(function() {
  const stream = document.querySelector(".term__stream");

  if (!stream) {
    return;
  }

  const prefersReducedMotion = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

  if (prefersReducedMotion) {
    return;
  }

  const CHAR_DELAY = 18;
  const AFTER_COMMAND_DELAY = 90;
  const AFTER_OUTPUT_DELAY = 130;

  // Build the playback script before hiding anything, so a thrown error here
  // leaves the page in its fully rendered state.
  // Commands type into their own span so the blinking caret beside them
  // survives the text rewrites.
  const steps = Array.from(stream.children).map((element) => {
    const target = element.querySelector(".cmd__text");

    return {
      element,
      target: target || element,
      isCommand: element.classList.contains("cmd"),
      text: (target || element).textContent
    };
  });

  if (!steps.some((step) => step.isCommand)) {
    return;
  }

  steps.forEach((step) => {
    if (step.isCommand) {
      step.target.textContent = "";
      return;
    }

    step.element.classList.add("is-typing-hidden");
  });

  const wait = (ms) => new Promise((resolve) => window.setTimeout(resolve, ms));

  const typeCommand = async (element, text) => {
    for (let index = 0; index < text.length; index += 1) {
      element.textContent = text.slice(0, index + 1);
      await wait(CHAR_DELAY);
    }
  };

  const play = async () => {
    for (const step of steps) {
      if (step.isCommand) {
        await typeCommand(step.target, step.text);
        await wait(AFTER_COMMAND_DELAY);
        continue;
      }

      step.element.classList.remove("is-typing-hidden");
      await wait(AFTER_OUTPUT_DELAY);
    }
  };

  play();
})();