PSP (Payment Service Provider) Project

This project is a multi-module Android application designed to provide payment and printing services on specialized POS hardware. It uses a modular architecture to separate core logic, hardware SDKs, and different application variants.

Module Structure

Core Modules

• :core: The backbone of the project. Contains shared domain models (PaymentResultEntity, PrintEntity), interfaces for services (PspService, Printer), and common utilities. It has no dependencies on other modules.
• :design_system: Contains shared UI components and utilities. The most critical component is PspWebView, a highly optimized WebView wrapper used across all app variants for rendering the web-based POS interface. It depends on :core.

Hardware Implementation Modules

These modules contain the specific SDK integrations for different POS hardware.

• :p3: Implementation of PspService and Printer for P3 hardware. Includes SDK-specific logic for handling payments and thermal printing.
• :ps4: Implementation for PS4 hardware variants.

Application Variants

• :app: The primary production application.
• :tis_app: A specialized version of the application targeting the TIS environment (https://tis.shift-am.ir).
• :stage_app: A development and staging variant used for testing. It often uses mock implementations (like StageViewModel) to simulate POS behavior without requiring physical hardware.

Architecture & Relationships

graph TD
    subgraph Apps
        tis_app --> core
        tis_app --> design_system
        stage_app --> core
        stage_app --> design_system
        app --> core
        app --> design_system
    end

    subgraph Hardware SDKs
        p3 --> core
        ps4 --> core
    end

    design_system --> core

1. Dependency Inversion: Apps depend on interfaces defined in :core. The actual hardware implementation (:p3 or :ps4) is injected via Hilt, allowing the same app logic to run on different devices.
2. Web-Native Bridge: The design_system module provides PspJavaScriptInterface, which allows the Web POS (running inside PspWebView) to communicate with native hardware features like the printer and payment terminal.
3. Hardware Performance: The WebView is optimized for weak POS hardware with features like pooled instances, hardware acceleration, and lean rendering profiles.

Key Features

• Thermal Printing: Optimized for RTL (Persian) text and high-performance bitmap rendering for logos (including VectorDrawable support).
• Payment Integration: Standardized bridge for processing payments and returning structured results to the web-front-end.
• Weak Hardware Optimization: Custom WebView configurations to handle smooth animations (drawers/sheets) on low-spec devices.