/**
 * @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 {
  ViewChild,
  Component,
  Input,
  Output,
  EventEmitter,
  OnInit,
  ElementRef,
  AfterViewChecked,
  ViewEncapsulation,
} from '@angular/core';
import {
  trigger,
  state,
  style,
  animate,
  transition,
  AnimationEvent,
} from '@angular/animations';
import {TemplatePortal, PortalHostDirective} from '@angular/cdk';

/**
 * These position states are used internally as animation states for the tab body. Setting the
 * position state to left, right, or center will transition the tab body from its current
 * position to its respective state. If there is not current position (void, in the case of a new
 * tab body), then there will be no transition animation to its state.
 *
 * In the case of a new tab body that should immediately be centered with an animating transition,
 * then left-origin-center or right-origin-center can be used, which will use left or right as its
 * psuedo-prior state.
 */
export type MdTabBodyPositionState =
    'left' | 'center' | 'right' | 'left-origin-center' | 'right-origin-center';

/**
 * The origin state is an internally used state that is set on a new tab body indicating if it
 * began to the left or right of the prior selected index. For example, if the selected index was
 * set to 1, and a new tab is created and selected at index 2, then the tab body would have an
 * origin of right because its index was greater than the prior selected index.
 */
export type MdTabBodyOriginState = 'left' | 'right';

/**
 * Wrapper for the contents of a tab.
 * @docs-private
 */
@Component({
  moduleId: module.id,
  selector: 'md-tab-body, mat-tab-body',
  templateUrl: 'tab-body.html',
  styleUrls: ['tab-body.scss'],
  encapsulation: ViewEncapsulation.None,
  host: {
    'class': 'mat-tab-body',
  },
  animations: [
    trigger('translateTab', [
      state('void', style({transform: 'translate3d(0%, 0, 0)'})),
      state('left', style({transform: 'translate3d(-100%, 0, 0)'})),
      state('left-origin-center', style({transform: 'translate3d(0%, 0, 0)'})),
      state('right-origin-center', style({transform: 'translate3d(0%, 0, 0)'})),
      state('center', style({transform: 'translate3d(0%, 0, 0)'})),
      state('right', style({transform: 'translate3d(100%, 0, 0)'})),
      transition('* => left, * => right, left => center, right => center',
          animate('500ms cubic-bezier(0.35, 0, 0.25, 1)')),
      transition('void => left-origin-center', [
        style({transform: 'translate3d(-100%, 0, 0)'}),
        animate('500ms cubic-bezier(0.35, 0, 0.25, 1)')
      ]),
      transition('void => right-origin-center', [
        style({transform: 'translate3d(100%, 0, 0)'}),
        animate('500ms cubic-bezier(0.35, 0, 0.25, 1)')
      ])
    ])
  ]
})
export class MdTabBody implements OnInit, AfterViewChecked {
  /** The portal host inside of this container into which the tab body content will be loaded. */
  @ViewChild(PortalHostDirective) _portalHost: PortalHostDirective;

  /** Event emitted when the tab begins to animate towards the center as the active tab. */
  @Output() onCentering: EventEmitter<number> = new EventEmitter<number>();

  /** Event emitted when the tab completes its animation towards the center. */
  @Output() onCentered: EventEmitter<void> = new EventEmitter<void>(true);

  /** The tab body content to display. */
  @Input('content') _content: TemplatePortal;

  /** The shifted index position of the tab body, where zero represents the active center tab. */
  _position: MdTabBodyPositionState;
  @Input('position') set position(position: number) {
    if (position < 0) {
      this._position = 'left';
    } else if (position > 0) {
      this._position = 'right';
    } else {
      this._position = 'center';
    }
  }

  /** The origin position from which this tab should appear when it is centered into view. */
  _origin: MdTabBodyOriginState;

  /** The origin position from which this tab should appear when it is centered into view. */
  @Input('origin') set origin(origin: number) {
    if (origin == null) { return; }

    if (origin <= 0) {
      this._origin = 'left';
    } else {
      this._origin = 'right';
    }
  }

  constructor(private _elementRef: ElementRef) { }

  /**
   * After initialized, check if the content is centered and has an origin. If so, set the
   * special position states that transition the tab from the left or right before centering.
   */
  ngOnInit() {
    if (this._position == 'center' && this._origin) {
      this._position = this._origin == 'left' ? 'left-origin-center' : 'right-origin-center';
    }
  }

  /**
   * After the view has been set, check if the tab content is set to the center and attach the
   * content if it is not already attached.
   */
  ngAfterViewChecked() {
    if (this._isCenterPosition(this._position) && !this._portalHost.hasAttached()) {
      this._portalHost.attach(this._content);
    }
  }

  _onTranslateTabStarted(e: AnimationEvent) {
    if (this._isCenterPosition(e.toState)) {
      this.onCentering.emit(this._elementRef.nativeElement.clientHeight);
    }
  }

  _onTranslateTabComplete(e: AnimationEvent) {
    // If the end state is that the tab is not centered, then detach the content.
    if (!this._isCenterPosition(e.toState) && !this._isCenterPosition(this._position)) {
      this._portalHost.detach();
    }

    // If the transition to the center is complete, emit an event.
    if (this._isCenterPosition(e.toState) && this._isCenterPosition(this._position)) {
      this.onCentered.emit();
    }
  }

  /** Whether the provided position state is considered center, regardless of origin. */
  private _isCenterPosition(position: MdTabBodyPositionState|string): boolean {
    return position == 'center' ||
        position == 'left-origin-center' ||
        position == 'right-origin-center';
  }
}