String Calculator

A simple string calculator built using Ruby on Rails for the backend and React.js for the frontend, with a focus on Test-Driven Development (TDD). This project implements the String Calculator Kata and exposes an API to calculate the sum of a string of comma-separated numbers, while also handling custom delimiters and edge cases like negative numbers.

Features

• Basic String Calculation: Sums a string of comma-separated numbers.
• Supports Newlines Between Numbers: Allows numbers to be separated by newlines as well as commas.
• Custom Delimiters: Supports custom delimiters defined at the start of the string.
• Negative Number Handling: Throws an exception if negative numbers are provided in the string.
• API Access: The calculator can be accessed through an API exposed by a Ruby on Rails backend.
• Frontend Interface: Simple React.js UI to interact with the calculator.

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Installation

Backend (Ruby on Rails)

1. Clone the repository:

   git clone https://github.com/yourusername/string-calculator.git
   cd string-calculator

2. Install dependencies:

   bundle install

3. Start the Rails server:

   rails server

   Your backend API should now be running on http://localhost:3000.

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Frontend (React.js)

1. Navigate to the frontend folder:

   cd frontend

2. Install dependencies:

   npm install

3. Start the React development server:

   npm start

   Your React app should now be running on http://localhost:3001.

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Usage

Backend API

• Endpoint: POST /calculate

• Request Body: A JSON object containing a numbers string.

  Example:

  {
    "numbers": "1,2,3"
  }

• Response: The sum of the numbers.

  Example:

  {
    "result": 6
  }

Frontend

The frontend provides a simple input box where users can enter the numbers in string format and click the Calculate button to trigger the calculation. The result is displayed dynamically on the page.

1. Input Field: Enter a comma-separated string of numbers (or numbers separated by newlines).
2. Calculate Button: Click to trigger the calculation.
3. Result: The sum of the numbers is displayed below the input field.

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Features

• Handles empty input: Returns 0 for an empty string.
• Supports multiple delimiters: Supports a default comma delimiter and custom delimiters defined at the start of the string (e.g., //;\n1;2).
• Negative numbers handling: Throws an error with a message listing all negative numbers if they are included in the input.

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Example

Example 1: Basic Calculation

• Input: "1,5"
• Output: 6

Example 2: Newline Separated Numbers

• Input: "1\n2,3"
• Output: 6

Example 3: Custom Delimiters

• Input: "//;\n1;2"
• Output: 3

Example 4: Negative Numbers

• Input: "1,-2,3"
• Output: Error: Negative numbers not allowed: -2

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Running Tests

To run tests using RSpec for the backend:

bundle exec rspec

For frontend tests, you can run:

npm test

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Contribution

We welcome contributions! If you want to contribute to this project, feel free to:

1. Fork the repository.
2. Create a new branch (git checkout -b feature/your-feature).
3. Commit your changes (git commit -m 'Add new feature').
4. Push to the branch (git push origin feature/your-feature).
5. Open a Pull Request.

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License

This project is licensed under the MIT License - see the LICENSE file for details.

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Acknowledgements

• Inspired by the String Calculator Kata.

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