<?php

function BuildTrigrams($keyword) 
{
	$t = "__" . $keyword . "__";
	$trigrams = "";
	for ($i = 0; $i < strlen($t) - 2; $i++)
		$trigrams .= substr($t, $i, 3) . " ";
	return $trigrams;
}

function MakeSuggestion($keyword,$ln) 
{
	$trigrams = BuildTrigrams($keyword);
	$query = "\"$trigrams\"/1";
	$len = strlen($keyword);

	$delta = LENGTH_THRESHOLD;
	$weight = 'weight()';
	if(SPHINX_20 == true) {
	    $weight ='@weight';
	}
	$stmt = $ln->prepare("SELECT *, $weight as w, w+:delta-ABS(len-:len) as myrank FROM suggest WHERE MATCH(:match) AND len BETWEEN :lowlen AND :highlen
			ORDER BY myrank DESC, freq DESC
			LIMIT 0,:topcount OPTION ranker=wordcount");

	$stmt->bindValue(':match', $query, PDO::PARAM_STR);
	$stmt->bindValue(':len', $len, PDO::PARAM_INT);
	$stmt->bindValue(':delta', $delta, PDO::PARAM_INT);
	$stmt->bindValue(':lowlen', $len - $delta, PDO::PARAM_INT);
	$stmt->bindValue(':highlen', $len + $delta, PDO::PARAM_INT);
	$stmt->bindValue(':topcount',TOP_COUNT, PDO::PARAM_INT);
	$stmt->execute();


	if (!$rows = $stmt->fetchAll())
		return false;
	// further restrict trigram matches with a sane Levenshtein distance limit
	foreach ($rows as $match) {
		$suggested = $match["keyword"];
		if (levenshtein($keyword, $suggested) <= LEVENSHTEIN_THRESHOLD)
			return $suggested;
	}

	return $keyword;
}

function MakePhaseSuggestion($words,$query,$ln_sph) 
{
	$suggested = array();
	$llimf = 0;
	$i = 0;
	foreach ($words  as $key => $word) {
		if ($word['docs'] != 0)
			$llimf +=$word['docs'];$i++;
	}
	$llimf = $llimf / ($i * $i);
	foreach ($words  as $key => $word) {
		if ($word['docs'] == 0 | $word['docs'] < $llimf) {
			$mis[] = $word['keyword'];
		}
	}
	if (count($mis) > 0) {
		foreach ($mis as $m) {
			$re = MakeSuggestion($m, $ln_sph);
			if ($re) {
				if($m!=$re)
					$suggested[$m] = $re;
			}
		}
		if(count($words) ==1 && empty($suggested)) {
			return false;
		}
		$phrase = explode(' ', $query);
		foreach ($phrase as $k => $word) {
			if (isset($suggested[strtolower($word)]))
				$phrase[$k] = $suggested[strtolower($word)];
		}
		$phrase = implode(' ', $phrase);
		return $phrase;
	}else{
		return false;
	}
}

?>