Currency Converter Application

A full-stack currency converter application built with Angular 19 and NestJS, featuring real-time and historical exchange rates powered by FreeCurrencyAPI.

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📋 Assignment Requirements Fulfilled

Requirement	Implementation
✅ Currency API for dynamic conversions	FreeCurrencyAPI integration with all supported currencies
✅ Directives and structured components	Angular standalone components with Reactive Forms
✅ Conversion history with date/time	SQLite database with TypeORM persistence
✅ History persists on reload	Server-side database storage
✅ Historical exchange rates	Date picker with historical API endpoint
✅ Dropdown for both currency ends	Material Select components for From/To
✅ Loaders for API requests	Progress bar + spinner in convert button
✅ Mobile-first responsive design	Flexbox layout with media queries
✅ API key secured on backend	Environment variables, never exposed to client
✅ Backend in NestJS	Full NestJS implementation with modules/controllers/services

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🛠️ Tech Stack

Frontend

• Angular 19 (Standalone Components)
• Angular Material (UI Components)
• SCSS (Styling)
• TypeScript

Backend

• NestJS (Node.js Framework)
• TypeORM (Database ORM)
• SQLite (Persistent Storage)
• Axios (HTTP Client)

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🚀 Getting Started

Prerequisites

• Node.js (v18+)
• npm or yarn

Installation

1. Clone the repository

   git clone https://github.com/rahimprz/currency-converter.git
   cd currency-converter

2. Setup Backend

   cd backend
   npm install

3. Configure Environment Variables

   Create a .env file in the backend folder:

   FREE_CURRENCY_API_KEY=your_api_key_here

4. Setup Frontend

   cd ../frontend
   npm install

Running the Application

1. Start Backend (Terminal 1)

   cd backend
   npm run start

   Backend runs on: http://localhost:3000

2. Start Frontend (Terminal 2)

   cd frontend
   npm start

   Frontend runs on: http://localhost:4200

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📁 Project Structure

Assignment/
├── backend/                 # NestJS Backend
│   ├── src/
│   │   ├── currency/        # Currency module
│   │   │   ├── currency.controller.ts
│   │   │   ├── currency.service.ts
│   │   │   ├── currency.module.ts
│   │   │   └── entities/
│   │   │       └── conversion-history.entity.ts
│   │   ├── app.module.ts
│   │   └── main.ts
│   ├── .env                 # API Key (not committed)
│   └── currency_db.sqlite   # SQLite Database
│
├── frontend/                # Angular Frontend
│   ├── src/
│   │   ├── app/
│   │   │   ├── components/
│   │   │   │   ├── converter/
│   │   │   │   └── history-list/
│   │   │   ├── services/
│   │   │   │   └── currency-api.service.ts
│   │   │   └── models/
│   │   └── styles.scss
│   └── angular.json
│
└── README.md

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🔌 API Endpoints

Method	Endpoint	Description
GET	/currency/latest	Get latest exchange rates
GET	/currency/historical?date=YYYY-MM-DD	Get historical rates
POST	/currency/convert	Convert currency and save to history
GET	/currency/history	Get last 20 conversion records

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✨ Features

• Real-time Currency Conversion - Convert between 10+ major currencies
• Historical Rates - Select any past date for historical exchange rates
• Persistent History - All conversions are saved and displayed in a table
• Responsive Design - Optimized for mobile, tablet, and desktop
• Loading States - Visual feedback during API calls
• Clean UI - Modern Material Design interface

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👤 Author

Muhammad Raahim

• GitHub: @rahimprz

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📝 Notes

• The FreeCurrencyAPI free tier limits the base currency to USD. The application handles this by calculating cross-rates automatically.
• Database file (currency_db.sqlite) is created automatically on first run.
• CORS is enabled for frontend-backend communication.

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Thank you for reviewing this submission. I look forward to hearing from you!