Managing Cases

ContactManager.module("Entities", function(Entities, ContactManager,
 Backbone, Marionette, $, _){
    Entities.FilteredCollection = function(options){
    var original = options.collection;
    var filtered = new original.constructor();
    filtered.add(original.models);
    filtered.filterFunction = options.filterFunction;
    var applyFilter = function(filterCriterion, filterStrategy){
        var collection = original;
        var criterion;
        if(filterStrategy == "filter"){
        criterion = filterCriterion.trim();
        }
        else{
        criterion = filterCriterion;
        }
        var items = [];
            if(criterion){
                if(filterStrategy == "filter"){
                    if( ! filtered.filterFunction){
                        throw("Attempted to use 'filter' function, but none was defined");
                    }
                        var filterFunction = filtered.filterFunction(criterion);
                        items = collection.filter(filterFunction);
                } 
                else{
                    items = collection.where(criterion);
                }
            } 
            else{
                items = collection.models;
            }
            // store current criterion
            filtered._currentCriterion = criterion;
            return items;
        };
        filtered.filter = function(filterCriterion){
            filtered._currentFilter = "filter";
            var items = applyFilter(filterCriterion, "filter");
            
            // reset the filtered collection with the new items
            filtered.reset(items);
            return filtered;
        };
        filtered.where = function(filterCriterion){
            filtered._currentFilter = "where";
            var items = applyFilter(filterCriterion, "where");
            
            // reset the filtered collection with the new items
            filtered.reset(items);
            return filtered;
        };
        
        return filtered;
    };
});