# Feature Specification: Garmin Connect Synchronization Service **Feature Branch**: `001-create-from-initialspec` **Created**: 2025-10-09 **Status**: Draft **Input**: User description: "the feature description is in @initialspec.md" ## User Scenarios & Testing *(mandatory)* ### User Story 1 - Connect Garmin Account (Priority: P1) As a single-app user, I want to securely connect my Garmin Connect account so that the application can access my fitness data. **Why this priority**: This is the foundational step required for any data synchronization. Without it, no other feature can work. **Independent Test**: Can be tested by initiating the connection process, authenticating with Garmin, and confirming the application shows a successful connection status. This delivers the core value of enabling data exchange. **Acceptance Scenarios**: 1. **Given** I am not connected to Garmin, **When** I choose to connect my Garmin account, **Then** I am securely redirected to a Garmin authentication page. 2. **Given** I have successfully authenticated with Garmin, **When** I am redirected back to the application, **Then** the application shows that my account is successfully linked. 3. **Given** I deny the authentication request on the Garmin page, **When** I am redirected back to the application, **Then** the application shows that the connection failed and allows me to try again. --- ### User Story 2 - Synchronize Activities (Priority: P1) As a connected user, I want the application to automatically download my latest activities (like runs, rides) from Garmin so my fitness dashboard is always up-to-date. **Why this priority**: This is the primary purpose of the synchronization service, providing users with their core fitness data. **Independent Test**: Can be tested by having a connected Garmin account with recent activities, triggering a sync, and verifying that the new activities appear within the application's database. **Acceptance Scenarios**: 1. **Given** my Garmin account is connected and has recent activities, **When** a synchronization event is triggered, **Then** the new activities are downloaded and stored by the application. 2. **Given** an activity has already been synchronized, **When** the sync runs again, **Then** the existing activity is not duplicated. 3. **Given** I manually trigger a sync, **When** the process starts, **Then** I can view the current status of the synchronization (e.g., "In Progress", "Completed", "Failed"). --- ### User Story 3 - Upload Workouts (Priority: P2) As a connected user, I want to be able to upload a planned workout from the application to my Garmin Connect calendar so I can use it on my device. **Why this priority**: This enables a two-way integration, allowing users to manage their training plans within the application and execute them on their Garmin devices. **Independent Test**: Can be tested by creating a workout in the application, triggering the upload, and verifying the workout appears in the user's Garmin Connect calendar. **Acceptance Scenarios**: 1. **Given** my Garmin account is connected, **When** I choose to upload a workout, **Then** the workout is sent to my Garmin Connect calendar. 2. **Given** the workout fails to upload due to a connection issue, **When** the process fails, **Then** I am notified of the failure with a clear error message. --- ### Edge Cases - What happens if the user revokes access to the application from their Garmin Connect account settings? - How does the system handle rate limits imposed by the Garmin API to avoid being blocked? - What happens if a synchronization job is interrupted midway (e.g., server restart)? - How are data conflicts resolved if data is modified in both places between syncs? ## Requirements *(mandatory)* ### Functional Requirements - **FR-001**: System MUST allow a user to securely connect their Garmin Connect account. - **FR-002**: System MUST be able to store and manage authentication tokens for the connected Garmin account, including securely handling refresh tokens. - **FR-003**: System MUST download and store a user's activities from their Garmin account. - **FR-004**: System MUST provide a mechanism to manually trigger a data synchronization with Garmin. - **FR-005**: System MUST provide a way for the user to check the status of an ongoing or completed synchronization. - **FR-006**: System MUST be able to upload a user's planned workouts to their Garmin Connect calendar. - **FR-007**: System MUST synchronize user health metrics from Garmin, including Daily Summary (Steps, Resting Heart Rate, Sleep), VO2 Max, Heart Rate Zones, FTP Zones, and Max Heart Rate. - **FR-008**: All synchronization processes MUST run in the background to not block the user interface. - **FR-009**: The system's interaction with the Garmin API MUST be rate-limited to prevent exceeding API quotas. - **FR-010**: The system MUST include error handling and retry logic for failed API requests to Garmin. - **FR-011**: The system MUST maintain a history of synchronization events and their outcomes. ### Key Entities *(include if feature involves data)* - **User Account**: Represents the single user of the application. - **Garmin Connection**: Stores the authentication tokens and connection status for a user's Garmin account. - **Activity**: Represents a fitness activity (e.g., run, cycle) with its associated data (e.g., distance, time, location data). - **Workout**: Represents a planned workout to be executed by the user. - **Health Metric**: Represents a specific point-in-time or daily health measurement (e.g., daily steps, resting heart rate). - **Sync Job**: Represents a single synchronization process, its status, and history. ## Success Criteria *(mandatory)* ### Measurable Outcomes - **SC-001**: 99% of synchronization requests should be successfully processed within 5 minutes of being initiated. - **SC-002**: Users can connect their Garmin account in under 60 seconds. - **SC-003**: The system must be able to handle and store at least 10 years of activity data for a single user without performance degradation. - **SC-004**: The synchronization process must accurately reflect the user's data from Garmin with a data discrepancy rate of less than 0.1%. - **SC-005**: No user-facing errors should occur during the background synchronization process. The user should only see the final status (Success/Failure).