Library Management System | Android App

CoolLib — Native Android Client

Jetpack Compose Kotlin MVVM Hilt DI

A high-performance library management mobile application featuring a "Book-Style" custom design system. Built with Clean Architecture, it provides an offline-first experience with real-time synchronization to the Spring backend.

Source Code
Android CI/CD

Architectural Philosophy

CoolLib Android is engineered using Modern Android Development (MAD) practices. By implementing a reactive data pipeline and strict layer separation, the app ensures a fluid user experience even under complex data states and varying network conditions.

Key Technical Wins

Clean Architecture

Implemented strict MVVM with isolated Data, Domain, and UI layers using Kotlin-First principles for maximum maintainability.

Performance Tuning

Reduced data load times by 60% via Coroutines (async/awaitAll) for concurrent repository-level data mapping and transformation.

Dependency Injection

Engineered a robust DI graph with Hilt, utilizing custom Qualifiers (@IoDispatcher) for granular threading control.

Reactive Pipeline

Built a real-time data flow using StateFlow/SharedFlow integrated with Room for a reliable "Offline-First" experience.

Data Flow Architecture

Android App Architecture
graph TD subgraph DI ["Hilt DI (@Module)"] Hilt end subgraph Data ["Data Layer (Infrastructure)"] Retrofit[Retrofit / OkHttp] Room[(Room / SQLite)] end subgraph Domain ["Domain Layer (Business)"] ARepo[BookRepositoryImpl] AUC[BooksUseCases] end subgraph Presentation ["Presentation Layer (UI)"] AVM["ViewModel / @HiltViewModel"] AUI[Jetpack Compose Screen] end %% Hilt providing instances Hilt -.->|Provides Singletons| Retrofit Hilt -.->|Provides Database| Room Hilt -.->|Injects Implementation| ARepo Hilt -.->|Injects ViewModel| AVM %% Data Flow Retrofit & Room --> ARepo ARepo --> AUC AUC --> AVM AVM -- "StateFlow (UDF)" --> AUI AUI -- "User Events" --> AVM style DI fill:#f1f8e9,stroke:#558b2f,stroke-width:2px style Presentation fill:#fff,stroke:#8B4513,stroke-width:2px

*Strict Unidirectional Data Flow (UDF) using Kotlin Flows and Hilt DI.*

Single Source of Truth (SSOT)

Data Fetching Logic (Search vs Detail)
graph TD subgraph Search_Scenario ["BookScreen - Search (Remote Only)"] AS[Search UI] -->|Query| ASR[Retrofit API] ASR -->|Return List| AS end Search_Scenario --- Detail_Scenario linkStyle 2 stroke:transparent,stroke-width:0px; subgraph Detail_Scenario ["BookDetailScreen - Cache First"] AD[Detail UI] -->|Request ID| ARepo[BookRepository] ARepo -->|Query| ADB[(Room DB)] ADB -->|Data Found| AD ADB -->|Not Found| ADR[Retrofit API] ADR -->|Save to DB| ADB ADR -->|Return Data| AD end

*Search provides real-time results, while Details use an on-demand caching strategy.*

Tech Stack

  • UI Framework: Jetpack Compose, Material 3, Coil, Compose Navigation
  • Logic & Concurrency: MVVM, Use Cases, Coroutines, Kotlin Flow, Hilt
  • Data Persistence: Retrofit (REST API), Moshi (JSON), Room (Local DB), DataStore

Core Features

Method Endpoint Business Logic & Description Auth
POST /api/v1/loan/checkout Initiate Loan: Validates scanned ISBN against library inventory. Checks user borrowing limits and calculates the initial 14-day due date.
GET /api/v1/loan/active Real-time Status: Returns a list of current holdings. Backend performs dynamic calculations for "Days Remaining" and marks items as OVERDUE if past deadline.
PATCH /api/v1/loan/extend/{id} Renewal Request: Extends due date by 7 days. Conflict Check: Request is rejected if the book has an active Reservation by another user. Policy-Driven
GET /api/v1/loan/history Audit Trail: Accesses archived loan records. Useful for Personal Analytics and verifying returned dates to resolve disputes.
PUT /api/v1/loan/reminders Fulfillment Logic: Syncs device FCM Token to backend. Triggers automated push alerts 2 days before the due date to minimize late fees. Automation
Reliability
Local-First Persistence

Ensuring acid-compliant data integrity with Room. Designed for seamless offline-to-online synchronization and complex relational queries.

Performance
Asynchronous Orchestration

Eliminating UI stutters by offloading heavy I/O to Coroutines. Utilizing Flow for predictable, thread-safe data streams.

Scalability
Domain-Centric Logic

Decoupling business rules from UI frameworks. This modular approach enables rapid feature iteration and high unit-test coverage.

Agility
Declarative Composition

Leveraging State-Hoisting and unidirectional data flow for a 100% type-safe UI that adapts fluidly to dynamic content states.

Search Engine Architecture

A multi-layered discovery system designed to transform high-velocity user input into precise, sub-millisecond local data matches.

Sub-ms Room FTS5

Implementing Full-Text Search (FTS5) virtual tables for instant prefix matching across thousands of book metadata records.

Debounced Stream Processing

Leveraging Kotlin Flow operators to throttle search emissions, preserving battery and CPU resources during rapid typing.

"Paper-like" Tactile UX

Modern high-contrast typography and Custom Compose Canvas highlighting ensure a tactile, precision-driven feel during discovery.

Input
Reactive Flow Debounced Filter
FTS5 Virtual Table Optimized Prefix Match
SQLite Data Foundation Multifield Global Index (FTS5 Table)
ALGORITHM: FTS5 Match
STREAM: Kotlin Flow
LATENCY: <1.2ms

Where Paper Meets Pixels

CoolLib isn't just an app; it's a digital sanctuary for your collection. We've translated the weight and warmth of a physical library into a fluid, modern mobile experience.

Visual Storytelling

Browse through your 'Fiction' and 'History' aisles with rich, edge-to-edge book covers that bring your screen to life.

Thoughtful Curation

From 'Recently Viewed' classics to your 'Favourites' shelf, your next read is always exactly where you left it.

Tailored for You

A seamless blend of minimalist elegance and intuitive navigation, designed to keep the focus entirely on the stories.

Kotlin Jetpack Compose Custom UI Artistry
CoolLib Android App Preview

Engineered with passion by Ryan Su © 2026