Case Study

PayPal

Payment Management System

A simple payment management system, inspired by PayPal, in the exact language in which the fin-tech giant started out.

This CLI based project integrates sign-in functionality, blocks more than 3 wrong password attempts including the following:

1. Instantiate Transaction
2. View Transaction History
3. View Account Details
4. View Card Details
5. View Bank Details
6. View Balance
7. View Currency Details

A few classes that are encapsulated for the project:

1. Currency: A custom interface that defines and holds the data about the currency, like the:

   i. currencyCode (String): The international code used to identify the currency, like for eg. INR for Indian Rupee

   ii. currencySymbol (String): The international symbol used along with the currency like ₹ for Indian Rupee

   iii. rupeeEquivalent (double): The present-day Indian Rupee equivalent of the currency

2. CardType is an enum class which differentiates if the card is debit (.DEBIT) or credit (.CREDIT)

3. Card: A custom class that holds confidential information regarding a banking card used for online transactions. It orchestrates the following details:

   i. cardNumber (String): The sixteen digit card number passed as a text String object

   ii. cardHolderName (String): The card holders name

   iii. expiryDate (String): The expiry date of the banking card in the format (MM/YYYY)

   iv. cvv (String): The 3 digit Card Verification Value of the banking card (Confidential)

   v. cardType (CardType): Indicates whether the card is a debit card or a credit card

4. Bank: A custom class that stores the publicly available details of a bank, that includes the following:

   i. bankName (String): The public registered name of the entity bank

   ii. ifscCode (String): The Indian Financial System code of the operating bank, used to instantiate transactions

   iii. branchName (String): The name of the branch of the bank entity is operating from

5. User: A custom class that encapsulates the details of the user who has logged in.

   i. id (String): The uniquely identified username of the user

   ii. name (String): The official name of the user, as per governement ID proof

   iii. email (String): The verififed email address of the user, used for all official communication.

   iv. password (String): The password used for logging into the service, created by the user at the time of account opening

   v. bank (Bank): The bank account of the user that is linked to his/her/their PayPal account, and is to be used for all transactions

   vi. accountNumber (String): The bank account number of the linked bank account

   vii. balance (double): The current available balance of the user (in currency units)

   viii. currency (Currency): The currency in which the specified user operates.

   ix. card (Card): The banking card linked to the user's bank and PayPal account, to be used for transactional purposes

6. Payment: a basic class to encapsulate the transaction related properties, methods and functions.

   i. paymentId (String): A random unique identifier (UUID) that is used to tag a particular transaction

   ii. amount (double): the actual amount to be transferred from the sender to the recepient, to be entered in the currency (Currency)

   iii. currency (Currency): the currency being used to handle the amount, used by the sender

   iv. convertedCurrency (Currency): the currency being used by the recepient

   v. recepient (User): the user who is recieving the funds, i.e, the user whose bank account is going to credited with the funds in the convertedCurrency

   vi. sender (User): the user who is sending the funds, i.e, the user whose bank account is going to debited with the funds in the currency

   vii. approved (boolean): a boolean flag to identify is the transaction is compliant

Tip

A few areas that could be ventured in the future include:

1. New user registration
2. checking transaction compliance
3. Update card details
4. Update bank details
5. Update credits to account
6. Update the user's default currency