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Settings Screen UI/UX Design

The Settings screen in FEN is the central hub for managing the user's cryptographic identity, storage backends, and local data footprint. Because FEN is local-first and heavily relies on cryptography, the settings must be intuitive while exposing powerful underlying controls.

1. Identity & Security (Top Section)​

This section manages the Ed25519 keypair that defines the user.

  • Current Identity Card:
    • Displays a visual avatar (e.g., identicon generated from pubkey) and the user's display name.
    • Shows a shortened version of the Public Key.
  • Backup & Recovery:
    • iCloud / Local Storage Backup (v1 Default): Toggle to automatically back up the encrypted identity. Restoring from iCloud is the primary method for transferring identities between devices.
    • Recovery Phrase: Button to reveal the 12-word BIP-39 mnemonic (requires biometric authentication).
    • Transfer via QR Code (v2): Generates a QR code of the encrypted keypair so another device can scan and import it. (Deferred to v2).
  • App Security:
    • Biometric Unlock: Toggle to require FaceID / Fingerprint to open the app.

2. Storage Configuration​

This section controls the owner's validated self-hosted backend. There is no developer-hosted Managed tier and no Provisioner URL. A clean install must collect this before the owner can create a syncable group.

  • Backend chooser:
    • Segmented control with S3-compatible and Nextcloud.
    • The same chooser appears during onboarding and in Settings for later changes.
  • S3-compatible form:
    • Fields: endpoint, region, bucket, access key ID, secret access key.
    • Test connection constructs the S3 storage adapter and runs probe().
  • Nextcloud form:
    • Fields: base URL, username, app password.
    • Test connection checks owner WebDAV access and OCS capabilities needed for in-app provisioning: public-link sharing and public upload. Group creation later uses the owner app password through NextcloudProvisioner to create the per-group folder and public share.
  • Validation result:
    • A backend is saved as active only after probe() reports BackendCaps.usable.
    • Failed tests show the failed capability (list, write, delete, or conditional write) or the backend error message.
    • Owner credentials are stored only through the Keychain-backed secure storage path. Drift stores only non-secret active-backend metadata such as S3 endpoint/region/bucket or Nextcloud base URL plus the validation timestamp.
  • Create group gate:
    • Create Group is disabled until a validated active backend exists and its owner credentials are available from Keychain.
    • Once configured, group creation calls the configured GroupProvisioner: S3 reuses the owner bucket/prefix descriptor; Nextcloud creates the group folder and password-protected public link in-app.

3. Notifications (v2 — hidden in v1)​

Manages how the app alerts the user to new expenses and group events. v1 ships no push notifications (sync is poll-based, fen.md §2.9), so this section is hidden until the v2 opt-in silent-push tier exists.

  • Global Notifications Toggle: Enable or disable push notifications entirely.
  • Notification Types: Toggles for "New Expenses", "Settlements", and "Group Invites".

4. Data & Storage Management​

This section gives the user visibility into their local storage footprint and Cold Archives.

  • Local Storage Usage:
    • Visual breakdown: Active Groups Cache vs. Cold Archives vs. Media/Receipts.
  • Cold Archives Management:
    • A list of all locally archived groups.
    • Tapping a group allows the user to export the archive (zip) or permanently delete it from the device.
  • Clear Cache: Button to wipe the local cache of active groups (forces a re-download from S3 on next open).

5. General Preferences​

  • Theme: System / Light / Dark.
  • Default Currency: Sets the default currency when creating a new group.
  • Developer / Debug Mode (Visible by default in v1):
    • Shows detailed sync logs, raw S3 connection status, backend latency, and manual force-sync buttons.