NAYANTHA NETHSARA

Kahavanu

An offline-first Android personal finance application built with Kotlin, Jetpack Compose, and Room.
GitHub Repository

The origin

Named after the historic gold coinage of ancient Sri Lanka, Kahavanu was built to solve a persistent frustration with modern expense trackers: reliance on constant internet connectivity.
Most contemporary finance applications behave like web wrappers. They require server handshakes for every transaction log, spin endlessly when mobile reception drops in a store, and lock your personal financial records behind third-party cloud availability.
I wanted a personal finance tool that felt instant, reliable, and completely functional offline, whether you are recording a small transit fare on spotty mobile data or reviewing monthly savings goals in airplane mode.

Local-first architecture

Kahavanu is engineered around a local-first philosophy, treating the device's local storage as the primary source of truth:
  • Room local database: Every transaction, income stream, and savings goal is committed immediately to an encrypted local Room SQLite database on the device, eliminating input latency.
  • WorkManager background synchronization: Changes made while offline are tracked in a mutation queue and synchronized seamlessly to Firebase Firestore whenever an active network connection is detected.
  • Recurring cash flow management: Automatically forecasts upcoming recurring subscriptions, scheduled bills, and expected income cycles to display true net balance.
  • Goal tracking: Allows users to establish dedicated savings targets with real-time progress calculations as surplus funds are allocated.

Modern Android engineering

The codebase follows Google's recommended Android architecture practices for long-term maintainability:
  • Jetpack Compose UI: Declarative UI built entirely with Jetpack Compose and Material 3 design tokens, providing dynamic dark mode support and fluid animations.
  • Unidirectional data flow: Built on the MVVM pattern where Compose screens observe immutable UI state exposed via Kotlin StateFlow from ViewModels.
  • Dependency injection: Dependency inversion managed via Dagger Hilt, keeping UI screens strictly decoupled from repository interfaces and database implementations.

Tech stack

  • Language: Kotlin 2.2
  • UI Framework: Jetpack Compose with Material 3
  • Local Storage: Android Room
  • Cloud Sync: Firebase Firestore and Firebase Authentication
  • Background Processing: Android WorkManager
  • Dependency Injection: Hilt

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