/**
@module ember
@submodule ember-runtime
*/
import Ember from "ember-metal/core"; // Ember.assert
import {get} from "ember-metal/property_get";
import {set} from "ember-metal/property_set";
import {meta} from "ember-metal/utils";
import {addObserver, removeObserver, addBeforeObserver, removeBeforeObserver} from "ember-metal/observer";
import {propertyWillChange, propertyDidChange} from "ember-metal/property_events";
import {computed} from "ember-metal/computed";
import {defineProperty} from "ember-metal/properties";
import {observer} from "ember-metal/mixin";
import EmberStringUtils from "ember-runtime/system/string";
import EmberObject from "ember-runtime/system/object";

function contentPropertyWillChange(content, contentKey) {
  var key = contentKey.slice(8); // remove "content."
  if (key in this) { return; }  // if shadowed in proxy
  propertyWillChange(this, key);
}

function contentPropertyDidChange(content, contentKey) {
  var key = contentKey.slice(8); // remove "content."
  if (key in this) { return; } // if shadowed in proxy
  propertyDidChange(this, key);
}

/**
  `Ember.ObjectProxy` forwards all properties not defined by the proxy itself
  to a proxied `content` object.

  ```javascript
  object = Ember.Object.create({
    name: 'Foo'
  });

  proxy = Ember.ObjectProxy.create({
    content: object
  });

  // Access and change existing properties
  proxy.get('name')          // 'Foo'
  proxy.set('name', 'Bar');
  object.get('name')         // 'Bar'

  // Create new 'description' property on `object`
  proxy.set('description', 'Foo is a whizboo baz');
  object.get('description')  // 'Foo is a whizboo baz'
  ```

  While `content` is unset, setting a property to be delegated will throw an
  Error.

  ```javascript
  proxy = Ember.ObjectProxy.create({
    content: null,
    flag: null
  });
  proxy.set('flag', true);
  proxy.get('flag');         // true
  proxy.get('foo');          // undefined
  proxy.set('foo', 'data');  // throws Error
  ```

  Delegated properties can be bound to and will change when content is updated.

  Computed properties on the proxy itself can depend on delegated properties.

  ```javascript
  ProxyWithComputedProperty = Ember.ObjectProxy.extend({
    fullName: function () {
      var firstName = this.get('firstName'),
          lastName = this.get('lastName');
      if (firstName && lastName) {
        return firstName + ' ' + lastName;
      }
      return firstName || lastName;
    }.property('firstName', 'lastName')
  });

  proxy = ProxyWithComputedProperty.create();


  proxy.get('fullName');  // 'Tom Dale'
  ```

  @class ObjectProxy
  @namespace Ember
  @extends Ember.Object
*/
var ObjectProxy = EmberObject.extend({
  /**
    The object whose properties will be forwarded.

    @property content
    @type Ember.Object
    @default null
  */
  content: null,
  _contentDidChange: observer('content', function() {
    Ember.assert("Can't set ObjectProxy's content to itself", get(this, 'content') !== this);
  }),

  isTruthy: computed.bool('content'),

  _debugContainerKey: null,

  willWatchProperty: function (key) {
    var contentKey = 'content.' + key;
    addBeforeObserver(this, contentKey, null, contentPropertyWillChange);
    addObserver(this, contentKey, null, contentPropertyDidChange);
  },

  didUnwatchProperty: function (key) {
    var contentKey = 'content.' + key;
    removeBeforeObserver(this, contentKey, null, contentPropertyWillChange);
    removeObserver(this, contentKey, null, contentPropertyDidChange);
  },

  unknownProperty: function (key) {
    var content = get(this, 'content');
    if (content) {
      return get(content, key);
    }
  },

  setUnknownProperty: function (key, value) {
    var m = meta(this);
    if (m.proto === this) {
      // if marked as prototype then just defineProperty
      // rather than delegate
      defineProperty(this, key, null, value);
      return value;
    }

    var content = get(this, 'content');
    Ember.assert(EmberStringUtils.fmt("Cannot delegate set('%@', %@) to the 'content' property of object proxy %@: its 'content' is undefined.", [key, value, this]), content);
    return set(content, key, value);
  }

});

export default ObjectProxy;
  proxy.get('fullName');  // undefined
  proxy.set('content', {
    firstName: 'Tom', lastName: 'Dale'
  }); // triggers property change for fullName on proxy