/**
 * @license
 * FOURBURNER CONFIDENTIAL
 * Unpublished Copyright (C) 2021 FourBurner Technologies, Inc. All Rights Reserved.
 *
 * NOTICE: All information contained herein is, and remains the property of FOURBURNER TECHNOLOGIES,
 * INC. The intellectual and technical concepts contained herein are proprietary to FOURBURNER
 * TECHNOLOGIES, INC. and may be covered by U.S. and Foreign Patents, patents in process, and are
 * protected by trade secret or copyright law. Dissemination of this information or reproduction of
 * this material is strictly forbidden unless prior written permission is obtained from FOURBURNER
 * TECHNOLOGIES, INC. Access to the source code contained herein is hereby forbidden to anyone
 * except current FOURBURNER TECHNOLOGIES, INC. employees, managers or contractors who have executed
 * Confidentiality and Non-disclosure agreements explicitly covering such access.
 *
 * The copyright notice above does not evidence any actual or intended publication or disclosure of
 * this source code, which includes information that is confidential and/or proprietary, and is a
 * trade secret, of FOURBURNER TECHNOLOGIES, INC. ANY REPRODUCTION, MODIFICATION, DISTRIBUTION,
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 */

import {Directionality} from '@angular/cdk/bidi';
import {BooleanInput, coerceBooleanProperty} from '@angular/cdk/coercion';
import {DOWN_ARROW, ENTER, ESCAPE, TAB, UP_ARROW, hasModifierKey} from '@angular/cdk/keycodes';
import {
  FlexibleConnectedPositionStrategy,
  Overlay,
  OverlayConfig,
  OverlayRef,
  PositionStrategy,
  ScrollStrategy,
  ConnectedPosition,
} from '@angular/cdk/overlay';
import {_getEventTarget} from '@angular/cdk/platform';
import {TemplatePortal} from '@angular/cdk/portal';
import {ViewportRuler} from '@angular/cdk/scrolling';
import {DOCUMENT} from '@angular/common';
import {
  AfterViewInit,
  ChangeDetectorRef,
  Directive,
  ElementRef,
  forwardRef,
  Host,
  Inject,
  InjectionToken,
  Input,
  NgZone,
  OnDestroy,
  Optional,
  ViewContainerRef,
  OnChanges,
  SimpleChanges,
} from '@angular/core';
import {ControlValueAccessor, NG_VALUE_ACCESSOR} from '@angular/forms';
import {
  _countGroupLabelsBeforeOption,
  _getOptionScrollPosition,
  TWNDOption,
  TWNDOptionSelectionChange,
  ngDevMode,
} from '@twnd/ux/core';
import {TWND_FORM, TWNDForm} from '@twnd/ux/form';
import {defer, fromEvent, merge, Observable, of as observableOf, Subject, Subscription} from 'rxjs';
import {delay, filter, map, switchMap, take, tap} from 'rxjs/operators';

import {
  _TWNDAutocompleteBase,
  TWND_AUTOCOMPLETE_DEFAULT_OPTIONS,
  TWNDAutocompleteDefaultOptions,
} from './autocomplete';
import {_TWNDAutocompleteOriginBase} from './autocomplete.origin';

/** Injection token that determines the scroll handling while the autocomplete panel is open. */
export const TWND_AUTOCOMPLETE_SCROLL_STRATEGY = new InjectionToken<() => ScrollStrategy>(
  'twnd-autocomplete-scroll-strategy',
);

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

/** @docs-private */
export const TWND_AUTOCOMPLETE_SCROLL_STRATEGY_FACTORY_PROVIDER = {
  provide : TWND_AUTOCOMPLETE_SCROLL_STRATEGY,
  deps : [ Overlay ],
  useFactory : TWND_AUTOCOMPLETE_SCROLL_STRATEGY_FACTORY,
};

/**
 * Provider that allows the autocomplete to register as a ControlValueAccessor.
 * @docs-private
 */
export const TWND_AUTOCOMPLETE_VALUE_ACCESSOR: any = {
  provide : NG_VALUE_ACCESSOR,
  useExisting : forwardRef(() => TWNDAutocompleteTrigger),
  multi : true,
};

/**
 * Creates an error to be thrown when attempting to use an autocomplete trigger without a panel.
 * @docs-private
 */
export function getTWNDAutocompleteMissingPanelError(): Error
{
  return Error(
    'Attempting to open an undefined instance of `twnd-autocomplete`. ' +
      'Make sure that the id passed to the `twndAutocomplete` is correct and that ' +
      "you're attempting to open it after the ngAfterContentInit hook.",
  );
}

/** Base class with all of the `TWNDAutocompleteTrigger` functionality. */
@Directive()
export abstract class _TWNDAutocompleteTriggerBase implements ControlValueAccessor, AfterViewInit,
                                                              OnChanges, OnDestroy
{
  private _overlayRef: OverlayRef|null;
  private _portal: TemplatePortal;
  private _componentDestroyed = false;
  private _autocompleteDisabled = false;
  private _scrollStrategy: () => ScrollStrategy;

  /** Old value of the native input. Used to work around issues with the `input` event on IE. */
  private _previousValue: string|number|null;

  /** Strategy that is used to position the panel. */
  private _positionStrategy: FlexibleConnectedPositionStrategy;

  /** Whether or not the label state is being overridden. */
  private _manuallyFloatingLabel = false;

  /** The subscription for closing actions (some are bound to document). */
  private _closingActionsSubscription: Subscription;

  /** Subscription to viewport size changes. */
  private _viewportSubscription = Subscription.EMPTY;

  /**
   * Whether the autocomplete can open the next time it is focused. Used to prevent a focused,
   * closed autocomplete from being reopened if the user switches to another browser tab and then
   * comes back.
   */
  private _canOpenOnNextFocus = true;

  /** Stream of keyboard events that can close the panel. */
  private readonly _closeKeyEventStream = new Subject<void>();

  /**
   * Event handler for when the window is blurred. Needs to be an
   * arrow function in order to preserve the context.
   */
  private _windowBlurHandler = () => {
    // If the user blurred the window while the autocomplete is focused, it means that it'll be
    // refocused when they come back. In this case we want to skip the first focus event, if the
    // pane was closed, in order to avoid reopening it unintentionally.
    this._canOpenOnNextFocus = this._document.activeElement !== this._element.nativeElement ||
                               this.panelOpen;
  };

  /** `View -> model callback called when value changes` */
  _onChange: (value: any) => void = () => {
  };

  /** `View -> model callback called when autocomplete has been touched` */
  _onTouched = () => {
  };

  /** The autocomplete panel to be attached to this trigger. */
  @Input('twndAutocomplete') autocomplete: _TWNDAutocompleteBase;

  /**
   * Position of the autocomplete panel relative to the trigger element. A position of `auto`
   * will render the panel underneath the trigger if there is enough space for it to fit in
   * the viewport, otherwise the panel will be shown above it. If the position is set to
   * `above` or `below`, the panel will always be shown above or below the trigger. no twndter
   * whether it fits completely in the viewport.
   */
  @Input('twndAutocompletePosition') position: 'auto'|'above'|'below' = 'auto';

  /**
   * Reference relative to which to position the autocomplete panel.
   * Defaults to the autocomplete trigger element.
   */
  @Input('twndAutocompleteConnectedTo') connectedTo: _TWNDAutocompleteOriginBase;

  /**
   * `autocomplete` attribute to be set on the input element.
   * @docs-private
   */
  @Input('autocomplete') autocompleteAttribute: string = 'off';

  /**
   * Whether the autocomplete is disabled. When disabled, the element will
   * act as a regular input and the user won't be able to open the panel.
   */
  @Input('twndAutocompleteDisabled') get autocompleteDisabled(): boolean
  {
    return this._autocompleteDisabled;
  }
  set autocompleteDisabled(value: boolean)
  {
    this._autocompleteDisabled = coerceBooleanProperty(value);
  }

  constructor(
    private _element: ElementRef<HTMLInputElement>,
    private _overlay: Overlay,
    private _viewContainerRef: ViewContainerRef,
    private _zone: NgZone,
    private _changeDetectorRef: ChangeDetectorRef,
    @Inject(TWND_AUTOCOMPLETE_SCROLL_STRATEGY) scrollStrategy: any,
    @Optional() private _dir: Directionality,
    @Optional() @Inject(TWND_FORM) @Host() private _formField: TWNDForm,
    @Optional() @Inject(DOCUMENT) private _document: any,
    private _viewportRuler: ViewportRuler,
    @Optional() @Inject(TWND_AUTOCOMPLETE_DEFAULT_OPTIONS) private _defaults?:
      TWNDAutocompleteDefaultOptions,
  )
  {
    this._scrollStrategy = scrollStrategy;
  }

  /** Class to apply to the panel when it's above the input. */
  protected abstract _aboveClass: string;

  ngAfterViewInit()
  {
    const window = this._getWindow();

    if (typeof window !== 'undefined') {
      this._zone.runOutsideAngular(() => window.addEventListener('blur', this._windowBlurHandler));
    }
  }

  ngOnChanges(changes: SimpleChanges)
  {
    if (changes['position'] && this._positionStrategy) {
      this._setStrategyPositions(this._positionStrategy);

      if (this.panelOpen) {
        this._overlayRef!.updatePosition();
      }
    }
  }

  ngOnDestroy()
  {
    const window = this._getWindow();

    if (typeof window !== 'undefined') {
      window.removeEventListener('blur', this._windowBlurHandler);
    }

    this._viewportSubscription.unsubscribe();
    this._componentDestroyed = true;
    this._destroyPanel();
    this._closeKeyEventStream.complete();
  }

  /** Whether or not the autocomplete panel is open. */
  get panelOpen(): boolean
  {
    return this._overlayAttached && this.autocomplete.showPanel;
  }
  private _overlayAttached: boolean = false;

  /** Opens the autocomplete suggestion panel. */
  openPanel(): void
  {
    this._attachOverlay();
    this._floatLabel();
  }

  /** Closes the autocomplete suggestion panel. */
  closePanel(): void
  {
    this._resetLabel();

    if (!this._overlayAttached) {
      return;
    }

    if (this.panelOpen) {
      // Only emit if the panel was visible.
      this.autocomplete.closed.emit();
    }

    this.autocomplete._isOpen = this._overlayAttached = false;

    if (this._overlayRef && this._overlayRef.hasAttached()) {
      this._overlayRef.detach();
      this._closingActionsSubscription.unsubscribe();
    }

    // Note that in some cases this can end up being called after the component is destroyed.
    // Add a check to ensure that we don't try to run change detection on a destroyed view.
    if (!this._componentDestroyed) {
      // We need to trigger change detection manually, because
      // `fromEvent` doesn't seem to do it at the proper time.
      // This ensures that the label is reset when the
      // user clicks outside.
      this._changeDetectorRef.detectChanges();
    }
  }

  /**
   * Updates the position of the autocomplete suggestion panel to ensure that it fits all options
   * within the viewport.
   */
  updatePosition(): void
  {
    if (this._overlayAttached) {
      this._overlayRef!.updatePosition();
    }
  }

  /**
   * A stream of actions that should close the autocomplete panel, including
   * when an option is selected, on blur, and when TAB is pressed.
   */
  get panelClosingActions(): Observable<TWNDOptionSelectionChange|null>
  {
    return merge(
             this.optionSelections,
             this.autocomplete._keyManager.tabOut.pipe(filter(() => this._overlayAttached)),
             this._closeKeyEventStream,
             this._getOutsideClickStream(),
             this._overlayRef ?
               this._overlayRef.detachments().pipe(filter(() => this._overlayAttached)) :
               observableOf(),
             )
      .pipe(
        // Normalize the output so we return a consistent type.
        map(event => (event instanceof TWNDOptionSelectionChange ? event : null)),
      );
  }

  /** Stream of autocomplete option selections. */
  readonly optionSelections: Observable<TWNDOptionSelectionChange> =
    defer(() => {
      if (this.autocomplete && this.autocomplete.options) {
        return merge(...this.autocomplete.options.map(option => option.onSelectionChange));
      }

      // If there are any subscribers before `ngAfterViewInit`, the `autocomplete` will be
      // undefined. Return a stream that we'll replace with the real one once everything is in
      // place.
      return this._zone.onStable.pipe(
        take(1),
        switchMap(() => this.optionSelections),
      );
    }) as Observable<TWNDOptionSelectionChange>;

  /** The currently active option, coerced to TWNDOption type. */
  get activeOption(): TWNDOption|null
  {
    if (this.autocomplete && this.autocomplete._keyManager) {
      return this.autocomplete._keyManager.activeItem;
    }

    return null;
  }

  /** Stream of clicks outside of the autocomplete panel. */
  private _getOutsideClickStream(): Observable<any>
  {
    return merge(
             fromEvent(this._document, 'click') as Observable<MouseEvent>,
             fromEvent(this._document, 'auxclick') as Observable<MouseEvent>,
             fromEvent(this._document, 'touchend') as Observable<TouchEvent>,
             )
      .pipe(
        filter(event => {
          // If we're in the Shadow DOM, the event target will be the shadow root, so we have to
          // fall back to check the first element in the path of the click event.
          const clickTarget = _getEventTarget<HTMLElement>(event)!;
          const formField = this._formField ? this._formField._elementRef.nativeElement : null;
          const customOrigin = this.connectedTo ? this.connectedTo.elementRef.nativeElement : null;

          return (this._overlayAttached && clickTarget !== this._element.nativeElement &&
                  (!formField || !formField.contains(clickTarget)) &&
                  (!customOrigin || !customOrigin.contains(clickTarget)) && !!this._overlayRef &&
                  !this._overlayRef.overlayElement.contains(clickTarget));
        }),
      );
  }

  // Implemented as part of ControlValueAccessor.
  writeValue(value: any): void
  {
    Promise.resolve(null).then(() => this._setTriggerValue(value));
  }

  // Implemented as part of ControlValueAccessor.
  registerOnChange(fn: (value: any) => {
                   }): void
  {
    this._onChange = fn;
  }

  // Implemented as part of ControlValueAccessor.
  registerOnTouched(fn: () => {
                    })
  {
    this._onTouched = fn;
  }

  // Implemented as part of ControlValueAccessor.
  setDisabledState(isDisabled: boolean)
  {
    this._element.nativeElement.disabled = isDisabled;
  }

  _handleKeydown(event: KeyboardEvent): void
  {
    const keyCode = event.keyCode;

    // Prevent the default action on all escape key presses. This is here primarily to bring IE
    // in line with other browsers. By default, pressing escape on IE will cause it to revert
    // the input value to the one that it had on focus, however it won't dispatch any events
    // which means that the model value will be out of sync with the view.
    if (keyCode === ESCAPE && !hasModifierKey(event)) {
      event.preventDefault();
    }

    if (this.activeOption && keyCode === ENTER && this.panelOpen) {
      this.activeOption._selectViaInteraction();
      this._resetActiveItem();
      event.preventDefault();
    } else if (this.autocomplete) {
      const prevActiveItem = this.autocomplete._keyManager.activeItem;
      const isArrowKey = keyCode === UP_ARROW || keyCode === DOWN_ARROW;

      if (this.panelOpen || keyCode === TAB) {
        this.autocomplete._keyManager.onKeydown(event);
      } else if (isArrowKey && this._canOpen()) {
        this.openPanel();
      }

      if (isArrowKey || this.autocomplete._keyManager.activeItem !== prevActiveItem) {
        this._scrollToOption(this.autocomplete._keyManager.activeItemIndex || 0);
      }
    }
  }

  _handleInput(event: KeyboardEvent): void
  {
    let target = event.target as HTMLInputElement;
    let value: number|string|null = target.value;

    // Based on `NumberValueAccessor` from forms.
    if (target.type === 'number') {
      value = value == '' ? null : parseFloat(value);
    }

    // If the input has a placeholder, IE will fire the `input` event on page load,
    // focus and blur, in addition to when the user actually changed the value. To
    // filter out all of the extra events, we save the value on focus and between
    // `input` events, and we check whether it changed.
    // See: https://connect.microsoft.com/IE/feedback/details/885747/
    if (this._previousValue !== value) {
      this._previousValue = value;
      this._onChange(value);

      if (this._canOpen() && this._document.activeElement === event.target) {
        this.openPanel();
      }
    }
  }

  _handleFocus(): void
  {
    if (!this._canOpenOnNextFocus) {
      this._canOpenOnNextFocus = true;
    } else if (this._canOpen()) {
      this._previousValue = this._element.nativeElement.value;
      this._attachOverlay();
      this._floatLabel(true);
    }
  }

  /**
   * In "auto" mode, the label will animate down as soon as focus is lost.
   * This causes the value to jump when selecting an option with the mouse.
   * This method manually floats the label until the panel can be closed.
   * @param shouldAnimate Whether the label should be animated when it is floated.
   */
  private _floatLabel(shouldAnimate = false): void
  {
    if (this._formField && this._formField.floatLabel === 'auto') {
      if (shouldAnimate) {
        this._formField._animateAndLockLabel();
      } else {
        this._formField.floatLabel = 'always';
      }

      this._manuallyFloatingLabel = true;
    }
  }

  /** If the label has been manually elevated, return it to its normal state. */
  private _resetLabel(): void
  {
    if (this._manuallyFloatingLabel) {
      this._formField.floatLabel = 'auto';
      this._manuallyFloatingLabel = false;
    }
  }

  /**
   * This method listens to a stream of panel closing actions and resets the
   * stream every time the option list changes.
   */
  private _subscribeToClosingActions(): Subscription
  {
    const firstStable = this._zone.onStable.pipe(take(1));
    const optionChanges = this.autocomplete.options.changes.pipe(
      tap(() => this._positionStrategy.reapplyLastPosition()),
      // Defer emitting to the stream until the next tick, because changing
      // bindings in here will cause "changed after checked" errors.
      delay(0),
    );

    // When the zone is stable initially, and when the option list changes...
    return (merge(firstStable, optionChanges)
              .pipe(
                // create a new stream of panelClosingActions, replacing any previous streams
                // that were created, and flatten it so our stream only emits closing events...
                switchMap(() => {
                  const wasOpen = this.panelOpen;
                  this._resetActiveItem();
                  this.autocomplete._setVisibility();

                  if (this.panelOpen) {
                    this._overlayRef!.updatePosition();

                    // If the `panelOpen` state changed, we need to make sure to emit the `opened`
                    // event, because we may not have emitted it when the panel was attached. This
                    // can happen if the users opens the panel and there are no options, but the
                    // options come in slightly later or as a result of the value changing.
                    if (wasOpen !== this.panelOpen) {
                      this.autocomplete.opened.emit();
                    }
                  }

                  return this.panelClosingActions;
                }),
                // when the first closing event occurs...
                take(1),
                )
              // set the value, close the panel, and complete.
              .subscribe(event => this._setValueAndClose(event)));
  }

  /** Destroys the autocomplete suggestion panel. */
  private _destroyPanel(): void
  {
    if (this._overlayRef) {
      this.closePanel();
      this._overlayRef.dispose();
      this._overlayRef = null;
    }
  }

  private _setTriggerValue(value: any): void
  {
    const toDisplay = this.autocomplete && this.autocomplete.displayWith ?
                        this.autocomplete.displayWith(value) :
                        value;

    // Simply falling back to an empty string if the display value is falsy does not work properly.
    // The display value can also be the number zero and shouldn't fall back to an empty string.
    const inputValue = toDisplay != null ? toDisplay : '';

    // If it's used within a `TWNDFormField`, we should set it through the property so it can go
    // through change detection.
    if (this._formField) {
      this._formField._control.value = inputValue;
    } else {
      this._element.nativeElement.value = inputValue;
    }

    this._previousValue = inputValue;
  }

  /**
   * This method closes the panel, and if a value is specified, also sets the associated
   * control to that value. It will also mark the control as dirty if this interaction
   * stemmed from the user.
   */
  private _setValueAndClose(event: TWNDOptionSelectionChange|null): void
  {
    if (event && event.source) {
      this._clearPreviousSelectedOption(event.source);
      this._setTriggerValue(event.source.value);
      this._onChange(event.source.value);
      this._element.nativeElement.focus();
      this.autocomplete._emitSelectEvent(event.source);
    }

    this.closePanel();
  }

  /**
   * Clear any previous selected option and emit a selection change event for this option
   */
  private _clearPreviousSelectedOption(skip: TWNDOption)
  {
    this.autocomplete.options.forEach(option => {
      if (option !== skip && option.selected) {
        option.deselect();
      }
    });
  }

  private _attachOverlay(): void
  {
    if (!this.autocomplete && (typeof ngDevMode === 'undefined' || ngDevMode)) {
      throw getTWNDAutocompleteMissingPanelError();
    }

    let overlayRef = this._overlayRef;

    if (!overlayRef) {
      this._portal = new TemplatePortal(this.autocomplete.template, this._viewContainerRef, {
        id : this._formField?.getLabelId(),
      });
      overlayRef = this._overlay.create(this._getOverlayConfig());
      this._overlayRef = overlayRef;

      // Use the `keydownEvents` in order to take advantage of
      // the overlay event targeting provided by the CDK overlay.
      overlayRef.keydownEvents().subscribe(event => {
        // Close when pressing ESCAPE or ALT + UP_ARROW, based on the a11y guidelines.
        // See: https://www.w3.org/TR/wai-aria-practices-1.1/#textbox-keyboard-interaction
        if ((event.keyCode === ESCAPE && !hasModifierKey(event)) ||
            (event.keyCode === UP_ARROW && hasModifierKey(event, 'altKey'))) {
          this._closeKeyEventStream.next();
          this._resetActiveItem();

          // We need to stop propagation, otherwise the event will eventually
          // reach the input itself and cause the overlay to be reopened.
          event.stopPropagation();
          event.preventDefault();
        }
      });

      this._viewportSubscription = this._viewportRuler.change().subscribe(() => {
        if (this.panelOpen && overlayRef) {
          overlayRef.updateSize({width : this._getPanelWidth()});
        }
      });
    } else {
      // Update the trigger, panel width and direction, in case anything has changed.
      this._positionStrategy.setOrigin(this._getConnectedElement());
      overlayRef.updateSize({width : this._getPanelWidth()});
    }

    if (overlayRef && !overlayRef.hasAttached()) {
      overlayRef.attach(this._portal);
      this._closingActionsSubscription = this._subscribeToClosingActions();
    }

    const wasOpen = this.panelOpen;

    this.autocomplete._setVisibility();
    this.autocomplete._isOpen = this._overlayAttached = true;

    // We need to do an extra `panelOpen` check in here, because the
    // autocomplete won't be shown if there are no options.
    if (this.panelOpen && wasOpen !== this.panelOpen) {
      this.autocomplete.opened.emit();
    }
  }

  private _getOverlayConfig(): OverlayConfig
  {
    return new OverlayConfig({
      positionStrategy : this._getOverlayPosition(),
      scrollStrategy : this._scrollStrategy(),
      width : this._getPanelWidth(),
      direction : this._dir,
      panelClass : this._defaults?.overlayPanelClass,
    });
  }

  private _getOverlayPosition(): PositionStrategy
  {
    const strategy = this._overlay.position()
                       .flexibleConnectedTo(this._getConnectedElement())
                       .withFlexibleDimensions(false)
                       .withPush(false);

    this._setStrategyPositions(strategy);
    this._positionStrategy = strategy;
    return strategy;
  }

  /** Sets the positions on a position strategy based on the directive's input state. */
  private _setStrategyPositions(positionStrategy: FlexibleConnectedPositionStrategy)
  {
    // Note that we provide horizontal fallback positions, even though by default the dropdown
    // width matches the input, because consumers can override the width. See #18854.
    const belowPositions: ConnectedPosition[] = [
      {originX : 'start', originY : 'bottom', overlayX : 'start', overlayY : 'top'},
      {originX : 'end', originY : 'bottom', overlayX : 'end', overlayY : 'top'},
    ];

    // The overlay edge connected to the trigger should have squared corners, while
    // the opposite end has rounded corners. We apply a CSS class to swap the
    // border-radius based on the overlay position.
    const panelClass = this._aboveClass;
    const abovePositions: ConnectedPosition[] = [
      {originX : 'start', originY : 'top', overlayX : 'start', overlayY : 'bottom', panelClass},
      {originX : 'end', originY : 'top', overlayX : 'end', overlayY : 'bottom', panelClass},
    ];

    let positions: ConnectedPosition[];

    if (this.position === 'above') {
      positions = abovePositions;
    } else if (this.position === 'below') {
      positions = belowPositions;
    } else {
      positions = [...belowPositions, ...abovePositions ];
    }

    positionStrategy.withPositions(positions);
  }

  private _getConnectedElement(): ElementRef<HTMLElement>
  {
    if (this.connectedTo) {
      return this.connectedTo.elementRef;
    }

    return this._formField ? this._formField.getConnectedOverlayOrigin() : this._element;
  }

  private _getPanelWidth(): number|string
  {
    return this.autocomplete.panelWidth || this._getHostWidth();
  }

  /** Returns the width of the input element, so the panel width can match it. */
  private _getHostWidth(): number
  {
    return this._getConnectedElement().nativeElement.getBoundingClientRect().width;
  }

  /**
   * Resets the active item to -1 so arrow events will activate the
   * correct options, or to 0 if the consumer opted into it.
   */
  private _resetActiveItem(): void
  {
    const autocomplete = this.autocomplete;

    if (autocomplete.autoActiveFirstOption) {
      // Note that we go through `setFirstItemActive`, rather than `setActiveItem(0)`, because
      // the former will find the next enabled option, if the first one is disabled.
      autocomplete._keyManager.setFirstItemActive();
    } else {
      autocomplete._keyManager.setActiveItem(-1);
    }
  }

  /** Determines whether the panel can be opened. */
  private _canOpen(): boolean
  {
    const element = this._element.nativeElement;
    return !element.readOnly && !element.disabled && !this._autocompleteDisabled;
  }

  /** Use defaultView of injected document if available or fallback to global window reference */
  private _getWindow(): Window
  {
    return this._document?.defaultView || window;
  }

  /** Scrolls to a particular option in the list. */
  private _scrollToOption(index: number): void
  {
    // Given that we are not actually focusing active options, we must manually adjust scroll
    // to reveal options below the fold. First, we find the offset of the option from the top
    // of the panel. If that offset is below the fold, the new scrollTop will be the offset -
    // the panel height + the option height, so the active option will be just visible at the
    // bottom of the panel. If that offset is above the top of the visible panel, the new scrollTop
    // will become the offset. If that offset is visible within the panel already, the scrollTop is
    // not adjusted.
    const autocomplete = this.autocomplete;
    const labelCount = _countGroupLabelsBeforeOption(
      index,
      autocomplete.options,
      autocomplete.optionGroups,
    );

    if (index === 0 && labelCount === 1) {
      // If we've got one group label before the option and we're at the top option,
      // scroll the list to the top. This is better UX than scrolling the list to the
      // top of the option, because it allows the user to read the top group's label.
      autocomplete._setScrollTop(0);
    } else if (autocomplete.panel) {
      const option = autocomplete.options.toArray()[index];

      if (option) {
        const element = option._getHostElement();
        const newScrollPosition = _getOptionScrollPosition(
          element.offsetTop,
          element.offsetHeight,
          autocomplete._getScrollTop(),
          autocomplete.panel.nativeElement.offsetHeight,
        );

        autocomplete._setScrollTop(newScrollPosition);
      }
    }
  }

  static ngAcceptInputType_autocompleteDisabled: BooleanInput;
}

@Directive({
  selector : `input[twndAutocomplete], textarea[twndAutocomplete]`,
  host : {
          'class' : 'twnd-autocomplete-trigger',
          '[attr.autocomplete]' : 'autocompleteAttribute',
          '[attr.role]' : 'autocompleteDisabled ? null : "combobox"',
          '[attr.aria-autocomplete]' : 'autocompleteDisabled ? null : "list"',
          '[attr.aria-activedescendant]' : '(panelOpen && activeOption) ? activeOption.id : null',
          '[attr.aria-expanded]' : 'autocompleteDisabled ? null : panelOpen.toString()',
          '[attr.aria-owns]' : '(autocompleteDisabled || !panelOpen) ? null : autocomplete?.id',
          '[attr.aria-haspopup]' : '!autocompleteDisabled',
          // Note: we use `focusin`, as opposed to `focus`, in order to open the panel
    // a little earlier. This avoids issues where IE delays the focusing of the input.
    '(focusin)' : '_handleFocus()',
          '(blur)' : '_onTouched()',
          '(input)' : '_handleInput($event)',
          '(keydown)' : '_handleKeydown($event)',
          },
  exportAs : 'twndAutocompleteTrigger',
  providers : [ TWND_AUTOCOMPLETE_VALUE_ACCESSOR ],
})
export class TWNDAutocompleteTrigger extends _TWNDAutocompleteTriggerBase
{
  protected _aboveClass = 'twnd-autocomplete-panel-above';
}