/**
 * 角色卡限流（独立于 agent 的 rate-limit.ts）。
 *
 * 仅对未登录用户（访客）生效，与 agent 采用相同的阈值与实现：
 * - 每会话上限 20 条
 * - 每 IP 每日上限 50 条
 * 内存计数（Map），按日期字符串跨天自动重置；进程重启即清零（与 agent 一致）。
 */

const SESSION_LIMIT = 20;
const IP_DAILY_LIMIT = 50;

interface RateCounter {
  count: number;
  date: string;
}

const sessionCounters = new Map<string, RateCounter>();
const ipCounters = new Map<string, RateCounter>();

function getTodayStr(): string {
  return new Date().toISOString().slice(0, 10);
}

function getCounter(map: Map<string, RateCounter>, key: string): RateCounter {
  const today = getTodayStr();
  let counter = map.get(key);
  if (!counter || counter.date !== today) {
    counter = { count: 0, date: today };
    map.set(key, counter);
  }
  return counter;
}

function buildSessionKey(cardSlug: string, sessionId: string): string {
  return `character:${cardSlug}:${sessionId}`;
}

function buildIpKey(cardSlug: string, ip: string): string {
  return `character:${cardSlug}:${ip}`;
}

export interface CharacterRateLimitResult {
  sessionRemaining: number;
  ipRemaining: number;
  blocked: boolean;
}

export function checkCharacterRateLimit(
  cardSlug: string,
  sessionId: string,
  ip: string,
): CharacterRateLimitResult {
  const sessionKey = buildSessionKey(cardSlug, sessionId);
  const ipKey = buildIpKey(cardSlug, ip);
  const sessionCounter = getCounter(sessionCounters, sessionKey);
  const ipCounter = getCounter(ipCounters, ipKey);

  const sessionRemaining = Math.max(0, SESSION_LIMIT - sessionCounter.count);
  const ipRemaining = Math.max(0, IP_DAILY_LIMIT - ipCounter.count);
  const blocked = sessionRemaining === 0 || ipRemaining === 0;

  return { sessionRemaining, ipRemaining, blocked };
}

export function incrementCharacterRateLimit(
  cardSlug: string,
  sessionId: string,
  ip: string,
): void {
  const sessionKey = buildSessionKey(cardSlug, sessionId);
  const ipKey = buildIpKey(cardSlug, ip);
  const sessionCounter = getCounter(sessionCounters, sessionKey);
  const ipCounter = getCounter(ipCounters, ipKey);
  sessionCounter.count++;
  ipCounter.count++;
}

export const CHARACTER_SESSION_LIMIT = SESSION_LIMIT;
export const CHARACTER_IP_DAILY_LIMIT = IP_DAILY_LIMIT;