import crypto from 'node:crypto';

export function createPageDataSessionStore(options = {}) {
  const ttlMs = Number(options.ttlMs ?? 30 * 60 * 1000);
  const sessions = new Map();

  function hashToken(token) {
    return crypto.createHash('sha256').update(String(token)).digest('hex');
  }

  function issue({ pageId, ownerUserId, publicationId, accessMode }) {
    const token = crypto.randomBytes(32).toString('base64url');
    const tokenHash = hashToken(token);
    const expiresAt = Date.now() + ttlMs;
    sessions.set(tokenHash, {
      pageId,
      ownerUserId,
      publicationId,
      accessMode,
      sessionId: crypto.randomUUID(),
      expiresAt,
    });
    return {
      token,
      expiresAt,
      sessionId: sessions.get(tokenHash).sessionId,
    };
  }

  function verify(token) {
    const session = sessions.get(hashToken(token));
    if (!session) return null;
    if (session.expiresAt <= Date.now()) {
      sessions.delete(hashToken(token));
      return null;
    }
    return session;
  }

  function revoke(token) {
    return sessions.delete(hashToken(token));
  }

  function revokeByPageId(pageId) {
    let count = 0;
    for (const [key, session] of sessions.entries()) {
      if (session.pageId === pageId) {
        sessions.delete(key);
        count += 1;
      }
    }
    return count;
  }

  function listByPageId(pageId) {
    const now = Date.now();
    const active = [];
    for (const session of sessions.values()) {
      if (session.pageId !== pageId) continue;
      if (session.expiresAt <= now) continue;
      active.push({
        sessionId: session.sessionId,
        pageId: session.pageId,
        ownerUserId: session.ownerUserId,
        accessMode: session.accessMode,
        expiresAt: session.expiresAt,
      });
    }
    return active;
  }

  function clearExpired() {
    const now = Date.now();
    for (const [key, session] of sessions.entries()) {
      if (session.expiresAt <= now) sessions.delete(key);
    }
  }

  return { issue, verify, revoke, revokeByPageId, listByPageId, clearExpired };
}

export function createPageDataRateLimiter(options = {}) {
  const windowMs = Number(options.windowMs ?? 60_000);
  const maxRequests = Number(options.maxRequests ?? 30);
  const buckets = new Map();

  function check(key) {
    const now = Date.now();
    const bucket = buckets.get(key) ?? { count: 0, resetAt: now + windowMs };
    if (now >= bucket.resetAt) {
      bucket.count = 0;
      bucket.resetAt = now + windowMs;
    }
    bucket.count += 1;
    buckets.set(key, bucket);
    if (bucket.count > maxRequests) {
      throw Object.assign(new Error('请求过于频繁，请稍后再试'), {
        code: 'rate_limited',
        status: 429,
      });
    }
    return { remaining: Math.max(0, maxRequests - bucket.count), resetAt: bucket.resetAt };
  }

  return { check };
}

export function hashClientMeta(value) {
  return crypto.createHash('sha256').update(String(value ?? '')).digest('hex').slice(0, 16);
}