[Reliability] Offline changes not synced — notes edited offline are lost when coming back online

[anshul23102]

Executive Summary

Users who edit notes while offline expect those changes to sync when reconnecting. Currently, offline edits are discarded when the connection is restored.

Root Cause

No offline queue or sync mechanism for note modifications.

Proposed Solution

class OfflineSyncManager {
  constructor(dbName = 'savebook_sync_queue') {
    this.dbName = dbName;
    this.db = null;
  }
  
  async initialize() {
    return new Promise((resolve, reject) => {
      const request = indexedDB.open(this.dbName, 1);
      request.onupgradeneeded = () => {
        const db = request.result;
        db.createObjectStore('sync_queue', { keyPath: 'id', autoIncrement: true });
      };
      request.onsuccess = () => {
        this.db = request.result;
        resolve();
      };
      request.onerror = reject;
    });
  }
  
  async queueNoteChange(noteId, content) {
    const store = this.db.transaction('sync_queue', 'readwrite').objectStore('sync_queue');
    return new Promise((resolve, reject) => {
      const request = store.add({
        noteId,
        content,
        timestamp: Date.now(),
        status: 'pending',
      });
      request.onsuccess = resolve;
      request.onerror = reject;
    });
  }
  
  async syncPendingChanges() {
    const store = this.db.transaction('sync_queue', 'readonly').objectStore('sync_queue');
    return new Promise((resolve, reject) => {
      const request = store.getAll();
      request.onsuccess = async () => {
        const pendingChanges = request.result;
        
        for (const change of pendingChanges) {
          try {
            await fetch(`/api/notes/${change.noteId}`, {
              method: 'PUT',
              body: JSON.stringify({ content: change.content }),
            });
            
            // Remove from queue after successful sync
            await this.removeFromQueue(change.id);
          } catch (error) {
            console.error('Sync failed:', error);
          }
        }
        
        resolve(pendingChanges.length);
      };
    });
  }
}

// Monitor online status and sync
window.addEventListener('online', async () => {
  const syncer = new OfflineSyncManager();
  await syncer.initialize();
  const synced = await syncer.syncPendingChanges();
  console.log(`Synced ${synced} pending notes`);
});

Checklist

• I have searched existing issues and confirmed this is not a duplicate
• I have read the CONTRIBUTING.md guidelines
• I have provided clear steps to reproduce the issue
• I have described expected vs. actual behavior clearly
• This issue title is clear and specific
• This repository has been verified as NSOC on https://www.nsoc.in/projects

@HarshYadav152 Could you please /assign this issue to me? I would like to implement offline sync for note changes under NSOC '26.

/assign

[anshul23102]

Hi @HarshYadav152 👋

I am the author of this issue and would like to work on the fix. This contribution is being made under NSoC 2026 (Nexus Spring of Code).

I have reviewed the issue and am ready to implement the solution. Could you please assign this to me?

Thank you!

[anshul23102]

Hi @HarshYadav152,

I've documented this data synchronization issue for offline-edited notes. This is part of my NSoC'26 contributions.

I'm ready to work on implementing a sync queue solution once assigned. Could a maintainer please assign this to me? Thank you!

[anshul23102]

Hi @HarshYadav152 👋

I'd like to work on this issue under NSoC 2026 (Nexus Spring of Code).

Offline sync is a critical reliability feature. I'm ready to:

1. Implement a local queue/pending buffer for edits made while offline
2. Add a sync mechanism that attempts to merge offline changes with server state
3. Handle merge conflicts (if a note was edited server-side while offline)
4. Show sync status UI (pending, syncing, synced, conflict)

Could you please assign this to me?

Thank you!