💱 Currency Exchange and Discount Calculation API

📝 Project Description

This Spring Boot application integrates with a third-party currency exchange API to retrieve real-time exchange rates. It calculates the total payable amount for a bill in a specified currency after applying applicable discounts. The project demonstrates object-oriented design, authentication, testing, and modern coding practices.

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📦 Features

• Real-time currency conversion using third-party APIs.
• Discounts based on user type and tenure.
• Supports flat discounts on bills over $100.
• Authentication for secure endpoints.

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🏗️ Tech Stack

• Java 23 with Spring Boot. 3.4.3
• Maven.
• JUnit5 and Mockito for testing.
• SonarQube for code quality.
• External Currency Exchange API (e.g., ExchangeRate-API or Open Exchange Rates).

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classDiagram
direction BT
    class AffiliateDiscount {
	    + checkEligibility(UserDto, Item) boolean
    }

    class CustomerDiscount {
	    + checkEligibility(UserDto, Item) boolean
    }

    class Discount {
	    + checkEligibility(UserDto, Item) boolean
    }

    class DiscountCalculateService {
	    + calculate(ShoppingCartEntity) InvoiceDto
	    + applyDiscount(Item, UserDto) void
    }

    class DiscountCalculateServiceImpl {
	    + calculate(ShoppingCartEntity) InvoiceDto
	    + applyDiscount(Item, UserDto) void
    }

    class EmployeeDiscount {
	    + checkEligibility(UserDto, Item) boolean
    }

    class FlatDiscount {
    }

    class FlatFiveForHundredBillDiscount {
	    + checkEligibility(UserDto, Item) boolean
    }

    class PercentageDiscount {
    }

	<<Interface>> DiscountCalculateService

    AffiliateDiscount --> PercentageDiscount
    CustomerDiscount --> PercentageDiscount
    DiscountCalculateServiceImpl ..> DiscountCalculateService
    EmployeeDiscount --> PercentageDiscount
    FlatDiscount --> Discount
    FlatFiveForHundredBillDiscount --> FlatDiscount
    PercentageDiscount --> Discount

	class Discount:::Peach
	class DiscountCalculateService:::Ash
	class FlatDiscount:::Sky
	class PercentageDiscount:::Sky

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⚙️ Setup Instructions

1. Clone the Repository:

git clone https://github.com/sachith89/CurrencyDiscountCalculator.git
cd CurrencyDiscountCalculator

2. Configure API Key:
   • Add your API key in application.properties:

currency.api.url=https://open.er-api.com/v6/latest/
currency.api.key=your-api-key

3. Build and Run:

./mvnw clean install
./mvnw spring-boot:run

4. Access the API:
   • Base URL: http://localhost:8080

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📤 API Endpoints

🧾 Calculate Payable Amount

Endpoint: POST /api/calculate

Request Body:

{
  "items": [
    {"name": "item1", "category": "grocery", "price": 50},
    {"name": "item2", "category": "electronics", "price": 150}
  ],
  "userType": "employee",  
  "customerTenure": 3,  
  "originalCurrency": "USD",
  "targetCurrency": "EUR"
}

Response:

{
  "payableAmount": 120.50,
  "currency": "EUR"
}

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🧪 Testing

1. Run Unit Tests:

./mvnw test

2. Generate Coverage Reports:

./mvnw jacoco:report

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📈 Code Quality

1. Run SonarQube:

./mvnw sonar:sonar

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⚙️ Build Automation

• Run build and tests with:

./mvnw clean install

• Generate reports and analyze code quality:

./mvnw verify

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📌 Assumptions

• Only one percentage-based discount applies per bill.
• Percentage-based discounts do not apply to groceries.
• A $5 flat discount applies per $100 on the bill.