# Implementation Plan: Fitbit/Garmin Data Sync

**Branch**: `002-fitbit-garmin-sync` | **Date**: 2025-12-24 | **Spec**: [link](./spec.md)
**Input**: Feature specification from `specs/002-fitbit-garmin-sync/spec.md`

## Summary

This feature will implement synchronization of activities and health metrics from Garmin Connect to the application's database. The implementation will involve wiring up existing backend stub endpoints to a sync service that uses the `garth` library to fetch data from Garmin. The synced data will be stored in a PostgreSQL database and exposed through a series of new API endpoints for querying and retrieval.

## Technical Context

**Language/Version**: Python 3.11
**Primary Dependencies**: FastAPI, Uvicorn, SQLAlchemy, Pydantic, garth
**Storage**: PostgreSQL
**Testing**: pytest, pytest-asyncio
**Target Platform**: Linux server (via Docker)
**Project Type**: Web application (backend)
**Performance Goals**: Standard web application performance, with API responses under 500ms p95.
**Constraints**: The solution should be implemented within the existing `backend` service.
**Scale/Scope**: The initial implementation will support syncing data for a single user.

## Constitution Check

*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*

- **Test-First**: The implementation will follow a test-driven approach. For each endpoint and service function, a corresponding set of unit and/or integration tests will be written before the implementation.

*VERDICT: The plan adheres to the core principles of the constitution.*

## Project Structure

### Documentation (this feature)

```text
specs/002-fitbit-garmin-sync/
├── plan.md              # This file
├── research.md          # Phase 0 output
├── data-model.md        # Phase 1 output
├── quickstart.md        # Phase 1 output
├── contracts/           # Phase 1 output
│   └── api-contract.yaml
└── tasks.md             # Phase 2 output (created by /speckit.tasks)
```

### Source Code (repository root)

The implementation will be contained within the existing `backend` directory structure.

```text
backend/
├── src/
│   ├── api/
│   │   ├── activities.py
│   │   ├── metrics.py
│   │   └── sync.py
│   ├── models/
│   │   ├── activity.py
│   │   └── health_metric.py
│   └── services/
│       ├── sync_app.py
│       └── garmin/
│           └── client.py
└── tests/
    ├── integration/
    │   ├── test_sync_flow.py
    └── unit/
        ├── test_api/
        │   ├── test_activities.py
        │   └── test_metrics.py
        └── test_services/
            └── test_sync_app.py
```

**Structure Decision**: The plan adheres to the existing project structure, which is a single backend service. New functionality will be added to the appropriate existing modules.

## Complexity Tracking
*No constitutional violations to justify.*