ionic-framework/core/src/components/item-sliding/item-sliding.tsx

import type { ComponentInterface, EventEmitter } from '@stencil/core';
import { Component, Element, Event, Host, Method, Prop, State, Watch, h } from '@stencil/core';
import { findClosestIonContent, disableContentScrollY, resetContentScrollY } from '@utils/content';
import { isEndSide } from '@utils/helpers';
import { printIonWarning } from '@utils/logging';
import { watchForOptions } from '@utils/watch-options';

import { getIonMode } from '../../global/ionic-global';
import type { Gesture, GestureDetail } from '../../interface';
import type { Side } from '../menu/menu-interface';

const SWIPE_MARGIN = 30;
const ELASTIC_FACTOR = 0.55;

const enum ItemSide {
  None = 0,
  Start = 1 << 0,
  End = 1 << 1,
  Both = Start | End,
}

const enum SlidingState {
  Disabled = 1 << 1,
  Enabled = 1 << 2,
  End = 1 << 3,
  Start = 1 << 4,

  SwipeEnd = 1 << 5,
  SwipeStart = 1 << 6,
}

let openSlidingItem: HTMLIonItemSlidingElement | undefined;

@Component({
  tag: 'ion-item-sliding',
  styleUrl: 'item-sliding.scss',
})
export class ItemSliding implements ComponentInterface {
  private item: HTMLIonItemElement | null = null;
  private openAmount = 0;
  private initialOpenAmount = 0;
  private optsWidthRightSide = 0;
  private optsWidthLeftSide = 0;
  private sides = ItemSide.None;
  private tmr?: ReturnType<typeof setTimeout>;
  private leftOptions?: HTMLIonItemOptionsElement;
  private rightOptions?: HTMLIonItemOptionsElement;
  private optsDirty = true;
  private gesture?: Gesture;
  private contentEl: HTMLElement | null = null;
  private initialContentScrollY = true;
  private mutationObserver?: MutationObserver;

  @Element() el!: HTMLIonItemSlidingElement;

  @State() state: SlidingState = SlidingState.Disabled;

  /**
   * If `true`, the user cannot interact with the sliding item.
   */
  @Prop() disabled = false;
  @Watch('disabled')
  disabledChanged() {
    if (this.gesture) {
      this.gesture.enable(!this.disabled);
    }
  }

  /**
   * Emitted when the sliding position changes.
   */
  @Event() ionDrag!: EventEmitter;

  async connectedCallback() {
    const { el } = this;

    this.item = el.querySelector('ion-item');
    this.contentEl = findClosestIonContent(el);

    /**
     * The MutationObserver needs to be added before we
     * call updateOptions below otherwise we may miss
     * ion-item-option elements that are added to the DOM
     * while updateOptions is running and before the MutationObserver
     * has been initialized.
     */
    this.mutationObserver = watchForOptions<HTMLIonItemOptionElement>(el, 'ion-item-option', async () => {
      await this.updateOptions();
    });

    await this.updateOptions();

    this.gesture = (await import('../../utils/gesture')).createGesture({
      el,
      gestureName: 'item-swipe',
      gesturePriority: 100,
      threshold: 5,
      canStart: (ev) => this.canStart(ev),
      onStart: () => this.onStart(),
      onMove: (ev) => this.onMove(ev),
      onEnd: (ev) => this.onEnd(ev),
    });
    this.disabledChanged();
  }

  disconnectedCallback() {
    if (this.gesture) {
      this.gesture.destroy();
      this.gesture = undefined;
    }

    this.item = null;
    this.leftOptions = this.rightOptions = undefined;

    if (openSlidingItem === this.el) {
      openSlidingItem = undefined;
    }

    if (this.mutationObserver) {
      this.mutationObserver.disconnect();
      this.mutationObserver = undefined;
    }
  }

  /**
   * Get the amount the item is open in pixels.
   */
  @Method()
  getOpenAmount(): Promise<number> {
    return Promise.resolve(this.openAmount);
  }

  /**
   * Get the ratio of the open amount of the item compared to the width of the options.
   * If the number returned is positive, then the options on the right side are open.
   * If the number returned is negative, then the options on the left side are open.
   * If the absolute value of the number is greater than 1, the item is open more than
   * the width of the options.
   */
  @Method()
  getSlidingRatio(): Promise<number> {
    return Promise.resolve(this.getSlidingRatioSync());
  }

  /**
   * Open the sliding item.
   *
   * @param side The side of the options to open. If a side is not provided, it will open the first set of options it finds within the item.
   */
  @Method()
  async open(side: Side | undefined) {
    /**
     * It is possible for the item to be added to the DOM
     * after the item-sliding component was created. As a result,
     * if this.item is null, then we should attempt to
     * query for the ion-item again.
     * However, if the item is already defined then
     * we do not query for it again.
     */
    const item = (this.item = this.item ?? this.el.querySelector('ion-item'));
    if (item === null) {
      return;
    }

    const optionsToOpen = this.getOptions(side);
    if (!optionsToOpen) {
      return;
    }

    /**
     * If side is not set, we need to infer the side
     * so we know which direction to move the options
     */
    if (side === undefined) {
      side = optionsToOpen === this.leftOptions ? 'start' : 'end';
    }

    // In RTL we want to switch the sides
    side = isEndSide(side) ? 'end' : 'start';

    const isStartOpen = this.openAmount < 0;
    const isEndOpen = this.openAmount > 0;

    /**
     * If a side is open and a user tries to
     * re-open the same side, we should not do anything
     */
    if (isStartOpen && optionsToOpen === this.leftOptions) {
      return;
    }
    if (isEndOpen && optionsToOpen === this.rightOptions) {
      return;
    }

    this.closeOpened();

    this.state = SlidingState.Enabled;

    requestAnimationFrame(() => {
      this.calculateOptsWidth();

      const width = side === 'end' ? this.optsWidthRightSide : -this.optsWidthLeftSide;
      openSlidingItem = this.el;

      this.setOpenAmount(width, false);
      this.state = side === 'end' ? SlidingState.End : SlidingState.Start;
    });
  }

  /**
   * Close the sliding item. Items can also be closed from the [List](./list).
   */
  @Method()
  async close() {
    this.setOpenAmount(0, true);
  }

  /**
   * Close all of the sliding items in the list. Items can also be closed from the [List](./list).
   */
  @Method()
  async closeOpened(): Promise<boolean> {
    if (openSlidingItem !== undefined) {
      openSlidingItem.close();
      openSlidingItem = undefined;
      return true;
    }
    return false;
  }

  /**
   * Given an optional side, return the ion-item-options element.
   *
   * @param side This side of the options to get. If a side is not provided it will
   * return the first one available.
   */
  private getOptions(side?: string): HTMLIonItemOptionsElement | undefined {
    if (side === undefined) {
      return this.leftOptions || this.rightOptions;
    } else if (side === 'start') {
      return this.leftOptions;
    } else {
      return this.rightOptions;
    }
  }

  private async updateOptions() {
    const options = this.el.querySelectorAll('ion-item-options');

    let sides = 0;

    // Reset left and right options in case they were removed
    this.leftOptions = this.rightOptions = undefined;

    for (let i = 0; i < options.length; i++) {
      const item = options.item(i);

      /**
       * We cannot use the componentOnReady helper
       * util here since we need to wait for all of these items
       * to be ready before we set `this.sides` and `this.optsDirty`.
       */
      // eslint-disable-next-line custom-rules/no-component-on-ready-method
      const option = (item as any).componentOnReady !== undefined ? await item.componentOnReady() : item;

      const side = isEndSide(option.side) ? 'end' : 'start';

      if (side === 'start') {
        this.leftOptions = option;
        sides |= ItemSide.Start;
      } else {
        this.rightOptions = option;
        sides |= ItemSide.End;
      }
    }
    this.optsDirty = true;
    this.sides = sides;
  }

  private canStart(gesture: GestureDetail): boolean {
    /**
     * If very close to start of the screen
     * do not open left side so swipe to go
     * back will still work.
     */
    const rtl = document.dir === 'rtl';
    const atEdge = rtl ? window.innerWidth - gesture.startX < 15 : gesture.startX < 15;
    if (atEdge) {
      return false;
    }

    const selected = openSlidingItem;
    if (selected && selected !== this.el) {
      this.closeOpened();
    }

    return !!(this.rightOptions || this.leftOptions);
  }

  private onStart() {
    /**
     * We need to query for the ion-item
     * every time the gesture starts. Developers
     * may toggle ion-item elements via *ngIf.
     */
    this.item = this.el.querySelector('ion-item');

    const { contentEl } = this;
    if (contentEl) {
      this.initialContentScrollY = disableContentScrollY(contentEl);
    }

    openSlidingItem = this.el;

    if (this.tmr !== undefined) {
      clearTimeout(this.tmr);
      this.tmr = undefined;
    }
    if (this.openAmount === 0) {
      this.optsDirty = true;
      this.state = SlidingState.Enabled;
    }
    this.initialOpenAmount = this.openAmount;
    if (this.item) {
      this.item.style.transition = 'none';
    }
  }

  private onMove(gesture: GestureDetail) {
    if (this.optsDirty) {
      this.calculateOptsWidth();
    }
    let openAmount = this.initialOpenAmount - gesture.deltaX;

    switch (this.sides) {
      case ItemSide.End:
        openAmount = Math.max(0, openAmount);
        break;
      case ItemSide.Start:
        openAmount = Math.min(0, openAmount);
        break;
      case ItemSide.Both:
        break;
      case ItemSide.None:
        return;
      default:
        printIonWarning('[ion-item-sliding] - invalid ItemSideFlags value', this.sides);
        break;
    }

    let optsWidth;
    if (openAmount > this.optsWidthRightSide) {
      optsWidth = this.optsWidthRightSide;
      openAmount = optsWidth + (openAmount - optsWidth) * ELASTIC_FACTOR;
    } else if (openAmount < -this.optsWidthLeftSide) {
      optsWidth = -this.optsWidthLeftSide;
      openAmount = optsWidth + (openAmount - optsWidth) * ELASTIC_FACTOR;
    }

    this.setOpenAmount(openAmount, false);
  }

  private onEnd(gesture: GestureDetail) {
    const { contentEl, initialContentScrollY } = this;
    if (contentEl) {
      resetContentScrollY(contentEl, initialContentScrollY);
    }

    const velocity = gesture.velocityX;

    let restingPoint = this.openAmount > 0 ? this.optsWidthRightSide : -this.optsWidthLeftSide;

    // Check if the drag didn't clear the buttons mid-point
    // and we aren't moving fast enough to swipe open
    const isResetDirection = this.openAmount > 0 === !(velocity < 0);
    const isMovingFast = Math.abs(velocity) > 0.3;
    const isOnCloseZone = Math.abs(this.openAmount) < Math.abs(restingPoint / 2);
    if (swipeShouldReset(isResetDirection, isMovingFast, isOnCloseZone)) {
      restingPoint = 0;
    }

    const state = this.state;
    this.setOpenAmount(restingPoint, true);

    if ((state & SlidingState.SwipeEnd) !== 0 && this.rightOptions) {
      this.rightOptions.fireSwipeEvent();
    } else if ((state & SlidingState.SwipeStart) !== 0 && this.leftOptions) {
      this.leftOptions.fireSwipeEvent();
    }
  }

  private calculateOptsWidth() {
    this.optsWidthRightSide = 0;
    if (this.rightOptions) {
      this.rightOptions.style.display = 'flex';
      this.optsWidthRightSide = this.rightOptions.offsetWidth;
      this.rightOptions.style.display = '';
    }

    this.optsWidthLeftSide = 0;
    if (this.leftOptions) {
      this.leftOptions.style.display = 'flex';
      this.optsWidthLeftSide = this.leftOptions.offsetWidth;
      this.leftOptions.style.display = '';
    }

    this.optsDirty = false;
  }

  private setOpenAmount(openAmount: number, isFinal: boolean) {
    if (this.tmr !== undefined) {
      clearTimeout(this.tmr);
      this.tmr = undefined;
    }
    if (!this.item) {
      return;
    }

    const { el } = this;

    const style = this.item.style;
    this.openAmount = openAmount;

    if (isFinal) {
      style.transition = '';
    }

    if (openAmount > 0) {
      this.state =
        openAmount >= this.optsWidthRightSide + SWIPE_MARGIN
          ? SlidingState.End | SlidingState.SwipeEnd
          : SlidingState.End;
    } else if (openAmount < 0) {
      this.state =
        openAmount <= -this.optsWidthLeftSide - SWIPE_MARGIN
          ? SlidingState.Start | SlidingState.SwipeStart
          : SlidingState.Start;
    } else {
      /**
       * The sliding options should not be
       * clickable while the item is closing.
       */
      el.classList.add('item-sliding-closing');

      /**
       * Item sliding cannot be interrupted
       * while closing the item. If it did,
       * it would allow the item to get into an
       * inconsistent state where multiple
       * items are then open at the same time.
       */
      if (this.gesture) {
        this.gesture.enable(false);
      }
      this.tmr = setTimeout(() => {
        this.state = SlidingState.Disabled;
        this.tmr = undefined;
        if (this.gesture) {
          this.gesture.enable(!this.disabled);
        }
        el.classList.remove('item-sliding-closing');
      }, 600);

      openSlidingItem = undefined;
      style.transform = '';
      return;
    }
    style.transform = `translate3d(${-openAmount}px,0,0)`;
    this.ionDrag.emit({
      amount: openAmount,
      ratio: this.getSlidingRatioSync(),
    });
  }

  private getSlidingRatioSync(): number {
    if (this.openAmount > 0) {
      return this.openAmount / this.optsWidthRightSide;
    } else if (this.openAmount < 0) {
      return this.openAmount / this.optsWidthLeftSide;
    } else {
      return 0;
    }
  }

  render() {
    const mode = getIonMode(this);
    return (
      <Host
        class={{
          [mode]: true,
          'item-sliding-active-slide': this.state !== SlidingState.Disabled,
          'item-sliding-active-options-end': (this.state & SlidingState.End) !== 0,
          'item-sliding-active-options-start': (this.state & SlidingState.Start) !== 0,
          'item-sliding-active-swipe-end': (this.state & SlidingState.SwipeEnd) !== 0,
          'item-sliding-active-swipe-start': (this.state & SlidingState.SwipeStart) !== 0,
        }}
      ></Host>
    );
  }
}

const swipeShouldReset = (isResetDirection: boolean, isMovingFast: boolean, isOnResetZone: boolean): boolean => {
  // The logic required to know when the sliding item should close (openAmount=0)
  // depends on three booleans (isResetDirection, isMovingFast, isOnResetZone)
  // and it ended up being too complicated to be written manually without errors
  // so the truth table is attached below: (0=false, 1=true)
  // isResetDirection | isMovingFast | isOnResetZone || shouldClose
  //         0        |       0      |       0       ||    0
  //         0        |       0      |       1       ||    1
  //         0        |       1      |       0       ||    0
  //         0        |       1      |       1       ||    0
  //         1        |       0      |       0       ||    0
  //         1        |       0      |       1       ||    1
  //         1        |       1      |       0       ||    1
  //         1        |       1      |       1       ||    1
  // The resulting expression was generated by resolving the K-map (Karnaugh map):
  return (!isMovingFast && isOnResetZone) || (isResetDirection && isMovingFast);
};