109 lines
2.8 KiB
Markdown
109 lines
2.8 KiB
Markdown
# Garmin Integration Specification
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## Job to Be Done
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When I connect my Garmin account, I want the app to automatically sync my biometrics daily, so that training decisions are based on real physiological data.
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## OAuth Flow
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### Initial Token Bootstrap (Manual)
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Garmin's Connect API uses OAuth 1.0a → OAuth 2.0 exchange.
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**Process:**
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1. User runs `scripts/garmin_auth.py` locally
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2. Script obtains OAuth 1.0a request token
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3. User authorizes in browser
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4. Script exchanges for OAuth 2.0 access token
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5. User pastes tokens into Settings > Garmin page
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**Tokens Stored:**
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- `oauth1` - OAuth 1.0a credentials (JSON, encrypted)
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- `oauth2` - OAuth 2.0 access token (JSON, encrypted)
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- `expires_at` - Token expiration timestamp
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### Token Storage
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Tokens encrypted with AES-256-GCM using `ENCRYPTION_KEY` env var.
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**Functions (`src/lib/encryption.ts`):**
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- `encrypt(plaintext: string): string` - Returns base64 ciphertext
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- `decrypt(ciphertext: string): string` - Returns plaintext
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## API Endpoints
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### GET `/api/garmin/status`
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Returns current Garmin connection status.
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**Response:**
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```json
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{
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"connected": true,
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"daysUntilExpiry": 85,
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"lastSync": "2024-01-10T07:00:00Z"
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}
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```
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### POST `/api/garmin/tokens`
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Updates stored Garmin tokens.
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**Request Body:**
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```json
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{
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"oauth1": { ... },
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"oauth2": { ... },
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"expires_at": "2024-04-10T00:00:00Z"
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}
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```
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## Garmin Data Fetching
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### Daily Sync (`/api/cron/garmin-sync`)
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Runs via cron job at 6:00 AM user's timezone.
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**Endpoints Called:**
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1. `/usersummary-service/stats/bodyBattery/dates/{date}` - Body Battery
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2. `/hrv-service/hrv/{date}` - HRV Status
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3. `/fitnessstats-service/activity` - Intensity Minutes
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**Data Extracted:**
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- `bodyBatteryCurrent` - Latest BB value
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- `bodyBatteryYesterdayLow` - Yesterday's minimum BB
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- `hrvStatus` - "Balanced" or "Unbalanced"
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- `weekIntensityMinutes` - 7-day rolling sum
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### Garmin Client (`src/lib/garmin.ts`)
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**Functions:**
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- `fetchGarminData(endpoint, { oauth2Token })` - Generic API caller
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- `isTokenExpired(tokens)` - Check if refresh needed
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- `daysUntilExpiry(tokens)` - Days until token expires
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## Token Expiration Handling
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Garmin OAuth 2.0 tokens expire after ~90 days.
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**Warning Triggers:**
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- 14 days before: Yellow warning in Settings
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- 7 days before: Email notification
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- 0 days: Red alert, manual refresh required
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## Success Criteria
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1. Tokens stored encrypted at rest
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2. Daily sync completes before 7 AM notification
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3. Token expiration warnings sent 14 and 7 days before
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4. Failed syncs logged with actionable error messages
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## Acceptance Tests
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- [ ] Encrypt/decrypt round-trips correctly
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- [ ] `/api/garmin/status` returns accurate days until expiry
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- [ ] `/api/garmin/tokens` validates token structure
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- [ ] Cron sync fetches all three Garmin endpoints
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- [ ] Expired token triggers appropriate error handling
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- [ ] Token expiration warning at 14-day threshold
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