import "server-only";

import { getVisitorTrackingConfig } from "@/lib/config/server";
import { getRedisClient } from "@/lib/redis";
import {
  getClientAddress,
  hashClientAddress,
} from "@/lib/visitor/visitor-identifiers";

const VISITOR_SET_KEY = "erika:unique_visitors:v2";
const LEGACY_VISITOR_SET_KEY = "erika:unique_visitors";

export async function trackUniqueVisitor(headers: Headers) {
  const client = await getRedisClient();
  const address = getClientAddress(headers);

  if (address) {
    const { secret } = getVisitorTrackingConfig();
    const identifier = hashClientAddress(address, secret);
    const [isLegacyVisitor, isPrivateVisitor] = await Promise.all([
      client.sismember(LEGACY_VISITOR_SET_KEY, address),
      client.sismember(VISITOR_SET_KEY, identifier),
    ]);

    if (isLegacyVisitor) {
      // Keep the legacy visitor in the old total without counting a revisit twice.
      if (isPrivateVisitor) await client.srem(VISITOR_SET_KEY, identifier);
    } else {
      await client.sadd(VISITOR_SET_KEY, identifier);
    }
  }

  const [legacyCount, privateCount] = await Promise.all([
    client.scard(LEGACY_VISITOR_SET_KEY),
    client.scard(VISITOR_SET_KEY),
  ]);
  return legacyCount + privateCount;
}