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<?php
/**
* SearchWP fuzzy matches logic.
*
* @package SearchWP
* @author Jon Christopher
*/
namespace SearchWP\Logic;
use SearchWP\Utils;
use SearchWP\Tokens;
/**
* Class FuzzyMatches is responsible for finding fuzzy matches for search strings.
*
* @since 4.0
*/
class FuzzyMatches {
/**
* Partial match handler.
*
* @since 4.0
*/
private $partial;
/**
* Fuzzy tokens.
*
* @since 4.0
* @var array
*/
private $tokens = [];
/**
* Tokens from the original search string.
*
* @since 4.0
* @var array
*/
private $keywords_tokens;
private $exact_matches;
private $query;
/**
* Fuzzy constructor.
*
* @param array $tokens Incoming tokens.
* @param array $args Arguments for partial match tokens.
* @since 4.0
*/
function __construct( array $partial_match_tokens, array $args ) {
// FUTURE: $partial_match_tokens not used now, but could they be useful. @see PartialMatches@find where this class is instantiated for usage.
// We want to ensure we're working with the original search string, not anything filtered.
$this->partial = $args['partial'];
$keywords_tokens = $args['keyword_tokens'];
$exact_matches = $args['exact_matches'];
$this->query = $args['query'];
// Remove exact match tokens.
$this->exact_matches = $exact_matches;
$this->keywords_tokens = array_diff( $keywords_tokens, $exact_matches );
if ( ! empty( $this->keywords_tokens ) ) {
$this->tokens = $this->get_fuzzy_tokens( $this->keywords_tokens );
}
}
/**
* Finds the best fuzzy match for any non-exact token matches.
*
* @since 4.0
* @return array Revised suggested search based on best fuzzy match(es).
*/
public function did_you_mean() {
$suggested_terms = [];
$original_search_tokens = Utils::tokenize( $this->partial->get_query()->get_keywords() )->get();
foreach ( $original_search_tokens as $search_token ) {
$suggested_term = '';
$shortest = -1;
// If this is an exact match, put it in place and continue.
if ( in_array( $search_token, $this->exact_matches, true ) ) {
$suggested_terms[] = $search_token;
continue;
}
// Loop through the fuzzy tokens to find the best match.
foreach ( $this->tokens as $fuzzy_token ) {
$lev = levenshtein( $fuzzy_token, $search_token );
if ( $lev <= $shortest || $shortest < 0 ) {
$suggested_term = $fuzzy_token;
$shortest = $lev;
}
}
if ( ! empty( $suggested_term ) ) {
$suggested_terms[] = $suggested_term;
}
$suggested_term = '';
$shortest = -1;
}
// Tell the Query that we've made a suggestion.
if ( ! empty( $suggested_terms ) && ! empty( array_diff( $suggested_terms, $original_search_tokens ) ) ) {
$this->partial->get_query()->set_suggested_search( new Tokens( implode( ' ', $suggested_terms ) ) );
}
return $suggested_terms;
}
/**
* Finds fuzzy matches for tokens.
*
* @since 4.0
* @return array Tokens with fuzzy matches.
*/
public function find( array $partial_match_tokens, array $args ) {
// Maybe bail out if finding fuzzy matches isn't applicable.
if ( ! empty( $partial_match_tokens ) && ! apply_filters( 'searchwp\query\partial_matches\fuzzy\force', false, [
'partial_match_tokens' => $partial_match_tokens,
'query' => $args['query'],
] ) ) {
return $partial_match_tokens;
}
// Making it this far means partial matching is enabled and it didn't find anything yet (or fuzzy is forced).
if ( ! apply_filters( 'searchwp\query\partial_matches\fuzzy', true, [
'partial_match_tokens' => $partial_match_tokens,
'query' => $args['query'],
] ) ) {
return $partial_match_tokens;
}
// If there were no fuzzy tokens found, there's nothing to do.
if ( empty( $this->tokens ) ) {
return $partial_match_tokens;
}
// Limit the tokens to those that meet the minimum similarity threshold.
return $this->refine_fuzzy_tokens( $this->tokens, $this->keywords_tokens );
}
/**
* Refines (very) fuzzy tokens to only those that meet a minimum similarity threshold.
*
* @since 4.0
* @param array $fuzzy_tokens Very fuzzy tokens needing refinement.
* @param array $search_tokens Original search tokens.
* @return mixed Refined tokens that meet our minimum similarity threshold.
*/
private function refine_fuzzy_tokens( array $fuzzy_tokens, array $search_tokens ) {
$threshold = absint( apply_filters( 'searchwp\query\partial_matches\fuzzy\threshold', 70 ) );
$fuzzy_tokens = call_user_func_array(
'array_merge',
array_map(
function( $search_term ) use ( $fuzzy_tokens, $threshold ) {
return array_filter(
$fuzzy_tokens,
function( $fuzzy_token ) use ( $search_term, $threshold ) {
similar_text(
$fuzzy_token,
$search_term,
$similarity_percentage
);
return $similarity_percentage >= $threshold;
}
);
},
$search_tokens
)
);
return $fuzzy_tokens;
}
/**
* Retrieves a (very) fuzzy set of potential matches.
*
* @since 4.0
* @param array $keywords_tokens Original search tokens.
* @return array Extremely fuzzy token matches.
*/
private function get_fuzzy_tokens( array $keywords_tokens ) {
global $wpdb;
$index = \SearchWP::$index;
// FUTURE: Do stems need to be considered here, or is the SOUNDEX too far off anyway?
return $wpdb->get_col( $wpdb->prepare(
"SELECT token
FROM {$index->get_tables()['tokens']->table_name}
WHERE "
. implode( ' OR ',
array_fill( 0, count( $keywords_tokens ), "SOUNDEX(token) LIKE SOUNDEX(%s)" )
) . " AND {$this->get_boundaries_sql()}",
$keywords_tokens
) );
}
/**
* Generates SQL clause to limit the length boundaries of tokens to find.
*
* @since 4.0
* @return string The gereated SQL clause.
*/
private function get_boundaries_sql() {
global $wpdb;
$min_length = absint( apply_filters(
'searchwp\query\partial_matches\fuzzy\minimum_length',
$this->partial->get_tokens()->get_minimum_length()
) );
$max_length = absint( apply_filters( 'searchwp\query\partial_matches\fuzzy\maximum_length', 0 ) );
$boundaries = [];
// Site limiter.
if ( 'all' !== $this->query->get_args()['site'] ) {
$index_table = \SearchWP::$index->get_tables()['index']->table_name;
$boundaries[] = $wpdb->prepare( "id IN (
SELECT token
FROM {$index_table}
WHERE site IN (" .
implode( ', ', array_fill( 0, count( $this->query->get_args()['site'] ), '%d' ) )
. ') )',
$this->query->get_args()['site'] );
}
if ( $min_length ) { $boundaries[] = "CHAR_LENGTH(token) >= {$min_length}"; }
if ( $max_length ) { $boundaries[] = "CHAR_LENGTH(token) <= {$max_length}"; }
return empty( $boundaries ) ? '' : '(' . implode( ' AND ', $boundaries ) . ')';
}
}
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