(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 = RenkanModel.extend({

        type: "user",

        prepare: function(options) {

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

            return options;

        },

        toJSON: function() {

            return {

                _id: this.get("_id"),

                title: this.get("title"),

                uri: this.get("uri"),

                description: this.get("description"),

                color: this.get("color"),

            };

        },

    });

    // NODE

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

        type: "node",

        relations: [{

            type: Backbone.HasOne,

            key: "created_by",

            relatedModel: User

        }],

        prepare: function(options) {

            project = options.project;

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

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

            return options;

        },

        toJSON: function() {

            return {

                _id: this.get("_id"),

                title: this.get("title"),

                uri: this.get("uri"),

                description: this.get("description"),

                position: this.get("position"),

                created_by: this.get("created_by").get("_id")

            };

        },

    });

    // EDGE

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

        type: "edge",

        relations: [

          {

            type: Backbone.HasOne,

            key: "created_by",

            relatedModel: User

          },

          {

            type: Backbone.HasOne,

            key: "from",

            relatedModel: Node

          },

          {

            type: Backbone.HasOne,

            key: "to",

            relatedModel: Node

          },

        ],

        prepare: function(options) {

            project = options.project;

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

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

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

            return options;

        },

        toJSON: function() {

            return {

                _id: this.get("_id"),

                title: this.get("title"),

                uri: this.get("uri"),

                description: this.get("description"),

                from: this.get("from").get("_id"),

                to: this.get("to").get("_id"),

                created_by: this.get("created_by").get("_id"),

            };

        },

    });

    // PROJECT

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

        type: "project",

        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'

            },

          }

        ],

        addUser: function(_props) {

            _props.project = this;

            var _user = new User(_props);

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

            return _user;

        },

        addNode: function(_props) {

            _props.project = this;

            var _node = new Node(_props);

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

            return _node;

        },

        addEdge: function(_props) {

            _props.project = this;

            var _edge = new Edge(_props);

            this.get("edges").push(_edge);

            return _edge;

        },

        removeNode: function(_model) {

            this.get("nodes").remove(_model);

        },

        removeEdge: function(_model) {

            this.get("edges").remove(_model);

        },

        validate: function(options) {

            var _project = this;

            _(options.users).each(function(_item) {

                _item.project = _project;

            });

            _(options.nodes).each(function(_item) {

                _item.project = _project;

            });

            _(options.edges).each(function(_item) {

                _item.project = _project;

            });

        },

        // Add event handler to remove edges when a node is removed

        initialize: function() {

            var _this = this;

            this.on("remove:nodes", function(_node) {

                _this.get("edges").remove(

                    _this.get("edges").filter(function(_edge) {

                        return _edge.get("from") == _node || _edge.get("to") == _node;

                    })

                );

            });

        }

    });

}).call(window);