import type { Event } from 'nostr-tools'
import { generatePurchaseHashId } from '../hashIdGenerator'
import type { ExtractedPurchase } from './types'
import { readAmountSats, readPaymentHash, readPayerPubkeyFromZapReceipt, readTagValue, readZapReceiptKind } from './utils'

export async function extractPurchaseFromEvent(event: Event): Promise<ExtractedPurchase | null> {
  if (event.kind !== 9735 || readZapReceiptKind(event) !== 'purchase') {
    return null
  }

  const payerPubkey = readPayerPubkeyFromZapReceipt(event)
  const authorPubkey = readTagValue(event, 'author') ?? readTagValue(event, 'p')
  const articleId = readTagValue(event, 'article') ?? readTagValue(event, 'e')
  const amount = readAmountSats(event)
  if (!payerPubkey || !authorPubkey || !articleId || amount === undefined) {
    console.error('[metadataExtractor] Invalid purchase zap receipt: missing required fields', { eventId: event.id })
    return null
  }

  const paymentHash = readPaymentHash(event)
  const id = await generatePurchaseHashId({ payerPubkey, articleId, authorPubkey, amount, paymentHash })
  return { type: 'purchase', id, payerPubkey, articleId, authorPubkey, amount, paymentHash, eventId: event.id }
}