TripnThrill

TripnThrill delivers an ultra-reliable offline travel management experience. It automatically caches routes, maps, and schedules. Once internet access is restored, it initiates idempotent REST requests to safely sync state changes without risking double-bookings.

RoleLead Full Stack App Engineer

PlatformsiOS, Android, Web

Timeline5 Months (2023)

ArchitectureBLoC Pattern

100% SafeConflict Resolution

Full AppOffline Mode

< 800msClient-Server Sync

Tech Stack & Concepts

BLoC PatternRepository PatternBackground SyncIdempotent APIs

Explore Repository

The Problem

Travelers frequently experience unstable internet in transit, causing sync errors, overlapping timelines, and lost booking updates during trip plans.

Product Thinking

An itinerary app must remain fully interactive offline. Any addition, re-ordering, or deletion should feel instantaneous to the traveler, with synchronization resolved automatically in the background.

Engineering Challenges

Reconciling conflicting edits to shared family travel itineraries that were made on different devices offline.

Key Learnings

Acquired deep proficiency in event-driven architecture, API idempotency headers, and background worker jobs.

Behind the Code

Architectural & Code Decisions

Deep technical breakdowns of individual structural choices and implementation patterns.

DECISION 01

BLoC Event Flow architecture

Enforced strict separation between UI touch inputs and data logic through BLoC events, maintaining immutable state models that are safe from race conditions.

dart

// Travel Itinerary BLoC Event Handler
class ItineraryBloc extends Bloc<ItineraryEvent, ItineraryState> {
  final TravelRepository repo;
  
  ItineraryBloc(this.repo) : super(ItineraryInitial()) {
    on<SyncOfflineChanges>(_onSyncOfflineChanges);
  }

  Future<void> _onSyncOfflineChanges(SyncOfflineChanges event, Emitter<ItineraryState> emit) async {
    emit(ItinerarySyncing());
    final result = await repo.pushLocalQueueToServer();
    emit(result ? ItinerarySynced() : ItinerarySyncFailed());
  }
}

DECISION 02

Idempotent Sync Queue

Engineered a persistent local SQLite queue to store offline write actions, using UUID headers to guarantee that duplicate server calls never create duplicate bookings.

dart

// Safe POST request with Idempotency Key
Future<Response> createItineraryStop(Stop stop) async {
  return await dio.post(
    '/stops',
    data: stop.toJson(),
    options: Options(
      headers: {
        'X-Idempotency-Key': stop.localUuid, // Client generated UUID
      },
    ),
  );
}