story-research-zapwall/lib/nostrZapVerification.ts

import type { Event } from 'nostr-tools'
import { SimplePool } from 'nostr-tools'

const RELAY_URL = process.env.NEXT_PUBLIC_NOSTR_RELAY_URL ?? 'wss://relay.damus.io'

function createZapFilters(targetPubkey: string, targetEventId: string, userPubkey: string) {
  return [
    {
      kinds: [9735], // Zap receipt
      '#p': [targetPubkey],
      '#e': [targetEventId],
      authors: [userPubkey], // Filter by the payer's pubkey
    },
  ]
}

async function isValidZapReceipt(
  event: Event,
  targetEventId: string,
  targetPubkey: string,
  userPubkey: string,
  amount: number
): Promise<boolean> {
  // Import verification service dynamically to avoid circular dependencies
  const { zapVerificationService } = await import('./zapVerification')

  return zapVerificationService.verifyZapReceiptForArticle(event, targetEventId, targetPubkey, userPubkey, amount)
}

/**
 * Check if user has paid for an article by looking for zap receipts
 */
export function checkZapReceipt(
  pool: SimplePool,
  targetPubkey: string,
  targetEventId: string,
  amount: number,
  userPubkey: string
): Promise<boolean> {
  if (!pool) {
    return false
  }

  return new Promise((resolve) => {
    let resolved = false
    const sub = pool.sub([RELAY_URL], createZapFilters(targetPubkey, targetEventId, userPubkey))

    const finalize = (value: boolean) => {
      if (resolved) {
        return
      }
      resolved = true
      sub.unsub()
      resolve(value)
    }

    sub.on('event', (event: Event) => {
      if (resolved) {
        return
      }
      void isValidZapReceipt(event, targetEventId, targetPubkey, userPubkey, amount).then((isValid) => {
        if (isValid) {
          finalize(true)
        }
      })
    })

    const end = () => finalize(false)
    sub.on('eose', end)
    setTimeout(end, 3000)
  })
}