const REDDITBOT_SESSION_FILENAME = 'redditbot-session.json';
export const REDDIT_CHAT_URL = 'https://chat.reddit.com/';

export function normalizeRedditAccountId(accountId) {
  const trimmed = String(accountId ?? '').trim();
  const normalized = trimmed.startsWith('t2_') ? trimmed : `t2_${trimmed}`;
  if (!/^t2_[a-z0-9]+$/i.test(normalized)) {
    throw new Error('Reddit returned an invalid account ID.');
  }
  return normalized;
}

export function assertMatchingSessionIdentity(redditIdentity, matrixUserId) {
  const accountId = normalizeRedditAccountId(redditIdentity?.accountId);
  const username = String(redditIdentity?.username ?? '').trim();
  if (!username) throw new Error('Reddit did not return an authenticated username.');
  const expectedMatrixUserId = `@${accountId}:reddit.com`;
  if (matrixUserId !== expectedMatrixUserId) {
    throw new Error(
      `Reddit is logged in as u/${username} (${accountId}), but Chat is authenticated as ${matrixUserId}. Reload Reddit Chat after switching accounts, then export again.`,
    );
  }
}

function isRedditDomain(domain) {
  const normalised = domain.toLowerCase().replace(/^\./, '');
  return normalised === 'reddit.com' || normalised.endsWith('.reddit.com');
}

function toExportCookie(cookie) {
  return {
    name: cookie.name,
    value: cookie.value,
    domain: cookie.domain,
    path: cookie.path,
    expires: cookie.expirationDate,
    httpOnly: cookie.httpOnly,
    secure: cookie.secure,
    sameSite: cookie.sameSite,
  };
}

export function createSessionExportDownload(cookies, matrix) {
  if (!matrix?.homeserver || !matrix?.accessToken || !matrix?.userId) {
    throw new Error('Open Reddit Chat before exporting so Matrix credentials can be captured.');
  }
  const exportFile = {
    cookies: cookies.filter((cookie) => isRedditDomain(cookie.domain)).map(toExportCookie),
    matrix,
  };

  return {
    filename: REDDITBOT_SESSION_FILENAME,
    url: `data:application/json;charset=utf-8,${encodeURIComponent(JSON.stringify(exportFile))}`,
  };
}