// Patch notes come from the site (or its cached copy) and are untrusted:
// Markdown is rendered with marked, then every byte of HTML goes through
// DOMPurify with a small allowlist before it reaches {@html}.
import { Marked, type Token, type TokensList } from "marked";
import DOMPurify from "dompurify";

const marked = new Marked({ gfm: true, breaks: false, async: false });

const ALLOWED_TAGS = [
  "h1", "h2", "h3", "h4", "h5", "h6",
  "p", "br", "hr", "blockquote",
  "ul", "ol", "li",
  "strong", "em", "b", "i", "del", "s", "code", "pre", "kbd", "sub", "sup",
  "a",
  "table", "thead", "tbody", "tr", "th", "td",
  "input", // GFM task-list checkboxes (forced disabled below)
];

const ALLOWED_ATTR = ["href", "title", "align", "start", "type", "checked", "disabled"];

const SAFE_HREF = /^(https?:|mailto:|#)/i;

DOMPurify.addHook("afterSanitizeAttributes", (node) => {
  if (node.tagName === "A") {
    const href = node.getAttribute("href") ?? "";
    if (!SAFE_HREF.test(href.trim())) node.removeAttribute("href");
    node.removeAttribute("target");
    node.setAttribute("rel", "noopener noreferrer");
    if (href && !node.getAttribute("title")) node.setAttribute("title", href);
  }
  if (node.tagName === "INPUT") {
    if (node.getAttribute("type") !== "checkbox") node.remove();
    else node.setAttribute("disabled", "");
  }
});

function sanitize(html: string): string {
  return DOMPurify.sanitize(html, {
    ALLOWED_TAGS,
    ALLOWED_ATTR,
    ALLOW_DATA_ATTR: false,
    ALLOW_ARIA_ATTR: false,
  });
}

function render(tokens: Token[], links: TokensList["links"]): string {
  const list = Object.assign(tokens, { links }) as TokensList;
  return sanitize(marked.parser(list));
}

function isRoadmapHeading(token: Token): boolean {
  return token.type === "heading" && token.depth === 2 && /^roadmap$/i.test(token.text.trim());
}

export interface RenderedNotes {
  /** Everything except the Roadmap section. */
  notes: string;
  /** Contents under `## Roadmap` (heading excluded), or null when absent/empty. */
  roadmap: string | null;
}

export function renderNotes(markdown: string): RenderedNotes {
  const tokens = marked.lexer(markdown);
  const notes: Token[] = [];
  const roadmap: Token[] = [];
  let inRoadmap = false;
  let sawRoadmap = false;

  for (const token of tokens) {
    if (isRoadmapHeading(token)) {
      inRoadmap = true;
      sawRoadmap = true;
      continue;
    }
    if (inRoadmap && token.type === "heading" && token.depth <= 2) inRoadmap = false;
    (inRoadmap ? roadmap : notes).push(token);
  }

  const hasRoadmapContent = roadmap.some((t) => t.type !== "space");
  return {
    notes: render(notes, tokens.links),
    roadmap: sawRoadmap && hasRoadmapContent ? render(roadmap, tokens.links) : null,
  };
}