import {Directive, Host, Inject, Input, OnChanges, OnDestroy, Optional, Output, Self, SimpleChanges, forwardRef} from '@angular/core';

import {EventEmitter, ObservableWrapper} from '../../facade/async';
import {BaseException} from '../../facade/exceptions';
import {FormControl} from '../model';
import {NG_ASYNC_VALIDATORS, NG_VALIDATORS} from '../validators';

import {ControlContainer} from './control_container';
import {ControlValueAccessor, NG_VALUE_ACCESSOR} from './control_value_accessor';
import {NgControl} from './ng_control';
import {composeAsyncValidators, composeValidators, controlPath, isPropertyUpdated, selectValueAccessor, setUpControl} from './shared';
import {AsyncValidatorFn, ValidatorFn} from './validators';

export const formControlBinding: any =
    /*@ts2dart_const*/ /* @ts2dart_Provider */ {
      provide: 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;
 * }
 *  ```
 *
 *  @experimental
 */
@Directive({
  selector: '[ngModel]:not([ngControl]):not([formControl])',
  providers: [formControlBinding],
  exportAs: 'ngForm'
})
export class NgModel extends NgControl implements OnChanges,
    OnDestroy {
  /** @internal */
  _control: FormControl;
  /** @internal */
  _added = false;
  viewModel: any;

  @Input('ngModel') model: any;
  @Input() name: string;

  @Output('ngModelChange') update = new EventEmitter();

  constructor(@Optional() @Host() private _parent: ControlContainer,
              @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);
                if (!this._parent) this._control = new FormControl();
              }

              ngOnChanges(changes: SimpleChanges) {
                this._checkName();
                if (!this._added) this._addControl();

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

              ngOnDestroy(): void { this.formDirective && this.formDirective.removeControl(this); }

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

              get path(): string[] {
                return this._parent ? controlPath(this.name, this._parent) : [];
              }

              get formDirective(): any { return this._parent ? this._parent.formDirective : null; }

              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);
              }

              private _addControl(): void {
                this._control = this.formDirective ? this.formDirective.addControl(this) :
                                                     this._addStandaloneControl();
                this._added = true;
              }

              private _addStandaloneControl(): FormControl {
                setUpControl(this._control, this);
                this._control.updateValueAndValidity({emitEvent: false});
                return this._control;
              }

              private _checkName() {
                if (this._parent && !this.name) {
                  throw new BaseException(
                      `Name attribute must be set if ngModel is used within a form.
                      Example: <input [(ngModel)]="person.firstName" name="first">`);
                }
              }
}