(function() {

	var root = this;

	var Backbone = root.Backbone;

	var Models = root.Rkns.Models = {};

	Models.getUID = function(obj) {

		var guid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {

		    var r = Math.random()*16|0, v = c == 'x' ? r : (r&0x3|0x8);

		    return v.toString(16);

		});

		return obj.type + "-" + guid; 

	};

	var RenkanModel = Backbone.RelationalModel.extend({

		idAttribute : "_id",

		constructor: function(options) {

			if (typeof options !== "undefined") {

	            options._id = options._id || options.id || Models.getUID(this);

	            options.title = options.title || "(untitled " + this.type + ")";

	            options.description = options.description || "";

	            options.uri = options.uri || "";

	            if(typeof this.prepare === "function") {

	            	options = this.prepare(options);

	            }

			}

			Backbone.RelationalModel.prototype.constructor.call(this, options);

		},

		validate: function() {

			if(!this.type) {

				return "object has no type";

			}

		},

		addReference : function(_options, _propName, _list, _id, _default) {

		    var _element = _list.get(_id);

		    if (typeof _element === "undefined" && typeof _default !== "undefined") {

		        _options[_propName ] = _default;

		    }

		    else {

		    	_options[_propName ] = _element;

		    }

		}

	});

	// USER

	var User = Models.User = root.Rkns.Models.User = RenkanModel.extend({

		type: "user",

		prepare: function(options) {

			options.color = options.color || "#666666";

			return options;

		}	

	});

	// NODE

	var Node = Models.Node = root.Rkns.Models.Node = RenkanModel.extend({

		type: "node",

		relations: [{

			type: Backbone.HasOne,

			key: "created_by",

			relatedModel: User,

			reverseRelation : {

				includeInJSON: '_id'

			}

		}],

		prepare: function(options) {

			project = options.project;

			delete options["project"];

			this.addReference(options, "created_by", project.get("users"), options.created_by, project.current_user);

			options.description = options.description || "";			

			return options;

		}

	});

	// EDGE

	var Edge = Models.Edge = root.Rkns.Models.Edge = RenkanModel.extend({

		type: "edge",

		relations: [

		  {

			type: Backbone.HasOne,

			key: "created_by",

			relatedModel: User,

			reverseRelation : {

				includeInJSON: '_id'

			}

		  },

		  {

		    type: Backbone.HasOne,

			key: "from",

			relatedModel: Node

		  },

		  {

		    type: Backbone.HasOne,

			key: "to",

			relatedModel: Node

		  },

		],

		prepare: function(options) {

			project = options.project;

			delete options.project;

			this.addReference(options, "created_by", options.created_by, project.get("users"), project.current_user);

			this.addReference(options, "from", options.from, project.get("nodes"));

			this.addReference(options, "to", options.to, project.get("nodes"));

			return options;

		}

	});

	// PROJECT

	var Project = Models.Project = root.Rkns.Models.Project = RenkanModel.extend({

		type: "project",

		current_user : null,

		relations: [

		  {

		    type: Backbone.HasMany,

		    key: "users",

		    relatedModel: User,

		    reverseRelation: {

	            key: 'project',

	            includeInJSON: '_id'

	        },

		  },

		  {

		    type: Backbone.HasMany,

		    key: "nodes",

		    relatedModel: Node,

		    reverseRelation: {

	            key: 'project',

	            includeInJSON: '_id'

	        },

		  },

		  {

		    type: Backbone.HasMany,

		    key: "edges",

		    relatedModel: Edge,

		    reverseRelation: {

	            key: 'project',

	            includeInJSON: '_id'

	        },

		  }

		],

		addNode: function(_props) {

			_props.project = this;

			this.get("nodes").push(_props);

		},

		addUser: function(_props) {

			this.get("users").push(_props);

		}

	});

}).call(this);