Equify

💸 Equify — Split group expenses and settle up instantly

Equify is a native Android app for splitting group expenses: trips, shared flats, dinners or any plan with friends. Track who paid what and Equify instantly works out who owes whom, keeping the number of transfers low. No sign-up: open the app and start — your data stays on your device.

📲 Get it on Google Play

Group summary	Settle up	About Equify

✨ Features

Groups: create groups and add participants in seconds, no accounts required.
Expenses: record who paid each expense and who it is split between.
Payments between members: log transfers to settle debts as you go.
“Settle up”: a settlement algorithm that resolves the group’s balances and proposes a small set of transfers to get everyone even.
Summary & PDF: total spent, outstanding balance and PDF export to share with the group.
5 languages: Spanish, English, French, Italian and Portuguese.
Optional ad-free: one-time in-app purchase to remove ads (Play Billing).

🛠️ Tech stack

Layer	Technology
Language	100% Kotlin (coroutines + Flow)
UI	Jetpack Compose + Material 3, single-activity, Navigation Compose
Dependency injection	Hilt
Persistence	Room (offline-first, versioned schemas in `app/schemas`) + DataStore Preferences
Monetization	Google AdMob + Play Billing (`remove_ads` purchase)
Firebase	Crashlytics, Remote Config (force update)
Quality	Unit tests (JUnit), R8/ProGuard in release

🏗️ Architecture

Clean Architecture organized by feature, with a strict data / domain / presentation split inside each one:

app/src/main/java/com/jarica/compartirgastos/
├── app/                  # Application class, global setup
├── core/                 # Code shared across features
│   ├── billing/          # Play Billing (remove ads)
│   ├── data/             # Room database, DataStore, mappers
│   ├── di/               # Hilt modules
│   ├── domain/           # Shared domain models
│   ├── forceUpdate/      # Forced update via Remote Config
│   ├── navigation/       # Type-safe Compose navigation
│   └── presentation/     # Theme and reusable composables
└── features/
    ├── groups/           # data / domain / presentation
    ├── groupDetail/
    ├── costs/
    ├── payments/
    ├── balances/         # Settlement algorithm ("settle up")
    ├── people/
    ├── appInfo/
    └── splash/

graph LR
    UI["Presentation<br/>(Compose + ViewModel)"] --> UC["Domain<br/>(Use Cases + Models)"]
    UC --> REPO["Data<br/>(Repositories + Room)"]
    REPO --> DB[("Room / DataStore")]

Every screen follows the ViewModel → Use Cases → Repository flow, exposing UI state as StateFlow and keeping business logic in pure, testable use cases.

🧠 Technical decisions

Money as cents (Long): all amounts are stored and computed in cents to eliminate floating-point rounding errors; formatting to decimal happens only in the presentation layer.
Settlement with few transfers: the DoTheCountsUseCase computes each member’s net balance and applies a greedy algorithm that matches the largest debtor with the largest creditor, settling the group in at most n−1 payments (the exact minimum is NP-hard). Covered by unit tests.
Offline-first: the app works fully offline; Room is the single source of truth.
Versioned Room schemas: every schema version is exported to app/schemas, enabling real, testable migrations.
Remote force update: Firebase Remote Config can enforce a minimum app version without shipping a new release.
No custom backend: privacy by design — user data never leaves the device.

🚀 Building the project

Clone the repository and open it in Android Studio (JDK 11+).
Add your own google-services.json to app/ (your own Firebase project).
Run:

./gradlew assembleDebug

Release builds require your own keystore configured in local.properties (RELEASE_STORE_FILE, RELEASE_STORE_PASSWORD, RELEASE_KEY_ALIAS, RELEASE_KEY_PASSWORD).

🗺️ Roadmap

Cloud sync and groups shared by code (Firestore + anonymous auth, keeping the offline-first approach)
Room migrations with automated tests
CI with GitHub Actions (build + tests on every push)
Broader domain test coverage
Split by shares and by percentage

🔒 Privacy

Data is stored locally on the device. Privacy policy: jaricagames.github.io/Equify

📜 License

This project is licensed under the MIT License.

Developed by Juan Antonio Rivero (@JaricaGames)

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