CreditSea - Loan Management System

CreditSea is a full-stack digital lending platform that handles the entire loan lifecycle. It features a multi-step Borrower Portal for submitting loan requests and an Operations Dashboard with role-based access control (RBAC) modules for backend executives.

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⚡ Quick Start: Seed Credentials

For immediate testing, use the pre-seeded credentials below:

Role	Email	Password	Allowed Module Access
Borrower	borrower@creditsea.com	Borrower@123	Borrower Application Form & Loan Tracker
Sales	sales@creditsea.com	Sales@123	Sales Lead Tracking Module
Sanction	sanction@creditsea.com	Sanction@123	Sanction Approval/Rejection Module
Disbursement	disburse@creditsea.com	Disburse@123	Disbursement Funds Release Module
Collection	collect@creditsea.com	Collect@123	Collection ledger / Payment recording
Admin	admin@creditsea.com	Admin@123	All Operations modules

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🛠️ Technology Stack

• Frontend: Next.js 15 (App Router) + TypeScript + Tailwind CSS
• Backend: Node.js + Express + TypeScript
• Database: MongoDB + Mongoose
• Auth & Security: JSON Web Tokens (JWT) + bcryptjs

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📂 Project Structure

creditSea/
├── backend/
│   ├── src/
│   │   ├── middlewares/  # Authentication & RBAC middleware
│   │   ├── models/       # Mongoose Schemas (User, BorrowerProfile, Loan, Payment)
│   │   ├── routes/       # API endpoints (auth, borrower, operations)
│   │   ├── utils/        # Business Rule Engine (BRE) checks
│   │   ├── seed.ts       # Database seeder script
│   │   └── server.ts     # Express entry point
│   ├── .env.example
│   └── tsconfig.json
└── frontend/
    ├── src/
    │   ├── app/          # Next.js pages and layouts
    │   └── context/      # React AuthContext state provider
    └── package.json

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⚙️ Installation & Setup

1. Prerequisites

• Node.js (v18 or higher recommended)
• MongoDB (Running locally on mongodb://127.0.0.1:27017/creditsea or a cloud Atlas URI)

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2. Backend Setup

1. Open a terminal and navigate to the backend/ directory:

   cd backend

2. Install dependencies:

   npm install

3. Create your .env configuration file:

   cp .env.example .env

4. Run the database seed script:

   npm run seed

5. Start the backend development server:

   npm run dev

   The server starts on http://localhost:5000.

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3. Frontend Setup

1. Open a new terminal and navigate to the frontend/ directory:

   cd frontend

2. Install dependencies:

   npm install

3. Start the Next.js development server:

   npm run dev

   The client app will launch at http://localhost:3000.

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💡 System Design Details

1. Business Rule Engine (BRE)

The BRE runs securely on the Express server (backend/src/utils/bre.ts) to validate borrower eligibility:

• Age Validation: Rejects applicants not aged between 23 and 50 (calculated dynamically from DOB).
• Salary Check: Rejects borrowers earning less than ₹25,000 per month.
• PAN Verification: Validates the PAN format using regex /^[A-Z]{5}[0-9]{4}[A-Z]{1}$/.
• Employment Check: Rejects candidates marked as Unemployed.

Client-side inputs display clear, responsive error layouts listing failed rules on BRE rejection.

2. Role-Based Access Control (RBAC)

• Enforced at the UI Layer via dynamic Next.js layout structures, rendering navigation lists relative to the user's role.
• Enforced at the API Layer using middleware (backend/src/middlewares/auth.ts). Attempts by unauthorized accounts to call restricted endpoints return 403 Forbidden.

3. Loan Math & Concurrency

• Interest: Simple Interest is computed using: $$\text{Simple Interest} = \frac{P \times R \times T}{365 \times 100}$$ Where P = Principal, R = 12% fixed rate, and T = Tenure in days.
• Financial Precision: Floating-point precision errors are mitigated in JavaScript by rounding intermediate values to 2 decimal places using math multipliers, preventing fractional pennies/paise mismatch.
• UTR Uniqueness: Enforced via MongoDB unique indexing on the utr field inside the payments schema, eliminating duplicate transaction claims.