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User Account Balance Simulator

Main Features

• Persistence of user game results
• Validation of user account balances based on game results

Architecture

The application is composed of two primary components:

1. API Handler

The API Handler manages HTTP requests related to game results.

API Endpoints

• GET /api/v1/health - Returns the health status of the service.
• POST /api/v1/users/{id}/game_results - Persists the game results for the specified user.

2. Game Results Validator

A background job that validates user account balance based on game results.

Database Schema

---
title: Tables.
---
erDiagram
   users }|..|{ game_results : "One-to-Many"
           

Build Process

• Execute make build to generate the binaries in the bin directory.

Entry Points

• API Handler: cmd/api_handler/main.go
• Game Results Validator: cmd/validator/main.go

Development

Environment Variables

The following environment variable is required for both application components:

• DATABASE_URL - The Postgres database URL, e.g., postgres://user:password@host:port/database

Deployment

To deploy the application using Docker Compose, follow these steps:

• Execute docker-compose up --build

To perform a manual test:

1. The database will be pre-populated with users having the following IDs:
   • 11111111-1111-1111-1111-111111111111
   • 22222222-2222-2222-2222-222222222222
   • 33333333-3333-3333-3333-333333333333
   • 44444444-4444-4444-4444-444444444444
   • 55555555-5555-5555-5555-555555555555
   • 66666666-6666-6666-6666-666666666666
   • 77777777-7777-7777-7777-777777777777
   • 88888888-8888-8888-8888-888888888888
   • 99999999-9999-9999-9999-999999999999
2. The Game Results Validator will run as a background process.
3. Send a POST request to the API endpoint, using the following command:

   curl -X POST http://localhost:8000/api/v1/users/11111111-1111-1111-1111-111111111111/game_results -H 'Content-Type: application/json' -H "Source-Type: game" -d "{\"state\": \"win\", \"amount\": \"10.15\", \"transactionId\": \"12\"}" 
   

Testing

Local Tests

Unit Tests

Unit tests are implemented using the standard Go testing library.

• Execute make unit-test to run the tests.

Test Coverage

• Execute make coverage-report to generate an HTML report of the test coverage.
• Execute make coverage-total to view the total test coverage.

Future Improvements

• Implement stored procedures to calculate account balances.
• Allow configuration of the Validator for pause intervals and the number of games to validate.
• Additional enhancements are pending.

Missing Features

• Achieving 90% test code coverage.

Considerations

• The requirement to "correct the balance" necessitates updating the balance twice, introducing a risk.
• This risk can be mitigated by adjusting the design.