//     VIE - Vienna IKS Editables
//     (c) 2011 Henri Bergius, IKS Consortium
//     (c) 2011 Sebastian Germesin, IKS Consortium
//     (c) 2011 Szaby Grünwald, IKS Consortium
//     VIE may be freely distributed under the MIT license.
//     For all details and documentation:
//     http://viejs.org/
VIE.prototype.Collection = Backbone.Collection.extend({
    model: VIE.prototype.Entity,
    
    get: function(id) {
        if (id === null) {
            return null;
        }
        
        id = (id.getSubject)? id.getSubject() : id;        
        if (typeof id === "string" && id.indexOf("_:") === 0) {
            if (id.indexOf("bnode") === 2) {
                //bnode!
                id = id.replace("_:bnode", 'c');
                return this._byCid[id];
            } else {
                return this._byId["<" + id + ">"];
            }
        } else {
            id = this.toReference(id);
            return this._byId[id];
        }
    },

    addOrUpdate: function(model, options) {
        options || (options = {});

        var collection = this;
        var existing;
        if (_.isArray(model)) {
            var entities = [];
            _.each(model, function(item) {
                entities.push(collection.addOrUpdate(item, options));
            });
            return entities;
        }

        if (model === undefined) {
            throw new Error("No model given");
        }

        if (_.isString(model) && collection.isReference(model)) {
          model = {
            '@subject': model
          };
        }

        if (!model.isEntity) {
            model = new this.model(model);
        }

        if (model.id && this.get(model.id)) {
            existing = this.get(model.id);
        }
        if (this.getByCid(model.cid)) {
            var existing = this.getByCid(model.cid);
        }
        if (existing) {
            var newAttribs = {};
            _.each(model.attributes, function(value, attribute) {
                if (!existing.has(attribute)) {
                    newAttribs[attribute] = value;
                    return true;
                }
                else if (existing.get(attribute) === value) {
                    return true;
                } else {
                    //merge existing attribute values with new ones!
                    //not just overwrite 'em!!
                    var oldVals = existing.attributes[attribute];
                    var newVals = value;
                    if (oldVals instanceof collection.vie.Collection) {
                        // TODO: Merge collections
                        return true;
                    }
                    if (options.overrideAttributes) {
                       newAttribs[attribute] = value;
                       return true;
                    } 
                    if (attribute === '@context') {
                        newAttribs[attribute] = jQuery.extend(true, {}, oldVals, newVals);
                    } else {
                        oldVals = (jQuery.isArray(oldVals))? oldVals : [ oldVals ];
                        newVals = (jQuery.isArray(newVals))? newVals : [ newVals ];
                        newAttribs[attribute] = _.uniq(oldVals.concat(newVals));
                        newAttribs[attribute] = (newAttribs[attribute].length === 1)? newAttribs[attribute][0] : newAttribs[attribute];
                    }
                }
            });

            if (!_.isEmpty(newAttribs)) {
                existing.set(newAttribs, options.updateOptions);
            }
            return existing;
        }
        this.add(model, options.addOptions);
        return model;
    },

    isReference: function(uri){
        var matcher = new RegExp("^\\<([^\\>]*)\\>$");
        if (matcher.exec(uri)) {
            return true;
        }
        return false;
    },
        
    toReference: function(uri){
        if (this.isReference(uri)) {
            return uri;
        }
        return '<' + uri + '>';
    },
        
    fromReference: function(uri){
        if (!this.isReference(uri)) {
            return uri;
        }
        return uri.substring(1, uri.length - 1);
    },
    
    isCollection: true
});