Sync System Improvements - Implementation Summary

Overview

Enhanced the Nostr subscription sync system to properly track feed deletions and read status across devices.

Changes Made

1. Database Schema Updates (prisma/schema.prisma)

Subscription Model

• Added updatedAt field to track when subscriptions change
• Added deletedAt field for soft-delete tracking (instead of hard deletes)
• Added indexes for efficient querying of deleted items

ReadItem Model

• Added syncedAt field to track when read status was last synced to Nostr
• Added index for efficient querying of unsynced items

2. Sync Library Updates (src/lib/nostr-sync.ts)

New Interfaces

• Extended SubscriptionList with deleted?: string[] array
• Added ReadStatusList interface for read status sync

New Event Kind

• Added READ_STATUS_KIND = 30405 for syncing read status

Enhanced Functions

• buildSubscriptionListFromFeeds() - Now includes deleted feeds in output
• mergeSubscriptionLists() - Now returns toRemove array for feeds deleted remotely
• Added publishReadStatus() - Publish read items to Nostr
• Added fetchReadStatus() - Fetch read items from Nostr

3. API Updates (src/server/api/routers/feed.ts)

Modified Endpoints

• getFeeds - Now filters out soft-deleted subscriptions (deletedAt: null)
• unsubscribeFeed - Changed from hard delete to soft delete (sets deletedAt)

New Endpoints

• getSubscriptionsForSync - Returns all subscriptions including deleted ones for sync
• cleanupDeletedSubscriptions - Hard deletes old soft-deleted records (cleanup)
• markReadItemsSynced - Marks read items as synced after publishing
• getUnsyncedReadItems - Gets read items that haven’t been synced yet

4. Documentation Updates (SUBSCRIPTION_SYNC.md)

• Added documentation for kind 30405 (read status sync)
• Added deleted field to subscription list schema
• Added ReadStatusList interface documentation

How It Works

Deletion Tracking

1. When a user unsubscribes from a feed, it’s soft-deleted (deletedAt timestamp set)
2. During sync, deleted feeds are included in the deleted array in the Nostr event
3. When another device syncs, it sees the deleted feeds and removes them locally
4. Old soft-deleted records can be cleaned up after 90 days (configurable)

Read Status Sync

1. When items are marked as read, they’re tracked in the local database
2. Unsynced read items can be published to Nostr (kind 30405)
3. When syncing on another device, the read status is fetched and applied
4. Items are marked with syncedAt timestamp after successful sync

Migration

A database migration has been created:

• File: prisma/migrations/20260128144700_add_sync_tracking/migration.sql
• Adds deletedAt and updatedAt to Subscription table
• Adds syncedAt to ReadItem table
• Creates necessary indexes

To apply: Run npx prisma migrate deploy in production or npx prisma migrate dev in development

Benefits

1. No More Re-adding Deleted Feeds: Deletions are now tracked and synced across devices
2. Read Status Sync: Read/unread status can be synced across devices (optional feature)
3. Conflict Resolution: Soft deletes allow for better conflict resolution in sync scenarios
4. Data Integrity: No loss of information during sync operations
5. Cleanup: Old deleted records can be purged after a grace period

Next Steps for Implementation

1. Apply the database migration
2. Update client-side sync logic to use new toRemove array from merge function
3. Implement UI for read status sync (optional feature)
4. Add periodic cleanup job for old deleted subscriptions
5. Test cross-device sync scenarios

Backward Compatibility

• Existing sync events (kind 30404) without deleted field will continue to work
• The deleted field is optional and only included when there are deletions
• Read status sync (kind 30405) is completely new and optional