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You received this repository because we liked your profile and decided to move forward to the technical step of our hiring process.

That is why we would like to see some code before a conversation. Please Fork this repository and submit a Pull Request with your code.

After you submit a Pull Request, our team will make a code review and schedule a call with you.

Note: We would LOVE to see some Ruby code. If you don't know Ruby (yet!) - you'll learn it here - send the PR using the programming language that you are proficient. (or learn at least the necessary to submit this challenge)

We are going to build a Credit Card Transactions API.

Our data modeling will follow something close to:

• A Customer may have one or more credit cards through an Account.
• A Credit Card has a spent limit, the customer full_name, a number, an expiration date, CVV code and has many Transactions.

Scaffold a simple Rails API only app (https://guides.rubyonrails.org/api_app.html) and models a Credit Card Transaction.

JSON data structure below:

  {
    "id": 9923,
    "created": 1389618241,
    "status": "paid",
    "amount": 4900,
    "currency": "usd",
    "credit_card_id" : 1232211
  }

• To avoid monetary round issues, the amount field is always in the respective currency cents
• A Transaction object has a credit card foreign key (credit_card_id).
• A transaction status could be failed, paid, dispute, refunded
• The Credit card should be related to a Customer through an Account.

Feel free to model these relations as you want, here is the step where we will test your Object-Oriented Programming skills including SOLID, Design, Clean Code amd Unit tests.

Advise: Models and Entity Objects are not only a representation of the database table, you can have objects that are not ActiveRecord / ORM classes (Concerns, UseCases, Services, etc).

Create a State Machine and unit tests to cover the following business rules:

1. A transaction status can't change from paid to failed.
2. A paid transaction can change only to refunded or dispute.
3. A transaction can be refunded only if it is in a dispute
4. A transaction under dispute state can go to the status: paid or refunded.
5. A Transaction will be automatically failed if the credit card does not have limit available.
6. Once a transaction is in a disputed state, the amount of the disputed transaction is not available on the Customer credit card limit.

You don't need to build a State Machine from the ground. If you don't know what a state machine is, please have a look at https://github.com/aasm/aasm or a similar project

Please, DO NOT submit your solution without Unit Tests.

This endpoint should respect the rules bellow

• return json as the default result
• paginate results automatically and return only 5 transactions per page
• accepts query parameters as filters for transactions statuses. For example: localhost:3000/api/v1/customer/{id}/credit_card/{id}/transactions?status=failed

The endpoint should receive nested attributes to support the /GET method similar to: localhost:3000/api/v1/customer/{id}/credit_card/{id}/transactions

The endpoint should receive a body containing the currency and amount attributes and support nested attributes on the /POST method localhost:3000/api/v1/customer/{id}/credit_card/{id}/charge

Customer 1: 
  First Name: Yukihiro 
  Last Name: Matsumoto

Customer 2: 
  First Name: Sandi
  Last Name: Matz

Customer 3: 
  First Name: Martin
  Last Name: Fowler

Customer 4: 
  First Name: Dr. Alan
  Last Name: Kay

• 10 Should be successful transactions:

  - 5 Should be linked to Customer 1 Visa Credit Card
  - 3 Should be linked to Customer 2 Visa Credit Card
  - 1 Should be linked to Customer 3 MasterCard Credit Card
  - 1 Should be linked to Customer 4 Visa Credit Card

• 5 Should be transactions that failed transactions:

  - 3 Should be linked to Customer 3 Mastercard Credit Card
  - 2 Should be linked to Customer 4 Visa Credit Card

• 5 should be disputed transactions:

  - 3 should be linked to Customer 1 Visa Credit Card
  - 2 should be linked to customer 2 Visa Credit Card

1. Commit and Push your code to your forked repository
2. Send us a pull request, we will review your code and get back to you.

If you have any question regarding the project, you can contact us directly by email