mev-beta/pkg/monitor/monitor.go

package monitor

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

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/ethclient"
)

// ArbitrumMonitor monitors the Arbitrum sequencer for transactions
type ArbitrumMonitor struct {
	client       *ethclient.Client
	rpcEndpoint  string
	pollInterval time.Duration
	running      bool
}

// NewArbitrumMonitor creates a new Arbitrum monitor
func NewArbitrumMonitor(rpcEndpoint string, pollInterval time.Duration) (*ArbitrumMonitor, error) {
	client, err := ethclient.Dial(rpcEndpoint)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to Arbitrum node: %v", err)
	}

	return &ArbitrumMonitor{
		client:       client,
		rpcEndpoint:  rpcEndpoint,
		pollInterval: pollInterval,
		running:      false,
	}, nil
}

// Start begins monitoring the Arbitrum sequencer
func (m *ArbitrumMonitor) Start(ctx context.Context) error {
	log.Println("Starting Arbitrum sequencer monitoring...")
	m.running = true

	// Get the latest block to start from
	header, err := m.client.HeaderByNumber(ctx, nil)
	if err != nil {
		return fmt.Errorf("failed to get latest block header: %v", err)
	}

	lastBlock := header.Number.Uint64()
	log.Printf("Starting from block: %d", lastBlock)

	for m.running {
		select {
		case <-ctx.Done():
			m.running = false
			return nil
		case <-time.After(m.pollInterval):
			// Get the latest block
			header, err := m.client.HeaderByNumber(ctx, nil)
			if err != nil {
				log.Printf("Failed to get latest block header: %v", err)
				continue
			}

			currentBlock := header.Number.Uint64()
			
			// Process blocks from lastBlock+1 to currentBlock
			for blockNum := lastBlock + 1; blockNum <= currentBlock; blockNum++ {
				if err := m.processBlock(ctx, blockNum); err != nil {
					log.Printf("Failed to process block %d: %v", blockNum, err)
				}
			}
			
			lastBlock = currentBlock
		}
	}

	return nil
}

// Stop stops the monitor
func (m *ArbitrumMonitor) Stop() {
	m.running = false
}

// processBlock processes a single block for potential swap transactions
func (m *ArbitrumMonitor) processBlock(ctx context.Context, blockNumber uint64) error {
	log.Printf("Processing block %d", blockNumber)
	
	// Get block by number
	block, err := m.client.BlockByNumber(ctx, big.NewInt(int64(blockNumber)))
	if err != nil {
		return fmt.Errorf("failed to get block %d: %v", blockNumber, err)
	}

	// Process each transaction in the block
	for _, tx := range block.Transactions() {
		if err := m.processTransaction(ctx, tx); err != nil {
			log.Printf("Failed to process transaction %s: %v", tx.Hash().Hex(), err)
		}
	}

	return nil
}

// processTransaction analyzes a transaction for potential swap opportunities
func (m *ArbitrumMonitor) processTransaction(ctx context.Context, tx *types.Transaction) error {
	// Check if this is a potential swap transaction
	// This is a simplified check - in practice, you would check for
	// specific function signatures of Uniswap-like contracts
	
	// For now, we'll just log all transactions
	from, err := m.client.TransactionSender(ctx, tx, common.Hash{}, 0)
	if err != nil {
		// This can happen for pending transactions
		from = common.HexToAddress("0x0")
	}
	
	log.Printf("Transaction: %s, From: %s, To: %s, Value: %s ETH", 
		tx.Hash().Hex(), 
		from.Hex(), 
		func() string {
			if tx.To() != nil {
				return tx.To().Hex()
			}
			return "contract creation"
		}(),
		new(big.Float).Quo(new(big.Float).SetInt(tx.Value()), big.NewFloat(1e18)).String(),
	)
	
	// TODO: Add logic to detect swap transactions and analyze them
	// This would involve:
	// 1. Checking if the transaction is calling a Uniswap-like contract
	// 2. Decoding the swap function call
	// 3. Extracting the token addresses and amounts
	// 4. Calculating potential price impact
	
	return nil
}

// GetPendingTransactions retrieves pending transactions from the mempool
func (m *ArbitrumMonitor) GetPendingTransactions(ctx context.Context) ([]*types.Transaction, error) {
	// This is a simplified implementation
	// In practice, you might need to use a different approach to access pending transactions
	
	// Query for pending transactions
	txs := make([]*types.Transaction, 0)
	
	// Note: ethclient doesn't directly expose pending transactions
	// You might need to use a different approach or a custom RPC call
	
	return txs, nil
}