/**
 * @license
 * Copyright Google LLC 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 {Directionality} from '@angular/cdk/bidi';
import {coerceBooleanProperty} from '@angular/cdk/coercion';
import {ESCAPE} from '@angular/cdk/keycodes';
import {
  Overlay,
  OverlayConfig,
  OverlayRef,
  PositionStrategy,
  RepositionScrollStrategy,
  ScrollStrategy,
} from '@angular/cdk/overlay';
import {ComponentPortal} from '@angular/cdk/portal';
import {take} from 'rxjs/operators/take';
import {
  AfterContentInit,
  ChangeDetectionStrategy,
  Component,
  ComponentRef,
  EventEmitter,
  Inject,
  InjectionToken,
  Input,
  NgZone,
  OnDestroy,
  Optional,
  Output,
  ViewChild,
  ViewContainerRef,
  ViewEncapsulation,
} from '@angular/core';
import {DateAdapter} from '@angular/material/core';
import {MatDialog, MatDialogRef} from '@angular/material/dialog';
import {DOCUMENT} from '@angular/common';
import {Subject} from 'rxjs/Subject';
import {Subscription} from 'rxjs/Subscription';
import {MatCalendar} from './calendar';
import {createMissingDateImplError} from './datepicker-errors';
import {MatDatepickerInput} from './datepicker-input';


/** Used to generate a unique ID for each datepicker instance. */
let datepickerUid = 0;

/** Injection token that determines the scroll handling while the calendar is open. */
export const MAT_DATEPICKER_SCROLL_STRATEGY =
    new InjectionToken<() => ScrollStrategy>('mat-datepicker-scroll-strategy');

/** @docs-private */
export function MAT_DATEPICKER_SCROLL_STRATEGY_PROVIDER_FACTORY(overlay: Overlay):
    () => RepositionScrollStrategy {
  return () => overlay.scrollStrategies.reposition();
}

/** @docs-private */
export const MAT_DATEPICKER_SCROLL_STRATEGY_PROVIDER = {
  provide: MAT_DATEPICKER_SCROLL_STRATEGY,
  deps: [Overlay],
  useFactory: MAT_DATEPICKER_SCROLL_STRATEGY_PROVIDER_FACTORY,
};


/**
 * Component used as the content for the datepicker dialog and popup. We use this instead of using
 * MatCalendar directly as the content so we can control the initial focus. This also gives us a
 * place to put additional features of the popup that are not part of the calendar itself in the
 * future. (e.g. confirmation buttons).
 * @docs-private
 */
@Component({
  moduleId: module.id,
  selector: 'mat-datepicker-content',
  templateUrl: 'datepicker-content.html',
  styleUrls: ['datepicker-content.css'],
  host: {
    'class': 'mat-datepicker-content',
    '[class.mat-datepicker-content-touch]': 'datepicker.touchUi',
    '(keydown)': '_handleKeydown($event)',
  },
  exportAs: 'matDatepickerContent',
  encapsulation: ViewEncapsulation.None,
  preserveWhitespaces: false,
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class MatDatepickerContent<D> implements AfterContentInit {
  datepicker: MatDatepicker<D>;

  @ViewChild(MatCalendar) _calendar: MatCalendar<D>;

  ngAfterContentInit() {
    this._calendar._focusActiveCell();
  }

  /**
   * Handles keydown event on datepicker content.
   * @param event The event.
   */
  _handleKeydown(event: KeyboardEvent): void {
    if (event.keyCode === ESCAPE) {
      this.datepicker.close();
      event.preventDefault();
      event.stopPropagation();
    }
  }
}


// TODO(mmalerba): We use a component instead of a directive here so the user can use implicit
// template reference variables (e.g. #d vs #d="matDatepicker"). We can change this to a directive
// if angular adds support for `exportAs: '$implicit'` on directives.
/** Component responsible for managing the datepicker popup/dialog. */
@Component({
  moduleId: module.id,
  selector: 'mat-datepicker',
  template: '',
  exportAs: 'matDatepicker',
  changeDetection: ChangeDetectionStrategy.OnPush,
  encapsulation: ViewEncapsulation.None,
  preserveWhitespaces: false,
})
export class MatDatepicker<D> implements OnDestroy {
  /** The date to open the calendar to initially. */
  @Input()
  get startAt(): D | null {
    // If an explicit startAt is set we start there, otherwise we start at whatever the currently
    // selected value is.
    return this._startAt || (this._datepickerInput ? this._datepickerInput.value : null);
  }
  set startAt(date: D | null) {
    this._startAt = this._getValidDateOrNull(this._dateAdapter.deserialize(date));
  }
  private _startAt: D | null;

  /** The view that the calendar should start in. */
  @Input() startView: 'month' | 'year' = 'month';

  /**
   * Whether the calendar UI is in touch mode. In touch mode the calendar opens in a dialog rather
   * than a popup and elements have more padding to allow for bigger touch targets.
   */
  @Input()
  get touchUi(): boolean {
    return this._touchUi;
  }
  set touchUi(value: boolean) {
    this._touchUi = coerceBooleanProperty(value);
  }
  private _touchUi = false;

  /** Whether the datepicker pop-up should be disabled. */
  @Input()
  get disabled(): boolean {
    return this._disabled === undefined && this._datepickerInput ?
        this._datepickerInput.disabled : !!this._disabled;
  }
  set disabled(value: boolean) {
    const newValue = coerceBooleanProperty(value);

    if (newValue !== this._disabled) {
      this._disabled = newValue;
      this._disabledChange.next(newValue);
    }
  }
  private _disabled: boolean;

  /**
   * Emits new selected date when selected date changes.
   * @deprecated Switch to the `dateChange` and `dateInput` binding on the input element.
   */
  @Output() selectedChanged = new EventEmitter<D>();

  /** Classes to be passed to the date picker panel. Supports the same syntax as `ngClass`. */
  @Input() panelClass: string | string[];

  /** Emits when the datepicker has been opened. */
  @Output('opened') openedStream: EventEmitter<void> = new EventEmitter<void>();

  /** Emits when the datepicker has been closed. */
  @Output('closed') closedStream: EventEmitter<void> = new EventEmitter<void>();

  /** Whether the calendar is open. */
  @Input()
  get opened(): boolean { return this._opened; }
  set opened(shouldOpen: boolean) { shouldOpen ? this.open() : this.close(); }
  private _opened = false;

  /** The id for the datepicker calendar. */
  id = `mat-datepicker-${datepickerUid++}`;

  /** The currently selected date. */
  get _selected(): D | null { return this._validSelected; }
  set _selected(value: D | null) { this._validSelected = value; }
  private _validSelected: D | null = null;

  /** The minimum selectable date. */
  get _minDate(): D | null {
    return this._datepickerInput && this._datepickerInput.min;
  }

  /** The maximum selectable date. */
  get _maxDate(): D | null {
    return this._datepickerInput && this._datepickerInput.max;
  }

  get _dateFilter(): (date: D | null) => boolean {
    return this._datepickerInput && this._datepickerInput._dateFilter;
  }

  /** A reference to the overlay when the calendar is opened as a popup. */
  private _popupRef: OverlayRef;

  /** A reference to the dialog when the calendar is opened as a dialog. */
  private _dialogRef: MatDialogRef<any> | null;

  /** A portal containing the calendar for this datepicker. */
  private _calendarPortal: ComponentPortal<MatDatepickerContent<D>>;

  /** The element that was focused before the datepicker was opened. */
  private _focusedElementBeforeOpen: HTMLElement | null = null;

  private _inputSubscription = Subscription.EMPTY;

  /** The input element this datepicker is associated with. */
  _datepickerInput: MatDatepickerInput<D>;

  /** Emits when the datepicker is disabled. */
  _disabledChange = new Subject<boolean>();

  constructor(private _dialog: MatDialog,
              private _overlay: Overlay,
              private _ngZone: NgZone,
              private _viewContainerRef: ViewContainerRef,
              @Inject(MAT_DATEPICKER_SCROLL_STRATEGY) private _scrollStrategy,
              @Optional() private _dateAdapter: DateAdapter<D>,
              @Optional() private _dir: Directionality,
              @Optional() @Inject(DOCUMENT) private _document: any) {
    if (!this._dateAdapter) {
      throw createMissingDateImplError('DateAdapter');
    }
  }

  ngOnDestroy() {
    this.close();
    this._inputSubscription.unsubscribe();
    this._disabledChange.complete();

    if (this._popupRef) {
      this._popupRef.dispose();
    }
  }

  /** Selects the given date */
  _select(date: D): void {
    let oldValue = this._selected;
    this._selected = date;
    if (!this._dateAdapter.sameDate(oldValue, this._selected)) {
      this.selectedChanged.emit(date);
    }
  }

  /**
   * Register an input with this datepicker.
   * @param input The datepicker input to register with this datepicker.
   */
  _registerInput(input: MatDatepickerInput<D>): void {
    if (this._datepickerInput) {
      throw Error('A MatDatepicker can only be associated with a single input.');
    }
    this._datepickerInput = input;
    this._inputSubscription =
        this._datepickerInput._valueChange.subscribe((value: D | null) => this._selected = value);
  }

  /** Open the calendar. */
  open(): void {
    if (this._opened || this.disabled) {
      return;
    }
    if (!this._datepickerInput) {
      throw Error('Attempted to open an MatDatepicker with no associated input.');
    }
    if (this._document) {
      this._focusedElementBeforeOpen = this._document.activeElement;
    }

    this.touchUi ? this._openAsDialog() : this._openAsPopup();
    this._opened = true;
    this.openedStream.emit();
  }

  /** Close the calendar. */
  close(): void {
    if (!this._opened) {
      return;
    }
    if (this._popupRef && this._popupRef.hasAttached()) {
      this._popupRef.detach();
    }
    if (this._dialogRef) {
      this._dialogRef.close();
      this._dialogRef = null;
    }
    if (this._calendarPortal && this._calendarPortal.isAttached) {
      this._calendarPortal.detach();
    }
    if (this._focusedElementBeforeOpen &&
      typeof this._focusedElementBeforeOpen.focus === 'function') {

      this._focusedElementBeforeOpen.focus();
      this._focusedElementBeforeOpen = null;
    }

    this._opened = false;
    this.closedStream.emit();
  }

  /** Open the calendar as a dialog. */
  private _openAsDialog(): void {
    this._dialogRef = this._dialog.open(MatDatepickerContent, {
      direction: this._dir ? this._dir.value : 'ltr',
      viewContainerRef: this._viewContainerRef,
      panelClass: 'mat-datepicker-dialog',
    });
    this._dialogRef.afterClosed().subscribe(() => this.close());
    this._dialogRef.componentInstance.datepicker = this;
  }

  /** Open the calendar as a popup. */
  private _openAsPopup(): void {
    if (!this._calendarPortal) {
      this._calendarPortal = new ComponentPortal(MatDatepickerContent, this._viewContainerRef);
    }

    if (!this._popupRef) {
      this._createPopup();
    }

    if (!this._popupRef.hasAttached()) {
      let componentRef: ComponentRef<MatDatepickerContent<D>> =
          this._popupRef.attach(this._calendarPortal);
      componentRef.instance.datepicker = this;

      // Update the position once the calendar has rendered.
      this._ngZone.onStable.asObservable().pipe(take(1)).subscribe(() => {
        this._popupRef.updatePosition();
      });
    }

    this._popupRef.backdropClick().subscribe(() => this.close());
  }

  /** Create the popup. */
  private _createPopup(): void {
    const overlayConfig = new OverlayConfig({
      positionStrategy: this._createPopupPositionStrategy(),
      hasBackdrop: true,
      backdropClass: 'mat-overlay-transparent-backdrop',
      direction: this._dir ? this._dir.value : 'ltr',
      scrollStrategy: this._scrollStrategy(),
      panelClass: 'mat-datepicker-popup',
    });

    this._popupRef = this._overlay.create(overlayConfig);
  }

  /** Create the popup PositionStrategy. */
  private _createPopupPositionStrategy(): PositionStrategy {
    const fallbackOffset = this._datepickerInput._getPopupFallbackOffset();

    return this._overlay.position()
      .connectedTo(this._datepickerInput.getPopupConnectionElementRef(),
        {originX: 'start', originY: 'bottom'},
        {overlayX: 'start', overlayY: 'top'}
      )
      .withFallbackPosition(
        {originX: 'start', originY: 'top'},
        {overlayX: 'start', overlayY: 'bottom'},
        undefined,
        fallbackOffset
      )
      .withFallbackPosition(
        {originX: 'end', originY: 'bottom'},
        {overlayX: 'end', overlayY: 'top'}
      )
      .withFallbackPosition(
        {originX: 'end', originY: 'top'},
        {overlayX: 'end', overlayY: 'bottom'},
        undefined,
        fallbackOffset
      );
  }

  /**
   * @param obj The object to check.
   * @returns The given object if it is both a date instance and valid, otherwise null.
   */
  private _getValidDateOrNull(obj: any): D | null {
    return (this._dateAdapter.isDateInstance(obj) && this._dateAdapter.isValid(obj)) ? obj : null;
  }
}