interface FeedTargetInput {
  feed_id?: string;
  xsec_token?: string;
  url?: string;
}

interface UserTargetInput {
  user_id?: string;
  xsec_token?: string;
  url?: string;
}

interface FeedTargetResolved {
  feedId: string;
  xsecToken: string;
}

interface UserTargetResolved {
  userId: string;
  xsecToken: string;
}

function parseXhsUrl(rawUrl: string): URL {
  const trimmed = rawUrl.trim();
  if (!trimmed) {
    throw new Error('url cannot be empty');
  }

  if (/^https?:\/\//i.test(trimmed)) {
    return new URL(trimmed);
  }

  if (trimmed.startsWith('/')) {
    return new URL(`https://www.xiaohongshu.com${trimmed}`);
  }

  return new URL(`https://${trimmed}`);
}

function extractFeedIdFromPath(pathname: string): string | undefined {
  const patterns = [
    /\/explore\/([a-zA-Z0-9_-]+)/,
    /\/discovery\/item\/([a-zA-Z0-9_-]+)/,
    /\/note\/([a-zA-Z0-9_-]+)/,
  ];

  for (const pattern of patterns) {
    const match = pathname.match(pattern);
    if (match?.[1]) return match[1];
  }
  return undefined;
}

function extractUserIdFromPath(pathname: string): string | undefined {
  const match = pathname.match(/\/user\/profile\/([a-zA-Z0-9_-]+)/);
  return match?.[1];
}

function extractXsecToken(url: URL): string | undefined {
  return url.searchParams.get('xsec_token') ?? url.searchParams.get('xsecToken') ?? undefined;
}

export function resolveFeedTarget(input: FeedTargetInput): FeedTargetResolved {
  let feedId = input.feed_id?.trim();
  let xsecToken = input.xsec_token?.trim();

  if (input.url) {
    const parsed = parseXhsUrl(input.url);
    feedId = feedId || extractFeedIdFromPath(parsed.pathname);
    xsecToken = xsecToken || extractXsecToken(parsed);
  }

  if (!feedId || !xsecToken) {
    throw new Error('xhs_get_feed_detail requires either url with feed_id/xsec_token, or both feed_id and xsec_token');
  }

  return { feedId, xsecToken };
}

export function resolveUserTarget(input: UserTargetInput): UserTargetResolved {
  let userId = input.user_id?.trim();
  let xsecToken = input.xsec_token?.trim();

  if (input.url) {
    const parsed = parseXhsUrl(input.url);
    userId = userId || extractUserIdFromPath(parsed.pathname);
    xsecToken = xsecToken || extractXsecToken(parsed);
  }

  if (!userId || !xsecToken) {
    throw new Error('xhs_get_user_profile requires either url with user_id/xsec_token, or both user_id and xsec_token');
  }

  return { userId, xsecToken };
}