feat: using sdk to refact examples (#1)

Author: reneecok

cex/go-example/.env

@@ -0,0 +1,11 @@
+#PAYMASTER_URL="https://bsc-megafuel.nodereal.io"
+#CHAIN_URL="https://bsc-dataseed4.binance.org"
+#SPONSOR_URL="https://open-platform.nodereal.io/{YOUR_API_KEY}/megafuel"
+PAYMASTER_URL="https://bsc-megafuel-testnet.nodereal.io"
+CHAIN_URL="https://data-seed-prebsc-2-s1.binance.org:8545/"
+SPONSOR_URL="https://open-platform.nodereal.io/{YOUR_API_KEY}/megafuel-testnet"
+
+POLICY_UUID="xxxxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxx"
+TOKEN_CONTRACT_ADDRESS="0xeD24F....12Ee"
+WITHDRAW_RECIPIENT_ADDRESS="0x8e92....3EA2"
+HOTWALLET_PRIVATE_KEY="69...929"

cex/go-example/go.mod

@@ -2,21 +2,36 @@ module paymaster-example
 
 go 1.21
 
-require github.com/ethereum/go-ethereum v1.12.0
+require (
+	github.com/ethereum/go-ethereum v1.14.8
+	github.com/gofrs/uuid v4.3.0+incompatible
+	github.com/joho/godotenv v1.5.1
+	github.com/node-real/megafuel-go-sdk v1.0.0
+)
 
 require (
-	github.com/StackExchange/wmi v0.0.0-20180116203802-5d049714c4a6 // indirect
-	github.com/btcsuite/btcd/btcec/v2 v2.2.0 // indirect
-	github.com/deckarep/golang-set/v2 v2.1.0 // indirect
+	github.com/Microsoft/go-winio v0.6.2 // indirect
+	github.com/bits-and-blooms/bitset v1.10.0 // indirect
+	github.com/btcsuite/btcd/btcec/v2 v2.3.4 // indirect
+	github.com/consensys/bavard v0.1.13 // indirect
+	github.com/consensys/gnark-crypto v0.12.1 // indirect
+	github.com/crate-crypto/go-kzg-4844 v1.0.0 // indirect
+	github.com/deckarep/golang-set/v2 v2.6.0 // indirect
 	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.0.1 // indirect
-	github.com/go-ole/go-ole v1.2.1 // indirect
-	github.com/go-stack/stack v1.8.1 // indirect
-	github.com/gorilla/websocket v1.4.2 // indirect
-	github.com/holiman/uint256 v1.2.2-0.20230321075855-87b91420868c // indirect
-	github.com/shirou/gopsutil v3.21.4-0.20210419000835-c7a38de76ee5+incompatible // indirect
-	github.com/tklauser/go-sysconf v0.3.5 // indirect
-	github.com/tklauser/numcpus v0.2.2 // indirect
-	golang.org/x/crypto v0.1.0 // indirect
-	golang.org/x/sys v0.7.0 // indirect
-	gopkg.in/natefinch/npipe.v2 v2.0.0-20160621034901-c1b8fa8bdcce // indirect
+	github.com/ethereum/c-kzg-4844 v1.0.0 // indirect
+	github.com/go-ole/go-ole v1.3.0 // indirect
+	github.com/gorilla/websocket v1.5.1 // indirect
+	github.com/holiman/uint256 v1.3.1 // indirect
+	github.com/mmcloughlin/addchain v0.4.0 // indirect
+	github.com/shirou/gopsutil v3.21.11+incompatible // indirect
+	github.com/supranational/blst v0.3.11 // indirect
+	github.com/tklauser/go-sysconf v0.3.13 // indirect
+	github.com/tklauser/numcpus v0.7.0 // indirect
+	github.com/yusufpapurcu/wmi v1.2.3 // indirect
+	golang.org/x/crypto v0.22.0 // indirect
+	golang.org/x/exp v0.0.0-20240213143201-ec583247a57a // indirect
+	golang.org/x/net v0.24.0 // indirect
+	golang.org/x/sync v0.7.0 // indirect
+	golang.org/x/sys v0.20.0 // indirect
+	rsc.io/tmplfunc v0.0.3 // indirect
 )

cex/go-example/go.sum

@@ -7,40 +7,68 @@ import (
 	"fmt"
 	"log"
 	"math/big"
+	"os"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/ethclient"
+	"github.com/gofrs/uuid"
+	"github.com/joho/godotenv"
+	"github.com/node-real/megafuel-go-sdk/pkg/paymasterclient"
+	"github.com/node-real/megafuel-go-sdk/pkg/sponsorclient"
 )
 
-const TokenContractAddress = "0x.."
-const WithdrawRecipientAddress = "0x.."
-const SponsorPolicyId = ".."
-const HotwalletPrivateKey = ".."
+var (
+	PaymasterURL string
+	ChainURL     string
+	SponsorURL   string
 
-const sponsorAPIEndpoint = "https://open-platform.nodereal.io/{Your_API_key}/megafuel"
-const paymasterEndpoint = "https://bsc-megafuel.nodereal.io"
+	PolicyUUID uuid.UUID
 
-// testnet endpoint
-// const sponsorAPIEndpoint = "https://open-platform.nodereal.io/{Your_API_key}/megafuel-testnet"
-// const paymasterEndpoint = "https://bsc-megafuel-testnet.nodereal.io'"
+	TokenContractAddress     common.Address
+	WithdrawRecipientAddress common.Address
+	HotwalletPrivateKey      string
+)
+
+func init() {
+	err := godotenv.Load(".env")
+
+	if err != nil {
+		log.Fatalf("Error loading .env file")
+	}
+
+	PaymasterURL = os.Getenv("PAYMASTER_URL")
+	ChainURL = os.Getenv("CHAIN_URL")
+	SponsorURL = os.Getenv("SPONSOR_URL")
+
+	PolicyUUID, err = uuid.FromString(os.Getenv("POLICY_UUID"))
+	if err != nil {
+		log.Fatalf("Error parsing POLICY_UUID")
+	}
+
+	TokenContractAddress = common.HexToAddress(os.Getenv("TOKEN_CONTRACT_ADDRESS"))
+	WithdrawRecipientAddress = common.HexToAddress(os.Getenv("WITHDRAW_RECIPIENT_ADDRESS"))
+	HotwalletPrivateKey = os.Getenv("HOTWALLET_PRIVATE_KEY")
+}
 
 func main() {
 	sponsorSetUpPolicyRules()
 	cexDoGaslessWithdrawl()
 }
 
 func sponsorSetUpPolicyRules() {
-	sponsorClient, err := NewSponsorClient(sponsorAPIEndpoint)
+	sponsorClient, err := sponsorclient.New(context.Background(), SponsorURL)
 	if err != nil {
 		log.Fatal(err)
 	}
+
 	// sponsor the tx that interact with the stable coin ERC20 contract
-	success, err := sponsorClient.AddToWhitelist(context.Background(), WhitelistParams{
-		PolicyUUID:    SponsorPolicyId,
-		WhitelistType: ToAccountWhitelist,
-		Values:        []string{TokenContractAddress},
+	success, err := sponsorClient.AddToWhitelist(context.Background(), sponsorclient.WhiteListArgs{
+		PolicyUUID:    PolicyUUID,
+		WhitelistType: sponsorclient.ToAccountWhitelist,
+		Values:        []string{TokenContractAddress.String()},
 	})
 	if err != nil || !success {
 		log.Fatal("failed to add token contract whitelist", err)
@@ -49,9 +77,9 @@ func sponsorSetUpPolicyRules() {
 	// sponsor the tx that from hotwallets
 	fromAddress := getAddressFromPrivateKey(HotwalletPrivateKey)
 
-	success, err = sponsorClient.AddToWhitelist(context.Background(), WhitelistParams{
-		PolicyUUID:    SponsorPolicyId,
-		WhitelistType: FromAccountWhitelist,
+	success, err = sponsorClient.AddToWhitelist(context.Background(), sponsorclient.WhiteListArgs{
+		PolicyUUID:    PolicyUUID,
+		WhitelistType: sponsorclient.FromAccountWhitelist,
 		Values:        []string{fromAddress.String()},
 	})
 	if err != nil || !success {
@@ -61,8 +89,14 @@ func sponsorSetUpPolicyRules() {
 
 func cexDoGaslessWithdrawl() {
 	withdrawAmount := big.NewInt(1e17)
+	// Connect to an Ethereum node (for transaction assembly)
+	client, err := ethclient.Dial(ChainURL)
+	if err != nil {
+		log.Fatalf("Failed to connect to the Ethereum network: %v", err)
+	}
+
 	// Create a PaymasterClient (for transaction sending)
-	paymasterClient, err := NewPaymasterClient(paymasterEndpoint)
+	paymasterClient, err := paymasterclient.New(context.Background(), PaymasterURL)
 	if err != nil {
 		log.Fatalf("Failed to create PaymasterClient: %v", err)
 	}
@@ -75,28 +109,24 @@ func cexDoGaslessWithdrawl() {
 
 	fromAddress := getAddressFromPrivateKey(HotwalletPrivateKey)
 
-	// Token contract address
-	tokenAddress := common.HexToAddress(TokenContractAddress)
-
 	// Create ERC20 transfer data
-	data, err := createERC20TransferData(common.HexToAddress(WithdrawRecipientAddress), withdrawAmount)
+	data, err := createERC20TransferData(WithdrawRecipientAddress, withdrawAmount)
 	if err != nil {
 		log.Fatalf("Failed to create ERC20 transfer data: %v", err)
 	}
 
-	// Get the pending nonce for the from address, strongly suggest to fetch nonce from paymaster endpoint when
-	// submitting multiple transactions in rapid succession, to ensure that the nonce are sequential.
-	nonce, err := paymasterClient.PendingNonceAt(context.Background(), fromAddress)
+	// Get the latest nonce for the from address
+	nonce, err := client.PendingNonceAt(context.Background(), fromAddress)
 	if err != nil {
 		log.Fatalf("Failed to get nonce: %v", err)
 	}
 
 	// Create the transaction
 	gasPrice := big.NewInt(0)
-	tx := types.NewTransaction(nonce, tokenAddress, big.NewInt(0), 300000, gasPrice, data)
+	tx := types.NewTransaction(nonce, TokenContractAddress, big.NewInt(0), 300000, gasPrice, data)
 
 	// Get the chain ID
-	chainID, err := paymasterClient.ChainID(context.Background())
+	chainID, err := client.ChainID(context.Background())
 	if err != nil {
 		log.Fatalf("Failed to get chain ID: %v", err)
 	}
@@ -107,10 +137,15 @@ func cexDoGaslessWithdrawl() {
 		log.Fatalf("Failed to sign transaction: %v", err)
 	}
 
+	txInput, err := signedTx.MarshalBinary()
+	if err != nil {
+		log.Fatalf("Failed to marshal transaction: %v", err)
+	}
+
 	// Convert to Transaction struct for IsSponsorable check
 	gasLimit := tx.Gas()
-	sponsorableTx := Transaction{
-		To:    &tokenAddress,
+	sponsorableTx := paymasterclient.TransactionArgs{
+		To:    &TokenContractAddress,
 		From:  fromAddress,
 		Value: (*hexutil.Big)(big.NewInt(0)),
 		Gas:   (*hexutil.Uint64)(&gasLimit),
@@ -128,7 +163,7 @@ func cexDoGaslessWithdrawl() {
 
 	if sponsorableInfo.Sponsorable {
 		// Send the transaction using PaymasterClient
-		err := paymasterClient.SendTransaction(context.Background(), signedTx)
+		_, err := paymasterClient.SendRawTransaction(context.Background(), txInput)
 		if err != nil {
 			log.Fatalf("Failed to send sponsorable transaction: %v", err)
 		}
@@ -152,3 +187,16 @@ func getAddressFromPrivateKey(pk string) common.Address {
 	}
 	return crypto.PubkeyToAddress(*publicKeyECDSA)
 }
+
+func createERC20TransferData(to common.Address, amount *big.Int) ([]byte, error) {
+	transferFnSignature := []byte("transfer(address,uint256)")
+	methodID := crypto.Keccak256(transferFnSignature)[:4]
+	paddedAddress := common.LeftPadBytes(to.Bytes(), 32)
+	paddedAmount := common.LeftPadBytes(amount.Bytes(), 32)
+
+	var data []byte
+	data = append(data, methodID...)
+	data = append(data, paddedAddress...)
+	data = append(data, paddedAmount...)
+	return data, nil
+}

cex/go-example/main.go

@@ -1,27 +1,32 @@
 # GO Example
+
 This repository contains a Go application demonstrating:
+
 1. Sponsor manage the policy to sponsor any transaction sent by Cex hotwallets.
 2. Cex do token withdrawal without pay gas fee through paymaster.
 
 ## Quick Start
 
-If the example is performed on BSC testnet, please ensure you have some test ERC20 on BSC testnet. (You can get some
-from the official faucet)
+The example is performed on BSC testnet or BSC mainnet, please ensure you have some test ERC20 on them. (You can get
+some from the official faucet when using testnet)
 
 1. Install dependencies
     ```shell
     $ go mod tidy
     ```
-2. Configure the file
-   Before running the application, you need to edit the `main.go` to set up the following:
-
-   - Set "TokenContractAddress" to the ERC20 token contract address that users want to withdraw.
-   - Set "WithdrawRecipientAddress" to the receiver address of user's withdrawal request.
-   - Set "SponsorPolicyId" to the policy ID created by the sponsor on MegaFuel Paymaster, create one 
-   from [here](https://docs.nodereal.io/docs/megafuel-sponsor-guidelines) if you don't have it.
-   - Set "SponsorAPIEndpoint" to the API key created by the sponsor in the Nodereal dashboard.
-     create one from [here](https://docs.nodereal.io/docs/megafuel-sponsor-guidelines) if you don't have it.
-   - Set "HotwalletPrivateKey" to the Cex's hotwallet private key, ensuring this wallet contains the required ERC20 tokens.
+2. Configure the .env file
+   Before running the application, you need to edit the `.env` to set up the following:
+
+    - 'PAYMASTER_URL' with the Paymaster URL.
+    - 'CHAIN_URL' with the BSC testnet or BSC mainnet chain URL.
+    - 'SPONSOR_URL' to the API key created by the sponsor in the Nodereal dashboard. create one
+      from [here](https://docs.nodereal.io/docs/megafuel-sponsor-guidelines) if you don't have it.
+    - 'POLICY_UUID' to the policy ID created by the sponsor on Megafuel Paymaster, create one
+      from [here](https://docs.nodereal.io/docs/megafuel-sponsor-guidelines) if you don't have it.
+    - 'TOKEN_CONTRACT_ADDRESS' to the ERC20 token contract address that users want to withdraw.
+    - 'WITHDRAW_RECIPIENT_ADDRESS' to the receiver address of user's withdrawal request.
+    - 'HOTWALLET_PRIVATE_KEY' to the Cex's hotwallet private key, ensuring this wallet contains the required ERC20
+      tokens.
 
 3. Run the example
    ```