💸 EqualPay

EqualPay is a collaborative expense-sharing web application inspired by Splitwise.
It allows users to create groups, log shared expenses, and track individual balances in a transparent and intuitive way.

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🧠 Project Vision

The goal of EqualPay is to provide a simple yet extensible foundation for managing shared expenses between friends, roommates, or colleagues.
The app is built following clean architecture principles, using Spring Boot, Thymeleaf, and PostgreSQL — while exploring a modern AI-assisted development workflow.

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🧩 Tech Stack

Layer	Technology
Backend	Java 21, Spring Boot 3
Frontend (views)	Thymeleaf, HTML5, CSS3
Database	PostgreSQL (Docker Compose)
ORM	Spring Data JPA
Migrations	Flyway (pinned: 11.14.0)
Build Tool	Maven
Testing	JUnit 5, Mockito, H2 (tests)
IDE	Cursor (AI-powered code editor)

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🤖 AI-Assisted Development Workflow

EqualPay was developed using an AI-driven workflow that combines:

• ChatGPT (GPT-5): conceptual design, UML modeling, and architecture decisions.
• Cursor IDE Agent: code generation, refactoring, and tests inside the project.
• Vibe Coding principles: deep collaboration between developer and AI to accelerate clean, maintainable code.

🧩 Process Overview

1. Ideation and UML Design

   • High-level entity and relationship modeling discussed and refined.
   • Mermaid-based UML to visualize system structure and iterate on the domain model.

2. Project Setup

   • Spring Boot base with structured packages:

     com.amb.EqualPay
       ├── model        # JPA entities
       ├── repository   # Spring Data JPA interfaces
       ├── service      # Business logic (@Transactional)
       ├── controller   # REST endpoints (if needed)
       ├── web          # MVC controllers returning Thymeleaf views
       ├── dto          # Data Transfer Objects
       ├── exception    # Custom exceptions and global handler
       └── config       # Configuration classes
     

3. Code Generation with Cursor

   • Entities, repositories, services, and initial tests authored with AI assistance.
   • Each class includes short explanatory comments for clarity.
   • Thymeleaf templates added for a minimal but functional UI.

4. Manual Refinement

   • Consistent naming, validation annotations, and constructor injection.
   • Flyway migrations curated and versioned.

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🗄️ Database & Migrations

• Local DB via Docker Compose (compose.yaml → PostgreSQL service).
• Flyway migrations:
  • V1__init.sql (baseline schema)
  • V2__model_alignment.sql (aligns schema with evolved domain model)
• H2 is used for test slices to keep tests fast and isolated.

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🚦 Getting Started

Prerequisites: Docker, Java 21, Maven.

# 1) Start PostgreSQL locally
docker compose up -d postgres

# 2) Run the app
./mvnw spring-boot:run

# (optional) Run tests
./mvnw test

App runs on http://localhost:8080/.

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🔐 Security (future milestone)

Upcoming after MVP:

• Spring Security with BCrypt password hashing.
• Role-based access control.
• Potential OAuth2 / external IdP integration.

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🧪 Testing Strategy

• Unit tests for repositories and services (Mockito for service logic).
• Flyway-backed schema for realistic persistence behavior; H2 used for test profile.
• Integration tests (planned) to exercise REST/MVC endpoints and database with the application context.

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📚 Learning Focus

Part of a Vibe Coding learning journey — exploring how human–AI collaboration enhances backend development.
The focus is on:

• Designing structured prompts for AI code generation.
• Supervising, validating, and refining AI-written code.
• Balancing productivity with clean architecture and testing.

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🚀 Roadmap

• Define domain model and UML diagram
• Generate entities, repositories, and services
• Integrate Thymeleaf for UI
• Align schema via Flyway V1/V2 migrations
• Add security with Spring Security
• Implement group balance calculations
• Deploy MVP online (Render / Railway)

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🧾 License

Intended license: MIT License. A LICENSE file can be added to formalize it.

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Developer: AlberteMB
Project: EqualPay
Approach: Vibe Coding + AI-Assisted Development 🧠⚙️