# ADR-0015: User Interface and Multi-Device Synchronization ## Status Proposed ## Context Our system is designed to empower users with complete control over their data while ensuring that file operations are consistent and synchronized across multiple devices and nodes. Users must be able to interact with the system through an intuitive interface that provides clear feedback on file operations, synchronization status, and network connectivity. Further, when users operate on multiple devices, the system must reliably merge changes and resolve conflicts to maintain data integrity (see FR-15 and FR-10). Key aspects of this ADR include: - **User Interface:** The initial interface will be a command-line interface (CLI) that offers direct control and feedback over file operations, audit logs, and synchronization status. Future plans include a graphical web-based interface to enhance usability. - **Multi-Device Synchronization:** The system must support seamless synchronization across devices. This involves merging manifest entries, tracking versions, and resolving conflicts in a deterministic manner. Changes initiated from one device should be transparently propagated to others while preserving auditability (FR-3, FR-10). - **Deterministic Testing:** Multi-device synchronization scenarios, including scenarios with simulated network latency or failures, must be deterministically testable. This ensures that synchronization remains robust under varied conditions, meeting our performance and maintainability goals (NFR-2, NFR-6). ## Decision We will implement a user interface and multi-device synchronization strategy that incorporates the following components: - **Intuitive User Interface (UI):** - **Command-Line Interface (CLI):** The initial UI will be CLI-based, offering clear, concise commands for file operations, status queries, and viewing audit logs. The CLI will provide immediate feedback to users regarding synchronization events and potential conflicts. - **Future Web Interface:** While the CLI is the primary interface in the initial release, the architecture will support a future web-based interface for users who prefer a graphical approach. This web interface will offer similar functionalities with additional visual aids for system status and history. - **Robust Multi-Device Synchronization:** - **Manifest-Based Synchronization:** Synchronization across devices is primarily achieved through a shared, immutable manifest. Each device maintains its own copy of the manifest, which is periodically merged with those from other devices. Conflict resolution and version tracking (as detailed in ADR-0010) ensure that changes are integrated consistently. - **Deterministic Conflict Resolution:** The synchronization mechanism relies on logical timestamps (e.g., Lamport timestamps) to order events, ensuring that conflicts are resolved in a consistent and predictable manner across devices. - **Status and Feedback:** The UI will display real-time synchronization status, including: - A summary of pending updates and recent activity. - Notifications of resolved conflicts or required user actions. - A detailed view of synchronization history for audit and troubleshooting purposes. - **Simulation and Testing Integration:** - The synchronization process is designed to work seamlessly in the deterministic simulation environment. This allows us to reproduce and verify multi-device coordination, performance under network latency, and disk failure scenarios during testing (NFR-2, NFR-6). ## Consequences - **Advantages:** - **Enhanced User Control and Transparency:** Users benefit from a clear view of the system state, including file changes and synchronization events, ensuring trust in the system’s operations. - **Seamless Multi-Device Experience:** The manifest-based synchronization mechanism along with deterministic conflict resolution ensures that users experience consistent data across all their devices. - **Future-Proofing:** The planned transition to a web interface builds upon the initial CLI, ensuring that the system can evolve to meet diverse user preferences without rearchitecting the core synchronization logic. - **Trade-offs:** - **Complexity in Synchronization Logic:** Merging multiple manifest logs and resolving conflicts in a distributed environment adds architectural and implementation complexity. However, this is justified by the need for robust multi-device synchronization. - **User Onboarding:** For users unfamiliar with a CLI, there may be an initial learning curve. This is mitigated by comprehensive documentation and the planned development of a more user-friendly graphical interface. ## References to Requirements - **Functional Requirements:** - FR-15: User Interface and Multi-Device Synchronization require that users can manage file operations and view the state of synchronization across devices. - FR-3 & FR-10: Versioning, change tracking, and conflict resolution in the manifest underpin the synchronization process. - **Non-Functional Requirements:** - NFR-4: Usability & User Experience – The UI design must be clear and intuitive to provide a good user experience. - NFR-2: Performance & Responsiveness – The synchronization mechanisms must perform efficiently, even under simulated network or disk latency. - NFR-6: Deployability & Maintainability – The synchronization process and UI must integrate with deterministic simulation testing to ensure reliability and ease of maintenance. ## Conclusion The proposed strategy for user interface design and multi-device synchronization ensures that users receive a consistent, transparent, and efficient experience when managing their data. By leveraging an intuitive CLI (with plans for a future web interface) alongside a robust, manifest-based synchronization mechanism, our system meets both the functional and non-functional requirements of reliability, auditability, and performance. This decision supports our mission to empower users with full control over their digital data across all devices.