# HTTP Transport Improvements - Implementation Summary

## Overview
Implemented 6 HTTP transport security and reliability improvements in `src/transport/http-hunchentoot.lisp` based on code review recommendations in `reports/code-review.md`.

## Changes Made

### 1. Configuration Variables Added
Added 6 global configuration variables at the top of `src/transport/http-hunchentoot.lisp`:

- `*max-concurrent-connections*` (default: 100) - Maximum concurrent HTTP connections
- `*http-request-timeout*` (default: 30 seconds) - Request processing timeout
- `*rate-limit-enabled*` (default: T) - Enable/disable rate limiting
- `*rate-limit-requests-per-minute*` (default: 60) - Max requests per minute per IP
- `*max-request-size*` (default: 10MB) - Maximum request body size
- `*http-connection-timeout*` (default: 10 seconds) - Connection timeout

### 2. Rate Limiting Implementation
Implemented `check-rate-limit` function:
- Tracks requests per IP address using a thread-safe hash table
- Returns `:rate-limited` when limit exceeded
- Automatically cleans up old entries (older than 1 minute)
- Uses `bordeaux-threads:make-lock` for thread safety

### 3. Request Size Validation
Updated `handle-rpc-body` function:
- Validates request body size against `*max-request-size*`
- Returns HTTP 413 (Payload Too Large) when exceeded
- Logs warning when size limit is violated

### 4. Rate Limiting in RPC Handlers
Added rate limiting checks to:
- `mcp-rpc` handler - Returns HTTP 429 (Too Many Requests) when rate limited
- `mcp-lisply-eval` handler - Returns HTTP 429 when rate limited

### 5. Hunchentoot Configuration
Updated `start-http-transport` function:
- Configured `hunchentoot:*request-timeout*` with `*http-request-timeout*`
- Configured `hunchentoot:*taskmaster*` with `*max-concurrent-connections*`
- Set connection timeout via `hunchentoot:*acceptor-timeout*`

### 6. Package Exports
Updated `src/transport/package.lisp` to export the 6 new configuration variables.

### 7. Bug Fix
Fixed syntax error in `src/protocol/handlers.lisp` (line 476) - missing closing parenthesis in `make-error-response` function.

## Testing

### Tests Added
Added 2 new test cases in `tests/transport-test.lisp`:
- `http-transport-config-test` - Verifies all configuration variables are properly set
- `http-transport-default-values-test` - Verifies default values are correct

### Test Results
All transport tests pass:
- ✓ HTTP response formatting tests
- ✓ HTTP 404 response tests
- ✓ HTTP transport configuration variables test
- ✓ HTTP transport default values test

## HTTP Status Codes Used
- **429 Too Many Requests** - Returned when rate limit is exceeded
- **413 Payload Too Large** - Returned when request size exceeds limit

## Security Improvements
1. **Connection Limits** - Prevents resource exhaustion from too many concurrent connections
2. **Request Timeouts** - Prevents hanging requests from consuming resources
3. **Rate Limiting** - Prevents abuse from single IP addresses
4. **Request Size Limits** - Prevents memory exhaustion from large payloads
5. **Connection Timeouts** - Prevents slowloris attacks
6. **Proper Error Handling** - Returns appropriate HTTP status codes and logs errors

## Configuration
All configuration variables can be customized by setting them before starting the HTTP transport:

```lisp
;; Example: Customize rate limiting
(setf cl-tron-mcp/transport:*rate-limit-enabled* t)
(setf cl-tron-mcp/transport:*rate-limit-requests-per-minute* 120)

;; Example: Increase max connections
(setf cl-tron-mcp/transport:*max-concurrent-connections* 200)

;; Example: Adjust timeouts
(setf cl-tron-mcp/transport:*http-request-timeout* 60)
(setf cl-tron-mcp/transport:*http-connection-timeout* 15)
```

## Files Modified
1. `src/transport/http-hunchentoot.lisp` - Main implementation (expanded from ~120 to ~210 lines)
2. `src/transport/package.lisp` - Added exports for configuration variables
3. `src/protocol/handlers.lisp` - Fixed syntax error
4. `tests/transport-test.lisp` - Added test cases

## Verification
All configuration variables are accessible and properly set:
- `*max-concurrent-connections*` = 100
- `*http-request-timeout*` = 30
- `*rate-limit-enabled*` = T
- `*rate-limit-requests-per-minute*` = 60
- `*max-request-size*` = 10485760 (10MB)
- `*http-connection-timeout*` = 10

## Next Steps (Optional)
- Test rate limiting with actual HTTP requests
- Test request size validation with large payloads
- Test timeout configurations with slow requests
- Verify proper error responses (429, 413 status codes) with HTTP client
- Consider adding metrics/monitoring for rate limit violations