shoelace/src/components/menu-item/menu-item.component.ts

import { classMap } from 'lit/directives/class-map.js';
import { getTextContent, HasSlotController } from '../../internal/slot.js';
import { html } from 'lit';
import { LocalizeController } from '../../utilities/localize.js';
import { property, query } from 'lit/decorators.js';
import { SubmenuController } from './submenu-controller.js';
import { watch } from '../../internal/watch.js';
import ShoelaceElement from '../../internal/shoelace-element.js';
import SlIcon from '../icon/icon.component.js';
import SlPopup from '../popup/popup.component.js';
import styles from './menu-item.styles.js';
import type { CSSResultGroup } from 'lit';

/**
 * @summary Menu items provide options for the user to pick from in a menu.
 * @documentation https://shoelace.style/components/menu-item
 * @status stable
 * @since 2.0
 *
 * @dependency sl-icon
 * @dependency sl-popup
 *
 * @slot - The menu item's label.
 * @slot prefix - Used to prepend an icon or similar element to the menu item.
 * @slot suffix - Used to append an icon or similar element to the menu item.
 * @slot submenu - Used to denote a nested menu.
 *
 * @csspart base - The component's base wrapper.
 * @csspart checked-icon - The checked icon, which is only visible when the menu item is checked.
 * @csspart prefix - The prefix container.
 * @csspart label - The menu item label.
 * @csspart suffix - The suffix container.
 * @csspart submenu-icon - The submenu icon, visible only when the menu item has a submenu (not yet implemented).
 *
 * @cssproperty [--submenu-offset=-2px] - The distance submenus shift to overlap the parent menu.
 */
export default class SlMenuItem extends ShoelaceElement {
  static styles: CSSResultGroup = styles;
  static dependencies = {
    'sl-icon': SlIcon,
    'sl-popup': SlPopup
  };

  private cachedTextLabel: string;

  @query('slot:not([name])') defaultSlot: HTMLSlotElement;
  @query('.menu-item') menuItem: HTMLElement;

  /** The type of menu item to render. To use `checked`, this value must be set to `checkbox`. */
  @property() type: 'normal' | 'checkbox' = 'normal';

  /** Draws the item in a checked state. */
  @property({ type: Boolean, reflect: true }) checked = false;

  /** A unique value to store in the menu item. This can be used as a way to identify menu items when selected. */
  @property() value = '';

  /** Draws the menu item in a disabled state, preventing selection. */
  @property({ type: Boolean, reflect: true }) disabled = false;

  private readonly localize = new LocalizeController(this);
  private readonly hasSlotController = new HasSlotController(this, 'submenu');
  private submenuController: SubmenuController = new SubmenuController(this, this.hasSlotController, this.localize);

  connectedCallback() {
    super.connectedCallback();
    this.addEventListener('click', this.handleHostClick);
    this.addEventListener('mouseover', this.handleMouseOver);
  }

  disconnectedCallback() {
    super.disconnectedCallback();
    this.removeEventListener('click', this.handleHostClick);
    this.removeEventListener('mouseover', this.handleMouseOver);
  }

  private handleDefaultSlotChange() {
    const textLabel = this.getTextLabel();

    // Ignore the first time the label is set
    if (typeof this.cachedTextLabel === 'undefined') {
      this.cachedTextLabel = textLabel;
      return;
    }

    // When the label changes, emit a slotchange event so parent controls see it
    if (textLabel !== this.cachedTextLabel) {
      this.cachedTextLabel = textLabel;
      this.emit('slotchange', { bubbles: true, composed: false, cancelable: false });
    }
  }

  private handleHostClick = (event: MouseEvent) => {
    // Prevent the click event from being emitted when the button is disabled or loading
    if (this.disabled) {
      event.preventDefault();
      event.stopImmediatePropagation();
    }
  };

  private handleMouseOver = (event: MouseEvent) => {
    this.focus();
    event.stopPropagation();
  };

  @watch('checked')
  handleCheckedChange() {
    // For proper accessibility, users have to use type="checkbox" to use the checked attribute
    if (this.checked && this.type !== 'checkbox') {
      this.checked = false;
      console.error('The checked attribute can only be used on menu items with type="checkbox"', this);
      return;
    }

    // Only checkbox types can receive the aria-checked attribute
    if (this.type === 'checkbox') {
      this.setAttribute('aria-checked', this.checked ? 'true' : 'false');
    } else {
      this.removeAttribute('aria-checked');
    }
  }

  @watch('disabled')
  handleDisabledChange() {
    this.setAttribute('aria-disabled', this.disabled ? 'true' : 'false');
  }

  @watch('type')
  handleTypeChange() {
    if (this.type === 'checkbox') {
      this.setAttribute('role', 'menuitemcheckbox');
      this.setAttribute('aria-checked', this.checked ? 'true' : 'false');
    } else {
      this.setAttribute('role', 'menuitem');
      this.removeAttribute('aria-checked');
    }
  }

  /** Returns a text label based on the contents of the menu item's default slot. */
  getTextLabel() {
    return getTextContent(this.defaultSlot);
  }

  isSubmenu() {
    return this.hasSlotController.test('submenu');
  }

  render() {
    const isRtl = this.localize.dir() === 'rtl';
    const isSubmenuExpanded = this.submenuController.isExpanded();

    return html`
      <div
        id="anchor"
        part="base"
        class=${classMap({
          'menu-item': true,
          'menu-item--rtl': isRtl,
          'menu-item--checked': this.checked,
          'menu-item--disabled': this.disabled,
          'menu-item--has-submenu': this.isSubmenu(),
          'menu-item--submenu-expanded': isSubmenuExpanded
        })}
        ?aria-haspopup="${this.isSubmenu()}"
        ?aria-expanded="${isSubmenuExpanded ? true : false}"
      >
        <span part="checked-icon" class="menu-item__check">
          <sl-icon name="check" library="system" aria-hidden="true"></sl-icon>
        </span>

        <slot name="prefix" part="prefix" class="menu-item__prefix"></slot>

        <slot part="label" class="menu-item__label" @slotchange=${this.handleDefaultSlotChange}></slot>

        <slot name="suffix" part="suffix" class="menu-item__suffix"></slot>

        <span part="submenu-icon" class="menu-item__chevron">
          <sl-icon name=${isRtl ? 'chevron-left' : 'chevron-right'} library="system" aria-hidden="true"></sl-icon>
        </span>

        ${this.submenuController.renderSubmenu()}
      </div>
    `;
  }
}