// The community board — "Thank you Senator BAM".
//
// Visitors post with a nickname only (no accounts, no email, by design —
// Daniel: the site is public and the barrier to saying thanks must be a
// text field, not a login). The board is an open guestbook: the abuse
// controls are deliberately light but real:
//
//   * per-IP rate limit: 3 posts / 10 min, 12 / day (lib/board.js, Mongo
//     rate collection, no Redis needed).
//   * hard content caps (nickname 24 chars, message 600 chars) so a drive-by
//     can't park a wall of text.
//   * message sanitisation: HTML is stripped to text. The UI renders plain
//     text nodes only — there is no markdown, no links, no images. A post
//     that is ONLY a URL is rejected (the classic guestbook spam shape).
//   * nothing is executed, fetched, or rendered as markup. Ever.
//
// The default title of the board is "Thank you Senator BAM" and every post
// is a thank-you / message to the senator — that is the page's social
// contract, stated in the copy, enforced lightly (tone is not machine-
// judged).

import { getCollections } from "./db.js";

const NICK_MAX = 24;
const MSG_MAX = 600;
const RATE_WINDOW_MS = 10 * 60 * 1000;
const RATE_LIMIT_WINDOW = 3; // per 10 min
const RATE_LIMIT_DAY = 12; // per 24h
const LIST_LIMIT = 200; // the board prints newest-first, capped

function cleanNick(s) {
  return String(s || "")
    .replace(/<[^>]*>/g, " ")
    .replace(/[\x00-\x1f]/g, "")
    .replace(/\s+/g, " ")
    .trim()
    .slice(0, NICK_MAX);
}
function cleanMsg(s) {
  // Strip markup/controls, collapse whitespace, cap length.
  const t = String(s || "")
    .replace(/<[^>]*>/g, " ")
    .replace(/[\x00-\x1f]/g, "")
    .replace(/\s+/g, " ")
    .trim();
  return t.slice(0, MSG_MAX);
}
// A message that is one URL (or a URL plus a couple of words) is spam-shaped.
// \b(?<=^|\s)https?://  = a URL at the start or after whitespace — the classic
// guestbook spam shape. A URL embedded in a real sentence ("read more at
// https://...") is left alone; plain words remain the rule, not the exception.
function looksLikeUrlOnly(t) {
  const withUrl = /(^|\s)(https?:\/\/|www\.)\S+/i.test(t);
  if (!withUrl) return false;
  const stripped = t.replace(/(^|\s)(https?:\/\/|www\.)\S+/gi, " ").replace(/\s+/g, " ").trim();
  return stripped.length < 12;
}

function ipOf(req) {
  const fwd = req.headers.get("x-forwarded-for");
  if (fwd) return fwd.split(",")[0].trim().slice(0, 64);
  return req.headers.get("x-real-ip") || "unknown";
}

export async function getBoard({ limit = LIST_LIMIT } = {}) {
  const { board } = await getCollections();
  const rows = await board
    .find({})
    .sort({ createdAt: -1 })
    .limit(Math.min(Math.max(1, limit), LIST_LIMIT))
    .toArray();
  return rows.map((r) => ({
    id: String(r._id),
    nick: r.nick,
    message: r.message,
    createdAt: r.createdAt,
  }));
}

export async function postBoard(req, body) {
  const ip = ipOf(req);
  const now = Date.now();
  const { rate, board } = await getCollections();

  // Rate limit: count this IP's posts in the 10-min and 24h windows.
  // createdAt is stored as a BSON Date, so the comparison MUST be a Date too —
  // a numeric epoch silently matches nothing (verified: the counter stayed 0).
  const dayAgo = now - 24 * 3600e3;
  const [inWindow, inDay] = await Promise.all([
    rate.countDocuments({ ip, createdAt: { $gte: new Date(now - RATE_WINDOW_MS) } }),
    rate.countDocuments({ ip, createdAt: { $gte: new Date(dayAgo) } }),
  ]);
  if (inWindow >= RATE_LIMIT_WINDOW) {
    return { ok: false, error: "Slow down — a few thanks at a time. Try again in a few minutes.", status: 429 };
  }
  if (inDay >= RATE_LIMIT_DAY) {
    return { ok: false, error: "That's plenty of thanks for today. Come back tomorrow.", status: 429 };
  }

  const nick = cleanNick(body && body.nick);
  const message = cleanMsg(body && body.message);
  if (nick.length < 2) return { ok: false, error: "Give us a nickname (2+ characters) so we know who to thank.", status: 400 };
  if (message.length < 3) return { ok: false, error: "Your message is empty.", status: 400 };
  if (looksLikeUrlOnly(message)) return { ok: false, error: "Plain words only, please — no links.", status: 400 };

  const doc = {
    nick,
    message,
    ip: ip.slice(0, 64),
    createdAt: new Date(now),
  };
  const res = await board.insertOne(doc);
  // Bump the rate row (upsert keeps one doc per ip+day, but we just count
  // recent createdAt values, so insert a lightweight marker per post).
  await rate.insertOne({ ip, createdAt: new Date(now) });

  return {
    ok: true,
    post: { id: String(res.insertedId), nick, message, createdAt: doc.createdAt },
  };
}

// A friendly, non-authoritative total for the masthead.
export async function boardCount() {
  try {
    const { board } = await getCollections();
    return await board.countDocuments({});
  } catch {
    return 0;
  }
}