mev-beta/pkg/contracts/flashloan_executor.go

package contracts

import (
	"context"
	"fmt"
	"math/big"

	"github.com/ethereum/go-ethereum/accounts/abi/bind"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/ethclient"
)

// FlashLoanExecutorConfig holds configuration for flash loan execution
type FlashLoanExecutorConfig struct {
	ContractAddress  common.Address
	BalancerVault    common.Address
	MaxSlippageBps   *big.Int
	MaxPathLength    *big.Int
	MinProfitWei     *big.Int
	OwnerPrivateKey  string
	RPCEndpoint      string
}

// FlashLoanExecutor manages flash loan arbitrage execution
type FlashLoanExecutor struct {
	config   *FlashLoanExecutorConfig
	client   *ethclient.Client
	contract *FlashLoanReceiverSecure
	auth     *bind.TransactOpts
}

// NewFlashLoanExecutor creates a new flash loan executor
func NewFlashLoanExecutor(config *FlashLoanExecutorConfig) (*FlashLoanExecutor, error) {
	client, err := ethclient.Dial(config.RPCEndpoint)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to RPC: %w", err)
	}

	contract, err := NewFlashLoanReceiverSecure(config.ContractAddress, client)
	if err != nil {
		return nil, fmt.Errorf("failed to instantiate contract: %w", err)
	}

	return &FlashLoanExecutor{
		config:   config,
		client:   client,
		contract: contract,
	}, nil
}

// ExecuteArbitrage executes a flash loan arbitrage opportunity
func (e *FlashLoanExecutor) ExecuteArbitrage(
	ctx context.Context,
	tokens []common.Address,
	amounts []*big.Int,
	path ArbitragePath,
) (*FlashLoanResult, error) {
	// Encode the arbitrage path
	userData, err := e.encodeArbitragePath(path)
	if err != nil {
		return nil, fmt.Errorf("failed to encode path: %w", err)
	}

	// Execute the flash loan arbitrage
	tx, err := e.contract.ExecuteArbitrage(
		e.auth,
		convertToIERC20Array(tokens),
		amounts,
		userData,
	)
	if err != nil {
		return nil, fmt.Errorf("flash loan execution failed: %w", err)
	}

	// Wait for transaction confirmation
	receipt, err := bind.WaitMined(ctx, e.client, tx)
	if err != nil {
		return nil, fmt.Errorf("transaction mining failed: %w", err)
	}

	return &FlashLoanResult{
		TxHash:    tx.Hash(),
		Success:   receipt.Status == 1,
		GasUsed:   receipt.GasUsed,
		BlockNum:  receipt.BlockNumber.Uint64(),
	}, nil
}

// WithdrawProfit withdraws accumulated profits from the contract
func (e *FlashLoanExecutor) WithdrawProfit(
	ctx context.Context,
	token common.Address,
	amount *big.Int,
) error {
	tx, err := e.contract.WithdrawProfit(e.auth, token, amount)
	if err != nil {
		return fmt.Errorf("withdraw failed: %w", err)
	}

	_, err = bind.WaitMined(ctx, e.client, tx)
	if err != nil {
		return fmt.Errorf("withdraw transaction mining failed: %w", err)
	}

	return nil
}

// EmergencyWithdraw withdraws all funds from the contract
func (e *FlashLoanExecutor) EmergencyWithdraw(
	ctx context.Context,
	token common.Address,
) error {
	tx, err := e.contract.EmergencyWithdraw(e.auth, token)
	if err != nil {
		return fmt.Errorf("emergency withdraw failed: %w", err)
	}

	_, err = bind.WaitMined(ctx, e.client, tx)
	if err != nil {
		return fmt.Errorf("emergency withdraw transaction mining failed: %w", err)
	}

	return nil
}

// GetBalance retrieves the balance of a token in the contract
func (e *FlashLoanExecutor) GetBalance(
	ctx context.Context,
	token common.Address,
) (*big.Int, error) {
	opts := &bind.CallOpts{Context: ctx}
	balance, err := e.contract.GetBalance(opts, token)
	if err != nil {
		return nil, fmt.Errorf("failed to get balance: %w", err)
	}

	return balance, nil
}

// ArbitragePath represents a multi-hop arbitrage path
type ArbitragePath struct {
	Tokens     []common.Address
	Exchanges  []common.Address
	Fees       []*big.Int
	IsV3       []bool
	MinProfit  *big.Int
	SlippageBps *big.Int
}

// FlashLoanResult contains the result of a flash loan execution
type FlashLoanResult struct {
	TxHash   common.Hash
	Success  bool
	GasUsed  uint64
	BlockNum uint64
}

// encodeArbitragePath encodes the arbitrage path into bytes for the contract
func (e *FlashLoanExecutor) encodeArbitragePath(path ArbitragePath) ([]byte, error) {
	// TODO: Implement proper ABI encoding for the userData parameter
	// This will encode: tokens, exchanges, fees, isV3, minProfit, slippageBps
	return []byte{}, nil
}

// convertToIERC20Array converts address array to IERC20 array for contract call
func convertToIERC20Array(addrs []common.Address) []common.Address {
	return addrs
}

// Close closes the RPC client connection
func (e *FlashLoanExecutor) Close() {
	if e.client != nil {
		e.client.Close()
	}
}