import {Component, Directive, Optional, ElementRef, Input, Renderer, HostListener} from 'angular2/core';
import {NgControl} from 'angular2/common';

import {Form} from '../../util/form';

/**
 * The checkbox is no different than the HTML checkbox input, except it's styled differently.
 *
 * See the [Angular 2 Docs](https://angular.io/docs/js/latest/api/core/Form-interface.html) for more info on forms and input.
 *
 * @property [checked] - whether or not the checkbox is checked (defaults to false)
 * @property [value] - the value of the checkbox component
 * @property [disabled] - whether or not the checkbox is disabled or not.
 *
 * @usage
 * ```html
 * <ion-checkbox checked="true" value="isChecked" ngControl="htmlCtrl">
 *   HTML5
 * </ion-checkbox>
 * ```
 * @demo /docs/v2/demos/checkbox/
 * @see {@link /docs/v2/components#checkbox Checkbox Component Docs}
 */
@Component({
  selector: 'ion-checkbox',
  host: {
    'role': 'checkbox',
    'class': 'item',
    'tappable': '',
    'tabindex': '0',
    '[attr.aria-disabled]': 'disabled'
  },
  template:
    '<div class="item-inner">' +
      '<div class="checkbox-media" disable-activated>' +
        '<div class="checkbox-icon"></div>' +
      '</div>' +
      '<ion-item-content id="{{labelId}}">' +
        '<ng-content></ng-content>' +
      '</ion-item-content>' +
    '</div>'
})
export class Checkbox {
  private _checked: boolean;
  private labelId: string;
  @Input() value: string = '';
  @Input() disabled: boolean = false;
  @Input() id: string;

  constructor(
    private _form: Form,
    private _elementRef: ElementRef,
    private _renderer: Renderer,
    @Optional() ngControl: NgControl
  ) {
    _form.register(this);

    if (ngControl) {
      ngControl.valueAccessor = this;
    }
  }

  /**
   * @private
   */
  ngOnInit() {
    if (!this.id) {
      this.id = 'chk-' + this._form.nextId();
      this._renderer.setElementAttribute(this._elementRef, 'id', this.id);
    }

    this.labelId = 'lbl-' + this.id;
    this._renderer.setElementAttribute(this._elementRef, 'aria-labelledby', this.labelId);
  }

  /**
   * @private
   * Toggle the checked state of the checkbox. Calls onChange to pass the updated checked state to the model (Control).
   */
  toggle() {
    this.checked = !this.checked;
  }

  get checked() {
    return !!this._checked;
  }

  @Input() 
  set checked(val) {
    this._checked = !!val;
    this._renderer.setElementAttribute(this._elementRef, 'aria-checked', this._checked.toString());
    this.onChange(this._checked);
  }

  /**
   * @private
   */
  @HostListener('click', ['$event'])
  _click(ev) {
    ev.preventDefault();
    ev.stopPropagation();
    this.toggle();
  }

  /**
   * @private
   * Angular2 Forms API method called by the model (Control) on change to update
   * the checked value.
   * https://github.com/angular/angular/blob/master/modules/angular2/src/forms/directives/shared.ts#L34
   */
  writeValue(value) {
    this.checked = value;
  }

  /**
   * @private
   */
  onChange(val) {
    // TODO: figure the whys and the becauses
  }

  /**
   * @private
   */
  onTouched(val) {
    // TODO: figure the whys and the becauses
  }

  /**
   * @private
   * Angular2 Forms API method called by the view (NgControl) to register the
   * onChange event handler that updates the model (Control).
   * https://github.com/angular/angular/blob/master/modules/angular2/src/forms/directives/shared.ts#L27
   * @param {Function} fn  the onChange event handler.
   */
  registerOnChange(fn) { this.onChange = fn; }

  /**
   * @private
   * Angular2 Forms API method called by the the view (NgControl) to register
   * the onTouched event handler that marks model (Control) as touched.
   * @param {Function} fn  onTouched event handler.
   */
  registerOnTouched(fn) { this.onTouched = fn; }

  /**
   * @private
   */
  ngOnDestroy() {
    this._form.deregister(this);
  }
}