import { later } from "@ember/runloop";
import loadScript from "discourse/lib/load-script";
import { cook } from "discourse/lib/text";

const PROGRESS_INTERVAL = 40;
const GIVE_UP_INTERVAL = 10000;
const LETTERS_PER_INTERVAL = 6;

let progressTimer = null;

function lastNonEmptyChild(element) {
  let lastChild = element.lastChild;
  while (
    lastChild &&
    lastChild.nodeType === Node.TEXT_NODE &&
    !/\S/.test(lastChild.textContent)
  ) {
    lastChild = lastChild.previousSibling;
  }
  return lastChild;
}

export function addProgressDot(element) {
  let lastBlock = element;

  while (true) {
    let lastChild = lastNonEmptyChild(lastBlock);
    if (!lastChild) {
      break;
    }

    if (lastChild.nodeType === Node.ELEMENT_NODE) {
      lastBlock = lastChild;
    } else {
      break;
    }
  }

  const dotElement = document.createElement("span");
  dotElement.classList.add("progress-dot");
  lastBlock.appendChild(dotElement);
}

async function applyProgress(postStatus, postStream) {
  postStatus.startTime = postStatus.startTime || Date.now();
  let post = postStream.findLoadedPost(postStatus.post_id);

  const postElement = document.querySelector(`#post_${postStatus.post_number}`);

  if (Date.now() - postStatus.startTime > GIVE_UP_INTERVAL) {
    if (postElement) {
      postElement.classList.remove("streaming");
    }
    return true;
  }

  if (!post) {
    // wait till later
    return false;
  }

  const oldRaw = post.get("raw") || "";

  if (postStatus.raw === oldRaw && !postStatus.done) {
    const hasProgressDot =
      postElement && postElement.querySelector(".progress-dot");
    if (hasProgressDot) {
      return false;
    }
  }

  if (postStatus.raw) {
    const newRaw = postStatus.raw.substring(
      0,
      oldRaw.length + LETTERS_PER_INTERVAL
    );
    const cooked = await cook(newRaw);

    post.set("raw", newRaw);
    post.set("cooked", cooked);

    // resets animation
    postElement.classList.remove("streaming");
    void postElement.offsetWidth;
    postElement.classList.add("streaming");

    const cookedElement = document.createElement("div");
    cookedElement.innerHTML = cooked;

    addProgressDot(cookedElement);

    const element = document.querySelector(
      `#post_${postStatus.post_number} .cooked`
    );

    await loadScript("/javascripts/diffhtml.min.js");
    window.diff.innerHTML(element, cookedElement.innerHTML);
  }

  if (postStatus.done) {
    if (postElement) {
      postElement.classList.remove("streaming");
    }
  }

  return postStatus.done;
}

async function handleProgress(postStream) {
  const status = postStream.aiStreamingStatus;

  let keepPolling = false;

  const promises = Object.keys(status).map(async (postId) => {
    let postStatus = status[postId];

    const done = await applyProgress(postStatus, postStream);

    if (done) {
      delete status[postId];
    } else {
      keepPolling = true;
    }
  });

  await Promise.all(promises);
  return keepPolling;
}

function ensureProgress(postStream) {
  if (!progressTimer) {
    progressTimer = later(async () => {
      const keepPolling = await handleProgress(postStream);

      progressTimer = null;

      if (keepPolling) {
        ensureProgress(postStream);
      }
    }, PROGRESS_INTERVAL);
  }
}

export default function streamText(postStream, data) {
  let status = (postStream.aiStreamingStatus =
    postStream.aiStreamingStatus || {});
  status[data.post_id] = data;
  ensureProgress(postStream);
}