ExpenseTracker

A simple expense tracker application using Phoenix LiveView. The application allows users to log in with a unique username, add expense entries, and see real-time updates.

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Requirements

• Code Management and Setup

  • All code should be shared via GitHub repository.
  • The solution should be built with Phoenix LiveView.
  • The solution should manage data in memory. No database should be used.
  • You are free to use any Elixir/Erlang library and any open-source CSS framework for the design.

• User Authentication

  • Users should be able to log in by entering a unique username.
  • No complex authentication is required; a simple unique username is sufficient.

• Expense Management

  • Users should be able to add new expenses with the following fields:
    • Amount (numeric, required)
    • Date (defaults to today’s date if not specified)
    • Description (optional)
  • Each user should only see their own expenses.
  • It should be possible to open the same user’s ledger in multiple tabs and see real-time updates across all tabs.

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How to run

If you have docker compose:

Just run docker compose up and you will have access to the app on port: localhost:4444.

OR

You can run your Phoenix server on your machine:

I used:

• ELIXIR: Set to 1.16.1.
• OTP: Set to 26.

• Run mix setup to install and setup dependencies
• Start Phoenix endpoint with mix phx.server or inside IEx with iex -S mix phx.server

Now you can visit localhost:4000 from your browser.

Main endpoints:

sign in: localhost:4000/users/log_in

sign up: localhost:4000/users/register"

dashboard: localhost:4000/dashboard

new expense: localhost:4000/dashboard/new-expense

Solution Overview

Using a GenServer for managing user data and expense management in memory is a suitable choice for the following reasons:

• Concurrent Data Management: GenServers can handle state and perform operations concurrently, making them ideal for managing user-specific data in a real-time application.
• Real-Time Updates: Since Phoenix LiveView works with real-time WebSocket connections, a GenServer can notify connected processes (tabs) of any state changes, ensuring synchronization.
• Isolation of Data:: By structuring the state to associate expenses with specific users, we ensure data integrity and security—each user only accesses their own data.
• In-Memory Speed: As there's no database involved, a GenServer provides quick access to state stored in memory.