Reference Source

coral-spectrum/coral-component-accordion/src/scripts/AccordionItem.js

/**
 * Copyright 2019 Adobe. All rights reserved.
 * This file is licensed to you under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License. You may obtain a copy
 * of the License at http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under
 * the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
 * OF ANY KIND, either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */

import {BaseComponent} from '../../../coral-base-component';
import base from '../templates/base';
import {commons, transform, validate} from '../../../coral-utils';
import {Icon} from '../../../coral-component-icon';

const CLASSNAME = '_coral-Accordion-item';

/**
 @class Coral.Accordion.Item
 @classdesc A Accordion item component
 @htmltag coral-accordion-item
 @extends {HTMLElement}
 @extends {BaseComponent}
 */
class AccordionItem extends BaseComponent(HTMLElement) {
  /** @ignore */
  constructor() {
    super();

    // Prepare templates
    this._elements = {
      // Create or fetch the content zones
      label: this.querySelector('coral-accordion-item-label') || document.createElement('coral-accordion-item-label'),
      content: this.querySelector('coral-accordion-item-content') || document.createElement('coral-accordion-item-content')
    };

    base.call(this._elements, {Icon});
  }

  /**
   The label of this accordion item.

   @type {AccordionItemLabel}
   @contentzone
   */
  get label() {
    return this._getContentZone(this._elements.label);
  }

  set label(value) {
    this._setContentZone('label', value, {
      handle: 'label',
      tagName: 'coral-accordion-item-label',
      insert: function (label) {
        this._setAria(this._elements.button, this._elements.content);

        this._elements.button.appendChild(label);
      }
    });
  }

  /**
   The content of this accordion item.

   @type {AccordionItemContent}
   @contentzone
   */
  get content() {
    return this._getContentZone(this._elements.content);
  }

  set content(value) {
    this._setContentZone('content', value, {
      handle: 'content',
      tagName: 'coral-accordion-item-content',
      insert: function (content) {
        content.classList.add(`${CLASSNAME}Content`);

        // WAI-ARIA 1.1
        content.setAttribute('role', 'region');

        this._setAria(this._elements.button, content);

        this.appendChild(content);
      }
    });
  }

  /**
   Whether the item is selected. If the item has an element with the `coral-interactive` attribute and is clicked,
   then the toggling of the accordion item will not occur.

   @type {Boolean}
   @default false
   @htmlattribute selected
   @htmlattributereflected
   */
  get selected() {
    return this._selected || false;
  }

  set selected(value) {
    let _value = transform.booleanAttr(value);
    let _selected = this.hasAttribute('disabled') ? false : _value;

    if(this._selected === _selected) {
      return;
    }

    this._selected = _selected;
    this._reflectAttribute('selected', this._selected);

    // Read it before applying is-open which adds additional padding
    const scrollHeight = this._elements.content.scrollHeight;

    this.classList.toggle('is-open', this._selected);
    this._elements.button.setAttribute('aria-expanded', this._selected);

    if (!this._selected) {
      this._elements.content.style.height = `${scrollHeight}px`;
      // We read the offset height to force a reflow, this is needed to start the transition between absolute values
      // https://blog.alexmaccaw.com/css-transitions under Redrawing
      // eslint-disable-next-line no-unused-vars
      const offsetHeight = this._elements.content.offsetHeight;
    }

    this._elements.content.style.height = this._selected ? `${scrollHeight}px` : '0';

    if (this._selected) {
      commons.transitionEnd(this._elements.content, () => {
        this._elements.content.style.height = '';
      });
    }

    this.trigger('coral-accordion-item:_selectedchanged');
  }

  /**
   Whether this item is disabled.
   @type {Boolean}
   @default false
   @htmlattribute disabled
   @htmlattributereflected
   */
  get disabled() {
    return this._disabled || false;
  }

  set disabled(value) {
    this._disabled = transform.booleanAttr(value);
    this._reflectAttribute('disabled', this._disabled);

    this.classList.toggle('is-disabled', this._disabled);
    this._elements.button[this._disabled ? 'setAttribute' : 'removeAttribute']('disabled', '');

    this.selected = this.selected;
  }


  /**
   The heading level for the Accordion item

   @type {Number}
   @default 3
   @htmlattribute level
   @htmlattributereflected
   */
  get level() {
    return this._level || 3;
  }

  set level(value) {
    value = transform.number(value);
    // If the value has changed,
    if (!validate.valueMustChange(value, this._level)) {
      return;
    }
    // and the value is greater than 0
    if (value > 0) {
      // set the value and reflect the attribute.
      this._level = value;
      this._reflectAttribute('level', this._level);

      // If the new value is not equal to the default,
      if (value !== 3) {
        // override the aria-level on the h3 element.
        this._elements.heading.setAttribute('aria-level', this._level);
        return;
      }
    }

    // If the value is the default or invalid, remove the aria-level override from the h3 element.
    this._elements.heading.removeAttribute('aria-level');
  }

  /** @private **/
  get _isTabTarget() {
    return this.__isTabTarget || false;
  }

  set _isTabTarget(value) {
    this.__isTabTarget = value;

    if (this.disabled) {
      this._elements.button.removeAttribute('tabindex');
    } else {
      this._elements.button.setAttribute('tabindex', this.__isTabTarget ? '0' : '-1');
    }
  }

  _setAria(button, content) {
    button.id = button.id || commons.getUID();
    content.id = content.id || commons.getUID();

    button.setAttribute('aria-controls', content.id);
    content.setAttribute('aria-labelledby', button.id);
  }

  /**
   Handles the focus of the item.

   @ignore
   */
  focus() {
    this._elements.label.focus();
  }

  get _contentZones() {
    return {'coral-accordion-item-label': 'label', 'coral-accordion-item-content': 'content'};
  }

  /** @ignore */
  static get observedAttributes() {
    return super.observedAttributes.concat(['selected', 'disabled', 'level']);
  }

  /** @ignore */
  render() {
    super.render();

    this.classList.add(CLASSNAME);

    // a11y
    this.setAttribute('role', 'presentation');

    // Support cloneNode
    const template = this.querySelector('._coral-Accordion-itemHeading');
    if (template) {
      template.remove();
    }

    // Move content into the content zone if not specified
    if (!this._elements.content.parentNode) {
      while (this.firstChild) {
        this._elements.content.appendChild(this.firstChild);
      }
    }

    this.appendChild(this._elements.heading);

    // Assign the content zones, moving them into place in the process
    this.label = this._elements.label;
    this.content = this._elements.content;

    // Defaults
    this.selected = this.selected;
  }
}

export default AccordionItem;