/**
 * @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 {FocusMonitor, FocusOrigin, isFakeMousedownFromScreenReader} from '@angular/cdk/a11y';
import {Direction, Directionality} from '@angular/cdk/bidi';
import {LEFT_ARROW, RIGHT_ARROW} from '@angular/cdk/keycodes';
import {
  FlexibleConnectedPositionStrategy,
  HorizontalConnectionPos,
  Overlay,
  OverlayConfig,
  OverlayRef,
  VerticalConnectionPos,
  ScrollStrategy,
} from '@angular/cdk/overlay';
import {TemplatePortal} from '@angular/cdk/portal';
import {
  AfterContentInit,
  Directive,
  ElementRef,
  EventEmitter,
  Inject,
  InjectionToken,
  Input,
  OnDestroy,
  Optional,
  Output,
  Self,
  ViewContainerRef,
} from '@angular/core';
import {normalizePassiveListenerOptions} from '@angular/cdk/platform';
import {asapScheduler, merge, of as observableOf, Subscription} from 'rxjs';
import {delay, filter, take, takeUntil} from 'rxjs/operators';
import {MatMenu} from './menu';
import {throwMatMenuMissingError} from './menu-errors';
import {MatMenuItem} from './menu-item';
import {MatMenuPanel} from './menu-panel';
import {MenuPositionX, MenuPositionY} from './menu-positions';

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

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

/** @docs-private */
export const MAT_MENU_SCROLL_STRATEGY_FACTORY_PROVIDER = {
  provide: MAT_MENU_SCROLL_STRATEGY,
  deps: [Overlay],
  useFactory: MAT_MENU_SCROLL_STRATEGY_FACTORY,
};

/** Default top padding of the menu panel. */
export const MENU_PANEL_TOP_PADDING = 8;

/** Options for binding a passive event listener. */
const passiveEventListenerOptions = normalizePassiveListenerOptions({passive: true});

// TODO(andrewseguin): Remove the kebab versions in favor of camelCased attribute selectors

/**
 * This directive is intended to be used in conjunction with an mat-menu tag.  It is
 * responsible for toggling the display of the provided menu instance.
 */
@Directive({
  selector: `[mat-menu-trigger-for], [matMenuTriggerFor]`,
  host: {
    'class': 'mat-menu-trigger',
    'aria-haspopup': 'true',
    '[attr.aria-expanded]': 'menuOpen || null',
    '(mousedown)': '_handleMousedown($event)',
    '(keydown)': '_handleKeydown($event)',
    '(click)': '_handleClick($event)',
  },
  exportAs: 'matMenuTrigger'
})
export class MatMenuTrigger implements AfterContentInit, OnDestroy {
  private _portal: TemplatePortal;
  private _overlayRef: OverlayRef | null = null;
  private _menuOpen: boolean = false;
  private _closingActionsSubscription = Subscription.EMPTY;
  private _hoverSubscription = Subscription.EMPTY;
  private _menuCloseSubscription = Subscription.EMPTY;
  private _scrollStrategy: () => ScrollStrategy;

  /**
   * Handles touch start events on the trigger.
   * Needs to be an arrow function so we can easily use addEventListener and removeEventListener.
   */
  private _handleTouchStart = () => this._openedBy = 'touch';

  // Tracking input type is necessary so it's possible to only auto-focus
  // the first item of the list when the menu is opened via the keyboard
  _openedBy: 'mouse' | 'touch' | null = null;

  /**
   * @deprecated
   * @breaking-change 8.0.0
   */
  @Input('mat-menu-trigger-for')
  get _deprecatedMatMenuTriggerFor(): MatMenuPanel { return this.menu; }
  set _deprecatedMatMenuTriggerFor(v: MatMenuPanel) {
    this.menu = v;
  }

  /** References the menu instance that the trigger is associated with. */
  @Input('matMenuTriggerFor')
  get menu() { return this._menu; }
  set menu(menu: MatMenuPanel) {
    if (menu === this._menu) {
      return;
    }

    this._menu = menu;
    this._menuCloseSubscription.unsubscribe();

    if (menu) {
      this._menuCloseSubscription = menu.close.asObservable().subscribe(reason => {
        this._destroyMenu();

        // If a click closed the menu, we should close the entire chain of nested menus.
        if ((reason === 'click' || reason === 'tab') && this._parentMenu) {
          this._parentMenu.closed.emit(reason);
        }
      });
    }
  }
  private _menu: MatMenuPanel;

  /** Data to be passed along to any lazily-rendered content. */
  @Input('matMenuTriggerData') menuData: any;

  /**
   * Whether focus should be restored when the menu is closed.
   * Note that disabling this option can have accessibility implications
   * and it's up to you to manage focus, if you decide to turn it off.
   */
  @Input('matMenuTriggerRestoreFocus') restoreFocus: boolean = true;

  /** Event emitted when the associated menu is opened. */
  @Output() readonly menuOpened: EventEmitter<void> = new EventEmitter<void>();

  /**
   * Event emitted when the associated menu is opened.
   * @deprecated Switch to `menuOpened` instead
   * @breaking-change 8.0.0
   */
  // tslint:disable-next-line:no-output-on-prefix
  @Output() readonly onMenuOpen: EventEmitter<void> = this.menuOpened;

  /** Event emitted when the associated menu is closed. */
  @Output() readonly menuClosed: EventEmitter<void> = new EventEmitter<void>();

  /**
   * Event emitted when the associated menu is closed.
   * @deprecated Switch to `menuClosed` instead
   * @breaking-change 8.0.0
   */
  // tslint:disable-next-line:no-output-on-prefix
  @Output() readonly onMenuClose: EventEmitter<void> = this.menuClosed;

  constructor(private _overlay: Overlay,
              private _element: ElementRef<HTMLElement>,
              private _viewContainerRef: ViewContainerRef,
              @Inject(MAT_MENU_SCROLL_STRATEGY) scrollStrategy: any,
              @Optional() private _parentMenu: MatMenu,
              @Optional() @Self() private _menuItemInstance: MatMenuItem,
              @Optional() private _dir: Directionality,
              // TODO(crisbeto): make the _focusMonitor required when doing breaking changes.
              // @breaking-change 8.0.0
              private _focusMonitor?: FocusMonitor) {

    _element.nativeElement.addEventListener('touchstart', this._handleTouchStart,
        passiveEventListenerOptions);

    if (_menuItemInstance) {
      _menuItemInstance._triggersSubmenu = this.triggersSubmenu();
    }

    this._scrollStrategy = scrollStrategy;
  }

  ngAfterContentInit() {
    this._checkMenu();
    this._handleHover();
  }

  ngOnDestroy() {
    if (this._overlayRef) {
      this._overlayRef.dispose();
      this._overlayRef = null;
    }

    this._element.nativeElement.removeEventListener('touchstart', this._handleTouchStart,
        passiveEventListenerOptions);

    this._menuCloseSubscription.unsubscribe();
    this._closingActionsSubscription.unsubscribe();
    this._hoverSubscription.unsubscribe();
  }

  /** Whether the menu is open. */
  get menuOpen(): boolean {
    return this._menuOpen;
  }

  /** The text direction of the containing app. */
  get dir(): Direction {
    return this._dir && this._dir.value === 'rtl' ? 'rtl' : 'ltr';
  }

  /** Whether the menu triggers a sub-menu or a top-level one. */
  triggersSubmenu(): boolean {
    return !!(this._menuItemInstance && this._parentMenu);
  }

  /** Toggles the menu between the open and closed states. */
  toggleMenu(): void {
    return this._menuOpen ? this.closeMenu() : this.openMenu();
  }

  /** Opens the menu. */
  openMenu(): void {
    if (this._menuOpen) {
      return;
    }

    this._checkMenu();

    const overlayRef = this._createOverlay();
    const overlayConfig = overlayRef.getConfig();

    this._setPosition(overlayConfig.positionStrategy as FlexibleConnectedPositionStrategy);
    overlayConfig.hasBackdrop = this.menu.hasBackdrop == null ? !this.triggersSubmenu() :
        this.menu.hasBackdrop;
    overlayRef.attach(this._getPortal());

    if (this.menu.lazyContent) {
      this.menu.lazyContent.attach(this.menuData);
    }

    this._closingActionsSubscription = this._menuClosingActions().subscribe(() => this.closeMenu());
    this._initMenu();

    if (this.menu instanceof MatMenu) {
      this.menu._startAnimation();
    }
  }

  /** Closes the menu. */
  closeMenu(): void {
    this.menu.close.emit();
  }

  /**
   * Focuses the menu trigger.
   * @param origin Source of the menu trigger's focus.
   */
  focus(origin: FocusOrigin = 'program', options?: FocusOptions) {
    if (this._focusMonitor) {
      this._focusMonitor.focusVia(this._element, origin, options);
    } else {
      this._element.nativeElement.focus(options);
    }
  }

  /** Closes the menu and does the necessary cleanup. */
  private _destroyMenu() {
    if (!this._overlayRef || !this.menuOpen) {
      return;
    }

    const menu = this.menu;

    this._closingActionsSubscription.unsubscribe();
    this._overlayRef.detach();

    if (menu instanceof MatMenu) {
      menu._resetAnimation();

      if (menu.lazyContent) {
        // Wait for the exit animation to finish before detaching the content.
        menu._animationDone
          .pipe(
            filter(event => event.toState === 'void'),
            take(1),
            // Interrupt if the content got re-attached.
            takeUntil(menu.lazyContent._attached)
          )
          .subscribe({
            next: () => menu.lazyContent!.detach(),
            // No matter whether the content got re-attached, reset the menu.
            complete: () => this._setIsMenuOpen(false)
          });
      } else {
        this._setIsMenuOpen(false);
      }
    } else {
      this._setIsMenuOpen(false);

      if (menu.lazyContent) {
        menu.lazyContent.detach();
      }
    }

    this._restoreFocus();
  }

  /**
   * This method sets the menu state to open and focuses the first item if
   * the menu was opened via the keyboard.
   */
  private _initMenu(): void {
    this.menu.parentMenu = this.triggersSubmenu() ? this._parentMenu : undefined;
    this.menu.direction = this.dir;
    this._setMenuElevation();
    this._setIsMenuOpen(true);
    this.menu.focusFirstItem(this._openedBy || 'program');
  }

  /** Updates the menu elevation based on the amount of parent menus that it has. */
  private _setMenuElevation(): void {
    if (this.menu.setElevation) {
      let depth = 0;
      let parentMenu = this.menu.parentMenu;

      while (parentMenu) {
        depth++;
        parentMenu = parentMenu.parentMenu;
      }

      this.menu.setElevation(depth);
    }
  }

  /** Restores focus to the element that was focused before the menu was open. */
  private _restoreFocus() {
    // We should reset focus if the user is navigating using a keyboard or
    // if we have a top-level trigger which might cause focus to be lost
    // when clicking on the backdrop.
    if (this.restoreFocus) {
      if (!this._openedBy) {
        // Note that the focus style will show up both for `program` and
        // `keyboard` so we don't have to specify which one it is.
        this.focus();
      } else if (!this.triggersSubmenu()) {
        this.focus(this._openedBy);
      }
    }

    this._openedBy = null;
  }

  // set state rather than toggle to support triggers sharing a menu
  private _setIsMenuOpen(isOpen: boolean): void {
    this._menuOpen = isOpen;
    this._menuOpen ? this.menuOpened.emit() : this.menuClosed.emit();

    if (this.triggersSubmenu()) {
      this._menuItemInstance._highlighted = isOpen;
    }
  }

  /**
   * This method checks that a valid instance of MatMenu has been passed into
   * matMenuTriggerFor. If not, an exception is thrown.
   */
  private _checkMenu() {
    if (!this.menu) {
      throwMatMenuMissingError();
    }
  }

  /**
   * This method creates the overlay from the provided menu's template and saves its
   * OverlayRef so that it can be attached to the DOM when openMenu is called.
   */
  private _createOverlay(): OverlayRef {
    if (!this._overlayRef) {
      const config = this._getOverlayConfig();
      this._subscribeToPositions(config.positionStrategy as FlexibleConnectedPositionStrategy);
      this._overlayRef = this._overlay.create(config);

      // Consume the `keydownEvents` in order to prevent them from going to another overlay.
      // Ideally we'd also have our keyboard event logic in here, however doing so will
      // break anybody that may have implemented the `MatMenuPanel` themselves.
      this._overlayRef.keydownEvents().subscribe();
    }

    return this._overlayRef;
  }

  /**
   * This method builds the configuration object needed to create the overlay, the OverlayState.
   * @returns OverlayConfig
   */
  private _getOverlayConfig(): OverlayConfig {
    return new OverlayConfig({
      positionStrategy: this._overlay.position()
          .flexibleConnectedTo(this._element)
          .withLockedPosition()
          .withTransformOriginOn('.mat-menu-panel, .mat-mdc-menu-panel'),
      backdropClass: this.menu.backdropClass || 'cdk-overlay-transparent-backdrop',
      scrollStrategy: this._scrollStrategy(),
      direction: this._dir
    });
  }

  /**
   * Listens to changes in the position of the overlay and sets the correct classes
   * on the menu based on the new position. This ensures the animation origin is always
   * correct, even if a fallback position is used for the overlay.
   */
  private _subscribeToPositions(position: FlexibleConnectedPositionStrategy): void {
    if (this.menu.setPositionClasses) {
      position.positionChanges.subscribe(change => {
        const posX: MenuPositionX = change.connectionPair.overlayX === 'start' ? 'after' : 'before';
        const posY: MenuPositionY = change.connectionPair.overlayY === 'top' ? 'below' : 'above';

        this.menu.setPositionClasses!(posX, posY);
      });
    }
  }

  /**
   * Sets the appropriate positions on a position strategy
   * so the overlay connects with the trigger correctly.
   * @param positionStrategy Strategy whose position to update.
   */
  private _setPosition(positionStrategy: FlexibleConnectedPositionStrategy) {
    let [originX, originFallbackX]: HorizontalConnectionPos[] =
        this.menu.xPosition === 'before' ? ['end', 'start'] : ['start', 'end'];

    let [overlayY, overlayFallbackY]: VerticalConnectionPos[] =
        this.menu.yPosition === 'above' ? ['bottom', 'top'] : ['top', 'bottom'];

    let [originY, originFallbackY] = [overlayY, overlayFallbackY];
    let [overlayX, overlayFallbackX] = [originX, originFallbackX];
    let offsetY = 0;

    if (this.triggersSubmenu()) {
      // When the menu is a sub-menu, it should always align itself
      // to the edges of the trigger, instead of overlapping it.
      overlayFallbackX = originX = this.menu.xPosition === 'before' ? 'start' : 'end';
      originFallbackX = overlayX = originX === 'end' ? 'start' : 'end';
      offsetY = overlayY === 'bottom' ? MENU_PANEL_TOP_PADDING : -MENU_PANEL_TOP_PADDING;
    } else if (!this.menu.overlapTrigger) {
      originY = overlayY === 'top' ? 'bottom' : 'top';
      originFallbackY = overlayFallbackY === 'top' ? 'bottom' : 'top';
    }

    positionStrategy.withPositions([
      {originX, originY, overlayX, overlayY, offsetY},
      {originX: originFallbackX, originY, overlayX: overlayFallbackX, overlayY, offsetY},
      {
        originX,
        originY: originFallbackY,
        overlayX,
        overlayY: overlayFallbackY,
        offsetY: -offsetY
      },
      {
        originX: originFallbackX,
        originY: originFallbackY,
        overlayX: overlayFallbackX,
        overlayY: overlayFallbackY,
        offsetY: -offsetY
      }
    ]);
  }

  /** Returns a stream that emits whenever an action that should close the menu occurs. */
  private _menuClosingActions() {
    const backdrop = this._overlayRef!.backdropClick();
    const detachments = this._overlayRef!.detachments();
    const parentClose = this._parentMenu ? this._parentMenu.closed : observableOf();
    const hover = this._parentMenu ? this._parentMenu._hovered().pipe(
      filter(active => active !== this._menuItemInstance),
      filter(() => this._menuOpen)
    ) : observableOf();

    return merge(backdrop, parentClose, hover, detachments);
  }

  /** Handles mouse presses on the trigger. */
  _handleMousedown(event: MouseEvent): void {
    if (!isFakeMousedownFromScreenReader(event)) {
      // Since right or middle button clicks won't trigger the `click` event,
      // we shouldn't consider the menu as opened by mouse in those cases.
      this._openedBy = event.button === 0 ? 'mouse' : null;

      // Since clicking on the trigger won't close the menu if it opens a sub-menu,
      // we should prevent focus from moving onto it via click to avoid the
      // highlight from lingering on the menu item.
      if (this.triggersSubmenu()) {
        event.preventDefault();
      }
    }
  }

  /** Handles key presses on the trigger. */
  _handleKeydown(event: KeyboardEvent): void {
    const keyCode = event.keyCode;

    if (this.triggersSubmenu() && (
            (keyCode === RIGHT_ARROW && this.dir === 'ltr') ||
            (keyCode === LEFT_ARROW && this.dir === 'rtl'))) {
      this.openMenu();
    }
  }

  /** Handles click events on the trigger. */
  _handleClick(event: MouseEvent): void {
    if (this.triggersSubmenu()) {
      // Stop event propagation to avoid closing the parent menu.
      event.stopPropagation();
      this.openMenu();
    } else {
      this.toggleMenu();
    }
  }

  /** Handles the cases where the user hovers over the trigger. */
  private _handleHover() {
    // Subscribe to changes in the hovered item in order to toggle the panel.
    if (!this.triggersSubmenu()) {
      return;
    }

    this._hoverSubscription = this._parentMenu._hovered()
      // Since we might have multiple competing triggers for the same menu (e.g. a sub-menu
      // with different data and triggers), we have to delay it by a tick to ensure that
      // it won't be closed immediately after it is opened.
      .pipe(
        filter(active => active === this._menuItemInstance && !active.disabled),
        delay(0, asapScheduler)
      )
      .subscribe(() => {
        this._openedBy = 'mouse';

        // If the same menu is used between multiple triggers, it might still be animating
        // while the new trigger tries to re-open it. Wait for the animation to finish
        // before doing so. Also interrupt if the user moves to another item.
        if (this.menu instanceof MatMenu && this.menu._isAnimating) {
          // We need the `delay(0)` here in order to avoid
          // 'changed after checked' errors in some cases. See #12194.
          this.menu._animationDone
            .pipe(take(1), delay(0, asapScheduler), takeUntil(this._parentMenu._hovered()))
            .subscribe(() => this.openMenu());
        } else {
          this.openMenu();
        }
      });
  }

  /** Gets the portal that should be attached to the overlay. */
  private _getPortal(): TemplatePortal {
    // Note that we can avoid this check by keeping the portal on the menu panel.
    // While it would be cleaner, we'd have to introduce another required method on
    // `MatMenuPanel`, making it harder to consume.
    if (!this._portal || this._portal.templateRef !== this.menu.templateRef) {
      this._portal = new TemplatePortal(this.menu.templateRef, this._viewContainerRef);
    }

    return this._portal;
  }

}