gistfile1.js

parseQuery = function (queryString) {
	
	var literalStrings 			= getLiteralStrings(queryString);
	var strippedString 			= stripLiteralStrings(queryString, literalStrings);
	var booleanExpression 	= getBooleanExpression(strippedString);
	var strippedComparisons = getStrippedComparisons(strippedString);
	var comparisons 				= constructComparisons(strippedComparisons, literalStrings);
	
	return { 	booleanExpression: booleanExpression,
						comparisons: strippedComparisons //temporary, will be comparisons then finished
				 };

};



getLiteralStrings = function (queryString) {
	
	// this function steps through the input string, recognizes literal strings,
	// remembers their position in the input string and returns an array that
	// contains objects like this:
	// {startPoint: n, endPoint: m, sequenceOfCharacters: s}
	
	var currentlyInString 				= false;
	var delimeterOfCurrentString 	= "";
	var numberOfCurrentString			= 0;
	var isStringDelimeter					= {"'": true, '"': true};
	var isEscapeCharacter					= {"\\": true};
	var currentCharacter 					= "";
	var previousCharacter					= "";
	
	var literalStrings						= [];			//to be returned
	
	// first find the strings start- and end-points:
	
	for (var i=0; i < queryString.length; i++) {
		currentCharacter = queryString[i];
		
		if ( currentlyInString ) {
			if ( currentCharacter == delimeterOfCurrentString 
				&& ! isEscapeCharacter[currentCharacter]  ) {
					
				currentlyInString = false;
				literalStrings[numberOfCurrentString].endPoint = i;
				numberOfCurrentString++;
			};
		}
		else {
			if ( isStringDelimeter[currentCharacter] ) {

				currentlyInString = true;
				delimeterOfCurrentString = currentCharacter;
				literalStrings[numberOfCurrentString] = {startPoint: i};
			};
		};
			
		previousCharacter = currentCharacter;
	};
	
	// then extract the strings:
	
	var s = literalStrings[0];
	for (var i=0; i < literalStrings.length; i++) {
		s = literalStrings[i];
		s.string = queryString.substring(s.startPoint+1, s.endPoint)
	};
	
	return literalStrings;
};

stripLiteralStrings = function (queryString, literalStrings) {
	
	/* ----------
	replaces every occurance of a literal string inside the queryString
	with a numbered placeholder, refering to the associated string in the
	array literalStrings
	
	motivation for this: after removing the literal strings we can 
	perform string manipulations on the query string without having to 
	worry about certain expressions (AND for Example) being present in literal strings
	---------- */
	
	var l = literalStrings;
	var q = queryString;
	
	for (var i=l.length-1; i>=0 ; i--) {
		q = q.substring(0,l[i].startPoint) 
				+ "strippedStrings[" + i + "]"
				+ q.substr(l[i].endPoint+1)
	};
	
	return q;
};

getBooleanExpression = function (strippedString) {
	
	var b = strippedString;
	var notBooleanStatement = /[^(\s\(\s|\s\)\s|\sAND\s|\sOR\s|\sNOT\s)]+/g ;
	
	// first lets add whitespace arround parenthesis, 
	// will make it easier to differentiate comparisons from boolen statement
	
	b = b.replace(/\(/g, " ( ");
	b = b.replace(/\)/g, " ) ");
	
	// now replace every comparison by a single character 'a'
	
	b = b.replace(notBooleanStatement, "a");

	// now add an incrementing number to these characters
	
	var count = 0;
	for (var i=0; i < b.length; i++) {
		if (b[i] == 'a') {
			b = b.slice(0,i+1)+"["+count+"]"+b.slice(i+1);
			count++;
		};
	};
	
	// strip unnesecary whitespace - just for cosmetic reason
	
	b = b.replace(/\s+/g, " ");
	
	// return the produced boolean Expression b
	
	return b;
};

getStrippedComparisons = function (strippedString) {
	
	var c = strippedString;
	var booleanStatements = /\s+(?:(?:\(|\)|AND|OR|NOT)\s+)+/g;
	var strippedComparisons = [];
	
	// make sure there is whitespace arround parenthesis
	
	c = c.replace(/\(/g, " ( ");
	c = c.replace(/\)/g, " ) ");
	
	// remove boolean statements at the beginning and the end
	
	c = c.replace(/^\s*(?:(?:\(|\)|AND|OR|NOT)\s+)+/g, "");
	c = c.replace(/\s+(?:(?:\(|\)|AND|OR|NOT)\s+)+$/g, "");
	
	// split the string
	
	strippedComparisons = c.split(booleanStatements);
	
	return strippedComparisons;
};

constructComparisons = function (strippedComparisons, literalStrings) {
	var comparisons = [];
	return comparisons;
};