import { Event, verifyEvent, getPublicKey } from 'nostr-tools'
import type { Article } from '@/types/nostr'

/**
 * Service for verifying zap receipts and their signatures
 */
export class ZapVerificationService {
  /**
   * Verify a zap receipt signature
   */
  verifyZapReceiptSignature(event: Event): boolean {
    try {
      return verifyEvent(event)
    } catch (error) {
      console.error('Error verifying zap receipt signature:', error)
      return false
    }
  }

  /**
   * Check if a zap receipt is valid for a specific article and user
   */
  verifyZapReceiptForArticle(
    zapReceipt: Event,
    articleId: string,
    articlePubkey: string,
    userPubkey: string,
    expectedAmount: number
  ): boolean {
    // Verify signature first
    if (!this.verifyZapReceiptSignature(zapReceipt)) {
      console.warn('Zap receipt signature verification failed')
      return false
    }

    // Verify the zap receipt is from the expected user
    // In zap receipts, the 'p' tag should contain the recipient (article author)
    // and the event pubkey should be from the payer or zap service
    const recipientTag = zapReceipt.tags.find((tag) => tag[0] === 'p')
    if (!recipientTag || recipientTag[1] !== articlePubkey) {
      console.warn('Zap receipt recipient does not match article author')
      return false
    }

    // Verify the article ID is referenced
    const eventTag = zapReceipt.tags.find((tag) => tag[0] === 'e')
    if (!eventTag || eventTag[1] !== articleId) {
      console.warn('Zap receipt does not reference the correct article')
      return false
    }

    // Verify the amount (in millisats, so we need to check if it's >= expectedAmount * 1000)
    const amountTag = zapReceipt.tags.find((tag) => tag[0] === 'amount')
    if (amountTag) {
      const amountInMillisats = parseInt(amountTag[1] || '0')
      const expectedAmountInMillisats = expectedAmount * 1000

      if (amountInMillisats < expectedAmountInMillisats) {
        console.warn(`Zap amount ${amountInMillisats} is less than expected ${expectedAmountInMillisats}`)
        return false
      }
    } else {
      console.warn('Zap receipt does not contain amount tag')
      return false
    }

    // Verify it's a zap receipt (kind 9735)
    if (zapReceipt.kind !== 9735) {
      console.warn('Event is not a zap receipt (kind 9735)')
      return false
    }

    return true
  }

  /**
   * Extract payment information from a zap receipt
   */
  extractPaymentInfo(zapReceipt: Event): {
    amount: number // in satoshis
    recipient: string
    articleId: string | null
    payer: string
  } | null {
    try {
      const amountTag = zapReceipt.tags.find((tag) => tag[0] === 'amount')
      const recipientTag = zapReceipt.tags.find((tag) => tag[0] === 'p')
      const eventTag = zapReceipt.tags.find((tag) => tag[0] === 'e')

      if (!amountTag || !recipientTag) {
        return null
      }

      const amountInMillisats = parseInt(amountTag[1] || '0')
      const amountInSats = Math.floor(amountInMillisats / 1000)

      return {
        amount: amountInSats,
        recipient: recipientTag[1],
        articleId: eventTag ? eventTag[1] : null,
        payer: zapReceipt.pubkey,
      }
    } catch (error) {
      console.error('Error extracting payment info:', error)
      return null
    }
  }
}

export const zapVerificationService = new ZapVerificationService()