import { Expression } from "./types";

export function parseWiktionaryData(
  prompt: string,
  data: string
): Expression | null {
  // Prevent next.js SSR from crashing here
  if (typeof window === "undefined") return null;

  const parser = new DOMParser();
  const document = parser.parseFromString(data, "text/html");

  // TODO settings-based language selection
  const header = document.getElementById("Finnish")?.parentElement;
  if (!header) return null;

  // Grab window of wanted elements and filter out unwanted elements within the window
  const elements: (Element | HTMLElement)[] = [];
  let current = header.nextElementSibling;
  while (
    current &&
    !["hr", "h2"].includes(current.tagName.toLocaleLowerCase()) &&
    !isReferences(current)
  ) {
    let include = true;
    include = include && current.tagName.toLocaleLowerCase() !== "style";
    include = include && !current.classList.contains("noprint");
    include = include && !current.classList.contains("inflection-table");
    include = include && !isDeclension(current);
    if (include) elements.push(current);

    current = current.nextElementSibling;
  }

  const content = document.createElement("div");
  content.className = "wiktionary-content";
  for (const element of elements) {
    content.append(safeTreeClone(element) as string | Node);
  }

  return {
    prompt,
    description: content.outerHTML,
  };
}

function isDeclension(element?: Element | HTMLElement) {
  if (!element) return false;
  if (element.id.includes("Conjugation")) return true;
  if (element.id.includes("Declension")) return true;
  let child = element.firstElementChild;
  while (child) {
    if (isDeclension(child)) return true;
    child = child.nextElementSibling;
  }
}

function isReferences(element?: Element | HTMLElement) {
  if (!element) return false;
  if (element.id.includes("References")) return true;
  let child = element.firstElementChild;
  while (child) {
    if (isReferences(child)) return true;
    child = child.nextElementSibling;
  }
}

function safeTreeClone(element?: string | Element | HTMLElement) {
  if (!element) return null;
  if (typeof element === "string") return document.createTextNode(element);

  if (element.tagName.toLowerCase() === "a")
    return document.createTextNode(element.textContent || "");
  if (element.classList.contains("mw-editsection")) return null;
  if (element.classList.contains("nyms-toggle")) return null;
  if (element.tagName.toLowerCase() === "sup") return null;

  const result = document.createElement(element.tagName);
  const children = element.childNodes;
  for (let i = 0; i < children.length; i++) {
    const child = children.item(i);
    if (child.nodeName === "#text") result.append(child.cloneNode());
    else {
      const cloned = safeTreeClone(child as Element);
      if (cloned) result.append(cloned);
    }
  }
  return result;
}