dojo.provide("dojo.data.util.sorter");

dojo.data.util.sorter.basicComparator = function(	/*anything*/ a, 
													/*anything*/ b){
	//	summary:  
	//		Basic comparision function that compares if an item is greater or less than another item
	//	description:  
	//		returns 1 if a > b, -1 if a < b, 0 if equal.
	//		undefined values are treated as larger values so that they're pushed to the end of the list.

	var ret = 0;
	if(a > b || typeof a === "undefined" || a === null){
		ret = 1;
	}else if(a < b || typeof b === "undefined" || b === null){
		ret = -1;
	}
	return ret; //int, {-1,0,1}
};

dojo.data.util.sorter.createSortFunction = function(	/* attributes array */sortSpec,
														/*dojo.data.core.Read*/ store){
	//	summary:  
	//		Helper function to generate the sorting function based off the list of sort attributes.
	//	description:  
	//		The sort function creation will look for a property on the store called 'comparatorMap'.  If it exists
	//		it will look in the mapping for comparisons function for the attributes.  If one is found, it will
	//		use it instead of the basic comparator, which is typically used for strings, ints, booleans, and dates.
	//		Returns the sorting function for this particular list of attributes and sorting directions.
	//
	//	sortSpec: array
	//		A JS object that array that defines out what attribute names to sort on and whether it should be descenting or asending.
	//		The objects should be formatted as follows:
	//		{
	//			attribute: "attributeName-string" || attribute,
	//			descending: true|false;   // Default is false.
	//		}
	//	store: object
	//		The datastore object to look up item values from.
	//
	var sortFunctions=[];   

	function createSortFunction(attr, dir){
		return function(itemA, itemB){
			var a = store.getValue(itemA, attr);
			var b = store.getValue(itemB, attr);
			//See if we have a override for an attribute comparison.
			var comparator = null;
			if(store.comparatorMap){
				if(typeof attr !== "string"){
					 attr = store.getIdentity(attr);
				}
				comparator = store.comparatorMap[attr]||dojo.data.util.sorter.basicComparator;
			}
			comparator = comparator||dojo.data.util.sorter.basicComparator; 
			return dir * comparator(a,b); //int
		};
	}

	for(var i = 0; i < sortSpec.length; i++){
		sortAttribute = sortSpec[i];
		if(sortAttribute.attribute){
			var direction = (sortAttribute.descending) ? -1 : 1;
			sortFunctions.push(createSortFunction(sortAttribute.attribute, direction));
		}
	}

	return function(rowA, rowB){
		var i=0;
		while(i < sortFunctions.length){
			var ret = sortFunctions[i++](rowA, rowB);
			if(ret !== 0){
				return ret;//int
			}
		}
		return 0; //int  
	};  //  Function
};
