🪙 CreditSim

This project is a simple credit simulator. It calculates a monthly amortization schedule (French system) and shows it in a table. The backend also saves each simulation in a database, and it runs a mock “risk audit” asynchronously (it does not block the main response).

Tech Stack 💻

• Frontend: React (Vite).
• Backend: FastAPI(Python).
• Database: SQLite.

Project Installation 🔽

Requirements:

• Node.js (recommended: LTS)
• Python (recommended: 3.10+)
• pip (Python package manager)

Backend

1. Create and activate a virtual environment.

Windows:

cd backend
python -m venv .venv
.\.venv\Scripts\Activate.ps1

MacOS/Linux:

cd backend
python3 -m venv .venv
source .venv/bin/activate

2. Install dependencies.

pip install -r requirements.txt

3. Run the API (local).

fastapi dev main.py

The backend will run at:

• http://127.0.0.1:8000

Optional (Swagger UI):

• http://127.0.0.1:8000/docs

Frontend

1. Install dependencies.

cd frontend
npm install

2. Run the app local.

npm run dev

How to use (local) ⌨️

1. Start the backend.

2. Start the frontend.

3. Open the frontend URL in your browser.

4. Enter:

   • Monto del crédito (Loan amount)
   • Interés anual (%) (Annual interest rate)
   • Plazo (meses) (Term in months)

5. Click "Calcular" to generate the amortization table.

API Endpoints 🎯

POST /simulate

Calculates the amortization schedule and saves the simulation in the database.

Request body (JSON):

{
  "amount": 50000,
  "rate": 24,
  "months": 1
}

Response (example):

{
  "ok": true,
  "simulation_id": 1,
  "audit_status": "PENDING",
  "data": {
    "monthly_payment": 25752.48,
    "total_paid": 1504.95,
    "total_interest": 51504.95,
    "schedule": [
        { "month": 1, "payment": 25752.48, "interest": 1000.00, "principal": 24752.48, "balance": 25247.52 },
        { "month": 2, "payment": 25752.48, "interest": 504.95, "principal": 25247.52, "balance": 0 }
    ]
  }
}

GET /simulations/{id}

Returns the current status of the risk audit for a given simulation.

Response (example):

{
  "id": 1,
  "audit_status": "SUCCESS"
}

Database 🗃️

The database is stored as a file: creditsim.db.

Location: it is created in the directory where the backend is executed.

This project stores:

• Input values (amount, annual rate, months).
• Calculation results (monthly payment, total interest and principal).
• Full amortization schedule (stored as JSON).
• Audit status (PENDING, SUCCESS, FAILED)

Risk Audit (Mock Scoring) 🚩

After each simulation:

• The API triggers a mock external scoring/audit process.
• It runs asynchronously (background) and does not block the /simulate response.
• It takes 1–3 seconds.
• It fails ~10% of the time (simulated).

License 📜

This project is licensed under the MIT License (2026). See the LICENSE file for details.