<?
#
# This script written by Eli Fulkerson.
# http://www.elifulkerson.com for more.
#

#
# Internal function, used to support "+keyword -keyword" syntax in addition
#   to "and keyword not keyword" syntax.
#
function bq_handle_shorthand($text) {
	$text = preg_replace("/ \+/", " and ", $text);
	$text = preg_replace("/ -/", " not ", $text);
	return $text;
}

#
# Internal function, used to keep quoted text together when building
#  the query.  i.e.... [fish and chips and "chipped ham"] syntax
#
# It essentially replaces " " with "~~~~" as long as we aren't within
# a set of quotes, in which case " " is retained.  The string is then
# split on "~~~~~" with the surviving spaces intact.
#
function bq_explode_respect_quotes($line) {
        $quote_level = 0;	#keep track if we are in or out of quote-space
        $buffer = "";

        for ($a = 0; $a < strlen($line); $a++) {
                if ($line[$a] == "\"") {
                        $quote_level++;
                        if ($quote_level == 2) { $quote_level = 0; }
                }
                else {
                        if ($line[$a] == " " and $quote_level == 0) {
                                $buffer = $buffer . "~~~~";   #Hackish magic key
                        }
                        else {
                                $buffer = $buffer . $line[$a];
                        }
                }

        }

	$buffer = str_replace("\\", "", $buffer);

        $array = explode("~~~~", $buffer);
        return $array;
}

#
# Internal function, used to apply a single keyword against an
#  arbitrary number of fields in the database in the same fashion.
#
# Works via replacing whitespace rather than interation
#
function bq_make_subquery($fields, $word, $mode) {

	if ($mode == "not") {
		$back = " LIKE '%$word%'))";
	}
	else {
		$back = " LIKE '%$word%')";
	}

	if ($mode == "not") {
		$front = "(NOT (";
		$glue = " LIKE '%$word%' OR ";
	}
	else {
		$front = "(";
		$glue = " LIKE '%$word%' OR ";
	}

	$text = str_replace(" ", $glue, $fields);
	$text = $front . $text . $back;

	return $text;
}

#
#  Generates the "WHERE" portion of a query, iterating over every keyphrase in the
#  given search string.  Is safe to link (e.g. with AND) with the output of repeated
#  calls
#

function bq_make_query($fields, $text) {
	#
	# We can't trust the user to give us a specific case
	#
	#$fields = strtolower($fields);
	$text = strtolower($text);

	#
	# Support +keyword -keyword
	#
	$text = bq_handle_shorthand($text);

	#
	# Split, but respect quotation
	#
	$wordarray = bq_explode_respect_quotes($text);

	$buffer = "";
	$output = "";

	#
	# work through each word (or "quoted phrase") in the text and build the
	#   outer shell of the query, filling the insides via bq_make_subquery
	#
	# "or" is assumed if neither "and" nor "not" is specified
	#
	for ($i = 0; $i<count($wordarray); $i++) {
		$word = $wordarray[$i];

		if ($word == "and" or $word == "or" or $word == "not" and $i > 0) {
			if ($word == "not") {
				#
				# $i++ kicks us to the actual keyword that the 'not' is working against, etc
				#
				$i++;
				if ($i == 1) {   #invalid sql syntax to prefix the first check with and/or/not
					$buffer = bq_make_subquery($fields, $wordarray[$i], "not");
				}
				else {
					$buffer = " AND " . bq_make_subquery($fields, $wordarray[$i], "not");
				}
			}
			else {
				if ($word == "or") {
					$i++;
					if ($i == 1) {
						$buffer = bq_make_subquery($fields, $wordarray[$i], "");
					}
					else {

						$buffer = " OR " . bq_make_subquery($fields, $wordarray[$i], "");
					}
				}
				else {
					if ($word == "and") {
						$i++;
						if ($i == 1) {
							$buffer = bq_make_subquery($fields, $wordarray[$i], "");
						}
						else {

							$buffer = " AND " . bq_make_subquery($fields, $wordarray[$i], "");
						}
					}
				}
			}
		}
		else {
			if ($i == 0) {  # 0 instead of 1 here because there was no conditional word to skip and no $i++;
				$buffer = bq_make_subquery($fields, $wordarray[$i], "");
			}
			else {
				$buffer = " OR " . bq_make_subquery($fields, $wordarray[$i], "");
			}
		}
		$output = $output . $buffer;
	}
	return $output;
}


#
# Generates a simple boolean query.  Use bq_make_query directly if you need to
#   add further levels of complexity (the output of bq_make_query can be and/or/etc'd
#   with any other output of bq_make_query)
#
#
#  $return_fields == The fields you want the query to return.
#      "blah1 blah2 blah3" --> "SELECT blah1, blah2, blah3...."
#
#  $tables == The tables you want the query to... query.
#      "t1 t2 t3" --> "FROM t1, t2
#

function bq_simple ($return_fields, $tables, $check_fields, $query_text) {

	#
	# Convert from space deliniated to comma deliniated for the query
	#
	$return_fields = str_replace(" ", ", ", $return_fields);
	$tables = str_replace(" ", ", ", $tables);

	#
	# build the query itself
	#
	$query = "SELECT $return_fields FROM $tables WHERE ";
	$query = $query . bq_make_query($check_fields, $query_text);
	$query = $query . ";";

	#
	# Uncomment to debug
	#
	echo $query;	

	return $query;
}

# Example usage to generate boolean query:
#echo bq_simple("hat cat mat", "seuss", "hat cat", "sam +i +am or \"I do not like them in a house\"");

?>