# MEV Bot Technical Specification

## Project Overview

High-performance MEV bot for Arbitrum focused on real-time swap detection and arbitrage opportunities from the Arbitrum sequencer feed.

## Core Architecture Principles

### 1. Channel-Based Concurrency
**ALL processing, parsing, and logging MUST use Go channels for optimal performance**

- Non-blocking message passing between components
- Worker pools for parallel processing
- Buffered channels to prevent backpressure
- No synchronous blocking operations in hot paths

### 2. Sequencer-First Architecture
**The Arbitrum sequencer feed is the PRIMARY data source**

- WebSocket connection to: `wss://arb1.arbitrum.io/feed`
- Real-time transaction broadcast before inclusion in blocks
- NO reliance on HTTP RPC endpoints except for historical data
- Sequencer MUST be isolated in its own channel

### 3. Official Contract Sources
**ALL contract ABIs MUST be derived from official contract sources**

- Store official DEX contracts in `contracts/lib/` via Foundry
- Build contracts using Foundry (`forge build`)
- Extract ABIs from build artifacts in `contracts/out/`
- Generate Go bindings using `abigen` from extracted ABIs
- ALL contracts in `contracts/src/` MUST have bindings
- NO manually written ABI JSON files
- NO hardcoded function selectors

## Sequencer Processing Pipeline

### Stage 1: Message Reception
```
Arbitrum Sequencer Feed
         ↓
  [Raw WebSocket Messages]
         ↓
   Message Channel
```

### Stage 2: Swap Filtering
```
Message Channel
      ↓
[Swap Filter Workers]  ← Pool Cache (read-only)
      ↓
 Swap Event Channel
```

**Swap Filter Responsibilities:**
- Identify swap transactions from supported DEXes
- Extract pool addresses from transactions
- Discover new pools not in cache
- Emit SwapEvent to downstream channel

**Supported DEXes:**
- Uniswap V2/V3/V4
- Camelot V2/V3/V4
- Balancer (all versions)
- Kyber (all versions)
- Curve (all versions)
- SushiSwap
- Other UniswapV2-compatible exchanges

### Stage 3: Pool Discovery
```
Swap Event Channel
       ↓
[Pool Discovery]
       ↓
   Pool Cache  ← Auto-save to disk
       ↓
  Pool Mapping (address → info)
```

**Pool Cache Behavior:**
- Thread-safe concurrent access (RWMutex)
- Automatic persistence to JSON every 100 new pools
- Periodic saves every 5 minutes
- Mapping prevents duplicate processing
- First seen timestamp tracking
- Swap count statistics

### Stage 4: Arbitrage Detection
```
Swap Event Channel
       ↓
[Arbitrage Scanner] ← Pool Cache (multi-index)
       ↓
 Opportunity Channel
```

## Contract Bindings Management

### Directory Structure
```
contracts/
├── lib/               # Foundry dependencies (official DEX contracts)
│   ├── v2-core/      # git submodule: Uniswap/v2-core
│   ├── v3-core/      # git submodule: Uniswap/v3-core
│   ├── camelot-amm/  # git submodule: CamelotLabs/camelot-amm-v2
│   └── ...
├── src/               # Custom wrapper contracts (if needed)
│   └── interfaces/    # Interface contracts for binding generation
├── out/               # Foundry build artifacts (gitignored)
│   └── *.sol/
│       └── *.json    # ABI + bytecode
└── foundry.toml       # Foundry configuration

bindings/
├── uniswap_v2/
│   ├── router.go     # Generated from IUniswapV2Router02
│   └── pair.go       # Generated from IUniswapV2Pair
├── uniswap_v3/
│   └── router.go     # Generated from ISwapRouter
├── camelot/
│   └── router.go     # Generated from ICamelotRouter
└── README.md          # Binding usage documentation
```

### Binding Generation Workflow

1. **Install Official Contracts**
   ```bash
   forge install Uniswap/v2-core
   forge install Uniswap/v3-core
   forge install Uniswap/v4-core
   forge install camelotlabs/camelot-amm-v2
   forge install balancer/balancer-v2-monorepo
   forge install KyberNetwork/ks-elastic-sc
   forge install curvefi/curve-contract
   ```

2. **Build Contracts**
   ```bash
   forge build
   ```

3. **Extract ABIs**
   ```bash
   # Example for UniswapV2Router02
   jq '.abi' contracts/out/IUniswapV2Router02.sol/IUniswapV2Router02.json > /tmp/router_abi.json
   ```

4. **Generate Bindings**
   ```bash
   abigen --abi=/tmp/router_abi.json \
          --pkg=uniswap_v2 \
          --type=UniswapV2Router \
          --out=bindings/uniswap_v2/router.go
   ```

5. **Automate with Script**
   - Use `scripts/generate-bindings.sh` to automate steps 3-4
   - Run after any contract update

### Binding Usage in Code

**DO THIS** (ABI-based detection):
```go
import (
    "github.com/ethereum/go-ethereum/accounts/abi"
    "strings"
)

routerABI, _ := abi.JSON(strings.NewReader(uniswap_v2.UniswapV2RouterABI))
method, err := routerABI.MethodById(txData[:4])
if err == nil {
    isSwap := strings.Contains(method.Name, "swap")
    if isSwap {
        params, _ := method.Inputs.Unpack(txData[4:])
        // Type-safe parameter access
        amountIn := params[0].(*big.Int)
        path := params[2].([]common.Address)
    }
}
```

**DON'T DO THIS** (hardcoded selectors):
```go
// WRONG - hardcoded, fragile, unmaintainable
if hex.EncodeToString(txData[0:4]) == "38ed1739" {
    // swapExactTokensForTokens
}
```

## Pool Cache Design

### Multi-Index Requirements
The pool cache MUST support efficient lookups by:

1. **Address** - Primary key
2. **Token Pair** - Find all pools for a pair (A,B)
3. **Protocol** - Find all Uniswap pools, all Camelot pools, etc.
4. **Liquidity** - Find top N pools by TVL

### Data Structure
```go
type PoolInfo struct {
    Address    common.Address
    Protocol   string // "UniswapV2", "Camelot", etc.
    Version    string // "V2", "V3", etc.
    Token0     common.Address
    Token1     common.Address
    Fee        uint32 // basis points
    FirstSeen  time.Time
    LastSeen   time.Time
    SwapCount  uint64
    Liquidity  *big.Int // Estimated TVL
}

type PoolCache struct {
    // Primary storage
    pools map[common.Address]*PoolInfo

    // Indexes
    byTokenPair map[TokenPair][]common.Address
    byProtocol  map[string][]common.Address
    byLiquidity []*PoolInfo // Sorted by liquidity

    mu sync.RWMutex
}
```

### Thread Safety
- Use `RWMutex` for concurrent read/write access
- Read locks for queries
- Write locks for updates
- No locks held during I/O operations (save to disk)

## Development Environment

### Containerized Development
**ALL development MUST occur in containers**

```yaml
# docker-compose.yml profiles
services:
  go-dev:       # Go 1.21 with full toolchain
  python-dev:   # Python 3.11 for scripts
  foundry:      # Forge, Cast, Anvil for contract work
```

**Start dev environment:**
```bash
./scripts/dev-up.sh
# or
podman-compose up -d go-dev python-dev foundry
```

**Enter containers:**
```bash
podman exec -it mev-go-dev sh
podman exec -it mev-foundry sh
```

### Build Process
```bash
# In go-dev container
cd /workspace
go build -o bin/mev-bot ./cmd/mev-bot/main.go
```

### Testing
```bash
# Unit tests
go test ./pkg/... -v

# Integration tests
go test ./tests/integration/... -v

# Benchmarks
go test ./pkg/... -bench=. -benchmem
```

## Observability

### Metrics (Prometheus)
Every component MUST export metrics:

- `sequencer_messages_received_total`
- `swaps_detected_total{protocol, version}`
- `pools_discovered_total{protocol}`
- `arbitrage_opportunities_found_total`
- `arbitrage_execution_attempts_total{result}`

### Logging (Structured)
Use go-ethereum's structured logger:

```go
logger.Info("swap detected",
    "protocol", swap.Protocol.Name,
    "hash", swap.TxHash,
    "pool", swap.Pool.Address.Hex(),
    "token0", swap.Pool.Token0.Hex(),
    "token1", swap.Pool.Token1.Hex())
```

### Health Monitoring
- Sequencer connection status
- Message processing rate
- Channel buffer utilization
- Pool cache hit rate
- Arbitrage execution success rate

## Validation Rules

### Swap Event Validation
MUST validate ALL parsed swap events:

1. **Non-zero addresses** - token0, token1, pool address
2. **Non-zero amounts** - amountIn, amountOut
3. **Valid token pair** - token0 < token1 (canonical ordering)
4. **Known protocol** - matches supported DEX list
5. **Reasonable amounts** - within sanity bounds

### Reject Invalid Data Immediately
- Log rejection with full context
- Increment rejection metrics
- NEVER propagate invalid data downstream

## Error Handling

### Fail-Fast Philosophy
- Reject bad data at the source
- Log all errors with stack traces
- Emit error metrics
- Never silent failures

### Graceful Degradation
- Circuit breakers for RPC failover
- Retry logic with exponential backoff
- Automatic reconnection for WebSocket
- Pool cache persistence survives restarts

## Configuration

### Environment Variables
```bash
# Sequencer (PRIMARY)
ARBITRUM_SEQUENCER_URL=wss://arb1.arbitrum.io/feed

# RPC (FALLBACK ONLY)
RPC_URL=https://arbitrum-mainnet.core.chainstack.com/<key>
WS_URL=wss://arbitrum-mainnet.core.chainstack.com/<key>

# Chain
CHAIN_ID=42161

# API Keys
ARBISCAN_API_KEY=<key>

# Wallet
PRIVATE_KEY=<key>
```

### Performance Tuning
```bash
# Worker pool sizes
SWAP_FILTER_WORKERS=16
ARBITRAGE_WORKERS=8

# Channel buffer sizes
MESSAGE_BUFFER=1000
SWAP_EVENT_BUFFER=500
OPPORTUNITY_BUFFER=100

# Pool cache
POOL_CACHE_AUTOSAVE_COUNT=100
POOL_CACHE_AUTOSAVE_INTERVAL=5m
```

## Git Workflow

### Branches
- `master` - Stable production branch
- `feature/v2-prep` - V2 planning and architecture
- `feature/<component>` - Feature branches for V2 components

### Commit Messages
```
type(scope): brief description

- Detailed changes
- Why the change was needed
- Breaking changes or migration notes

🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
```

**Types**: `feat`, `fix`, `perf`, `refactor`, `test`, `docs`, `build`, `ci`

## Critical Rules

### MUST DO
✅ Use Arbitrum sequencer feed as primary data source
✅ Use channels for ALL inter-component communication
✅ Derive contract ABIs from official sources via Foundry
✅ Generate Go bindings for all contracts with `abigen`
✅ Validate ALL parsed data before propagation
✅ Use thread-safe concurrent data structures
✅ Emit comprehensive metrics and structured logs
✅ Run all development in containers
✅ Write tests for all components

### MUST NOT DO
❌ Use HTTP RPC as primary data source (sequencer only!)
❌ Write manual ABI JSON files (use Foundry builds!)
❌ Hardcode function selectors (use ABI lookups!)
❌ Allow zero addresses or zero amounts to propagate
❌ Use blocking operations in hot paths
❌ Modify shared state without locks
❌ Silent failures without logging
❌ Run builds outside of containers

## References

- [Arbitrum Sequencer Feed](https://www.degencode.com/p/decoding-the-arbitrum-sequencer-feed)
- [Foundry Book](https://book.getfoundry.sh/)
- [Abigen Documentation](https://geth.ethereum.org/docs/tools/abigen)
- V2 Architecture: `docs/planning/00_V2_MASTER_PLAN.md`
- V2 Task Breakdown: `docs/planning/07_TASK_BREAKDOWN.md`
- Project Guidelines: `CLAUDE.md`