/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {Directive, Host, Inject, Input, OnDestroy, OnInit, Optional, Self, SkipSelf, forwardRef} from '@angular/core';

import {NG_ASYNC_VALIDATORS, NG_VALIDATORS} from '../validators';

import {AbstractFormGroupDirective} from './abstract_form_group_directive';
import {ControlContainer} from './control_container';
import {NgForm} from './ng_form';
import {TemplateDrivenErrors} from './template_driven_errors';

export const modelGroupProvider: any = {
  provide: ControlContainer,
  useExisting: forwardRef(() => NgModelGroup)
};

/**
 * @whatItDoes Creates and binds a {@link FormGroup} instance to a DOM element.
 *
 * @howToUse
 *
 * This directive can only be used as a child of {@link NgForm} (or in other words,
 * within `<form>` tags).
 *
 * Use this directive if you'd like to create a sub-group within a form. This can
 * come in handy if you want to validate a sub-group of your form separately from
 * the rest of your form, or if some values in your domain model make more sense to
 * consume together in a nested object.
 *
 * Pass in the name you'd like this sub-group to have and it will become the key
 * for the sub-group in the form's full value. You can also export the directive into
 * a local template variable using `ngModelGroup` (ex: `#myGroup="ngModelGroup"`).
 *
 * {@example forms/ts/ngModelGroup/ng_model_group_example.ts region='Component'}
 *
 * * **npm package**: `@angular/forms`
 *
 * * **NgModule**: `FormsModule`
 *
 * @stable
 */
@Directive({selector: '[ngModelGroup]', providers: [modelGroupProvider], exportAs: 'ngModelGroup'})
export class NgModelGroup extends AbstractFormGroupDirective implements OnInit, OnDestroy {
  @Input('ngModelGroup') name: string;

  constructor(
      @Host() @SkipSelf() parent: ControlContainer,
      @Optional() @Self() @Inject(NG_VALIDATORS) validators: any[],
      @Optional() @Self() @Inject(NG_ASYNC_VALIDATORS) asyncValidators: any[]) {
    super();
    this._parent = parent;
    this._validators = validators;
    this._asyncValidators = asyncValidators;
  }

  /** @internal */
  _checkParentType(): void {
    if (!(this._parent instanceof NgModelGroup) && !(this._parent instanceof NgForm)) {
      TemplateDrivenErrors.modelGroupParentException();
    }
  }
}