Files
nearle_pos/lib/app/providers.dart
Suriya 0a49323858 Drain bills to the back office automatically, over MQTT or HTTP
Turns the orders table into a queue that empties itself. Bills were only
uploaded when a cashier pressed Sync at end of day; a till that was never
pressed held a day's takings indefinitely.

Drain engine (lib/data/sync/sync_engine.dart)
- Triggers on sale committed, network regained, 5-minute poll, head-office
  request, and the manual button.
- Single flight: a busy till firing a trigger per sale would otherwise have
  several passes reading the same pending rows and send every bill twice.
  A trigger arriving mid-drain is queued and replayed, so nothing is dropped.
- Exponential backoff with +/-20% jitter to a 5-minute ceiling. The jitter
  matters: a store's terminals all fail at the same instant when the line
  drops, and would retry in lockstep without it.
- Halts rather than loops on a failure retrying cannot fix (bad credential,
  refused batch). Pressing Sync clears the halt.

Transports (lib/data/remote/)
- OrderTransport interface; MQTT, HTTP and simulated implementations. The
  repository does not know which is in use.
- MQTT: QoS 1 uplink, application-level ACK correlated by batch_id on a return
  topic, retained Last Will for terminal-offline detection, downlink for
  catalogue pushes and remote sync requests.
- A broker PUBACK is never treated as acceptance. It means the broker holds
  the bytes, not that the ledger took the sale. Only ids the back office names
  are marked synced; silence leaves a bill pending.
- HTTP carries a stable idempotency key across retries of the same bills.

Retention
- Accepted bills are kept 7 days instead of deleted, so a batch the back
  office later loses can be re-sent in full. Purged after that; archived
  totals stay forever.
- forBusinessDate now reads pending rows only. A retained bill exists in both
  the orders table and day_archive, and summing both would overstate the day.

Fixes found while building this
- SyncEngine._refreshPending wrote state.copyWith(pending: await ...). Dart
  evaluates the receiver before the awaited argument, so a connectivity drop
  during the wait was silently overwritten by the stale snapshot. Caught by
  the first run of the new engine tests.
- PrinterSettingsController wrote state after four awaits with no mounted
  check, throwing "used after dispose" when Settings was left mid-load. This
  was pre-existing and reached the cashier as a red screen.

Also
- Header pill now reports real sync state: LIVE / n QUEUED / SYNCING /
  SYNC HALTED, with an explanation of where the bills are.
- Settings shows the route, last upload, next retry and retention window.
- docs/sync-contract.md states what the back office must implement, including
  the idempotency requirement that at-least-once delivery makes mandatory.

Tests: 90 -> 129 passing. New coverage for backoff shape and jitter band,
single flight, halting, ACK correlation and partial acceptance, at-least-once
duplicate handling, retention and purge, and no double-counting after a sync.
Suite run six times clean.

Not addressed: bills already synced by an older build went up overstated and
still need server-side reconciliation. Broker credentials have no Settings
editor yet.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-08-01 10:57:29 +05:30

163 lines
5.8 KiB
Dart

import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../core/config/sync_config.dart';
import '../core/services/connectivity_service.dart';
import '../core/services/receipt_service.dart';
import '../core/services/sound_service.dart';
import '../data/datasources/local_store.dart';
import '../data/repositories/customer_repository_impl.dart';
import '../data/repositories/product_repository_impl.dart';
import '../data/datasources/remote_catalogue_source.dart';
import '../data/remote/http_order_transport.dart';
import '../data/remote/mqtt_order_transport.dart';
import '../data/remote/order_transport.dart';
import '../data/remote/simulated_order_transport.dart';
import '../data/repositories/sync_repository_impl.dart';
import '../data/repositories/transaction_repository_impl.dart';
import '../data/sync/sync_engine.dart';
import '../domain/repositories/customer_repository.dart';
import '../domain/repositories/product_repository.dart';
import '../domain/repositories/sync_repository.dart';
import '../domain/repositories/transaction_repository.dart';
import '../domain/usecases/checkout_sale.dart';
/// Root data source. Overridden in tests with an in-memory double.
final localStoreProvider = Provider<LocalStore>((ref) => LocalStore.instance);
// ---------------------------------------------------------- Repositories
final productRepositoryProvider = Provider<ProductRepository>(
(ref) => ProductRepositoryImpl(ref.watch(localStoreProvider)),
);
final customerRepositoryProvider = Provider<CustomerRepository>(
(ref) => CustomerRepositoryImpl(ref.watch(localStoreProvider)),
);
final transactionRepositoryProvider = Provider<TransactionRepository>(
(ref) => TransactionRepositoryImpl(ref.watch(localStoreProvider)),
);
/// Mirrors the Settings "Simulate offline" switch so the header can show it.
///
/// Without this the terminal claims LIVE while every call is being failed on
/// purpose, which reads as a real network fault.
final simulateOfflineProvider = StateProvider<bool>((ref) => false);
/// Simulated back-office endpoints. Held as singletons so the offline toggle
/// in Settings affects every call.
final remoteCatalogueProvider = Provider<RemoteCatalogueSource>(
(ref) => RemoteCatalogueSource(
isOffline: () => ref.read(simulateOfflineProvider),
),
);
// ------------------------------------------------------------------- Sync
/// How this terminal reaches the back office.
///
/// Defaults to the simulated route so a fresh install is usable with no broker
/// and no endpoint; Settings re-points it.
final syncConfigProvider = StateProvider<SyncConfig>((ref) => const SyncConfig());
/// Real network state, folded with the Settings offline switch.
final connectivityServiceProvider = Provider<ConnectivityService>((ref) {
final service = ConnectivityService(
isSimulatedOffline: () => ref.read(simulateOfflineProvider),
);
ref.onDispose(service.dispose);
return service;
});
/// The wire itself. Rebuilt when the configuration changes, and the old one is
/// closed so a re-pointed terminal does not keep a stale broker session open.
final orderTransportProvider = Provider<OrderTransport>((ref) {
final config = ref.watch(syncConfigProvider);
final transport = switch (config.transport) {
TransportKind.mqtt => MqttOrderTransport(config: config),
TransportKind.http => HttpOrderTransport(config: config),
TransportKind.simulated => SimulatedOrderTransport(
isOffline: () => ref.read(simulateOfflineProvider),
),
};
ref.onDispose(transport.dispose);
return transport;
});
final syncRepositoryProvider = Provider<SyncRepository>(
(ref) => SyncRepositoryImpl(
ref.watch(localStoreProvider),
ref.watch(remoteCatalogueProvider),
ref.watch(orderTransportProvider),
batchSize: ref.watch(syncConfigProvider).batchSize,
),
);
/// Decides when bills are uploaded. Started once, by the app shell.
final syncEngineProvider = Provider<SyncEngine>((ref) {
final transport = ref.watch(orderTransportProvider);
final engine = SyncEngine(
repository: ref.watch(syncRepositoryProvider),
connectivity: ref.watch(connectivityServiceProvider).onlineChanges,
downlink: transport.downlink,
onCatalogueChanged: () async {
await ref.read(syncRepositoryProvider).importCatalogue();
ref.invalidate(localStoreProvider);
},
);
ref.onDispose(engine.dispose);
return engine;
});
/// Live engine state for the header pill and the events screen.
final syncEngineStateProvider = StreamProvider<SyncEngineState>((ref) {
final engine = ref.watch(syncEngineProvider);
return engine.states.map((s) => s);
});
// ------------------------------------------------------------- Use cases
final checkoutSaleProvider = Provider<CheckoutSale>(
(ref) => CheckoutSale(
productRepository: ref.watch(productRepositoryProvider),
customerRepository: ref.watch(customerRepositoryProvider),
transactionRepository: ref.watch(transactionRepositoryProvider),
),
);
// -------------------------------------------------------------- Services
final soundServiceProvider =
Provider<SoundService>((ref) => SoundService.instance);
final receiptServiceProvider =
Provider<ReceiptService>((ref) => ReceiptService.instance);
// --------------------------------------------------------------- Session
class CashierSession {
const CashierSession({
required this.name,
required this.role,
required this.terminalId,
});
final String name;
final String role;
final String terminalId;
}
final cashierSessionProvider = StateProvider<CashierSession>(
(ref) => const CashierSession(
name: 'Suriya',
role: 'ADMIN',
terminalId: 'TERM-01',
),
);
/// Ticks once a minute to drive the header clock without rebuilding on every
/// frame.
final clockProvider = StreamProvider<DateTime>((ref) async* {
yield DateTime.now();
yield* Stream.periodic(const Duration(seconds: 20), (_) => DateTime.now());
});