whatsapp-bot/src/lib/deduplication.ts

import type Redis from 'ioredis'
import { getLogger } from './logger.js'

const log = getLogger('deduplication')

const DEDUP_TTL = 86400 // 24 hours

export class MessageDeduplicator {
  constructor(private redis: Redis) {}

  async isDuplicate(messageId: string): Promise<boolean> {
    const key = `wa:dedup:${messageId}`
    const result = await this.redis.set(key, '1', 'EX', DEDUP_TTL, 'NX')
    if (result === null) {
      log.warn({ messageId }, 'Duplicate message detected')
      return true
    }
    return false
  }
}