icon.tsx

import { Build, Component, Element, Host, Prop, State, Watch, h } from '@stencil/core';
import { getSvgContent, ioniconContent } from './request';
import { getName, getUrl } from './utils';


@Component({
  tag: 'ion-icon',
  assetsDir: 'svg',
  styleUrl: 'icon.css',
  shadow: true
})
export class Icon {
  private io?: IntersectionObserver;

  @Element() el!: HTMLElement;

  @State() private svgContent?: string;
  @State() private isVisible = false;

  /**
   * The mode determines which platform styles to use.
   */
  @Prop({ mutable: true }) mode = getIonMode();

  /**
   * The color to use for the background of the item.
   */
  @Prop() color?: string;

  /**
   * Specifies the label to use for accessibility. Defaults to the icon name.
   */
  @Prop({ mutable: true, reflectToAttr: true }) ariaLabel?: string;

  /**
   * Specifies which icon to use on `ios` mode.
   */
  @Prop() ios?: string;

  /**
   * Specifies which icon to use on `md` mode.
   */
  @Prop() md?: string;

  /**
   * Specifies whether the icon should horizontally flip when `dir` is `"rtl"`.
   */
  @Prop() flipRtl?: boolean;

  /**
   * Specifies which icon to use from the built-in set of icons.
   */
  @Prop() name?: string;

  /**
   * Specifies the exact `src` of an SVG file to use.
   */
  @Prop() src?: string;

  /**
   * A combination of both `name` and `src`. If a `src` url is detected
   * it will set the `src` property. Otherwise it assumes it's a built-in named
   * SVG and set the `name` property.
   */
  @Prop() icon?: any;

  /**
   * The size of the icon.
   * Available options are: `"small"` and `"large"`.
   */
  @Prop() size?: string;

  /**
   * If enabled, ion-icon will be loaded lazily when it's visible in the viewport.
   * Default, `false`.
   */
  @Prop() lazy = false;

  connectedCallback() {
    // purposely do not return the promise here because loading
    // the svg file should not hold up loading the app
    // only load the svg if it's visible
    this.waitUntilVisible(this.el, '50px', () => {
      this.isVisible = true;
      this.loadIcon();
    });
  }

  disconnectedCallback() {
    if (this.io) {
      this.io.disconnect();
      this.io = undefined;
    }
  }

  private waitUntilVisible(el: HTMLElement, rootMargin: string, cb: () => void) {
    if (Build.isBrowser && this.lazy && typeof window !== 'undefined' && (window as any).IntersectionObserver) {
      const io = this.io = new (window as any).IntersectionObserver((data: IntersectionObserverEntry[]) => {
        if (data[0].isIntersecting) {
          io.disconnect();
          this.io = undefined;
          cb();
        }
      }, { rootMargin });

      io.observe(el);

    } else {
      // browser doesn't support IntersectionObserver
      // so just fallback to always show it
      cb();
    }
  }


  @Watch('name')
  @Watch('src')
  @Watch('icon')
  loadIcon() {
    if (Build.isBrowser && this.isVisible) {
      const url = getUrl(this);
      if (url) {
        if (ioniconContent.has(url)) {
          // sync if it's already loaded
          this.svgContent = ioniconContent.get(url);
        } else {
          // async if it hasn't been loaded
          getSvgContent(url).then(() => this.svgContent = ioniconContent.get(url));
        }
      }
    }

    if (!this.ariaLabel) {
      const label = getName(this.name, this.icon, this.mode, this.ios, this.md);
      // user did not provide a label
      // come up with the label based on the icon name
      if (label) {
        this.ariaLabel = label.replace(/\-/g, ' ');
      }
    }
  }

  render() {
    const mode = this.mode || 'md';
    const flipRtl = this.flipRtl || (this.ariaLabel && (this.ariaLabel.indexOf('arrow') > -1 || this.ariaLabel.indexOf('chevron') > -1) && this.flipRtl !== false);

    return (
      <Host role="img" class={{
        [mode]: true,
        ...createColorClasses(this.color),
        [`icon-${this.size}`]: !!this.size,
        'flip-rtl': !!flipRtl && (this.el.ownerDocument as Document).dir === 'rtl'
        }}>{(
          (Build.isBrowser && this.svgContent)
            ? <div class="icon-inner" innerHTML={this.svgContent}></div>
            : <div class="icon-inner"></div>
        )}
      </Host>
    );
  }
}


const getIonMode = () => (Build.isBrowser && document.documentElement.getAttribute('mode')) || 'md';


const createColorClasses = (color: string | undefined) => {
  return (color) ? {
    'ion-color': true,
    [`ion-color-${color}`]: true
  } : null;
};