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(agentSlug: string, sessionId: string): string {
  return `${agentSlug}:${sessionId}`;
}

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

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

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

export function getRateLimitInfo(agentSlug: string, sessionId: string, ip: string): RateLimitResult {
  return checkRateLimit(agentSlug, sessionId, ip);
}

export const SESSION_LIMIT_VALUE = SESSION_LIMIT;
export const IP_DAILY_LIMIT_VALUE = IP_DAILY_LIMIT;