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Architecture

This page summarizes the technical shape of the project for visitors. The repository itself is the living source of truth — this page links out to the full documentation rather than duplicating it, so the two never quietly drift apart.

Stack

  • Flutter / Dart, one codebase across macOS, iOS, Android, and Windows.
  • Drift, a typed, reactive layer over SQLite, for the local database — one file per device, opened only by this app.
  • Provider for state management; ViewModels extend ChangeNotifier.
  • go_router for declarative routing.
  • No backend. No server, no cloud storage, no telemetry, no analytics.

Layering: MVVM + Repository

The app is organized in three layers, each with a single job:

  • Views render UI and forward user actions. They hold no business logic and never call a Repository directly.
  • ViewModels hold UI state, expose it as streams/listenables, and call into Repositories to read or change data.
  • Repositories are the single source of truth for a domain area — the only layer that talks to the database.

Data flows one direction: Views listen to ViewModels, ViewModels call Repositories, Repositories talk to Drift. This keeps business logic out of widgets and out of the database layer, and makes each piece testable on its own.

Security and privacy stance

All ledger data stays on the device, in a local SQLite database. There's no account, no cloud sync, and nothing sent off-device by default. The one optional exception is a reference exchange-rate lookup, off by default, which — when a user turns it on — sends only a currency pair to a chosen provider for a comparison figure, never any ledger data.

The device's signing identity lives in the OS-level secure keystore, not in the SQLite file itself, and every posted journal entry is signed and hash-chained so that tampering with a past entry breaks verification from that point forward, detected the next time the app starts.

Full documentation

For the complete, current picture — project structure, data flow diagrams, the full technology-choice rationale, and the engineering discipline (testing rules, dependency policy, Definition of Done) — see: