Disclosure

---
/**
 * APG Disclosure Pattern - Astro Implementation
 *
 * A button that controls the visibility of a section of content.
 * Uses Web Components for client-side state management.
 *
 * @see https://www.w3.org/WAI/ARIA/apg/patterns/disclosure/
 */

export interface Props {
  /** Content displayed in the disclosure trigger button */
  trigger: string;
  /** When true, the panel is expanded on initial render */
  defaultExpanded?: boolean;
  /** When true, the disclosure cannot be expanded/collapsed */
  disabled?: boolean;
  /** Additional CSS class */
  class?: string;
}

const { trigger, defaultExpanded = false, disabled = false, class: className = '' } = Astro.props;

// Generate unique ID for this instance
const instanceId = crypto.randomUUID();
const panelId = `${instanceId}-panel`;
---

<apg-disclosure class:list={['apg-disclosure', className]} data-expanded={defaultExpanded}>
  <button
    type="button"
    aria-expanded={defaultExpanded}
    aria-controls={panelId}
    disabled={disabled}
    class="apg-disclosure-trigger"
  >
    <span class="apg-disclosure-icon" aria-hidden="true">
      <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
        <polyline points="9 6 15 12 9 18"></polyline>
      </svg>
    </span>
    <span class="apg-disclosure-trigger-content">{trigger}</span>
  </button>
  <div
    id={panelId}
    class="apg-disclosure-panel"
    aria-hidden={!defaultExpanded}
    inert={!defaultExpanded ? true : undefined}
  >
    <div class="apg-disclosure-panel-content">
      <slot />
    </div>
  </div>
</apg-disclosure>

<script>
  class ApgDisclosure extends HTMLElement {
    private button: HTMLButtonElement | null = null;
    private panel: HTMLElement | null = null;
    private expanded = false;
    private rafId: number | null = null;

    connectedCallback() {
      // Use requestAnimationFrame to ensure DOM is fully constructed
      this.rafId = requestAnimationFrame(() => this.initialize());
    }

    private initialize() {
      this.rafId = null;
      this.button = this.querySelector('.apg-disclosure-trigger');
      this.panel = this.querySelector('.apg-disclosure-panel');

      if (!this.button || !this.panel) {
        console.warn('apg-disclosure: button or panel not found');
        return;
      }

      this.expanded = this.dataset.expanded === 'true';

      // Attach event listener
      this.button.addEventListener('click', this.handleClick);
    }

    disconnectedCallback() {
      // Cancel pending initialization
      if (this.rafId !== null) {
        cancelAnimationFrame(this.rafId);
        this.rafId = null;
      }
      // Remove event listener
      this.button?.removeEventListener('click', this.handleClick);
      // Clean up references
      this.button = null;
      this.panel = null;
    }

    private toggle() {
      this.expanded = !this.expanded;
      this.updateDOM();

      // Dispatch custom event
      this.dispatchEvent(
        new CustomEvent('expandedchange', {
          detail: { expanded: this.expanded },
          bubbles: true,
        })
      );
    }

    private updateDOM() {
      if (!this.button || !this.panel) return;

      // Update button aria-expanded
      this.button.setAttribute('aria-expanded', String(this.expanded));

      // Update panel aria-hidden
      this.panel.setAttribute('aria-hidden', String(!this.expanded));

      // Toggle inert attribute
      if (this.expanded) {
        this.panel.removeAttribute('inert');
      } else {
        this.panel.setAttribute('inert', '');
      }
    }

    private handleClick = () => {
      if (this.button?.disabled) return;
      this.toggle();
    };
  }

  // Register the custom element
  if (!customElements.get('apg-disclosure')) {
    customElements.define('apg-disclosure', ApgDisclosure);
  }
</script>