<button class="app" type="button">
  <div class="app__badge">
    <div class="app__badge-count" role="status" aria-label="" aria-atomic="true" aria-live="polite" data-count></div>
    <div class="app__badge-text" data-preview></div>
  </div>
  <svg class="app__icon" viewBox="0 0 512 512" width="32px" height="32px" aria-hidden="true">
    <path fill="currentcolor" d="M256,0C114.6,0,0,85.9,0,192c0,75,57.5,139.8,141.1,171.4L85.3,512l160.5-128.4c3.4,0.1,6.7,0.4,10.2,0.4c141.4,0,256-85.9,256-192C512,85.9,397.4,0,256,0z"/>
    <g fill="hsl(0,0%,100%)">
      <circle class="app__icon-dot" r="32" cx="144" cy="192" />
      <circle class="app__icon-dot" r="32" cx="256" cy="192" />
      <circle class="app__icon-dot" r="32" cx="368" cy="192" />
    </g>
  </svg>
</button>

@use "sass:map";

$badgeExpandedWidth: 3.75em;
$timings: (
  "ease-in-out": cubic-bezier(0.65,0,0.35,1),
  "ease-in": cubic-bezier(0.33,0,0.67,0),
  "ease-out": cubic-bezier(0.33,1,0.67,1),
);

* {
  border: 0;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
:root {
  --hue: 223;
  --hue2: 133;
  --hue3: 3;
  --bg: hsl(var(--hue2),90%,70%);
  --fg: hsl(var(--hue),90%,10%);
  --primary: hsl(var(--hue),90%,50%);
  --trans-dur: 0.3s;
  --trans-timing: cubic-bezier(0.65,0,0.35,1);
  font-size: calc(20px + (60 - 20) * (100vw - 280px) / (3840 - 280));
}
body,
button {
  font: 1em/1.5 -apple-system, BlinkMacSystemFont, "Helvetica Neue", Helvetica, sans-serif;
}
body {
  background-color: var(--bg);
  color: var(--fg);
  display: flex;
  height: 100vh;
  transition:
    background-color var(--trans-dur),
    color var(--trans-dur);
}
.app {
  --dot-dur: 1s;
  background-color: hsl(0,0%,100%);
  border-radius: 1em;
  box-shadow:
    0 0 0 0.333em hsla(0,0%,56%,0),
    0 0.75em 1.5em hsla(var(--hue2),90%,30%,0.3);
  cursor: pointer;
  display: flex;
  margin: auto;
  outline: transparent;
  position: relative;
  width: 4em;
  height: 4em;
  transition: box-shadow calc(var(--trans-dur) / 2) var(--trans-timing);
  -webkit-appearance: none;
  appearance: none;
  -webkit-tap-highlight-color: transparent;

  &__badge {
    background-color: hsl(var(--hue3),90%,50%);
    border-radius: 0.75em;
    box-shadow: 0 0.28125em 0.5625em hsla(var(--hue3),90%,30%,0.5);
    overflow: hidden;
    padding: 0 0.375em;
    position: absolute;
    top: 0;
    right: 0;
    min-width: 1.5em;
    height: 1.5em;
    transform: translate(0.625em,-0.625em);
    transition: min-width var(--trans-dur) var(--trans-timing);

    &-count,
    &-text {
      color: hsl(0,0%,100%);
      font-weight: 300;
      transition: opacity var(--trans-dur) var(--trans-timing);
    }
    &-count {
      text-align: center;
    }
    &-text {
      opacity: 0;
      position: absolute;
      top: 0;
      left: 100%;
      width: max-content;
    }
    &:has(&-count:empty) {
      display: none;
    }
  }
  &:focus-visible {
    box-shadow:
      0 0 0 0.333em hsla(0,0%,56%,1),
      0 0.75em 1.5em hsla(var(--hue2),90%,30%,0.3);
  }
  &__icon {
    color: var(--primary);
    display: block;
    overflow: visible;
    pointer-events: none;
    margin: auto;
    width: 2.75em;
    height: 2.75em;
  }
  &:hover &,
  &:focus-visible & {
    &__badge {
      min-width: $badgeExpandedWidth;

      &-count {
        opacity: 0;
      }
      &-text {
        animation: marquee 5s linear infinite;
        opacity: 1;
      }
    }
  }
  &--animating &__icon {
    &-dot {
      animation: dot var(--dot-dur) map.get($timings,"ease-in-out");

      &:nth-child(2) {
        animation-delay: calc(var(--dot-dur) * 0.05);
      }
      &:nth-child(3) {
        animation-delay: calc(var(--dot-dur) * 0.1);
      }
    }
  }
}

/* Animations */
@keyframes dot {
  from,
  90%,
  to {
    animation-timing-function: map.get($timings,"ease-in-out");
    transform: translateY(0);
  }
  30% {
    animation-timing-function: map.get($timings,"ease-in");
    transform: translateY(-32px);
  }
  60% {
    animation-timing-function: map.get($timings,"ease-out");
    transform: translateY(32px);
  }
}
@keyframes marquee {
  from {
    transform: translateX(0);
  }
  to {
    transform: translateX(calc(-100% - #{$badgeExpandedWidth}));
  }
}

window.addEventListener("DOMContentLoaded",() => {
  const app = new MessageApp(".app");
});

class MessageApp {
  /** Element used for this component */
  el: HTMLElement | null;
  /** Number of messages */
  messageCount = 1;
  /** Preview of the first message */
  messagePreview = "honey we need to talk…";
  /** Animation is active */
  isAnimating = false;
  /** Class used for the animation state */
  animationClass = "app--animating";
  /** Events to trigger the animation */
  downEvents = ["focus","mouseover","touchstart"];
  /** Events to stop the animation */
  upEvents = ["blur","mouseout","touchend"];
  /**
   * @param el CSS selector
   */
  constructor(el: string) {
    this.el = document.querySelector(el);
    this.setupListeners();
    this.displayBadge();
  }
  /** Run the animation upon user interaction. */
  addAnimation(): void {
    this.isAnimating = true;
    this.checkInteraction();
  }
  /** Check if the user is still interacting before replaying the animation. */
  checkInteraction(): void {
    this.el?.classList.remove(this.animationClass);

    if (this.isAnimating) {
      void this.el?.offsetWidth;
      this.el?.classList.add(this.animationClass);
    }
  }
  /** Show the notification count and first message. */
  displayBadge(): void {
    const count = this.el?.querySelector("[data-count]") as HTMLElement;
    const preview = this.el?.querySelector("[data-preview]") as HTMLElement;

    if (count) {
      count.innerText = this.messageCount > 0 ? `${this.messageCount}` : "";
      count.ariaLabel = `${this.messageCount} message(s)`;
    }
    if (preview) {
      preview.innerText = this.messagePreview;
    }
  }
  /** Stop the animation after its last iteration. */
  removeAnimation(): void {
    this.isAnimating = false;
  }
  /** Set up the event listeners. */
  setupListeners(): void {
    for (let downEvent of this.downEvents) {
      this.el?.addEventListener(downEvent,this.addAnimation.bind(this));
    }
    for (let upEvent of this.upEvents) {
      this.el?.addEventListener(upEvent,this.removeAnimation.bind(this));
    }
    // use the last dot for checking user interaction
    const dots = Array.from(this.el?.querySelectorAll("circle") || []);
    const lastDot = dots.pop();
    lastDot?.addEventListener("animationend",this.checkInteraction.bind(this));
  }
}