# Monitor Package Documentation

## Overview

The monitor package provides comprehensive monitoring of the Arbitrum sequencer for MEV opportunities. It implements concurrent processing, rate limiting, DEX event subscription, and real-time transaction analysis to detect potential arbitrage opportunities in the mempool and confirmed blocks.

## Core Components

### `ArbitrumMonitor` Structure

The main monitor structure provides sequencer monitoring capabilities:

1. **Configuration** - Arbitrum and bot configuration
2. **Client** - Ethereum client for RPC calls
3. **L2Parser** - Arbitrum L2 transaction parser
4. **Logger** - Structured logging
5. **RateLimiter** - Rate limiting for RPC calls
6. **MarketManager** - Market data management
7. **Scanner** - Market scanner for opportunities
8. **Pipeline** - Processing pipeline for transactions
9. **FanManager** - Concurrent processing manager
10. **Limiter** - Additional rate limiting
11. **PollInterval** - Block polling interval
12. **Running** - Monitor state flag

## Initialization

### `NewArbitrumMonitor()` Function

Creates a new Arbitrum monitor with all required components:

1. **Ethereum Client** - Connects to Arbitrum node
2. **Price Oracle** - Creates price oracle for L2 parsing
3. **L2 Parser** - Initializes Arbitrum L2 transaction parser
4. **Rate Limiter** - Configures rate limiting based on settings
5. **Pipeline** - Creates market processing pipeline
6. **Fan Manager** - Initializes concurrent processing manager
7. **Event Parser** - Prepares DEX event parsing (future use)
8. **Pool Discovery** - Prepares pool discovery (future use)

## Monitoring Functions

### `Start(ctx context.Context) error`

Begins monitoring the Arbitrum sequencer:

1. **State Management** - Sets running flag
2. **Block Tracking** - Gets latest block number to start from
3. **Event Subscription** - Subscribes to DEX events
4. **Polling Loop** - Continuously polls for new blocks
5. **Block Processing** - Processes blocks for DEX transactions
6. **Rate Limiting** - Applies rate limits for RPC calls
7. **Context Handling** - Respects context cancellation

### `Stop()`

Stops the monitor gracefully:

1. **State Management** - Clears running flag
2. **Cleanup** - Performs necessary cleanup operations
3. **Logging** - Logs stop event

## Block Processing

### `processBlock(ctx context.Context, blockNumber uint64) error`

Processes a single block for potential swap transactions:

1. **Rate Limiting** - Waits for rate limiter
2. **Block Retrieval** - Gets block using L2 parser
3. **DEX Parsing** - Parses DEX transactions from block
4. **Performance Logging** - Logs RPC and parsing metrics
5. **Transaction Analysis** - Analyzes DEX transactions
6. **Empty Block Handling** - Reports empty blocks

### L2 Parsing Benefits

The L2 parser provides several advantages:
- **Bypass Transaction Type Issues** - Handles Arbitrum-specific transaction types
- **Enhanced DEX Detection** - Better identification of DEX transactions
- **Improved Performance** - More efficient block processing
- **Reduced Errors** - Fewer parsing failures

## DEX Event Monitoring

### `subscribeToDEXEvents(ctx context.Context) error`

Subscribes to DEX contract events for real-time monitoring:

1. **Contract Definitions** - Defines official DEX contracts:
   - Uniswap V2/V3 factories and routers
   - SushiSwap factories and routers
   - High-volume pools
   - Universal routers
   - GMX router

2. **Event Signatures** - Defines common DEX event signatures:
   - Uniswap V2 Swap, Mint, Burn
   - Uniswap V3 Swap, Mint, Burn

3. **Filter Query** - Creates filter for DEX events
4. **Subscription** - Subscribes to logs
5. **Event Processing** - Processes events in goroutine

### `processDEXEvent(ctx context.Context, log types.Log)`

Processes a DEX event log:

1. **Event Identification** - Identifies event type by signature
2. **Logging** - Logs detected events
3. **Receipt Fetching** - Gets transaction receipt
4. **Transaction Processing** - Processes receipt for opportunities

### `processTransactionReceipt(ctx context.Context, receipt *types.Receipt, blockNumber uint64, blockHash common.Hash)`

Processes a transaction receipt for DEX events:

1. **Log Analysis** - Analyzes receipt logs for DEX events
2. **Event Counting** - Counts DEX events in transaction
3. **Pipeline Processing** - Processes through market pipeline
4. **Legacy Compatibility** - Maintains compatibility with legacy systems

## Transaction Processing

### `processTransaction(ctx context.Context, tx *types.Transaction) error`

Analyzes a transaction for potential swap opportunities:

1. **Sender Identification** - Gets transaction sender
2. **Basic Logging** - Logs transaction details
3. **Swap Detection** - (TODO) Detects swap transactions
4. **Price Impact** - (TODO) Calculates potential price impact

### Future Enhancements

The transaction processing includes placeholders for:
- Swap transaction detection
- Function signature checking
- Token address extraction
- Amount parsing
- Price impact calculation

## Rate Limiting

### Integrated Rate Limiting

The monitor implements comprehensive rate limiting:

1. **Configuration-Based** - Uses config.RateLimit settings
2. **Token Bucket** - Implements token bucket algorithm
3. **Per-Endpoint** - Rate limits per RPC endpoint
4. **Wait Mechanism** - Blocks until rate limit allows
5. **Error Handling** - Handles rate limit errors gracefully

### Rate Limit Configuration

- **RequestsPerSecond** - Maximum requests per second
- **MaxConcurrent** - Maximum concurrent requests
- **Burst** - Burst size for rate limiting

## Performance Monitoring

### RPC Performance Logging

The monitor logs RPC call performance:
- **Duration Tracking** - Measures call durations
- **Success/Failure** - Tracks call success rates
- **Error Reporting** - Logs RPC errors
- **Endpoint Monitoring** - Tracks per-endpoint performance

### Block Processing Metrics

The monitor logs block processing metrics:
- **Transaction Counts** - Total and DEX transaction counts
- **Processing Time** - Block processing duration
- **Parse Rates** - Transactions per second parsing rate
- **DEX Detection** - DEX transaction identification rates

## Concurrency Support

### Fan Manager

The monitor uses a fan manager for concurrent processing:
- **Parallel Processing** - Processes multiple items concurrently
- **Resource Management** - Manages worker pool resources
- **Load Distribution** - Distributes load across workers
- **Backpressure Handling** - Handles processing backpressure

### Pipeline Processing

The monitor implements a processing pipeline:
- **Stage Management** - Manages processing stages
- **Data Flow** - Controls data flow through pipeline
- **Error Handling** - Handles pipeline errors
- **Performance Monitoring** - Monitors pipeline performance

## Error Handling

### Retry Mechanisms

The monitor implements retry mechanisms:
- **Exponential Backoff** - Increases delay between retries
- **Max Retry Limits** - Limits retry attempts
- **Context Respect** - Respects context cancellation
- **Error Classification** - Classifies retryable errors

### `getTransactionReceiptWithRetry()` Function

Implements retry logic for receipt fetching:
1. **Attempt Tracking** - Tracks retry attempts
2. **Exponential Backoff** - Increases delay between attempts
3. **Context Checking** - Respects context cancellation
4. **Error Logging** - Logs retry attempts and failures

## Security Features

### Rate Limiting

Prevents abuse of RPC endpoints:
- **Configurable Limits** - Adjustable rate limits
- **Burst Handling** - Handles request bursts
- **Endpoint Protection** - Protects individual endpoints
- **Fair Usage** - Ensures fair RPC usage

### Event Validation

Validates DEX events:
- **Signature Checking** - Verifies event signatures
- **Contract Verification** - Verifies contract addresses
- **Data Validation** - Validates event data
- **Error Prevention** - Prevents invalid data processing

## Best Practices

### Monitoring Optimization

1. **Rate Limiting** - Always respect RPC rate limits
2. **Efficient Parsing** - Use optimized parsing methods
3. **Selective Logging** - Log only necessary information
4. **Resource Management** - Manage memory and goroutines
5. **Error Recovery** - Handle errors gracefully
6. **Performance Monitoring** - Monitor performance metrics

### Event Processing

1. **Event Identification** - Quickly identify relevant events
2. **Data Extraction** - Efficiently extract required data
3. **Validation** - Validate all extracted data
4. **Processing** - Process events through appropriate pipelines
5. **Logging** - Log important events and metrics

### Concurrency Management

1. **Worker Pools** - Use appropriate worker pool sizes
2. **Resource Limits** - Limit concurrent resource usage
3. **Backpressure** - Handle processing backpressure
4. **Cleanup** - Clean up resources properly
5. **Monitoring** - Monitor concurrent operations

## Future Improvements

### Enhanced Features

1. **Advanced DEX Detection** - Improved DEX transaction identification
2. **Mempool Monitoring** - Real-time mempool transaction analysis
3. **Machine Learning** - ML-based opportunity prediction
4. **Cross-Chain** - Multi-chain monitoring support
5. **Advanced Analytics** - Enhanced performance analytics

### Performance Enhancements

1. **Optimized Parsing** - Further L2 parsing optimizations
2. **Caching** - Intelligent caching strategies
3. **Parallel Processing** - Enhanced concurrent processing
4. **Memory Management** - Improved memory usage
5. **Network Optimization** - Optimized RPC usage

### Security Improvements

1. **Enhanced Validation** - More thorough data validation
2. **Rate Limiting** - Advanced rate limiting strategies
3. **Access Control** - Enhanced access controls
4. **Audit Logging** - Comprehensive audit trails
5. **Threat Detection** - Advanced threat detection