story-research-zapwall/lib/nostrPrivateMessages.ts

import { Event, nip04 } from 'nostr-tools'
import { SimplePool } from 'nostr-tools'

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

function createPrivateMessageFilters(eventId: string, publicKey: string, authorPubkey: string) {
  return [
    {
      kinds: [4], // Encrypted direct messages
      '#p': [publicKey],
      '#e': [eventId], // Filter by event ID to find relevant private messages
      authors: [authorPubkey], // Filter by author of the original article
      limit: 10, // Limit to recent messages
    },
  ]
}

function decryptContent(privateKey: string, event: Event): Promise<string | null> {
  return Promise.resolve(nip04.decrypt(privateKey, event.pubkey, event.content)).then((decrypted) =>
    decrypted ? decrypted : null
  )
}

/**
 * Get private content for an article (encrypted message from author)
 */
export function getPrivateContent(
  pool: SimplePool,
  eventId: string,
  authorPubkey: string,
  privateKey: string,
  publicKey: string
): Promise<string | null> {
  if (!privateKey || !pool || !publicKey) {
    throw new Error('Private key not set or pool not initialized')
  }

  return new Promise((resolve) => {
    let resolved = false
    const sub = pool.sub([RELAY_URL], createPrivateMessageFilters(eventId, publicKey, authorPubkey))

    const finalize = (result: string | null) => {
      if (resolved) {
        return
      }
      resolved = true
      sub.unsub()
      resolve(result)
    }

    sub.on('event', (event: Event) => {
      void decryptContent(privateKey, event)
        .then((content) => {
          if (content) {
            finalize(content)
          }
        })
        .catch((e) => {
          console.error('Error decrypting content:', e)
        })
    })
    sub.on('eose', () => finalize(null))
    setTimeout(() => finalize(null), 5000)
  })
}