Architecture & Design

This page outlines the technical foundation of the POS application. The project is built with a focus on speed, offline-first reliability, and a modern developer experience.

Feature-Based MVVM

We utilize a Feature-based MVVM (Model-View-ViewModel) structure. By grouping code by functionality rather than technical layers, we ensure that the codebase remains scalable and easy to navigate.

Core Pillars

1. The Composable View

   • Built entirely with Jetpack Compose.
   • Uses State Hoisting for modularity.
   • Observes StateFlow from the ViewModel for real-time UI updates.

2. The Feature ViewModel

   • Manages UI state for specific features (e.g., Payments, History).
   • Communicates directly with Room DAOs and Ktor to reduce boilerplate.
   • Handles asynchronous tasks via Kotlin Coroutines.

3. Data Sources

   • Room Database: Local persistence for transactions and settings.
   • Ktor: High-performance networking for terminal communication.

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Technical Stack

Layer	Technology
UI	Jetpack Compose (Material 3)
Logic	Kotlin Coroutines & Flow
DI	Dagger 2 (via KSP)
Database	Room SQLite
Networking	Ktor Client
Animations	Lottie Compose

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Project Structure

com.example.pos_app
├── features               # Functional modules (UI + Logic)
│   ├── payment            # Checkout UI & Transaction ViewModels
│   └── history            # Transaction logs & History ViewModels
├── data                   # Global Data Engine
│   ├── dao                # Room Data Access Objects (SQL Queries)
│   ├── entity             # Database Tables / Data Models
│   ├── repository         # Data coordination (Local vs Remote)
│   └── utils              # Data-related helpers & formatters
├── di                     # Dependency Injection (Dagger/Hilt)
└── ui.theme               # Design System (Color, Type, Theme)