CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Build Commands

# Build debug APK
./gradlew assembleDebug

# Build release APK
./gradlew assembleRelease

# Run unit tests
./gradlew test

# Run instrumented tests (requires connected device/emulator)
./gradlew connectedAndroidTest

# Run a single unit test class
./gradlew :app:test --tests "com.mob.utsmyammer.ExampleUnitTest"

# Clean build
./gradlew clean assembleDebug

Architecture Overview

MOBPOS is a mobile Point-of-Sale system for Myanmar, targeting Sunmi hardware devices (card readers, PIN pads, thermal printers). It processes EMV card transactions (sale, void, refund, settlement) and QR payments (MMQR, Wave Pay).

Single-Activity Compose App

MainActivity hosts the entire app. Navigation is handled by Compose Navigation (AppNavGraph.kt) with typed routes defined in a sealed Routes object.

MVVM with Shared State

Each screen has a dedicated ViewModel (Hilt-injected)
SharedViewModel in viewmodel/ is the central state holder for cross-screen transaction data (card info, amount, transaction type, approval codes)
Hardware interaction is abstracted into CardReaderViewModel and EmvTransactionProcessViewModel
State is a mix of LiveData (older screens) and StateFlow (newer screens like card reading)

Screen Structure Pattern

Every feature follows: ui/<feature>/ containing:

*Screen.kt — Composable UI
*ViewModel.kt — business logic and state

Key Transaction Flow

Dashboard → InputAmount → CardWaiting → ProcessingCard → SendingToHost → TransactionResult → PrintReceipt

Local Modules

The app depends on several local library modules (in settings.gradle.kts):

:baselib — Room DB, Retrofit, Hilt base setup
:paylibs / :paysdk-lib — Payment SDK wrappers
:ecr / :ecr-service-lib — Electronic Cash Register integration
:mpulib / :mpu-lib — Mini POS Unit hardware
:sunmiui-lib — Sunmi device UI components
:qrgen-lib — QR code generation

Key Dependencies

UI: Jetpack Compose + Material 3, Compose Navigation
DI: Hilt 2.59.2 with KSP
Async: RxJava 3 + RxAndroid (primary async pattern)
Network: Retrofit 3 + OkHttp 4 + GSON
DB: Room 2.4.3 with RxJava 3 support
Hardware: Sunmi SDK (card reader, PIN pad, printer APIs)

Package Layout

com.mob.utsmyammer/
├── config/          # Constants, SunmiPayManager
├── model/           # Data models (CardTransactionType, ProcessCode, TransactionStatus)
│   └── ecr/         # ECR-specific models
├── ui/              # All Compose screens (one subdir per feature)
│   ├── components/  # Shared reusables (NumericEntryScreen, SquareButton, AppBar)
│   ├── navigation/  # AppNavGraph, Routes
│   └── theme/       # Compose theme and colors
├── utils/           # Utility functions
└── viewmodel/       # Shared ViewModels (SharedViewModel, CardReaderViewModel, etc.)

Hardware Integration Notes

Sunmi device permissions are declared in AndroidManifest.xml (LED, MSR, ICC, PINPAD, PRINTER). When modifying card reading or PIN entry flows, be aware that CardReaderViewModel and the Sunmi ECR service handle hardware callbacks via RxJava subjects. Hardware callbacks arrive on background threads — always observe on the main thread before updating UI state.

Build Configuration

compileSdk 36, minSdk 24, targetSdk 36
Java 11 toolchain, Kotlin 2.2.10
Compose BOM 2026.02.01
ProGuard/minification is disabled for all build types
Application ID: com.mob.ustmm

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