import { marked } from "./third_party/marked/marked.esm.js";

export const messageMarkdownOptions = Object.freeze({
  gfm: true,
  breaks: false,
  renderer: messageMarkdownRenderer()
});

export function renderMessageMarkdown(markdown) {
  return marked.parse(String(markdown ?? ""), messageMarkdownOptions);
}

export function hardenRenderedMarkdown(root) {
  for (const element of root.querySelectorAll("script, style, iframe, object, embed, form, input, button, textarea, select")) {
    element.replaceWith(document.createTextNode(element.textContent ?? ""));
  }
  for (const element of root.querySelectorAll("*")) {
    for (const attribute of [...element.attributes]) {
      const name = attribute.name.toLowerCase();
      if (name.startsWith("on") || name === "style") {
        element.removeAttribute(attribute.name);
      }
    }
  }
  for (const anchor of root.querySelectorAll("a[href]")) {
    const href = safeMarkdownHref(anchor.getAttribute("href"));
    if (!href) {
      anchor.removeAttribute("href");
    } else {
      anchor.setAttribute("href", href);
      anchor.setAttribute("rel", "noreferrer");
    }
  }
}

function messageMarkdownRenderer() {
  const renderer = new marked.Renderer();
  renderer.html = ({ text }) => escapeHtml(text);
  renderer.link = ({ href, title, tokens }) => {
    const text = renderer.parser.parseInline(tokens);
    const safeHref = safeMarkdownHref(href);
    if (!safeHref) return text;
    const safeTitle = title ? ` title="${escapeHtml(title)}"` : "";
    return `<a href="${escapeHtml(safeHref)}"${safeTitle} rel="noreferrer">${text}</a>`;
  };
  renderer.image = ({ text }) => escapeHtml(text ?? "");
  return renderer;
}

function safeMarkdownHref(value) {
  const href = String(value ?? "").trim();
  if (!href) return null;
  if (/^(?:https?:|mailto:)/iu.test(href)) return href;
  if (/^[#/?]/u.test(href)) return href;
  return null;
}

function escapeHtml(value) {
  return String(value ?? "").replace(/[&<>"']/g, (char) => ({
    "&": "&amp;",
    "<": "&lt;",
    ">": "&gt;",
    "\"": "&quot;",
    "'": "&#39;"
  })[char]);
}