CanJS custom Api

api.js

// All calls reponses are converted into model instances or attributes are applied to current instance
var Api = can.Model('Api', {
  callEndpoint: function(url) {
    var ajax    = this._ajax({}, url).call(this),
        def     = new can.Deferred(),
        promise = def.promise(),
        self    = this;

    promise.abort = ajax.abort

    ajax
      .done(function(data, status, xhr) {        
        def.resolveWith(self, [self._getModelsFromResponse(data), status, xhr])
      })
      .fail(function() {
        def.rejectWith(self, arguments)
      })

    return promise;
  },
  _getModelsFromResponse: function(response) {
    if(can.isArray(response)) {
      return this.models(response)
    }

    return response
  }
},{
  _getModelFromResponse: function(response) {
    var data;

    if(can.isPlainObject(response)) {
      this.attr(response)
      return this
    }

    return response
  },
  callEndpoint: function(url) {
    var ajax  = this.constructor._ajax({}, url).call(this),
        def     = new can.Deferred(),
        promise = def.promise(),
        self    = this;

    promise.abort = ajax.abort

    ajax
      .done(function(data, status, xhr) {
        def.resolveWith(self, [self._getModelFromResponse(data), status, xhr])
      })
      .fail(function() {
        def.rejectWith(self, arguments)
      })

    return promise;
  }
})

example.js

Api('User', {
  findAll: "GET /users",
  findOne: "GET /users/{id}",
  // Not native calling
  findAvailable: function() {
    return this.callEndpoint("GET /users/available")
  },
  // Not native calling
  // Call which returns user with some special properties for html form or anything else
  new: function() {
    var newUser = new this(),
        def     = newUser.prepareNew();
        
    def.done(function(user) {
      user.editing()
    })
    
    return def
  }
}, {
  // Not native calling
  prepareNew: function() {
    return this.callEndpoint("GET /users/new")
  },
  editing: function() {
    this.attr('editable', true)
    this.bind('someProperty', this.proxy('somePropertyChanged'))
  },
  somethingChanged: function() {
    console.log("someProperty changed!")
  },
  // Not native calling
  makeAvailable: function() {
    return this.callEndpoint("GET /users/{id}/make_available")
  }
})

// All this calls returns deffered obj like ajax.
var onlyAvailableUsers = User.findAvailable()
var notAvailableUser = User.findOne({id:100}) // This one is not available :)

notAvailableUser.makeAvailable()

notAvailableUser.attr('editable') != false

User.new().done(function(newUser) {
  newUser.attr('editable') == true
})

Hey there.. would it be possible to explain whats happening in the code?
U have functions that do the same thing in instance and static methods of API. Little confused there