Issue #4843: Implemented improved text filtering

The free text filter box now searches for individual terms in the field
separately, obeys quoting patterns, and allows for negation.  All terms
found are required to be found somewhere in the issue (or not found
anywhere for negated terms) in order for the issue to match the filter.

Example searches and their expected results:

  bus car
    Should find any issue that mentions both "bus" and "car"

  "micro computer"
    Should find any issue that mentions "micro computer" exactly; this
    matches the existing search behaviors

  apple -banana
    Should find any issue that mentions "apple" but has no mention of
    "banana"

  circuit -"power line"
    Should find any issue that mentions "circuit" but has no mention of
    "power line"

core/filter_api.php

@@ -1917,23 +1917,53 @@ function filter_get_bug_rows( &$p_page_number, &$p_per_page, &$p_page_count, &$p
 
 	# Text search
 	if( !is_blank( $t_filter[FILTER_PROPERTY_FREE_TEXT] ) ) {
-		$c_search = '%' . $t_filter[FILTER_PROPERTY_FREE_TEXT] . '%';
-		$t_textsearch_where_clause = '(' . db_helper_like( 'summary' ) . ' OR ' . db_helper_like( "$t_bug_text_table.description" ) . ' OR ' . db_helper_like( "$t_bug_text_table.steps_to_reproduce" ) . ' OR ' . db_helper_like( "$t_bug_text_table.additional_information" ) . ' OR ' . db_helper_like( "$t_bugnote_text_table.note" );
-
-		$t_where_params[] = $c_search;
-		$t_where_params[] = $c_search;
-		$t_where_params[] = $c_search;
-		$t_where_params[] = $c_search;
-		$t_where_params[] = $c_search;
-
-		if( is_numeric( $t_filter[FILTER_PROPERTY_FREE_TEXT] ) ) {
-			$c_search_int = (int) $t_filter[FILTER_PROPERTY_FREE_TEXT];
-			$t_textsearch_where_clause .= " OR $t_bug_table.id = " . db_param();
-			$t_textsearch_where_clause .= " OR $t_bugnote_table.id = " . db_param();
-			$t_where_params[] = $c_search_int;
-			$t_where_params[] = $c_search_int;
-		}
-		$t_textsearch_where_clause .= " )";
+
+		# break up search terms by spacing or quoting
+		preg_match_all( "/-?([^'\"\s]+|\"[^\"]+\"|'[^']+')/", $t_filter[FILTER_PROPERTY_FREE_TEXT], $t_matches, PREG_SET_ORDER );
+
+		# organize terms without quoting, paying attention to negation
+		$t_search_terms = array();
+		foreach( $t_matches as $t_match ) {
+			$t_search_terms[ trim( $t_match[1], "\'\"" ) ] = ( $t_match[0][0] == '-' );
+		}
+
+		# build a big where-clause and param list for all search terms, including negations
+		$t_first = true;
+		$t_textsearch_where_clause = "( ";
+		foreach( $t_search_terms as $t_search_term => $t_negate ) {
+			if ( !$t_first ) {
+				$t_textsearch_where_clause .= ' AND ';
+			}
+
+			if ( $t_negate ) {
+				$t_textsearch_where_clause .= 'NOT ';
+			}
+
+			$c_search = '%' . $t_search_term . '%';
+			$t_textsearch_where_clause .= '( ' . db_helper_like( 'summary' ) .
+				' OR ' . db_helper_like( "$t_bug_text_table.description" ) .
+				' OR ' . db_helper_like( "$t_bug_text_table.steps_to_reproduce" ) .
+				' OR ' . db_helper_like( "$t_bug_text_table.additional_information" ) .
+				' OR ' . db_helper_like( "$t_bugnote_text_table.note" );
+
+			$t_where_params[] = $c_search;
+			$t_where_params[] = $c_search;
+			$t_where_params[] = $c_search;
+			$t_where_params[] = $c_search;
+			$t_where_params[] = $c_search;
+
+			if( is_numeric( $t_search_term ) ) {
+				$c_search_int = (int) $t_search_term;
+				$t_textsearch_where_clause .= " OR $t_bug_table.id = " . db_param();
+				$t_textsearch_where_clause .= " OR $t_bugnote_table.id = " . db_param();
+				$t_where_params[] = $c_search_int;
+				$t_where_params[] = $c_search_int;
+			}
+
+			$t_textsearch_where_clause .= ' )';
+			$t_first = false;
+		}
+		$t_textsearch_where_clause .= ' )';
 
 		# add text query elements to arrays
 		$t_from_clauses[] = "$t_bug_text_table";