source: branches/1888_OaaS/HeuristicLab.Services.Optimization.Web/Content/backbone/backbone-relational.js @ 17169

/* vim: set tabstop=4 softtabstop=4 shiftwidth=4 noexpandtab: */
/**
 * Backbone-relational.js 0.7.1
 * (c) 2011-2013 Paul Uithol and contributors (https://github.com/PaulUithol/Backbone-relational/graphs/contributors)
 * 
 * Backbone-relational may be freely distributed under the MIT license; see the accompanying LICENSE.txt.
 * For details and documentation: https://github.com/PaulUithol/Backbone-relational.
 * Depends on Backbone (and thus on Underscore as well): https://github.com/documentcloud/backbone.
 */
( function( undefined ) {
  "use strict";
  
  /**
   * CommonJS shim
   **/
  var _, Backbone, exports;
  if ( typeof window === 'undefined' ) {
    _ = require( 'underscore' );
    Backbone = require( 'backbone' );
    exports = module.exports = Backbone;
  }
  else {
    _ = window._;
    Backbone = window.Backbone;
    exports = window;
  }

  Backbone.Relational = {
    showWarnings: true
  };

  /**
   * Semaphore mixin; can be used as both binary and counting.
   **/
  Backbone.Semaphore = {
    _permitsAvailable: null,
    _permitsUsed: 0,
    
    acquire: function() {
      if ( this._permitsAvailable && this._permitsUsed >= this._permitsAvailable ) {
        throw new Error( 'Max permits acquired' );
      }
      else {
        this._permitsUsed++;
      }
    },
    
    release: function() {
      if ( this._permitsUsed === 0 ) {
        throw new Error( 'All permits released' );
      }
      else {
        this._permitsUsed--;
      }
    },
    
    isLocked: function() {
      return this._permitsUsed > 0;
    },
    
    setAvailablePermits: function( amount ) {
      if ( this._permitsUsed > amount ) {
        throw new Error( 'Available permits cannot be less than used permits' );
      }
      this._permitsAvailable = amount;
    }
  };
  
  /**
   * A BlockingQueue that accumulates items while blocked (via 'block'),
   * and processes them when unblocked (via 'unblock').
   * Process can also be called manually (via 'process').
   */
  Backbone.BlockingQueue = function() {
    this._queue = [];
  };
  _.extend( Backbone.BlockingQueue.prototype, Backbone.Semaphore, {
    _queue: null,
    
    add: function( func ) {
      if ( this.isBlocked() ) {
        this._queue.push( func );
      }
      else {
        func();
      }
    },
    
    process: function() {
      while ( this._queue && this._queue.length ) {
        this._queue.shift()();
      }
    },
    
    block: function() {
      this.acquire();
    },
    
    unblock: function() {
      this.release();
      if ( !this.isBlocked() ) {
        this.process();
      }
    },
    
    isBlocked: function() {
      return this.isLocked();
    }
  });
  /**
   * Global event queue. Accumulates external events ('add:<key>', 'remove:<key>' and 'update:<key>')
   * until the top-level object is fully initialized (see 'Backbone.RelationalModel').
   */
  Backbone.Relational.eventQueue = new Backbone.BlockingQueue();
  
  /**
   * Backbone.Store keeps track of all created (and destruction of) Backbone.RelationalModel.
   * Handles lookup for relations.
   */
  Backbone.Store = function() {
    this._collections = [];
    this._reverseRelations = [];
    this._subModels = [];
    this._modelScopes = [ exports ];
  };
  _.extend( Backbone.Store.prototype, Backbone.Events, {
    addModelScope: function( scope ) {
      this._modelScopes.push( scope );
    },

    /**
     * Add a set of subModelTypes to the store, that can be used to resolve the '_superModel'
     * for a model later in 'setupSuperModel'.
     *
     * @param {Backbone.RelationalModel} subModelTypes
     * @param {Backbone.RelationalModel} superModelType
     */
    addSubModels: function( subModelTypes, superModelType ) {
      this._subModels.push({
        'superModelType': superModelType,
        'subModels': subModelTypes
      });
    },

    /**
     * Check if the given modelType is registered as another model's subModel. If so, add it to the super model's
     * '_subModels', and set the modelType's '_superModel', '_subModelTypeName', and '_subModelTypeAttribute'.
     *
     * @param {Backbone.RelationalModel} modelType
     */
    setupSuperModel: function( modelType ) {
      _.find( this._subModels || [], function( subModelDef ) {
        return _.find( subModelDef.subModels || [], function( subModelTypeName, typeValue ) {
          var subModelType = this.getObjectByName( subModelTypeName );

          if ( modelType === subModelType ) {
            // Set 'modelType' as a child of the found superModel
            subModelDef.superModelType._subModels[ typeValue ] = modelType;

            // Set '_superModel', '_subModelTypeValue', and '_subModelTypeAttribute' on 'modelType'.
            modelType._superModel = subModelDef.superModelType;
            modelType._subModelTypeValue = typeValue;
            modelType._subModelTypeAttribute = subModelDef.superModelType.prototype.subModelTypeAttribute;
            return true;
          }
        }, this );
      }, this );
    },
    
    /**
     * Add a reverse relation. Is added to the 'relations' property on model's prototype, and to
     * existing instances of 'model' in the store as well.
     * @param {Object} relation
     * @param {Backbone.RelationalModel} relation.model
     * @param {String} relation.type
     * @param {String} relation.key
     * @param {String|Object} relation.relatedModel
     */
    addReverseRelation: function( relation ) {
      var exists = _.any( this._reverseRelations || [], function( rel ) {
          return _.all( relation || [], function( val, key ) {
              return val === rel[ key ];
            });
        });
      
      if ( !exists && relation.model && relation.type ) {
        this._reverseRelations.push( relation );
        
        var addRelation = function( model, relation ) {
          if ( !model.prototype.relations ) {
            model.prototype.relations = [];
          }
          model.prototype.relations.push( relation );
          
          _.each( model._subModels || [], function( subModel ) {
              addRelation( subModel, relation );
            }, this );
        };
        
        addRelation( relation.model, relation );
        
        this.retroFitRelation( relation );
      }
    },
    
    /**
     * Add a 'relation' to all existing instances of 'relation.model' in the store
     * @param {Object} relation
     */
    retroFitRelation: function( relation ) {
      var coll = this.getCollection( relation.model );
      coll.each( function( model ) {
        if ( !( model instanceof relation.model ) ) {
          return;
        }

        new relation.type( model, relation );
      }, this);
    },
    
    /**
     * Find the Store's collection for a certain type of model.
     * @param {Backbone.RelationalModel} model
     * @return {Backbone.Collection} A collection if found (or applicable for 'model'), or null
     */
    getCollection: function( model ) {
      if ( model instanceof Backbone.RelationalModel ) {
        model = model.constructor;
      }
      
      var rootModel = model;
      while ( rootModel._superModel ) {
        rootModel = rootModel._superModel;
      }
      
      var coll = _.detect( this._collections, function( c ) {
        return c.model === rootModel;
      });
      
      if ( !coll ) {
        coll = this._createCollection( rootModel );
      }
      
      return coll;
    },
    
    /**
     * Find a type on the global object by name. Splits name on dots.
     * @param {String} name
     * @return {Object}
     */
    getObjectByName: function( name ) {
      var parts = name.split( '.' ),
        type = null;

      _.find( this._modelScopes || [], function( scope ) {
        type = _.reduce( parts || [], function( memo, val ) {
          return memo ? memo[ val ] : undefined;
        }, scope );

        if ( type && type !== scope ) {
          return true;
        }
      }, this );

      return type;
    },
    
    _createCollection: function( type ) {
      var coll;
      
      // If 'type' is an instance, take its constructor
      if ( type instanceof Backbone.RelationalModel ) {
        type = type.constructor;
      }
      
      // Type should inherit from Backbone.RelationalModel.
      if ( type.prototype instanceof Backbone.RelationalModel ) {
        coll = new Backbone.Collection();
        coll.model = type;
        
        this._collections.push( coll );
      }
      
      return coll;
    },

    /**
     * Find the attribute that is to be used as the `id` on a given object
     * @param type
     * @param {String|Number|Object|Backbone.RelationalModel} item
     * @return {String|Number}
     */
    resolveIdForItem: function( type, item ) {
      var id = _.isString( item ) || _.isNumber( item ) ? item : null;

      if ( id === null ) {
        if ( item instanceof Backbone.RelationalModel ) {
          id = item.id;
        }
        else if ( _.isObject( item ) ) {
          id = item[ type.prototype.idAttribute ];
        }
      }

      // Make all falsy values `null` (except for 0, which could be an id.. see '/issues/179')
      if ( !id && id !== 0 ) {
        id = null;
      }

      return id;
    },

    /**
     *
     * @param type
     * @param {String|Number|Object|Backbone.RelationalModel} item
     */
    find: function( type, item ) {
      var id = this.resolveIdForItem( type, item );
      var coll = this.getCollection( type );
      
      // Because the found object could be of any of the type's superModel
      // types, only return it if it's actually of the type asked for.
      if ( coll ) {
        var obj = coll.get( id );

        if ( obj instanceof type ) {
          return obj;
        }
      }

      return null;
    },
    
    /**
     * Add a 'model' to it's appropriate collection. Retain the original contents of 'model.collection'.
     * @param {Backbone.RelationalModel} model
     */
    register: function( model ) {
      var coll = this.getCollection( model );

      if ( coll ) {
        if ( coll.get( model ) ) {
          throw new Error( "Cannot instantiate more than one Backbone.RelationalModel with the same id per type!" );
        }

        var modelColl = model.collection;
        coll.add( model );
        model.bind( 'destroy', this.unregister, this );
        model.collection = modelColl;
      }
    },
    
    /**
     * Explicitly update a model's id in it's store collection
     * @param {Backbone.RelationalModel} model
     */
    update: function( model ) {
      var coll = this.getCollection( model );
      coll._onModelEvent( 'change:' + model.idAttribute, model, coll );
    },
    
    /**
     * Remove a 'model' from the store.
     * @param {Backbone.RelationalModel} model
     */
    unregister: function( model ) {
      model.unbind( 'destroy', this.unregister );
      var coll = this.getCollection( model );
      coll && coll.remove( model );
    }
  });
  Backbone.Relational.store = new Backbone.Store();
  
  /**
   * The main Relation class, from which 'HasOne' and 'HasMany' inherit. Internally, 'relational:<key>' events
   * are used to regulate addition and removal of models from relations.
   *
   * @param {Backbone.RelationalModel} instance
   * @param {Object} options
   * @param {string} options.key
   * @param {Backbone.RelationalModel.constructor} options.relatedModel
   * @param {Boolean|String} [options.includeInJSON=true] Serialize the given attribute for related model(s)' in toJSON, or just their ids.
   * @param {Boolean} [options.createModels=true] Create objects from the contents of keys if the object is not found in Backbone.store.
   * @param {Object} [options.reverseRelation] Specify a bi-directional relation. If provided, Relation will reciprocate
   *    the relation to the 'relatedModel'. Required and optional properties match 'options', except that it also needs
   *    {Backbone.Relation|String} type ('HasOne' or 'HasMany').
   */
  Backbone.Relation = function( instance, options ) {
    this.instance = instance;
    // Make sure 'options' is sane, and fill with defaults from subclasses and this object's prototype
    options = _.isObject( options ) ? options : {};
    this.reverseRelation = _.defaults( options.reverseRelation || {}, this.options.reverseRelation );
    this.reverseRelation.type = !_.isString( this.reverseRelation.type ) ? this.reverseRelation.type :
      Backbone[ this.reverseRelation.type ] || Backbone.Relational.store.getObjectByName( this.reverseRelation.type );
    this.model = options.model || this.instance.constructor;
    this.options = _.defaults( options, this.options, Backbone.Relation.prototype.options );
    
    this.key = this.options.key;
    this.keySource = this.options.keySource || this.key;
    this.keyDestination = this.options.keyDestination || this.keySource || this.key;

    // 'exports' should be the global object where 'relatedModel' can be found on if given as a string.
    this.relatedModel = this.options.relatedModel;
    if ( _.isString( this.relatedModel ) ) {
      this.relatedModel = Backbone.Relational.store.getObjectByName( this.relatedModel );
    }

    if ( !this.checkPreconditions() ) {
      return;
    }

    if ( instance ) {
      var contentKey = this.keySource;
      if ( contentKey !== this.key && typeof this.instance.get( this.key ) === 'object' ) {
        contentKey = this.key;
      }

      this.keyContents = this.instance.get( contentKey );

      // Explicitly clear 'keySource', to prevent a leaky abstraction if 'keySource' differs from 'key'.
      if ( this.keySource !== this.key ) {
        this.instance.unset( this.keySource, { silent: true } );
      }

      // Add this Relation to instance._relations
      this.instance._relations.push( this );
    }

    // Add the reverse relation on 'relatedModel' to the store's reverseRelations
    if ( !this.options.isAutoRelation && this.reverseRelation.type && this.reverseRelation.key ) {
      Backbone.Relational.store.addReverseRelation( _.defaults( {
          isAutoRelation: true,
          model: this.relatedModel,
          relatedModel: this.model,
          reverseRelation: this.options // current relation is the 'reverseRelation' for it's own reverseRelation
        },
        this.reverseRelation // Take further properties from this.reverseRelation (type, key, etc.)
      ) );
    }

    _.bindAll( this, '_modelRemovedFromCollection', '_relatedModelAdded', '_relatedModelRemoved' );

    if ( instance ) {
      this.initialize();

      if ( options.autoFetch ) {
        this.instance.fetchRelated( options.key, _.isObject( options.autoFetch ) ? options.autoFetch : {} );
      }

      // When a model in the store is destroyed, check if it is 'this.instance'.
      Backbone.Relational.store.getCollection( this.instance )
        .bind( 'relational:remove', this._modelRemovedFromCollection );

      // When 'relatedModel' are created or destroyed, check if it affects this relation.
      Backbone.Relational.store.getCollection( this.relatedModel )
        .bind( 'relational:add', this._relatedModelAdded )
        .bind( 'relational:remove', this._relatedModelRemoved );
    }
  };
  // Fix inheritance :\
  Backbone.Relation.extend = Backbone.Model.extend;
  // Set up all inheritable **Backbone.Relation** properties and methods.
  _.extend( Backbone.Relation.prototype, Backbone.Events, Backbone.Semaphore, {
    options: {
      createModels: true,
      includeInJSON: true,
      isAutoRelation: false,
      autoFetch: false
    },
    
    instance: null,
    key: null,
    keyContents: null,
    relatedModel: null,
    reverseRelation: null,
    related: null,
    
    _relatedModelAdded: function( model, coll, options ) {
      // Allow 'model' to set up it's relations, before calling 'tryAddRelated'
      // (which can result in a call to 'addRelated' on a relation of 'model')
      var dit = this;
      model.queue( function() {
        dit.tryAddRelated( model, options );
      });
    },
    
    _relatedModelRemoved: function( model, coll, options ) {
      this.removeRelated( model, options );
    },
    
    _modelRemovedFromCollection: function( model ) {
      if ( model === this.instance ) {
        this.destroy();
      }
    },
    
    /**
     * Check several pre-conditions.
     * @return {Boolean} True if pre-conditions are satisfied, false if they're not.
     */
    checkPreconditions: function() {
      var i = this.instance,
        k = this.key,
        m = this.model,
        rm = this.relatedModel,
        warn = Backbone.Relational.showWarnings && typeof console !== 'undefined';

      if ( !m || !k || !rm ) {
        warn && console.warn( 'Relation=%o; no model, key or relatedModel (%o, %o, %o)', this, m, k, rm );
        return false;
      }
      // Check if the type in 'model' inherits from Backbone.RelationalModel
      if ( !( m.prototype instanceof Backbone.RelationalModel ) ) {
        warn && console.warn( 'Relation=%o; model does not inherit from Backbone.RelationalModel (%o)', this, i );
        return false;
      }
      // Check if the type in 'relatedModel' inherits from Backbone.RelationalModel
      if ( !( rm.prototype instanceof Backbone.RelationalModel ) ) {
        warn && console.warn( 'Relation=%o; relatedModel does not inherit from Backbone.RelationalModel (%o)', this, rm );
        return false;
      }
      // Check if this is not a HasMany, and the reverse relation is HasMany as well
      if ( this instanceof Backbone.HasMany && this.reverseRelation.type === Backbone.HasMany ) {
        warn && console.warn( 'Relation=%o; relation is a HasMany, and the reverseRelation is HasMany as well.', this );
        return false;
      }

      // Check if we're not attempting to create a duplicate relationship
      if ( i && i._relations.length ) {
        var exists = _.any( i._relations || [], function( rel ) {
            var hasReverseRelation = this.reverseRelation.key && rel.reverseRelation.key;
            return rel.relatedModel === rm && rel.key === k &&
              ( !hasReverseRelation || this.reverseRelation.key === rel.reverseRelation.key );
          }, this );

        if ( exists ) {
          warn && console.warn( 'Relation=%o between instance=%o.%s and relatedModel=%o.%s already exists',
            this, i, k, rm, this.reverseRelation.key );
          return false;
        }
      }

      return true;
    },

    /**
     * Set the related model(s) for this relation
     * @param {Backbone.Model|Backbone.Collection} related
     * @param {Object} [options]
     */
    setRelated: function( related, options ) {
      this.related = related;

      this.instance.acquire();
      this.instance.attributes[ this.key ] = related;
      this.instance.release();
    },
    
    /**
     * Determine if a relation (on a different RelationalModel) is the reverse
     * relation of the current one.
     * @param {Backbone.Relation} relation
     * @return {Boolean}
     */
    _isReverseRelation: function( relation ) {
      if ( relation.instance instanceof this.relatedModel && this.reverseRelation.key === relation.key &&
          this.key === relation.reverseRelation.key ) {
        return true;
      }
      return false;
    },
    
    /**
     * Get the reverse relations (pointing back to 'this.key' on 'this.instance') for the currently related model(s).
     * @param {Backbone.RelationalModel} [model] Get the reverse relations for a specific model.
     *    If not specified, 'this.related' is used.
     * @return {Backbone.Relation[]}
     */
    getReverseRelations: function( model ) {
      var reverseRelations = [];
      // Iterate over 'model', 'this.related.models' (if this.related is a Backbone.Collection), or wrap 'this.related' in an array.
      var models = !_.isUndefined( model ) ? [ model ] : this.related && ( this.related.models || [ this.related ] );
      _.each( models || [], function( related ) {
          _.each( related.getRelations() || [], function( relation ) {
              if ( this._isReverseRelation( relation ) ) {
                reverseRelations.push( relation );
              }
            }, this );
        }, this );
      
      return reverseRelations;
    },
    
    /**
     * Rename options.silent to options.silentChange, so events propagate properly.
     * (for example in HasMany, from 'addRelated'->'handleAddition')
     * @param {Object} [options]
     * @return {Object}
     */
    sanitizeOptions: function( options ) {
      options = options ? _.clone( options ) : {};
      if ( options.silent ) {
        options.silentChange = true;
        delete options.silent;
      }
      return options;
    },

    /**
     * Rename options.silentChange to options.silent, so events are silenced as intended in Backbone's
     * original functions.
     * @param {Object} [options]
     * @return {Object}
     */
    unsanitizeOptions: function( options ) {
      options = options ? _.clone( options ) : {};
      if ( options.silentChange ) {
        options.silent = true;
        delete options.silentChange;
      }
      return options;
    },
    
    // Cleanup. Get reverse relation, call removeRelated on each.
    destroy: function() {
      Backbone.Relational.store.getCollection( this.instance )
        .unbind( 'relational:remove', this._modelRemovedFromCollection );
      
      Backbone.Relational.store.getCollection( this.relatedModel )
        .unbind( 'relational:add', this._relatedModelAdded )
        .unbind( 'relational:remove', this._relatedModelRemoved );
      
      _.each( this.getReverseRelations() || [], function( relation ) {
          relation.removeRelated( this.instance );
        }, this );
    }
  });
  
  Backbone.HasOne = Backbone.Relation.extend({
    options: {
      reverseRelation: { type: 'HasMany' }
    },
    
    initialize: function() {
      _.bindAll( this, 'onChange' );

      this.instance.bind( 'relational:change:' + this.key, this.onChange );

      var model = this.findRelated( { silent: true } );
      this.setRelated( model );

      // Notify new 'related' object of the new relation.
      _.each( this.getReverseRelations() || [], function( relation ) {
          relation.addRelated( this.instance );
        }, this );
    },
    
    findRelated: function( options ) {
      var item = this.keyContents;
      var model = null;
      
      if ( item instanceof this.relatedModel ) {
        model = item;
      }
      else if ( item || item === 0 ) { // since 0 can be a valid `id` as well
        model = this.relatedModel.findOrCreate( item, { create: this.options.createModels } );
      }
      
      return model;
    },
    
    /**
     * If the key is changed, notify old & new reverse relations and initialize the new relation
     */
    onChange: function( model, attr, options ) {
      // Don't accept recursive calls to onChange (like onChange->findRelated->findOrCreate->initializeRelations->addRelated->onChange)
      if ( this.isLocked() ) {
        return;
      }
      this.acquire();
      options = this.sanitizeOptions( options );
      
      // 'options._related' is set by 'addRelated'/'removeRelated'. If it is set, the change
      // is the result of a call from a relation. If it's not, the change is the result of 
      // a 'set' call on this.instance.
      var changed = _.isUndefined( options._related );
      var oldRelated = changed ? this.related : options._related;
      
      if ( changed ) {  
        this.keyContents = attr;
        
        // Set new 'related'
        if ( attr instanceof this.relatedModel ) {
          this.related = attr;
        }
        else if ( attr ) {
          var related = this.findRelated( options );
          this.setRelated( related );
        }
        else {
          this.setRelated( null );
        }
      }
      
      // Notify old 'related' object of the terminated relation
      if ( oldRelated && this.related !== oldRelated ) {
        _.each( this.getReverseRelations( oldRelated ) || [], function( relation ) {
            relation.removeRelated( this.instance, options );
          }, this );
      }
      
      // Notify new 'related' object of the new relation. Note we do re-apply even if this.related is oldRelated;
      // that can be necessary for bi-directional relations if 'this.instance' was created after 'this.related'.
      // In that case, 'this.instance' will already know 'this.related', but the reverse might not exist yet.
      _.each( this.getReverseRelations() || [], function( relation ) {
          relation.addRelated( this.instance, options );
        }, this);
      
      // Fire the 'update:<key>' event if 'related' was updated
      if ( !options.silentChange && this.related !== oldRelated ) {
        var dit = this;
        Backbone.Relational.eventQueue.add( function() {
          dit.instance.trigger( 'update:' + dit.key, dit.instance, dit.related, options );
        });
      }
      this.release();
    },
    
    /**
     * If a new 'this.relatedModel' appears in the 'store', try to match it to the last set 'keyContents'
     */
    tryAddRelated: function( model, options ) {
      if ( this.related ) {
        return;
      }
      options = this.sanitizeOptions( options );
      
      var item = this.keyContents;
      if ( item || item === 0 ) { // since 0 can be a valid `id` as well
        var id = Backbone.Relational.store.resolveIdForItem( this.relatedModel, item );
        if ( !_.isNull( id ) && model.id === id ) {
          this.addRelated( model, options );
        }
      }
    },
    
    addRelated: function( model, options ) {
      if ( model !== this.related ) {
        var oldRelated = this.related || null;
        this.setRelated( model );
        this.onChange( this.instance, model, { _related: oldRelated } );
      }
    },
    
    removeRelated: function( model, options ) {
      if ( !this.related ) {
        return;
      }
      
      if ( model === this.related ) {
        var oldRelated = this.related || null;
        this.setRelated( null );
        this.onChange( this.instance, model, { _related: oldRelated } );
      }
    }
  });
  
  Backbone.HasMany = Backbone.Relation.extend({
    collectionType: null,
    
    options: {
      reverseRelation: { type: 'HasOne' },
      collectionType: Backbone.Collection,
      collectionKey: true,
      collectionOptions: {}
    },
    
    initialize: function() {
      _.bindAll( this, 'onChange', 'handleAddition', 'handleRemoval', 'handleReset' );
      this.instance.bind( 'relational:change:' + this.key, this.onChange );
      
      // Handle a custom 'collectionType'
      this.collectionType = this.options.collectionType;
      if ( _.isString( this.collectionType ) ) {
        this.collectionType = Backbone.Relational.store.getObjectByName( this.collectionType );
      }
      if ( !this.collectionType.prototype instanceof Backbone.Collection ){
        throw new Error( 'collectionType must inherit from Backbone.Collection' );
      }

      // Handle cases where a model/relation is created with a collection passed straight into 'attributes'
      if ( this.keyContents instanceof Backbone.Collection ) {
        this.setRelated( this._prepareCollection( this.keyContents ) );
      }
      else {
        this.setRelated( this._prepareCollection() );
      }

      this.findRelated( { silent: true } );
    },
    
    _getCollectionOptions: function() {
      return _.isFunction( this.options.collectionOptions ) ?
        this.options.collectionOptions( this.instance ) :
        this.options.collectionOptions;
    },

    /**
     * Bind events and setup collectionKeys for a collection that is to be used as the backing store for a HasMany.
     * If no 'collection' is supplied, a new collection will be created of the specified 'collectionType' option.
     * @param {Backbone.Collection} [collection]
     */
    _prepareCollection: function( collection ) {
      if ( this.related ) {
        this.related
          .unbind( 'relational:add', this.handleAddition )
          .unbind( 'relational:remove', this.handleRemoval )
          .unbind( 'relational:reset', this.handleReset )
      }

      if ( !collection || !( collection instanceof Backbone.Collection ) ) {
        collection = new this.collectionType( [], this._getCollectionOptions() );
      }

      collection.model = this.relatedModel;
      
      if ( this.options.collectionKey ) {
        var key = this.options.collectionKey === true ? this.options.reverseRelation.key : this.options.collectionKey;
        
        if ( collection[ key ] && collection[ key ] !== this.instance ) {
          if ( Backbone.Relational.showWarnings && typeof console !== 'undefined' ) {
            console.warn( 'Relation=%o; collectionKey=%s already exists on collection=%o', this, key, this.options.collectionKey );
          }
        }
        else if ( key ) {
          collection[ key ] = this.instance;
        }
      }
      
      collection
        .bind( 'relational:add', this.handleAddition )
        .bind( 'relational:remove', this.handleRemoval )
        .bind( 'relational:reset', this.handleReset );
      
      return collection;
    },
    
    findRelated: function( options ) {
      if ( this.keyContents ) {
        var models = [];

        if ( this.keyContents instanceof Backbone.Collection ) {
          models = this.keyContents.models;
        }
        else {
          // Handle cases the an API/user supplies just an Object/id instead of an Array
          this.keyContents = _.isArray( this.keyContents ) ? this.keyContents : [ this.keyContents ];

          // Try to find instances of the appropriate 'relatedModel' in the store
          _.each( this.keyContents || [], function( item ) {
              var model = null;
              if ( item instanceof this.relatedModel ) {
                model = item;
              }
              else if ( item || item === 0 ) { // since 0 can be a valid `id` as well
                model = this.relatedModel.findOrCreate( item, { create: this.options.createModels } );
              }

              if ( model && !this.related.get( model ) ) {
                models.push( model );
              }
            }, this );
        }

        // Add all found 'models' in on go, so 'add' will only be called once (and thus 'sort', etc.)
        if ( models.length ) {
          options = this.unsanitizeOptions( options );
          this.related.add( models, options );
        }
      }
    },
    
    /**
     * If the key is changed, notify old & new reverse relations and initialize the new relation
     */
    onChange: function( model, attr, options ) {
      options = this.sanitizeOptions( options );
      this.keyContents = attr;
      
      // Replace 'this.related' by 'attr' if it is a Backbone.Collection
      if ( attr instanceof Backbone.Collection ) {
        this._prepareCollection( attr );
        this.related = attr;
      }
      // Otherwise, 'attr' should be an array of related object ids.
      // Re-use the current 'this.related' if it is a Backbone.Collection, and remove any current entries.
      // Otherwise, create a new collection.
      else {
        var oldIds = {}, newIds = {};

        if (!_.isArray( attr ) && attr !== undefined) {
          attr = [ attr ];
        }

        _.each( attr, function( attributes ) {
          newIds[ attributes.id ] = true;
        });

        var coll = this.related;
        if ( coll instanceof Backbone.Collection ) {
          // Make sure to operate on a copy since we're removing while iterating
          _.each( coll.models.slice(0) , function( model ) {
            // When fetch is called with the 'keepNewModels' option, we don't want to remove
            // client-created new models when the fetch is completed.
            if ( !options.keepNewModels || !model.isNew() ) {
              oldIds[ model.id ] = true;
              coll.remove( model, { silent: (model.id in newIds) } );
            }
          });
        } else {
          coll = this._prepareCollection();
        }

        _.each( attr, function( attributes ) {
          var model = this.relatedModel.findOrCreate( attributes, { create: this.options.createModels } );
          if (model) {
            coll.add( model, { silent: (attributes.id in oldIds)} );
          }
        }, this);

        this.setRelated( coll );

      }
      
      var dit = this;
      Backbone.Relational.eventQueue.add( function() {
        !options.silentChange && dit.instance.trigger( 'update:' + dit.key, dit.instance, dit.related, options );
      });
    },
    
    tryAddRelated: function( model, options ) {
      options = this.sanitizeOptions( options );
      if ( !this.related.get( model ) ) {
        // Check if this new model was specified in 'this.keyContents'
        var item = _.any( this.keyContents || [], function( item ) {
            var id = Backbone.Relational.store.resolveIdForItem( this.relatedModel, item );
            return !_.isNull( id ) && id === model.id;
          }, this );
        
        if ( item ) {
          this.related.add( model, options );
        }
      }
    },
    
    /**
     * When a model is added to a 'HasMany', trigger 'add' on 'this.instance' and notify reverse relations.
     * (should be 'HasOne', must set 'this.instance' as their related).
     */
    handleAddition: function( model, coll, options ) {
      //console.debug('handleAddition called; args=%o', arguments);
      // Make sure the model is in fact a valid model before continuing.
      // (it can be invalid as a result of failing validation in Backbone.Collection._prepareModel)
      if ( !( model instanceof Backbone.Model ) ) {
        return;
      }
      
      options = this.sanitizeOptions( options );
      
      _.each( this.getReverseRelations( model ) || [], function( relation ) {
          relation.addRelated( this.instance, options );
        }, this );

      // Only trigger 'add' once the newly added model is initialized (so, has it's relations set up)
      var dit = this;
      Backbone.Relational.eventQueue.add( function() {
        !options.silentChange && dit.instance.trigger( 'add:' + dit.key, model, dit.related, options );
      });
    },
    
    /**
     * When a model is removed from a 'HasMany', trigger 'remove' on 'this.instance' and notify reverse relations.
     * (should be 'HasOne', which should be nullified)
     */
    handleRemoval: function( model, coll, options ) {
      //console.debug('handleRemoval called; args=%o', arguments);
      if ( !( model instanceof Backbone.Model ) ) {
        return;
      }

      options = this.sanitizeOptions( options );
      
      _.each( this.getReverseRelations( model ) || [], function( relation ) {
          relation.removeRelated( this.instance, options );
        }, this );
      
      var dit = this;
      Backbone.Relational.eventQueue.add( function() {
        !options.silentChange && dit.instance.trigger( 'remove:' + dit.key, model, dit.related, options );
      });
    },

    handleReset: function( coll, options ) {
      options = this.sanitizeOptions( options );

      var dit = this;
      Backbone.Relational.eventQueue.add( function() {
        !options.silentChange && dit.instance.trigger( 'reset:' + dit.key, dit.related, options );
      });
    },
    
    addRelated: function( model, options ) {
      var dit = this;
      options = this.unsanitizeOptions( options );
      model.queue( function() { // Queued to avoid errors for adding 'model' to the 'this.related' set twice
        if ( dit.related && !dit.related.get( model ) ) {
          dit.related.add( model, options );
        }
      });
    },
    
    removeRelated: function( model, options ) {
      options = this.unsanitizeOptions( options );
      if ( this.related.get( model ) ) {
        this.related.remove( model, options );
      }
    }
  });
  
  /**
   * A type of Backbone.Model that also maintains relations to other models and collections.
   * New events when compared to the original:
   *  - 'add:<key>' (model, related collection, options)
   *  - 'remove:<key>' (model, related collection, options)
   *  - 'update:<key>' (model, related model or collection, options)
   */
  Backbone.RelationalModel = Backbone.Model.extend({
    relations: null, // Relation descriptions on the prototype
    _relations: null, // Relation instances
    _isInitialized: false,
    _deferProcessing: false,
    _queue: null,
    
    subModelTypeAttribute: 'type',
    subModelTypes: null,
    
    constructor: function( attributes, options ) {
      // Nasty hack, for cases like 'model.get( <HasMany key> ).add( item )'.
      // Defer 'processQueue', so that when 'Relation.createModels' is used we:
      // a) Survive 'Backbone.Collection.add'; this takes care we won't error on "can't add model to a set twice"
      //    (by creating a model from properties, having the model add itself to the collection via one of
      //    it's relations, then trying to add it to the collection).
      // b) Trigger 'HasMany' collection events only after the model is really fully set up.
      // Example that triggers both a and b: "p.get('jobs').add( { company: c, person: p } )".
      var dit = this;
      if ( options && options.collection ) {
        this._deferProcessing = true;
        
        var processQueue = function( model ) {
          if ( model === dit ) {
            dit._deferProcessing = false;
            dit.processQueue();
            options.collection.unbind( 'relational:add', processQueue );
          }
        };
        options.collection.bind( 'relational:add', processQueue );
        
        // So we do process the queue eventually, regardless of whether this model really gets added to 'options.collection'.
        _.defer( function() {
          processQueue( dit );
        });
      }
      
      this._queue = new Backbone.BlockingQueue();
      this._queue.block();
      Backbone.Relational.eventQueue.block();
      
      Backbone.Model.apply( this, arguments );
      
      // Try to run the global queue holding external events
      Backbone.Relational.eventQueue.unblock();
    },
    
    /**
     * Override 'trigger' to queue 'change' and 'change:*' events
     */
    trigger: function( eventName ) {
      if ( eventName.length > 5 && 'change' === eventName.substr( 0, 6 ) ) {
        var dit = this, args = arguments;
        Backbone.Relational.eventQueue.add( function() {
            Backbone.Model.prototype.trigger.apply( dit, args );
          });
      }
      else {
        Backbone.Model.prototype.trigger.apply( this, arguments );
      }
      
      return this;
    },
    
    /**
     * Initialize Relations present in this.relations; determine the type (HasOne/HasMany), then creates a new instance.
     * Invoked in the first call so 'set' (which is made from the Backbone.Model constructor).
     */
    initializeRelations: function() {
      this.acquire(); // Setting up relations often also involve calls to 'set', and we only want to enter this function once
      this._relations = [];
      
      _.each( this.relations || [], function( rel ) {
          var type = !_.isString( rel.type ) ? rel.type : Backbone[ rel.type ] || Backbone.Relational.store.getObjectByName( rel.type );
          if ( type && type.prototype instanceof Backbone.Relation ) {
            new type( this, rel ); // Also pushes the new Relation into _relations
          }
          else {
            Backbone.Relational.showWarnings && typeof console !== 'undefined' && console.warn( 'Relation=%o; missing or invalid type!', rel );
          }
        }, this );
      
      this._isInitialized = true;
      this.release();
      this.processQueue();
    },

    /**
     * When new values are set, notify this model's relations (also if options.silent is set).
     * (Relation.setRelated locks this model before calling 'set' on it to prevent loops)
     */
    updateRelations: function( options ) {
      if ( this._isInitialized && !this.isLocked() ) {
        _.each( this._relations || [], function( rel ) {
          // Update from data in `rel.keySource` if set, or `rel.key` otherwise
          var val = this.attributes[ rel.keySource ] || this.attributes[ rel.key ];
          if ( rel.related !== val ) {
            this.trigger( 'relational:change:' + rel.key, this, val, options || {} );
          }
        }, this );
      }
    },
    
    /**
     * Either add to the queue (if we're not initialized yet), or execute right away.
     */
    queue: function( func ) {
      this._queue.add( func );
    },
    
    /**
     * Process _queue
     */
    processQueue: function() {
      if ( this._isInitialized && !this._deferProcessing && this._queue.isBlocked() ) {
        this._queue.unblock();
      }
    },
    
    /**
     * Get a specific relation.
     * @param key {string} The relation key to look for.
     * @return {Backbone.Relation} An instance of 'Backbone.Relation', if a relation was found for 'key', or null.
     */
    getRelation: function( key ) {
      return _.detect( this._relations, function( rel ) {
        if ( rel.key === key ) {
          return true;
        }
      }, this );
    },
    
    /**
     * Get all of the created relations.
     * @return {Backbone.Relation[]}
     */
    getRelations: function() {
      return this._relations;
    },
    
    /**
     * Retrieve related objects.
     * @param key {string} The relation key to fetch models for.
     * @param [options] {Object} Options for 'Backbone.Model.fetch' and 'Backbone.sync'.
     * @param [update=false] {boolean} Whether to force a fetch from the server (updating existing models).
     * @return {jQuery.when[]} An array of request objects
     */
    fetchRelated: function( key, options, update ) {
      options || ( options = {} );
      var setUrl,
        requests = [],
        rel = this.getRelation( key ),
        keyContents = rel && rel.keyContents,
        toFetch = keyContents && _.select( _.isArray( keyContents ) ? keyContents : [ keyContents ], function( item ) {
          var id = Backbone.Relational.store.resolveIdForItem( rel.relatedModel, item );
          return !_.isNull( id ) && ( update || !Backbone.Relational.store.find( rel.relatedModel, id ) );
        }, this );
      
      if ( toFetch && toFetch.length ) {
        // Create a model for each entry in 'keyContents' that is to be fetched
        var models = _.map( toFetch, function( item ) {
          var model;

          if ( _.isObject( item ) ) {
            model = rel.relatedModel.findOrCreate( item );
          }
          else {
            var attrs = {};
            attrs[ rel.relatedModel.prototype.idAttribute ] = item;
            model = rel.relatedModel.findOrCreate( attrs );
          }

          return model;
        }, this );
        
        // Try if the 'collection' can provide a url to fetch a set of models in one request.
        if ( rel.related instanceof Backbone.Collection && _.isFunction( rel.related.url ) ) {
          setUrl = rel.related.url( models );
        }
        
        // An assumption is that when 'Backbone.Collection.url' is a function, it can handle building of set urls.
        // To make sure it can, test if the url we got by supplying a list of models to fetch is different from
        // the one supplied for the default fetch action (without args to 'url').
        if ( setUrl && setUrl !== rel.related.url() ) {
          var opts = _.defaults(
            {
              error: function() {
                var args = arguments;
                _.each( models || [], function( model ) {
                    model.trigger( 'destroy', model, model.collection, options );
                    options.error && options.error.apply( model, args );
                  });
              },
              url: setUrl
            },
            options,
            { add: true }
          );

          requests = [ rel.related.fetch( opts ) ];
        }
        else {
          requests = _.map( models || [], function( model ) {
            var opts = _.defaults(
              {
                error: function() {
                  model.trigger( 'destroy', model, model.collection, options );
                  options.error && options.error.apply( model, arguments );
                }
              },
              options
            );
            return model.fetch( opts );
          }, this );
        }
      }
      
      return requests;
    },
    
    set: function( key, value, options ) {
      Backbone.Relational.eventQueue.block();
      
      // Duplicate backbone's behavior to allow separate key/value parameters, instead of a single 'attributes' object
      var attributes;
      if ( _.isObject( key ) || key == null ) {
        attributes = key;
        options = value;
      }
      else {
        attributes = {};
        attributes[ key ] = value;
      }
      
      var result = Backbone.Model.prototype.set.apply( this, arguments );
      
      // Ideal place to set up relations :)
      if ( !this._isInitialized && !this.isLocked() ) {
        this.constructor.initializeModelHierarchy();

        Backbone.Relational.store.register( this );

        this.initializeRelations();
      }
      // Update the 'idAttribute' in Backbone.store if; we don't want it to miss an 'id' update due to {silent:true}
      else if ( attributes && this.idAttribute in attributes ) {
        Backbone.Relational.store.update( this );
      }
      
      if ( attributes ) {
        this.updateRelations( options );
      }
      
      // Try to run the global queue holding external events
      Backbone.Relational.eventQueue.unblock();
      
      return result;
    },
    
    unset: function( attribute, options ) {
      Backbone.Relational.eventQueue.block();
      
      var result = Backbone.Model.prototype.unset.apply( this, arguments );
      this.updateRelations( options );
      
      // Try to run the global queue holding external events
      Backbone.Relational.eventQueue.unblock();
      
      return result;
    },
    
    clear: function( options ) {
      Backbone.Relational.eventQueue.block();
      
      var result = Backbone.Model.prototype.clear.apply( this, arguments );
      this.updateRelations( options );
      
      // Try to run the global queue holding external events
      Backbone.Relational.eventQueue.unblock();
      
      return result;
    },

    clone: function() {
      var attributes = _.clone( this.attributes );
      if ( !_.isUndefined( attributes[ this.idAttribute ] ) ) {
        attributes[ this.idAttribute ] = null;
      }

      _.each( this.getRelations() || [], function( rel ) {
          delete attributes[ rel.key ];
        });

      return new this.constructor( attributes );
    },
    
    /**
     * Convert relations to JSON, omits them when required
     */
    toJSON: function(options) {
      // If this Model has already been fully serialized in this branch once, return to avoid loops
      if ( this.isLocked() ) {
        return this.id;
      }
      
      this.acquire();
      var json = Backbone.Model.prototype.toJSON.call( this, options );
      
      if ( this.constructor._superModel && !( this.constructor._subModelTypeAttribute in json ) ) {
        json[ this.constructor._subModelTypeAttribute ] = this.constructor._subModelTypeValue;
      }
      
      _.each( this._relations || [], function( rel ) {
          var value = json[ rel.key ];

          if ( rel.options.includeInJSON === true) {
            if ( value && _.isFunction( value.toJSON ) ) {
              json[ rel.keyDestination ] = value.toJSON( options );
            }
            else {
              json[ rel.keyDestination ] = null;
            }
          }
          else if ( _.isString( rel.options.includeInJSON ) ) {
            if ( value instanceof Backbone.Collection ) {
              json[ rel.keyDestination ] = value.pluck( rel.options.includeInJSON );
            }
            else if ( value instanceof Backbone.Model ) {
              json[ rel.keyDestination ] = value.get( rel.options.includeInJSON );
            } 
            else {
              json[ rel.keyDestination ] = null;
            }
          }
          else if ( _.isArray( rel.options.includeInJSON ) ) {
            if ( value instanceof Backbone.Collection ) {
              var valueSub = [];
              value.each( function( model ) {
                var curJson = {};
                _.each( rel.options.includeInJSON, function( key ) {
                  curJson[ key ] = model.get( key );
                });
                valueSub.push( curJson );
              });
              json[ rel.keyDestination ] = valueSub;
            }
            else if ( value instanceof Backbone.Model ) {
              var valueSub = {};
              _.each( rel.options.includeInJSON, function( key ) {
                valueSub[ key ] = value.get( key );
              });
              json[ rel.keyDestination ] = valueSub;
            }
            else {
              json[ rel.keyDestination ] = null;
            }
          }
          else {
            delete json[ rel.key ];
          }

          if ( rel.keyDestination !== rel.key ) {
            delete json[ rel.key ];
          }
        });
      
      this.release();
      return json;
    }
  },
  {
    setup: function( superModel ) {
      // We don't want to share a relations array with a parent, as this will cause problems with
      // reverse relations.
      this.prototype.relations = ( this.prototype.relations || [] ).slice( 0 );

      this._subModels = {};
      this._superModel = null;

      // If this model has 'subModelTypes' itself, remember them in the store
      if ( this.prototype.hasOwnProperty( 'subModelTypes' ) ) {
        Backbone.Relational.store.addSubModels( this.prototype.subModelTypes, this );
      }
      // The 'subModelTypes' property should not be inherited, so reset it.
      else {
        this.prototype.subModelTypes = null;
      }

      // Initialize all reverseRelations that belong to this new model.
      _.each( this.prototype.relations || [], function( rel ) {
          if ( !rel.model ) {
            rel.model = this;
          }

          if ( rel.reverseRelation && rel.model === this ) {        
            var preInitialize = true;
            if ( _.isString( rel.relatedModel ) ) {
              /**
               * The related model might not be defined for two reasons
               *  1. it never gets defined, e.g. a typo
               *  2. it is related to itself
               * In neither of these cases do we need to pre-initialize reverse relations.
               */
              var relatedModel = Backbone.Relational.store.getObjectByName( rel.relatedModel );
              preInitialize = relatedModel && ( relatedModel.prototype instanceof Backbone.RelationalModel );
            }

            var type = !_.isString( rel.type ) ? rel.type : Backbone[ rel.type ] || Backbone.Relational.store.getObjectByName( rel.type );
            if ( preInitialize && type && type.prototype instanceof Backbone.Relation ) {
              new type( null, rel );
            }
          }
        }, this );
      
      return this;
    },

    /**
     * Create a 'Backbone.Model' instance based on 'attributes'.
     * @param {Object} attributes
     * @param {Object} [options]
     * @return {Backbone.Model}
     */
    build: function( attributes, options ) {
      var model = this;

      // 'build' is a possible entrypoint; it's possible no model hierarchy has been determined yet.
      this.initializeModelHierarchy();

      // Determine what type of (sub)model should be built if applicable.
      // Lookup the proper subModelType in 'this._subModels'.
      if ( this._subModels && this.prototype.subModelTypeAttribute in attributes ) {
        var subModelTypeAttribute = attributes[ this.prototype.subModelTypeAttribute ];
        var subModelType = this._subModels[ subModelTypeAttribute ];
        if ( subModelType ) {
          model = subModelType;
        }
      }
      
      return new model( attributes, options );
    },

    initializeModelHierarchy: function() {
      // If we're here for the first time, try to determine if this modelType has a 'superModel'.
      if ( _.isUndefined( this._superModel ) || _.isNull( this._superModel ) ) {
        Backbone.Relational.store.setupSuperModel( this );

        // If a superModel has been found, copy relations from the _superModel if they haven't been
        // inherited automatically (due to a redefinition of 'relations').
        // Otherwise, make sure we don't get here again for this type by making '_superModel' false so we fail
        // the isUndefined/isNull check next time.
        if ( this._superModel ) {
          //
          if ( this._superModel.prototype.relations ) {
            var supermodelRelationsExist = _.any( this.prototype.relations || [], function( rel ) {
              return rel.model && rel.model !== this;
            }, this );

            if ( !supermodelRelationsExist ) {
              this.prototype.relations = this._superModel.prototype.relations.concat( this.prototype.relations );
            }
          }
        }
        else {
          this._superModel = false;
        }
      }

      // If we came here through 'build' for a model that has 'subModelTypes', and not all of them have been resolved yet, try to resolve each.
      if ( this.prototype.subModelTypes && _.keys( this.prototype.subModelTypes ).length !== _.keys( this._subModels ).length ) {
        _.each( this.prototype.subModelTypes || [], function( subModelTypeName ) {
          var subModelType = Backbone.Relational.store.getObjectByName( subModelTypeName );
          subModelType && subModelType.initializeModelHierarchy();
        });
      }
    },

    /**
     * Find an instance of `this` type in 'Backbone.Relational.store'.
     * - If `attributes` is a string or a number, `findOrCreate` will just query the `store` and return a model if found.
     * - If `attributes` is an object and is found in the store, the model will be updated with `attributes` unless `options.update` is `false`. 
     *   Otherwise, a new model is created with `attributes` (unless `options.create` is explicitly set to `false`).
     * @param {Object|String|Number} attributes Either a model's id, or the attributes used to create or update a model.
     * @param {Object} [options]
     * @param {Boolean} [options.create=true]
     * @param {Boolean} [options.update=true]
     * @return {Backbone.RelationalModel}
     */
    findOrCreate: function( attributes, options ) {
      options || ( options = {} );
      var parsedAttributes = (_.isObject( attributes ) && this.prototype.parse) ? this.prototype.parse( attributes ) : attributes;
      // Try to find an instance of 'this' model type in the store
      var model = Backbone.Relational.store.find( this, parsedAttributes );

      // If we found an instance, update it with the data in 'item' (unless 'options.update' is false).
      // If not, create an instance (unless 'options.create' is false).
      if ( _.isObject( attributes ) ) {
        if ( model && options.update !== false ) {
          model.set( parsedAttributes, options );
        }
        else if ( !model && options.create !== false ) {
          model = this.build( attributes, options );
        }
      }

      return model;
    }
  });
  _.extend( Backbone.RelationalModel.prototype, Backbone.Semaphore );
  
  /**
   * Override Backbone.Collection._prepareModel, so objects will be built using the correct type
   * if the collection.model has subModels.
   */
  Backbone.Collection.prototype.__prepareModel = Backbone.Collection.prototype._prepareModel;
  Backbone.Collection.prototype._prepareModel = function ( attrs, options ) {
    var model;
    
    if ( attrs instanceof Backbone.Model ) {
      if ( !attrs.collection ) {
        attrs.collection = this;
      }
      model = attrs;
    }
    else {
      options || (options = {});
      options.collection = this;
      
      if ( typeof this.model.findOrCreate !== 'undefined' ) {
        model = this.model.findOrCreate( attrs, options );
      }
      else {
        model = new this.model( attrs, options );
      }
      
      if ( !model._validate( attrs, options ) ) {
        model = false;
      }
    }
    
    return model;
  };

  
  /**
   * Override Backbone.Collection.add, so objects fetched from the server multiple times will
   * update the existing Model. Also, trigger 'relational:add'.
   */
  var add = Backbone.Collection.prototype.__add = Backbone.Collection.prototype.add;
  Backbone.Collection.prototype.add = function( models, options ) {
    options || (options = {});
    if ( !_.isArray( models ) ) {
      models = [ models ];
    }

    var modelsToAdd = [];

    //console.debug( 'calling add on coll=%o; model=%o, options=%o', this, models, options );
    _.each( models || [], function( model ) {
      if ( !( model instanceof Backbone.Model ) ) {
        // `_prepareModel` attempts to find `model` in Backbone.store through `findOrCreate`,
        // and sets the new properties on it if is found. Otherwise, a new model is instantiated.
        model = Backbone.Collection.prototype._prepareModel.call( this, model, options );
      }

        if ( model instanceof Backbone.Model && !this.get( model ) ) {
          modelsToAdd.push( model );
        }
      }, this );

    // Add 'models' in a single batch, so the original add will only be called once (and thus 'sort', etc).
    if ( modelsToAdd.length ) {
      add.call( this, modelsToAdd, options );

      _.each( modelsToAdd || [], function( model ) {
        this.trigger( 'relational:add', model, this, options );
      }, this );
    }
    
    return this;
  };
  
  /**
   * Override 'Backbone.Collection.remove' to trigger 'relational:remove'.
   */
  var remove = Backbone.Collection.prototype.__remove = Backbone.Collection.prototype.remove;
  Backbone.Collection.prototype.remove = function( models, options ) {
    options || (options = {});
    if ( !_.isArray( models ) ) {
      models = [ models ];
    }
    else {
      models = models.slice( 0 );
    }

    //console.debug('calling remove on coll=%o; models=%o, options=%o', this, models, options );
    _.each( models || [], function( model ) {
        model = this.get( model );

        if ( model instanceof Backbone.Model ) {
          remove.call( this, model, options );
          this.trigger('relational:remove', model, this, options);
        }
      }, this );
    
    return this;
  };

  /**
   * Override 'Backbone.Collection.reset' to trigger 'relational:reset'.
   */
  var reset = Backbone.Collection.prototype.__reset = Backbone.Collection.prototype.reset;
  Backbone.Collection.prototype.reset = function( models, options ) {
    reset.call( this, models, options );
    this.trigger( 'relational:reset', this, options );

    return this;
  };

  /**
   * Override 'Backbone.Collection.sort' to trigger 'relational:reset'.
   */
  var sort = Backbone.Collection.prototype.__sort = Backbone.Collection.prototype.sort;
  Backbone.Collection.prototype.sort = function( options ) {
    sort.call( this, options );
    this.trigger( 'relational:reset', this, options );

    return this;
  };
  
  /**
   * Override 'Backbone.Collection.trigger' so 'add', 'remove' and 'reset' events are queued until relations
   * are ready.
   */
  var trigger = Backbone.Collection.prototype.__trigger = Backbone.Collection.prototype.trigger;
  Backbone.Collection.prototype.trigger = function( eventName ) {
    if ( eventName === 'add' || eventName === 'remove' || eventName === 'reset' ) {
      var dit = this, args = arguments;
      
      if (eventName === 'add') {
        args = _.toArray( args );
        // the fourth argument in case of a regular add is the option object.
        // we need to clone it, as it could be modified while we wait on the eventQueue to be unblocked
        if (_.isObject( args[3] ) ) {
          args[3] = _.clone( args[3] );
        }
      }
      
      Backbone.Relational.eventQueue.add( function() {
          trigger.apply( dit, args );
        });
    }
    else {
      trigger.apply( this, arguments );
    }
    
    return this;
  };

  // Override .extend() to automatically call .setup()
  Backbone.RelationalModel.extend = function( protoProps, classProps ) {
    var child = Backbone.Model.extend.apply( this, arguments );
    
    child.setup( this );

    return child;
  };
})();