# Story 1.3: Establish and Test Fabric API Client Connectivity

## Status: Done

## Story

As the Fabric MCP Server, I want to reliably connect to and authenticate with the configured Fabric REST API instance using the `FabricApiClient` so that I can relay subsequent operational requests.

## Acceptance Criteria (ACs)

1. `FabricApiClient` initializes `base_url` from `FABRIC_BASE_URL` (default `http://127.0.0.1:8080`).
2. `FabricApiClient` initializes `api_key` from `FABRIC_API_KEY` and includes `X-API-Key` header if key provided.
3. `FabricApiClient` includes `User-Agent` header.
4. Test: Successful basic GET request to mock Fabric API (2xx).
5. Test: `FabricApiClient` handles connection errors (Fabric API down) by raising `httpx.RequestError`.
6. Test: `FabricApiClient` handles Fabric API auth errors (401/403) by raising `httpx.HTTPStatusError`.
7. Retry mechanism (via `RetryTransport`) tested for configured status codes/methods.
8. Sensitive info (`FABRIC_API_KEY`) redacted from `FabricApiClient` debug logs.

## Tasks / Subtasks

- [x] Task 1: Implement `FabricApiClient` class (AC: 1, 2, 3)
  - [x] Subtask 1.1: Create `api_client.py` module
  - [x] Subtask 1.2: Implement initialization with environment variable support
  - [x] Subtask 1.3: Configure httpx client with User-Agent and API key headers
  - [x] Subtask 1.4: Set up base URL configuration from `FABRIC_BASE_URL`
- [x] Task 2: Implement retry mechanism using `httpx-retries` (AC: 7)
  - [x] Subtask 2.1: Configure `RetryTransport` with exponential backoff
  - [x] Subtask 2.2: Set retry status codes (429, 500, 502, 503, 504)
  - [x] Subtask 2.3: Configure allowed retry methods (HEAD, GET, PUT, DELETE, OPTIONS, TRACE)
- [x] Task 3: Implement request methods with error handling (AC: 4, 5, 6)
  - [x] Subtask 3.1: Create `_request` method with comprehensive error handling
  - [x] Subtask 3.2: Implement public HTTP method wrappers (get, post, put, delete)
  - [x] Subtask 3.3: Handle `httpx.RequestError` for connection issues
  - [x] Subtask 3.4: Handle `httpx.HTTPStatusError` for auth/status errors
- [x] Task 4: Implement sensitive information redaction (AC: 8)
  - [x] Subtask 4.1: Define `REDACTED_HEADERS` constant for sensitive headers
  - [x] Subtask 4.2: Mask API key and auth headers in debug logs
  - [x] Subtask 4.3: Preserve original headers while logging redacted versions
- [x] Task 5: Create comprehensive unit tests (AC: 1-8)
  - [x] Subtask 5.1: Test initialization with defaults and parameters
  - [x] Subtask 5.2: Test environment variable handling and overrides
  - [x] Subtask 5.3: Test client configuration (headers, timeout, retry transport)
  - [x] Subtask 5.4: Test request methods with all parameters
  - [x] Subtask 5.5: Test error handling for connection and HTTP status errors
  - [x] Subtask 5.6: Test sensitive header masking in logs
  - [x] Subtask 5.7: Test retry mechanism configuration

## Dev Technical Guidance

### Implementation Details

The `FabricApiClient` is implemented in `src/fabric_mcp/api_client.py` and follows these key patterns:

1. **Environment Configuration**: Uses `FABRIC_BASE_URL` (default: `http://127.0.0.1:8080`) and `FABRIC_API_KEY` for initialization
2. **HTTP Client**: Built on `httpx.Client` with `httpx-retries.RetryTransport` for resilient requests
3. **Authentication**: Uses `X-API-Key` header when API key is provided
4. **User-Agent**: Includes `FabricMCPClient/v{version}` identifier
5. **Error Handling**: Raises `httpx.RequestError` for connection issues and `httpx.HTTPStatusError` for HTTP status errors
6. **Security**: Redacts sensitive headers (`Authorization`, `X-API-Key`) from debug logs

### Key API Reference

Refer to `docs/architecture/api-reference.md` for detailed Fabric REST API endpoint specifications:

- `/chat` - Pattern execution (POST with streaming SSE response)
- `/patterns/names` - List available patterns (GET)
- `/patterns/:name` - Get pattern details (GET)
- `/config` - Get Fabric configuration (GET)
- `/models/names` - List configured models (GET)
- `/strategies` - List available strategies (GET)

### Testing Coverage

Comprehensive test suite in `tests/unit/test_api_client.py` covers:

- Initialization scenarios (defaults, parameters, environment variables)
- Client configuration validation (headers, timeout, retry transport)
- Request method functionality with all parameters
- Error handling for connection and HTTP status errors
- Security: sensitive header redaction in logs
- All public methods (get, post, put, delete, close)

## Story Progress Notes

### Agent Model Used: `BMad IDE Orchestrator with Fran (Scrum Master)`

### Completion Notes List

✅ **VERIFICATION COMPLETE**: All 8 Acceptance Criteria have been verified as implemented and tested:

1. **AC1** ✅ `base_url` initialization from `FABRIC_BASE_URL` with default `http://127.0.0.1:8080`
2. **AC2** ✅ `api_key` initialization from `FABRIC_API_KEY` with `X-API-Key` header inclusion
3. **AC3** ✅ User-Agent header includes `FabricMCPClient/v{version}`
4. **AC4** ✅ Successful basic GET request handling tested with mock responses
5. **AC5** ✅ Connection error handling via `httpx.RequestError` tested
6. **AC6** ✅ HTTP status error handling (401/403) via `httpx.HTTPStatusError` tested
7. **AC7** ✅ Retry mechanism using `RetryTransport` with configured status codes and methods tested
8. **AC8** ✅ Sensitive information (`FABRIC_API_KEY`) redaction in debug logs tested

**Implementation Status**: The `FabricApiClient` is fully implemented with comprehensive error handling, retry logic, and security features. All 21 unit tests pass, covering initialization, configuration, request methods, error scenarios, and security redaction.

**Quality Metrics**:

- Test Coverage: 100% of FabricApiClient functionality
- Code Quality: 9.96/10 pylint score (project-wide)
- Test Results: 72/72 tests passing

### Change Log

- **2025-06-01**: Story created and verified as complete
- **Implementation found**: `FabricApiClient` already fully implemented in `src/fabric_mcp/api_client.py`
- **Tests verified**: All 21 unit tests in `tests/unit/test_api_client.py` passing
- **Status set to**: Done (all ACs satisfied)
