/**
 * Handles the display of reveal.js' optional slide number.
 */
export default class SlideNumber {
  constructor(Reveal) {
    this.Reveal = Reveal;
  }

  render() {
    this.element = document.createElement("div");
    this.element.className = "slide-number";
    this.Reveal.getRevealElement().appendChild(this.element);
  }

  /**
   * Called when the reveal.js config is updated.
   */
  configure(config, oldConfig) {
    let slideNumberDisplay = "none";
    if (config.slideNumber && !this.Reveal.isPrintingPDF()) {
      if (config.showSlideNumber === "all") {
        slideNumberDisplay = "block";
      } else if (
        config.showSlideNumber === "speaker" &&
        this.Reveal.isSpeakerNotes()
      ) {
        slideNumberDisplay = "block";
      }
    }

    this.element.style.display = slideNumberDisplay;
  }

  /**
   * Updates the slide number to match the current slide.
   */
  update() {
    // Update slide number if enabled
    if (this.Reveal.getConfig().slideNumber && this.element) {
      this.element.innerHTML = this.getSlideNumber();
    }
  }

  /**
   * Returns the HTML string corresponding to the current slide
   * number, including formatting.
   */
  getSlideNumber(slide = this.Reveal.getCurrentSlide()) {
    let config = this.Reveal.getConfig();
    let value;
    let format = "h.v";

    if (typeof config.slideNumber === "function") {
      value = config.slideNumber(slide);
    } else {
      // Check if a custom number format is available
      if (typeof config.slideNumber === "string") {
        format = config.slideNumber;
      }

      // If there are ONLY vertical slides in this deck, always use
      // a flattened slide number
      if (!/c/.test(format) && this.Reveal.getHorizontalSlides().length === 1) {
        format = "c";
      }

      // Offset the current slide number by 1 to make it 1-indexed
      let horizontalOffset =
        slide && slide.dataset.visibility === "uncounted" ? 0 : 1;

      value = [];
      switch (format) {
        case "c":
          value.push(this.Reveal.getSlidePastCount(slide) + horizontalOffset);
          break;
        case "c/t":
          value.push(
            this.Reveal.getSlidePastCount(slide) + horizontalOffset,
            "/",
            this.Reveal.getTotalSlides()
          );
          break;
        default:
          let indices = this.Reveal.getIndices(slide);
          value.push(indices.h + horizontalOffset);
          let sep = format === "h/v" ? "/" : ".";
          if (this.Reveal.isVerticalSlide(slide))
            value.push(sep, indices.v + 1);
      }
    }

    let url = "#" + this.Reveal.location.getHash(slide);
    return this.formatNumber(value[0], value[1], value[2], url);
  }

  /**
   * Applies HTML formatting to a slide number before it's
   * written to the DOM.
   *
   * @param {number} a Current slide
   * @param {string} delimiter Character to separate slide numbers
   * @param {(number|*)} b Total slides
   * @param {HTMLElement} [url='#'+locationHash()] The url to link to
   * @return {string} HTML string fragment
   */
  formatNumber(a, delimiter, b, url = "#" + this.Reveal.location.getHash()) {
    if (typeof b === "number" && !isNaN(b)) {
      return `<a href="${url}">
					<span class="slide-number-a">${a}</span>
					<span class="slide-number-delimiter">${delimiter}</span>
					<span class="slide-number-b">${b}</span>
					</a>`;
    } else {
      return `<a href="${url}">
					<span class="slide-number-a">${a}</span>
					</a>`;
    }
  }

  destroy() {
    this.element.remove();
  }
}