import {CONST_EXPR} from 'angular2/src/facade/lang';
import {EventEmitter, ObservableWrapper} from 'angular2/src/facade/async';
import {
  OnChanges,
  SimpleChange,
  Directive,
  forwardRef,
  Provider,
  Inject,
  Optional,
  Self
} from 'angular2/core';
import {ControlValueAccessor, NG_VALUE_ACCESSOR} from './control_value_accessor';
import {NgControl} from './ng_control';
import {Control} from '../model';
import {NG_VALIDATORS, NG_ASYNC_VALIDATORS} from '../validators';
import {
  setUpControl,
  isPropertyUpdated,
  selectValueAccessor,
  composeValidators,
  composeAsyncValidators
} from './shared';
import {ValidatorFn, AsyncValidatorFn} from './validators';

const formControlBinding =
    CONST_EXPR(new Provider(NgControl, {useExisting: forwardRef(() => NgModel)}));

/**
 * Binds a domain model to a form control.
 *
 * ### Usage
 *
 * `ngModel` binds an existing domain model to a form control. For a
 * two-way binding, use `[(ngModel)]` to ensure the model updates in
 * both directions.
 *
 * ### Example ([live demo](http://plnkr.co/edit/R3UX5qDaUqFO2VYR0UzH?p=preview))
 *  ```typescript
 * @Component({
 *      selector: "search-comp",
 *      directives: [FORM_DIRECTIVES],
 *      template: `<input type='text' [(ngModel)]="searchQuery">`
 *      })
 * class SearchComp {
 *  searchQuery: string;
 * }
 *  ```
 */
@Directive({
  selector: '[ngModel]:not([ngControl]):not([ngFormControl])',
  bindings: [formControlBinding],
  inputs: ['model: ngModel'],
  outputs: ['update: ngModelChange'],
  exportAs: 'ngForm'
})
export class NgModel extends NgControl implements OnChanges {
  /** @internal */
  _control = new Control();
  /** @internal */
  _added = false;
  update = new EventEmitter();
  model: any;
  viewModel: any;

  constructor(@Optional() @Self() @Inject(NG_VALIDATORS) private _validators: any[],
              @Optional() @Self() @Inject(NG_ASYNC_VALIDATORS) private _asyncValidators: any[],
              @Optional() @Self() @Inject(NG_VALUE_ACCESSOR)
              valueAccessors: ControlValueAccessor[]) {
    super();
    this.valueAccessor = selectValueAccessor(this, valueAccessors);
  }

  ngOnChanges(changes: {[key: string]: SimpleChange}) {
    if (!this._added) {
      setUpControl(this._control, this);
      this._control.updateValueAndValidity({emitEvent: false});
      this._added = true;
    }

    if (isPropertyUpdated(changes, this.viewModel)) {
      this._control.updateValue(this.model);
      this.viewModel = this.model;
    }
  }

  get control(): Control { return this._control; }

  get path(): string[] { return []; }

  get validator(): ValidatorFn { return composeValidators(this._validators); }

  get asyncValidator(): AsyncValidatorFn { return composeAsyncValidators(this._asyncValidators); }

  viewToModelUpdate(newValue: any): void {
    this.viewModel = newValue;
    ObservableWrapper.callEmit(this.update, newValue);
  }
}