Crypto Price Tracker – Full Stack Developer Challenge - Dwayne Love

📋 Objective

This challenge is designed to evaluate your skills as a full stack developer using .NET 6 (C#), Entity Framework Core, Razor Pages, and REST API integration.

You'll be working with a project that simulates tracking cryptocurrency prices using the CoinGecko API.

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🧠 What You Need to Do

✅ 1. Fix the Service Logic

• Open CryptoPriceService.cs and fix the logic so it correctly:

  • Fetches coin data from CoinGecko for all existing coins
    Documentation: https://docs.coingecko.com/v3.0.1/reference/introduction
  • Handles async operations properly
  • Prevents duplicate entries
  • Saves the results to the SQLite database

  ⚠️ If you encounter duplicate entries or errors from the CoinGecko API, decide how to handle them.
  You're free to choose the best approach — just make sure you explain your reasoning in a short code comment.

  ⚠️ Some files may have outdated or incorrect namespace declarations. Please review and update them as needed to ensure consistency across the project.

✅ 2. Complete the Controller

• Open CryptoController.cs and:
  • Complete the POST /api/crypto/update-prices endpoint
  • Add a GET /api/crypto/latest-prices endpoint to return the most recent price per asset. All available cryptocoins must be saved.

✅ 3. Test the Razor Frontend

• The view in /Views/Home/Index.cshtml includes a button to call the API.
• Ensure that the interface provides clear feedback to the user indicating whether the update succeeded or failed.

✅ 4. Create the Frontend Visualization in Index.cshtml

Build a clean and user-friendly visualization directly in the existing Razor view:
/Views/Home/Index.cshtml

This page must:

• Display each cryptocurrency asset with at least the following fields:

  • ✅ Name
  • ✅ Symbol
  • ✅ Current Price
  • ✅ Currency
  • ✅ Icon
    • Add the IconUrl property to the CryptoAsset model
    • Retrieve the image url from CoinGecko
    • Save it to the database
  • ✅ Last Updated
    • This value must be converted to the client's local timezone using JavaScript
  • ✅ Trend
    • Add a visual indicator showing whether the price has increased, decreased, or stayed the same compared to the previous saved price (e.g., 🔼, 🔽, ➖)
    • Optionally, include the percentage change

• Use the existing "Update Prices" button to trigger the API and refresh the data displayed in the view.

🎯 Goal: The user should be able to open the page, see the most recent cryptocurrency data clearly presented, and update it with one click.

💡 Bonus points for improved UI, animations, or anything that enhances clarity and usability.

✅ 5. Add Improvements

• Add validation logic or error handling where needed
• Create unit tests for validator or service logic

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⚙️ How to Run the Project

1. Make sure you have .NET 6 SDK installed.
2. Navigate to the backend project folder:

   cd Backend/CryptoPriceTracker.Api

3. Restore dependencies:

   dotnet restore

4. Generate your own migrations and update the database:

   dotnet ef migrations add InitialCreate
   dotnet ef database update

5. Run the project:

   dotnet run

6. Navigate to http://localhost:5000 to test the Razor page.

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🧪 Testing

You may add unit tests to demonstrate how you validate business logic (e.g., in the PriceValidator class).

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🛠️ Updated Setup & Run Instructions

To run this solution, ensure you have the .NET 6 SDK installed.

1. Install Entity Framework Tools

Since this is a .NET 6 project, you must install the compatible version of the EF tool:

dotnet tool install --global dotnet-ef --version "6.*"

Note: If the command is not found after installation, add the tools to your path: export PATH="$PATH:$HOME/.dotnet/tools"

2. Prepare the Database

Navigate to the API project folder and apply the migrations:

cd CryptoPriceTracker.Api
dotnet ef migrations add AddIconUrl
dotnet ef database update

3. Run the Project

dotnet run

Navigate to http://localhost:5000 to view the dashboard.

4. Run Unit Tests

A separate test project has been added to validate business logic:

cd ..
dotnet test

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🧠 Architecture & Technical Decisions

1. Project Structure

• Namespaces: Standardized all project files with CryptoPriceTracker.Api.* namespaces for better organization and consistency.
• Test Project: Added CryptoPriceTracker.Tests using xUnit to isolate business logic testing from the main API.

2. Service Logic (CoinGecko Integration)

• Endpoint: Switched to /coins/markets to retrieve names, symbols, current prices, and icon URLs in a single optimized request.
• User-Agent: Added a custom User-Agent header to the HttpClient as required by the CoinGecko API to prevent request blocking.

3. Duplicate Handling

• Strategy: Duplicates are prevented by checking if a record already exists for the same asset with the same price on the same calendar day. This ensures the history remains clean while still allowing daily tracking.

4. Frontend UI

• Technology: Built a custom, responsive dashboard using Vanilla CSS and JavaScript within the Razor view.
• Timezone: All "Last Updated" timestamps are converted to the user's local timezone in the browser to ensure accuracy for global users.

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🧾 Deliverables Checklist

• CryptoPriceService.cs fetches, saves, and avoids duplicates correctly
• namespace declarations are consistent and correct across all files
• POST /api/crypto/update-prices endpoint is functional
• GET /api/crypto/latest-prices endpoint returns most recent prices
• IconUrl property added to CryptoAsset model and stored in DB
• Razor page (Index.cshtml) includes:
  • Name
  • Symbol
  • Current Price and currency
  • Icon
  • Last Updated (adjusted to client timezone)
  • Trend (up/down indicator and percentage change)
• Button updates data and refreshes the view
• Clear UI feedback after update attempts (success/failure)
• Validation/error handling is implemented where needed
• At least one unit test demonstrates validation logic
• Comments provided for any assumptions or technical decisions

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Good luck, and thank you for taking the time to complete this challenge!