/**
 * Class represeting the box to display text from all game elements.
 * @extends HTMLElement
 */
class TextDisplay extends HTMLElement {

  /**
   * Create the text display.
   */
  constructor() {
    super();

    const shadow = this.attachShadow({mode: 'open'});

    shadow.innerHTML = `
    <style>
      :host {
        --primary-color: #000;
        --secondary-color: #fff;
        contain: strict;
      }

      @media (prefers-color-scheme: dark) {
        :host {
          --primary-color: #fff;
          --secondary-color: #000;
        }
      }

      .text-box,
      .continue {
        position: fixed;
        bottom: 10px;
        left: 50%;
        transform: translateX(-50%);
        font-family: monospace;
        border: 2px solid var(--primary-color);
        box-shadow: 1px 1px 0px var(--secondary-color), -1px -1px 0px var(--secondary-color);
      }

      .text-box {
        padding: 1em;
        background-color: var(--secondary-color);
        color: var(--primary-color);
        line-height: 1.2;
        width: 40ch;
        height: 9.5em;
        box-sizing: border-box;
        hyphens: auto;
      }

      @media screen and (orientation: portrait) {
        .text-box {
          bottom: var(--utility-bar-size);
        }
      }

      .char {
        opacity: 0;
        visibility: hidden;
      }

      .char.visible {
        opacity: 1;
        visibility: visible;
      }

      .ellipsis-before::before {
        content: '…';
      }

      .ellipsis-after::after {
        content: '…';
      }

      .continue {
        cursor: pointer;
        border: 2px solid var(--primary-color);
        font-family: monospace;
        font-size: 1em;
        color: var(--primary-color);
        background-color: var(--secondary-color);
        bottom: 1em;
      }

      .continue:hover {
        background-color: var(--primary-color);
        color: var(--secondary-color);
      }

      .accessible-text-box {
        clip: rect(1px, 1px, 1px, 1px);
        clip-path: inset(50%);
        height: 1px;
        width: 1px;
        margin: -1px;
        overflow: hidden;
        padding: 0;
        position: absolute;
      }
    </style>
    <p id="text-box" class="text-box" hidden></p>
    <div id="accessible-text-box" class="accessible-text-box" role="region" aria-live="assertive" aria-atomic="true" aria-relevant="additions"></div>
    <button id="continue" class="continue" hidden>Continue…</button>`;

    this.continueButton = shadow.getElementById('continue');
    this.textBox = shadow.getElementById('text-box');
    this.accessibleTextBox = shadow.getElementById('accessible-text-box');

    const self = this;
    this.continueButton.addEventListener('pointerup', event => {
      if (this.textBox.hasAttribute('data-complete')) {
        this.continueButton.hidden = true;
        this.textBox.hidden = true;
        this.textBox.removeAttribute('data-complete');
        return;
      }
      Array.from(self.shadowRoot.querySelectorAll('.visible'))
        .map(item => item.hidden = true);
      event.target.hidden = true;
      self.showLetters();
    }, {passive: true});
  }

  /**
   * Set the attributes to watch for changes.
   * @return {Array} An array of attributes.
   */
  static get observedAttributes() { return ['text']; }

  /**
   * Generator to retrieve the next letter in the sequence.
   * @param {Array} letters - An array of characters.
   * @yields {string} The next letter in sequence.
   */
  *letterGenerator(letters) {
    let index = 0;
    while (index < letters.length) {
      yield letters[index];
      index++;
    }
  }

  /**
   * Print letters in typewriter effect. Automatically page content to fit
   * the dimesions of the box.
   * @return {number} either the current index if we haven't reached the end
   * of the page, or the intervalID if we have.
   */
  showLetters() {
    let index = 1;
    // Try to break pages on a whitespace character.
    let lookForWhitespaceChar = false;
    const intervalID = window.setInterval(() => {
      let letter = this.letters.next();
      if (letter.done) {
        this.continueButton.textContent = 'Done';
        this.continueButton.hidden = false;
        this.textBox.setAttribute('data-complete', '');
        return window.clearInterval(intervalID);
      }
      lookForWhitespaceChar = lookForWhitespaceChar ? lookForWhitespaceChar : false;
      if (index % 200 === 0) lookForWhitespaceChar = true;
      letter.value.classList.add('visible');
      if (lookForWhitespaceChar && !letter.value.textContent.trim()) {
        window.clearInterval(intervalID);
        letter.value.previousElementSibling.classList.add('ellipsis-after');
        letter.value.nextElementSibling.classList.add('ellipsis-before');
        this.continueButton.hidden = false;
        return index;
      }
      index++;
    }, 25);
  }

  /**
   * Respond to attribute changes.
   * @param {string} name - The name of the attribute changed.
   * @param {string} oldValue - The previous value of the attrbute.
   * @param {string} newValue - The just-changed value of the attribute.
   * @see {@linkcode TextDisplay#observedAttributes}
   * @return {void}
   */
  attributeChangedCallback(name, oldValue, newValue) {
    if (!newValue) return;
    this.accessibleTextBox.textContent = newValue;
    this.continueButton.textContent = 'Continue…';
    this.textBox.hidden = false;
    this.textBox.innerHTML = newValue
      .trim()
      .split('')
      .map(char => `<span class="char">${char}</span>`)
      .join('');
    this.letters = this.letterGenerator(Array.from(this.textBox.children));
    this.showLetters();
  }
}
customElements.define('text-display', TextDisplay);

/* Demo enabling code */

const textBox = document.getElementById('text-box');

const demoText = {
  indy: "The plot is set in the fictional Indiana Jones universe and revolves around the eponymous protagonist's global search for the legendary sunken city of Atlantis. Sophia Hapgood, an old co-worker of Indiana Jones who gave up her archaeological career to become a psychic, supports him along the journey. The two partners are pursued by the Nazis who seek to use the power of Atlantis for warfare, and serve as the adventure's antagonists. The story was written by Hal Barwood and Noah Falstein, the game's designers, who had rejected the original plan to base it on an unused movie script. They came up with the final concept while researching real-world sources for a suitable plot device.",
  tentacle: "The game's plot follows Bernard Bernoulli and his friends Hoagie and Laverne as they attempt to stop the evil Purple Tentacle—a sentient, disembodied tentacle—from taking over the world. The player takes control of the trio and solves puzzles while using time travel to explore different periods of history." 
};

document.documentElement.addEventListener('pointerup', event => {
  const button = event.target.closest('button');
  if (!button) return;
  if (button.id === 'custom-submit') {
    textBox.setAttribute('text', document.getElementById('custom').value);
    return;
  }
  textBox.setAttribute('text', demoText[button.id]);
});