Field-Staff & Delivery Fleet Apps

[Online-First App (Fails in India)]
User Action ──► HTTP Request ──► [Network Drop] ──► Error Screen & Lost Data!

[KaamLabs Offline-First Architecture (Never Fails)]
User Action ──► Local SQLite/WatermelonDB (0ms Instant Write) ──► UI Updates Instantly
                      │
                      ▼ (Background Daemon monitors connectivity)
              [Network Available?]
                      │
                      ├──► YES ──► Push Change-Set Queue to Central Cloud (Supabase/PostgreSQL)
                      └──► NO  ──► Hold safely in local encrypted storage; retry seamlessly

// services/sync/offlineOrderSync.ts
import { database } from '../db';
import { Q } from '@nozbe/watermelondb';

export async function createOfflineOrder(orderPayload: {
  customerId: string;
  items: Array<{ sku: string; quantity: number; unitPrice: number }>;
  totalAmount: number;
  latitude: number;
  longitude: number;
}) {
  return await database.write(async () => {
    // 1. Write immediately to local on-device SQLite database
    const newOrder = await database.get('orders').create((order: any) => {
      order.customerId = orderPayload.customerId;
      order.itemsJson = JSON.stringify(orderPayload.items);
      order.totalAmount = orderPayload.totalAmount;
      order.syncStatus = 'pending_sync'; // 'pending_sync' | 'synced' | 'failed'
      order.clientCreatedAt = new Date().toISOString();
      order.geoLat = orderPayload.latitude;
      order.geoLng = orderPayload.longitude;
    });

    // 2. Schedule background sync without blocking the UI
    triggerBackgroundSync();

    return newOrder;
  });
}

// Background sync worker
export async function triggerBackgroundSync() {
  const pendingOrders = await database
    .get('orders')
    .query(Q.where('syncStatus', 'pending_sync'))
    .fetch();

  if (pendingOrders.length === 0) return;

  try {
    const payload = pendingOrders.map((o: any) => ({
      id: o.id,
      customerId: o.customerId,
      items: JSON.parse(o.itemsJson),
      totalAmount: o.totalAmount,
      timestamp: o.clientCreatedAt,
    }));

    const response = await fetch('https://api.kaamlabs.in/v1/sync/orders', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ batch: payload }),
    });

    if (response.ok) {
      await database.write(async () => {
        for (const order of pendingOrders) {
          await order.update((o: any) => {
            o.syncStatus = 'synced';
          });
        }
      });
    }
  } catch (err) {
    // Silent fail; device will retry automatically when signal stabilizes
    console.log('Sync queued: device offline or network unreachable');
  }
}