feat: mint to multicall3 then transfer to wallets

Signed-off-by: Ji Hwan <jkim@polygon.technology>

Author: jhkimqd

cmd/fund/fund.go

@@ -418,15 +418,15 @@ func fundWalletsWithMulticall3(ctx context.Context, c *ethclient.Client, tops *b
 				var tx *types.Transaction
 				if params.TokenAddress != "" {
 					tokenAddress := common.HexToAddress(params.TokenAddress)
-					var txApprove *types.Transaction
-					txApprove, tx, iErr = util.Multicall3FundAccountsWithERC20Token(ctx, c, tops, accs, tokenAddress, params.TokenAmount, multicall3Addr)
-					if txApprove != nil {
+					var txMint *types.Transaction
+					txMint, tx, iErr = util.Multicall3FundAccountsWithERC20Token(ctx, c, tops, accs, tokenAddress, params.TokenAmount, multicall3Addr)
+					if txMint != nil {
 						log.Info().
-							Stringer("txHash", txApprove.Hash()).
+							Stringer("txHash", txMint.Hash()).
 							Int("done", i+1).
 							Uint64("of", uint64(len(wallets))).
-							Msg("transaction to approve ERC20 token spending by multicall3 sent")
-						txsCh <- txApprove
+							Msg("transaction to mint ERC20 tokens to multicall3 sent")
+						txsCh <- txMint
 					}
 				} else {
 					tx, iErr = util.Multicall3FundAccountsWithNativeToken(c, tops, accs, params.FundingAmountInWei, multicall3Addr)

util/multicall3.go

@@ -3,9 +3,11 @@ package util
 import (
 	"context"
 	"math/big"
+	"strings"
 
 	"github.com/0xPolygon/polygon-cli/bindings/multicall3"
 	"github.com/0xPolygon/polygon-cli/bindings/tokens"
+	"github.com/ethereum/go-ethereum/accounts/abi"
 	"github.com/ethereum/go-ethereum/accounts/abi/bind/v2"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -145,16 +147,20 @@ func Multicall3FundAccountsWithERC20Token(ctx context.Context, c *ethclient.Clie
 		return nil, nil, err
 	}
 
-	erc20, err := tokens.NewERC20(tokenAddress, c)
+	// Calculate total amount needed
+	totalAmount := big.NewInt(0).Mul(amount, big.NewInt(int64(len(accounts))))
+
+	// Create ABI for mint(address, uint256) function to mint tokens to multicall3
+	mintABI, err := abi.JSON(strings.NewReader(`[{"type":"function","name":"mint","inputs":[{"name":"to","type":"address"},{"name":"amount","type":"uint256"}],"outputs":[],"stateMutability":"nonpayable"}]`))
 	if err != nil {
 		return nil, nil, err
 	}
 
-	// Calculate total amount to approve
-	totalAmount := big.NewInt(0).Mul(amount, big.NewInt(int64(len(accounts))))
+	// Create bound contract for minting
+	mintContract := bind.NewBoundContract(tokenAddress, mintABI, c, c, c)
 
-	// Prepare approve calldata for the Multicall3 contract to spend tokens
-	approveTx, err = erc20.Approve(tops, scAddr, totalAmount)
+	// Mint tokens directly to multicall3 contract so it can distribute them
+	approveTx, err = mintContract.Transact(tops, "mint", scAddr, totalAmount)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -169,9 +175,11 @@ func Multicall3FundAccountsWithERC20Token(ctx context.Context, c *ethclient.Clie
 		return approveTx, nil, err
 	}
 
+	// Now prepare multicall3 calls to transfer tokens from multicall3 to each account
+	// Using transfer instead of transferFrom since multicall3 now owns the tokens
 	calls := make([]multicall3.Multicall3Call3, 0, len(accounts))
 	for _, account := range accounts {
-		callData, iErr := erc20ABI.Pack("transferFrom", tops.From, account, amount)
+		callData, iErr := erc20ABI.Pack("transfer", account, amount)
 		if iErr != nil {
 			return approveTx, nil, iErr
 		}