreach($query_stas["exclude"] as $excl_term) {
if(mb_strpos($lit_title, $excl_term) !== false) {
$skip = true;
// Delete it from the candidate matches (it might be present in the tags / title but not the body)
if(isset($matching_pages[$excl_term]))
unset($matching_pages[$excl_term]);
break;
}
}
if($skip) continue;
// Consider matches in the page title
if(in_array($term_def["location"], ["all", "title"])) {
// FUTURE: We may be able to optimise this further by using preg_match_all + preg_quote instead of mb_stripos_all. Experimentation / benchmarking is required to figure out which one is faster
$title_matches = mb_stripos_all($lit_title, $term_def["term"]);
$title_matches_count = $title_matches !== false ? count($title_matches) : 0;
if($title_matches_count > 0) {
$pageid = ids::getid($pagename); // Fetch the page id
// We found the qterm in the title
if(!isset($matching_pages[$pageid]))
$matching_pages[$pageid] = $match_template; // Assign by copy
$matching_pages[$pageid]["rank_title"] += $title_matches_count * $term_def["weight"];
}
}
// If this page doesn't have any tags, skip it
if($lit_tags == null)
continue;
if(!in_array($term_def["location"], ["all", "tags"]))
continue; // If we shouldn't search the tags, no point in continuing
// Consider matches in the page's tags
$tag_matches = isset($pagedata->tags) ? mb_stripos_all($lit_tags, $term_def["term"]) : false;
$tag_matches_count = $tag_matches !== false ? count($tag_matches) : 0;
if($tag_matches_count > 0) {// And we found the qterm in the tags
if($pageid === null) // Fill out the page id if it hasn't been already
$pageid = ids::getid($pagename);
if(!isset($matching_pages[$pageid]))
$matching_pages[$pageid] = $match_template; // Assign by copy
$matching_pages[$pageid]["rank_tags"] += $tag_matches_count * $term_def["weight"];
}
}
}
// TODO: Implement the rest of STAS here
reset($matching_pages);
foreach($matching_pages as $pageid => &$pagedata) {
$pagedata["pagename"] = ids::getpagename($pageid);
$pagedata["rank"] = 0;
$pageOffsets = [];
// Loop over each search term found on this page
reset($pagedata["nterms"]);
foreach($pagedata["nterms"] as $pterm => $frequency) {
// Add the number of occurrences of this search term to the ranking
// Multiply it by the length of the word
$pagedata["rank"] += $frequency * strlen($pterm);
}
// Consider matches in the title / tags
$pagedata["rank"] += $pagedata["rank_title"] + $pagedata["rank_tags"];
// TODO: Consider implementing kernel density estimation here.
// https://en.wikipedia.org/wiki/Kernel_density_estimation
// We want it to have more of an effect the more words that are present in the query. Maybe a logarithmic function would be worth investigating here?
// TODO: Remove items if the computed rank is below a threshold
}
uasort($matching_pages, function($a, $b) {
if($a["rank"] == $b["rank"]) return 0;
return ($a["rank"] < $b["rank"]) ? +1 : -1;
});
return $matching_pages;
}
/**
* Extracts a context string (in HTML) given a search query that could be displayed
* in a list of search results.
* @param string $pagename The name of the paget that this source belongs to. Used when consulting the inverted index.
* @param string $query The search queary to generate the context for.
* @param string $source The page source to extract the context from.
* @return string The generated context string.
*/
public static function extract_context($pagename, $query, $source)
{
global $settings;
$pageid = ids::getid($pagename);
$nterms = self::stas_parse(self::stas_split($query))["terms"];
// Query the inverted index for offsets
$matches = [];
foreach($nterms as $nterm) {
// Skip if the page isn't found in the inverted index for this word
if(!self::$invindex->has("{$nterm["term"]}|$pageid"))
continue;
$nterm_offsets = self::$invindex->get("{$nterm["term"]}|$pageid")->offsets;
foreach($nterm_offsets as $next_offset)
$matches[] = [ $nterm["term"], $next_offset ];
}
// Sort the matches by offset
usort($matches, function($a, $b) {
if($a[1] == $b[1]) return 0;
return ($a[1] > $b[1]) ? +1 : -1;
});
$sourceLength = mb_strlen($source);
$contexts = [];
$matches_count = count($matches);
$total_context_length = 0;
for($i = 0; $i < $matches_count; $i++) {
$next_context = [
"from" => max(0, $matches[$i][1] - $settings->search_characters_context),
"to" => min($sourceLength, $matches[$i][1] + mb_strlen($matches[$i][0]) + $settings->search_characters_context)
];
if(end($contexts) !== false && end($contexts)["to"] > $next_context["from"]) {
// This next context overlaps with the previous one
// Extend the last one instead of adding a new one
// The array pointer is pointing at the last element now because we called end() above
// Update the total context length counter appropriately
$total_context_length += $next_context["to"] - $contexts[key($contexts)]["to"];
$contexts[key($contexts)]["to"] = $next_context["to"];
}
else { // No overlap here! Business as usual.
$contexts[] = $next_context;
// Update the total context length counter as normal
$total_context_length += $next_context["to"] - $next_context["from"];
}
end($contexts);
$last_context = &$contexts[key($contexts)];
if($total_context_length > $settings->search_characters_context_total) {
// We've reached the limit on the number of characters this context should contain. Trim off the context to fit and break out
$last_context["to"] -= $total_context_length - $settings->search_characters_context_total;
break;
}
}
$contexts_text = [];
foreach($contexts as $context) {
$contexts_text[] = substr($source, $context["from"], $context["to"] - $context["from"]);
}
// BUG: Make sure that a snippet is centred on the word in question if we have to cut it short
$result = implode(" … ", $contexts_text);
end($contexts); // If there's at least one item in the list and were not at the very end of the page, add an extra ellipsis
if(isset($contexts[0]) && $contexts[key($contexts)]["to"] < $sourceLength) $result .= "… ";
// Prepend an ellipsis if the context doesn't start at the beginning of a page
if(isset($contexts[0]) && $contexts[0]["from"] > 0) $result = " …$result";
return $result;
}
/**
* Highlights the keywords of a context string.
* @param string $query The query to use when highlighting.
* @param string $context The context string to highlight.
* @return string The highlighted (HTML) string.
*/
public static function highlight_context($query, $context)
{
$qterms = self::stas_parse(self::stas_split($query))["terms"];
foreach($qterms as $qterm) {
// Stop words are marked by STAS
if($qterm["weight"] == -1)
continue;
// From http://stackoverflow.com/a/2483859/1460422
$context = preg_replace("/" . preg_replace('/\\//u', "\/", preg_quote($qterm["term"])) . "/iu", "<strong class='search-term-highlight'>$0</strong>", $context);
}
return $context;
}
}
// Run the init function
search::init();
?>
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