sol-mem-gen/src/utils/verifyPayment.ts

import assert from 'assert';
import BN from 'bn.js';

import { Connection } from '@solana/web3.js';
import { TOKEN_PROGRAM_ID } from '@solana/spl-token';

import { AppDataSource } from '../data-source';
import { Payment } from '../entity/Payment';

assert(process.env.NEXT_PUBLIC_SOLANA_RPC_URL, 'SOLANA_RPC_URL is required');

const SOLANA_RPC_URL = process.env.NEXT_PUBLIC_SOLANA_RPC_URL;
const SOLANA_WEBSOCKET_URL = process.env.NEXT_PUBLIC_SOLANA_WEBSOCKET_URL;

const connection = new Connection(
  SOLANA_RPC_URL,
  {
    commitment: 'confirmed',
    wsEndpoint: SOLANA_WEBSOCKET_URL,
    confirmTransactionInitialTimeout: 60000,
  }
);

export async function isSignatureUsed(transactionSignature: string): Promise<boolean> {
  const paymentRepository = AppDataSource.getRepository(Payment);
  const payment = await paymentRepository.findOneBy({ transactionSignature });
  if (payment) {
    return true;
  }
  return false;
}

export async function markSignatureAsUsed(transactionSignature: string): Promise<void> {
  await AppDataSource.transaction(async (transactionalEntityManager) => {
    const paymentRepository = transactionalEntityManager.getRepository(Payment);

    // Check if the payment with the given signature already exists
    const exists = await paymentRepository.exists({ where: { transactionSignature } });

    // If not, create a new payment entry
    if (!exists) {
      const newPayment = paymentRepository.create({ transactionSignature });
      await paymentRepository.save(newPayment);
    }
  });
}

export async function verifyPayment(
  transactionSignature: string,
  tokenAmount: BN,
): Promise<boolean> {
  try {
    // Check if the signature is already used
    if (await isSignatureUsed(transactionSignature)) {
      return false;
    }

    const transaction = await connection.getParsedTransaction(transactionSignature, 'confirmed');
    if (!transaction) {
      throw new Error('Transaction not found');
    }

    const transferInstruction = transaction.transaction.message.instructions.find(
      (instr) => 'parsed' in instr && instr.programId.equals(TOKEN_PROGRAM_ID)
    );

    if (!transferInstruction || !('parsed' in transferInstruction)) {
      throw new Error('Transfer instruction not found');
    }

    const { parsed } = transferInstruction;
    const { info } = parsed;
    const { amount } = info;

    const transactionAmount = new BN(amount);

    if (transactionAmount.gte(tokenAmount)) {
      return true;
    }
    console.log('Transaction amount is less than minimum amount. Rejecting request');
    return false;
  } catch (error) {
    console.error('Verification error:', error);
    return false;
  }
}