# Go Porting Implementation Plan

## Project Structure
```text
/go-garminconnect
├── cmd/            # CLI example applications
├── garminconnect/  # Core API wrapper package
├── fit/            # FIT encoding package
├── internal/       # Internal helpers and utilities
├── examples/       # Example usage
├── PORTING_PLAN.md
├── JUNIOR_ENGINEER_GUIDE.md
└── README.md
```

## Phase Implementation Details

### Phase 1: Setup & Core Structure
- [x] Initialize Go module: `go mod init github.com/sstent/go-garminconnect`
- [x] Create directory structure
- [x] Set up CI/CD pipeline
- [x] Create Makefile with build/test targets
- [x] Add basic README with project overview

### Phase 2: Authentication Implementation
- [x] Implement OAuth2 authentication flow with MFA support
- [x] Create token storage interface
- [x] Implement session management with auto-refresh
- [x] Handle MFA authentication
- [x] Test against sandbox environment

### Phase 3: API Client Core
- [x] Create Client struct with configuration
- [x] Implement generic request handler
- [x] Add automatic token refresh
- [x] Implement rate limiting
- [x] Set up connection pooling
- [x] Create response parsing utilities

### Phase 4: Endpoint Implementation
#### Health Data Endpoints
- [ ] Body composition
- [ ] Sleep data
- [ ] Heart rate/HRV/RHR
- [ ] Stress data
- [ ] Body battery

#### Activity Endpoints
- [x] Activity list/search
  - Implemented with pagination support
- [x] Activity details
  - Added GPS track point timestamp parsing
  - Custom time handling with garminTime structure
  - Comprehensive table-driven tests
- [x] Activity upload/download
  - Added FIT validation
  - Implemented multipart upload
  - Added endpoint for downloading activities in FIT format
- [x] Gear management
  - Implemented GetGearStats
  - Implemented GetGearActivities with pagination
  - Comprehensive tests

#### User Data Endpoints
- [ ] User summary
- [ ] Daily stats
- [ ] Goals/badges

### Phase 5: FIT Handling
- [x] Port FIT encoder from Python
  - Implemented core encoder with header/CRC
  - Added support for activity messages
- [x] Implement weight composition encoding
- [x] Create streaming FIT encoder
  - Supports io.WriteSeeker interface
  - Implements incremental CRC calculation
  - Handles large files with minimal memory
- [x] Add FIT parser

### Phase 6: Testing & Quality
- [ ] Table-driven endpoint tests
- [ ] Mock server implementation
- [ ] FIT golden file tests
- [ ] Performance benchmarks
- [ ] Static analysis integration

### Phase 7: Documentation & Examples
- [ ] Complete GoDoc coverage
- [ ] Create usage examples
- [ ] Build CLI example app
- [x] Write migration guide

## Weekly Milestones
| Week | Focus Area | Key Deliverables |
|------|------------|------------------|
| 1 | Setup + Auth | Auth working, CI green |
| 2 | Core + Health | 40% test coverage, health endpoints |
| 3 | Activity + User | All endpoints implemented |
| 4 | FIT Handling | FIT encoding complete, 85% coverage |
| 5 | Documentation | Examples, guides, v1.0 release |