const TEMPLATE = document.createElement("template");
TEMPLATE.innerHTML = `<style>
    :host {
        display: flex;
        flex-direction: row;
        justify-content: flex-start;
        align-items: flex-start;

        overflow: auto;
        width: 100%;
        scrollbar-width: none;

        --markee-speed: 100;
        --markee-play-state: running;
        --markee-interaction-pause-delay: 3s;
    }

    .host::-webkit-scrollbar {
        display: none;
    }
    
    ::slotted(*) {
      flex-shrink: 0;
      width: fit-content;
    }
</style><slot></slot>`;

const CHECK_OPTIONS_INTERVAL = 100;

class MarkeeComponent extends HTMLElement {
  #options = {
    speed: 0,
    scrollPauseDelay: 1000,
    playing: true,
    scrollPlaying: true,
  };

  #lastFrame = 0;

  #animationFrameRequest = -1;

  #checkOptionInterval = -1;

  #scrollPlayingTimeout = -1;

  /** @type {{element: Element, rect: DOMRect, margin: number}?} */
  #nextCollectedElement = null;

  constructor() {
    super();

    this.requestTick = this.requestTick.bind(this);
    this.updateOptions = this.updateOptions.bind(this);

    this.attachShadow({ mode: "open" });
    this.shadowRoot.appendChild(TEMPLATE.content.cloneNode(true));
  }

  tick() {
    let now = Date.now();
    let delta = (now - this.#lastFrame) / 1000;
    this.#lastFrame = now;
    
    if (!this.#options.playing || !this.#options.scrollPlaying || this.scrollWidth - 800 <= this.clientWidth) return;
    
    this.scrollLeft += Math.max(this.#options.speed * delta, 1);

    this.checkElementRecycling();
  }

  requestTick() {
    this.tick();
    if (this.#options.playing) {
      this.#animationFrameRequest = requestAnimationFrame(this.requestTick, 30);
    }
  }

  updateOptions() {
    let style = window.getComputedStyle(this);

    let speed = parseFloat(style.getPropertyValue("--markee-speed"));
    if (!Number.isNaN(speed)) {
      this.#options.speed = speed;
    }

    let wasPlaying = this.#options.playing;

    let playState = style.getPropertyValue("--markee-play-state");
    if (playState) {
      this.#options.playing = playState != "paused";
    } else {
      this.#options.playing = true;
    }

    let scrollPauseDelay = style.getPropertyValue(
      "--markee-interaction-pause-delay"
    );
    if (scrollPauseDelay) {
      let value = parseFloat(scrollPauseDelay);
      if (scrollPauseDelay.endsWith("ms")) {
        this.#options.scrollPauseDelay = value;
      } else if (scrollPauseDelay.endsWith("s")) {
        this.#options.scrollPauseDelay = value * 1000;
      } else {
        this.#options.scrollPauseDelay = 1000;
      }
    }

    if (wasPlaying != this.#options.playing) {
      this.#lastFrame = Date.now();
      cancelAnimationFrame(this.#animationFrameRequest);
      this.requestTick();
    }
  }

  checkElementRecycling() {
    if (
      this.children.length > 0 &&
      (!this.#nextCollectedElement ||
        this.#nextCollectedElement.element != this.children[0])
    ) {
      let element = this.children[0];
      {
        let i = 0;
        while(element.style.display == "none" && i < this.children.length){
          i += 1;
          element = this.children[i]
        }
      }

      let style = window.getComputedStyle(element);

      this.#nextCollectedElement = {
        element,
        rect: element.getBoundingClientRect(),
        margin: parseFloat(style.marginLeft) + parseFloat(style.marginRight),
      };
    }

    if (!this.#nextCollectedElement) return;

    let lastElement = this.children[this.children.length-1];
    {
      let i = lastElement.children.length-1;
      while(lastElement && lastElement.style.display == "none" && i >= 0){
        i -= 1;
        lastElement = this.children[i]
      }
    }


    if (lastElement) {
      let rect = lastElement.getBoundingClientRect();
      let thisRect = this.getBoundingClientRect();
      let style = window.getComputedStyle(lastElement);
      let margin = parseFloat(style.marginLeft) + parseFloat(style.marginRight);

      if (thisRect.width == 0) {
        return;
      }

      if (rect.right + margin < thisRect.left + this.clientWidth) {
        return;
      }
    }

    if (
      this.scrollLeft >=
      this.scrollWidth -
        this.clientWidth -
        this.#nextCollectedElement.rect.width -
        this.#nextCollectedElement.margin
    ) {
      this.scrollLeft -=
        this.#nextCollectedElement.rect.width +
        this.#nextCollectedElement.margin;
      this.appendChild(this.#nextCollectedElement.element);
      this.#nextCollectedElement = null;
    }
  }

  handlePointer(e) {
    this.#options.scrollPlaying = false;
    clearTimeout(this.#scrollPlayingTimeout);
    this.#scrollPlayingTimeout = setTimeout(() => {
      this.#options.scrollPlaying = true;
    }, this.#options.scrollPauseDelay);
  }

  connectedCallback() {
    this.updateOptions();
    this.#lastFrame = Date.now();
    this.requestTick();
    this.#checkOptionInterval = setInterval(
      this.updateOptions,
      CHECK_OPTIONS_INTERVAL
    );
  }

  disconnectedCallback() {
    clearInterval(this.#checkOptionInterval);
  }
}

customElements.define("gavle-marquee", MarkeeComponent);