Pay2Gateway/lib/crypto-engine.ts

import { ethers } from 'ethers';
import { Connection, PublicKey, Keypair, Transaction, SystemProgram, clusterApiUrl, LAMPORTS_PER_SOL } from '@solana/web3.js';
import { getAssociatedTokenAddress, getAccount } from '@solana/spl-token';
import bs58 from 'bs58';
import cryptoConfig from './crypto-config.json';

// ERC20 ABI for checking USDT/USDC balances
const ERC20_ABI = [
    "function balanceOf(address owner) view returns (uint256)",
    "function decimals() view returns (uint8)",
    "function symbol() view returns (string)",
    "function transfer(address to, uint256 value) public returns (bool)"
];

export class CryptoEngine {
    private provider!: ethers.JsonRpcProvider;
    private solConnection!: Connection;
    private network: string;
    private config: any;

    constructor(networkId: string = 'POLYGON') {
        this.network = networkId;
        this.config = cryptoConfig.networks.find(n => n.id === networkId);
        
        if (!this.config) throw new Error(`Network ${networkId} not found in config.`);

        if (this.network === 'SOLANA') {
            this.solConnection = new Connection(this.config.rpc, 'confirmed');
        } else {
            this.provider = new ethers.JsonRpcProvider(this.config.rpc);
        }
    }

    /**
     * Helper to get token config from JSON
     */
    private getTokenConfig(symbol: string) {
        return this.config.tokens.find((t: any) => t.symbol === symbol);
    }

    /**
     * Generates a temporary wallet for a transaction.
     */
    static async createTemporaryWallet(network: string = 'POLYGON'): Promise<{ address: string, privateKey: string }> {
        if (network === 'SOLANA') {
            const keypair = Keypair.generate();
            return {
                address: keypair.publicKey.toBase58(),
                privateKey: bs58.encode(keypair.secretKey)
            };
        } else {
            const wallet = ethers.Wallet.createRandom();
            return {
                address: wallet.address,
                privateKey: wallet.privateKey
            };
        }
    }

    /**
     * Sweeps funds from temporary wallet to Platform and Merchant
     */
    async sweepFunds(
        tempWalletPrivateKey: string,
        merchantAddress: string,
        platformAddress: string,
        tokenSymbol: string = 'USDT'
    ) {
        if (this.network === 'SOLANA') {
            return this.sweepSolana(tempWalletPrivateKey, merchantAddress, platformAddress, tokenSymbol);
        } else {
            return this.sweepEVM(tempWalletPrivateKey, merchantAddress, platformAddress, tokenSymbol);
        }
    }

    private async sweepEVM(
        tempWalletPrivateKey: string,
        merchantAddress: string,
        platformAddress: string,
        tokenSymbol: string
    ) {
        const tempWallet = new ethers.Wallet(tempWalletPrivateKey, this.provider);
        const tokenConfig = this.getTokenConfig(tokenSymbol);
        if (!tokenConfig) throw new Error(`Unsupported token ${tokenSymbol} on ${this.network}`);

        console.log(`[Sweep EVM] Network: ${this.network} Total for ${tokenSymbol}`);

        // Mocking the real transfer for demo
        return {
            success: true,
            platformTx: '0x' + Math.random().toString(16).slice(2, 66),
            merchantTx: '0x' + Math.random().toString(16).slice(2, 66)
        };
    }

    async fuelWallet(targetAddress: string, amount: string) {
        const gasTankKey = process.env.CRYPTO_GAS_TANK_KEY;
        if (!gasTankKey) {
            console.warn("[CryptoEngine] No CRYPTO_GAS_TANK_KEY provided. Fueling skipped (Demo mode).");
            return;
        }

        try {
            const gasTank = new ethers.Wallet(gasTankKey, this.provider);
            const tx = await gasTank.sendTransaction({
                to: targetAddress,
                value: ethers.parseEther(amount)
            });
            await tx.wait();
            console.log(`[CryptoEngine] Fueled ${targetAddress} with ${amount} native currency. Hash: ${tx.hash}`);
        } catch (error) {
            console.error("[CryptoEngine] Fueling failed:", error);
        }
    }

    private async sweepSolana(
        tempWalletPrivateKey: string,
        merchantAddress: string,
        platformAddress: string,
        tokenSymbol: string
    ) {
        const tempKeypair = Keypair.fromSecretKey(bs58.decode(tempWalletPrivateKey));
        const pubKey = tempKeypair.publicKey;

        // Check if wallet needs SOL for gas
        const solBalance = await this.solConnection.getBalance(pubKey);
        if (solBalance < 5000000 && tokenSymbol !== 'SOL') { 
            console.log(`[Sweep SOL] Low SOL for gas, fueling...`);
        }

        return {
            success: true,
            platformTx: 'sol_mock_tx_' + Math.random().toString(36).substring(7),
            merchantTx: 'sol_mock_tx_' + Math.random().toString(36).substring(7)
        };
    }

    /**
     * Verifies if a specific amount has arrived at the address.
     */
    async verifyPayment(address: string, expectedAmount: string, tokenSymbol?: string): Promise<{
        success: boolean;
        txHash?: string;
        error?: string;
    }> {
        try {
            const tokenConfig = this.getTokenConfig(tokenSymbol || 'USDT');
            if (!tokenConfig) return { success: false, error: "Token not supported in config" };

            if (this.network === 'SOLANA') {
                const pubKey = new PublicKey(address);
                if (tokenConfig.address === 'NATIVE') {
                    const balance = await this.solConnection.getBalance(pubKey);
                    const balanceInSol = balance / LAMPORTS_PER_SOL;
                    if (balanceInSol >= parseFloat(expectedAmount)) return { success: true };
                } else {
                    const tokenMint = new PublicKey(tokenConfig.address);
                    const ata = await getAssociatedTokenAddress(tokenMint, pubKey);
                    try {
                        const accountInfo = await getAccount(this.solConnection, ata);
                        const balance = Number(accountInfo.amount) / Math.pow(10, tokenConfig.decimals);
                        if (balance >= parseFloat(expectedAmount)) return { success: true };
                    } catch (e) {}
                }
            } else {
                if (tokenConfig.address === 'NATIVE') {
                    const balance = await this.provider.getBalance(address);
                    const balanceInEth = ethers.formatEther(balance);
                    if (parseFloat(balanceInEth) >= parseFloat(expectedAmount)) return { success: true };
                } else {
                    const contract = new ethers.Contract(tokenConfig.address, ERC20_ABI, this.provider);
                    const balance = await contract.balanceOf(address);
                    const formattedBalance = ethers.formatUnits(balance, tokenConfig.decimals);
                    if (parseFloat(formattedBalance) >= parseFloat(expectedAmount)) return { success: true };
                }
            }
            return { success: false };
        } catch (error: any) {
            return { success: false, error: error.message };
        }
    }
}