Module 2 Capstone - TEnmo

Congratulations—you've landed a job with TEnmo, whose product is an online payment service for transferring "TE bucks" between friends. However, they don't have a product yet. You've been tasked with writing a RESTful API server and command-line application.

Use cases

Required use cases

You should attempt to complete all of the following required use cases.

1. [COMPLETE] As a user of the system, I need to be able to register myself with a username and password.
   1. A new registered user starts with an initial balance of 1,000 TE Bucks.
   2. The ability to register has been provided in your starter code.
2. [COMPLETE] As a user of the system, I need to be able to log in using my registered username and password.
   1. Logging in returns an Authentication Token. I need to include this token with all my subsequent interactions with the system outside of registering and logging in.
   2. The ability to log in has been provided in your starter code.
3. As an authenticated user of the system, I need to be able to see my Account Balance.
4. As an authenticated user of the system, I need to be able to send a transfer of a specific amount of TE Bucks to a registered user.
   1. I should be able to choose from a list of users to send TE Bucks to.
   2. I must not be allowed to send money to myself.
   3. A transfer includes the User IDs of the from and to users and the amount of TE Bucks.
   4. The receiver's account balance is increased by the amount of the transfer.
   5. The sender's account balance is decreased by the amount of the transfer.
   6. I can't send more TE Bucks than I have in my account.
   7. I can't send a zero or negative amount.
   8. A Sending Transfer has an initial status of Approved.
5. As an authenticated user of the system, I need to be able to see transfers I have sent or received.
6. As an authenticated user of the system, I need to be able to retrieve the details of any transfer based upon the transfer ID.

Optional use cases

If you complete all of the required use cases and are looking for additional challenge, complete as many of the following optional use cases as you can.

7. As an authenticated user of the system, I need to be able to request a transfer of a specific amount of TE Bucks from another registered user.
   1. I should be able to choose from a list of users to request TE Bucks from.
   2. I must not be allowed to request money from myself.
   3. I can't request a zero or negative amount.
   4. A transfer includes the User IDs of the from and to users and the amount of TE Bucks.
   5. A Request Transfer has an initial status of Pending.
   6. No account balance changes until the request is approved.
   7. The transfer request should appear in both users' list of transfers (use case #5).
8. As an authenticated user of the system, I need to be able to see my Pending transfers.
9. As an authenticated user of the system, I need to be able to either approve or reject a Request Transfer.
   1. I can't "approve" a given Request Transfer for more TE Bucks than I have in my account.
   2. The Request Transfer status is Approved if I approve, or Rejected if I reject the request.
   3. If the transfer is approved, the requester's account balance is increased by the amount of the request.
   4. If the transfer is approved, the requestee's account balance is decreased by the amount of the request.
   5. If the transfer is rejected, no account balance changes.

Sample screens

Use case 3: Current balance

Your current account balance is: $9999.99

Use case 4: Send TE Bucks

-------------------------------------------
Users
ID          Name
-------------------------------------------
313         Bernice
54          Larry
---------

Enter ID of user you are sending to (0 to cancel):
Enter amount:

Use case 5: View transfers

-------------------------------------------
Transfers
ID          From/To                 Amount
-------------------------------------------
23          From: Bernice          $ 903.14
79          To:    Larry           $  12.55
---------
Please enter transfer ID to view details (0 to cancel): "

Use case 6: Transfer details

--------------------------------------------
Transfer Details
--------------------------------------------
 Id: 23
 From: Bernice
 To: Me Myselfandi
 Type: Send
 Status: Approved
 Amount: $903.14

Use case 7: Requesting TE Bucks

-------------------------------------------
Users
ID          Name
-------------------------------------------
313         Bernice
54          Larry
---------

Enter ID of user you are requesting from (0 to cancel):
Enter amount:

Use case 8: Pending requests

-------------------------------------------
Pending Transfers
ID          To                     Amount
-------------------------------------------
88          Bernice                $ 142.56
147         Larry                  $  10.17
---------
Please enter transfer ID to approve/reject (0 to cancel): "

Use case 9: Approve or reject pending transfer

1: Approve
2: Reject
0: Don't approve or reject
---------
Please choose an option:

Database schema

tenmo_user table

Stores the login information for users of the system.

Field	Description
user_id	Unique identifier of the user
username	String that identifies the name of the user; used as part of the login process
password_hash	Hashed version of the user's password

account table

Stores the accounts of users in the system.

Field	Description
account_id	Unique identifier of the account
user_id	Foreign key to the users table; identifies user who owns account
balance	The amount of TE bucks currently in the account

transfer_type table

Stores the types of transfers that are possible.

Field	Description
transfer_type_id	Unique identifier of the transfer type
transfer_type_desc	String description of the transfer type

There are two types of transfers:

transfer_type_id	transfer_type_desc	Purpose
1	Request	Identifies transfer where a user requests money from another user
2	Send	Identifies transfer where a user sends money to another user

transfer_status table

Stores the statuses of transfers that are possible.

Field	Description
transfer_status_id	Unique identifier of the transfer status
transfer_status_desc	String description of the transfer status

There are three statuses of transfers:

transfer_status_id	transfer_status_desc	Purpose
1	Pending	Identifies transfer that hasn't occurred yet and requires approval from the other user
2	Approved	Identifies transfer that has been approved and occurred
3	Rejected	Identifies transfer that wasn't approved

transfer table

Stores the transfers of TE bucks.

Field	Description
transfer_id	Unique identifier of the transfer
transfer_type_id	Foreign key to the transfer_types table; identifies type of transfer
transfer_status_id	Foreign key to the transfer_statuses table; identifies status of transfer
account_from	Foreign key to the accounts table; identifies the account that the funds are being taken from
account_to	Foreign key to the accounts table; identifies the account that the funds are going to
amount	Amount of the transfer

Note: there are two check constraints in the DDL that creates the transfer table. Be sure to take a look at tenmo.sql to understand these constraints.

How to set up the database

Create a new Postgres database called tenmo. Run the database/tenmo.sql script in pgAdmin to set up the database.

Authentication

The user registration and authentication functionality for the system has already been implemented. If you review the login code, you'll notice that after successful authentication, an instance of AuthenticatedUser is stored in the currentUser member variable of App. The user's authorization token—meaning JWT—can be accessed from App as currentUser.getToken().

When the use cases refer to an "authenticated user", this means a request that includes the token as a header. You can also reference other information about the current user by using the User object retrieved from currentUser.getUser().