# Type Safety Improvements
## Summary of Changes
### 1. Eliminated `any` Types
- Created proper interfaces for all data structures
- Replaced all `any` types with specific interfaces:
- `ErrorDetails` for error information
- `ApiRequest/ApiResponse` for extended Express types
- `ApiInfoResponse` for API information endpoint
- `NotificationData` for SSE notifications
### 2. Added Request Body Validation
- Implemented type guards for all request bodies:
- `isCreateSessionRequest()` validates session creation requests
- `isSendMessageRequest()` validates message sending requests
- `getValidationError()` provides specific validation error messages
- All endpoints now validate request bodies before processing
### 3. Implemented OpenAPI Validation Middleware
- Installed `express-openapi-validator` package
- Created configurable validation middleware
- Integration options in `ClaudeCodeApiConfig`:
```typescript
openApiValidation?: {
enabled?: boolean;
specPath?: string;
}
```
- Validates requests and responses against OpenAPI spec when enabled
### 4. Created Response Type Interfaces
- `ErrorResponse` interface for standardized error responses
- `ApiInfoResponse` for root endpoint information
- All response structures are now properly typed
### 5. Extended Express Types Properly
- `ApiRequest extends Request` with `requestId` property
- `ApiResponse extends Response` with optional `requestId`
- No more type assertions like `(req as any).requestId`
## Error Handling Improvements
- Created `getErrorMessage()` helper for safe error message extraction
- All catch blocks now handle unknown error types safely
- Consistent error response format across all endpoints
## Benefits
1. **Compile-time Safety**: TypeScript catches type errors before runtime
2. **Better IDE Support**: Autocomplete and type hints for all API structures
3. **Runtime Validation**: OpenAPI validation ensures requests match specification
4. **Maintainability**: Clear interfaces make code easier to understand and modify
5. **API Contract Enforcement**: OpenAPI spec serves as single source of truth
## Usage Example
### Enabling OpenAPI Validation
```typescript
const claudeCodeRouter = createClaudeCodeApi({
openApiValidation: {
enabled: true,
specPath: './docs/openapi/claude-code-api.yaml'
}
});
```
### Type-Safe Error Handling
```typescript
try {
// ... operation
} catch (error) {
const errorMessage = getErrorMessage(error);
handleError(res, 'ERROR_CODE', errorMessage, 500);
}
```
## Next Steps
- Consider adding request/response logging middleware
- Add integration tests that verify type safety
- Consider generating TypeScript types from OpenAPI spec
- Add API versioning support
