Financial app

Intro

The task is to implement a function that generates a simple financial report based on transactions (like bank or credit card transactions).

The report will be an object whose keys are expense categories (like vacation, public transportation etc) and values are the total amount spent on those categories in the relevant timeframe.

Each transaction looks like this:

{
  "amount": 166,
  "description": "Star taxis",
  "date": "12/04/2017"
}

The report you will generate looks like this:

{
  "EATING_OUT": 4325,
  "GROCERIES": 0,
  "VACATION": 228,
  "MEDICAL": 780,
  "PUBLIC_TRANSPORTATION": 0,
  "CAR_MAINTENANCE": 2000,
  "SAVINGS": 350,
  "BILLS": 0,
  "ENTERTAINMENT": 0,
  "NO_CATEGORY": 780
}

Each transaction will be categorized to one of the expense categories based on the transaction's description text.

For example, the transaction in the example above, will be categorized as PUBLIC_TRANSPORTATION based on the description Star taxis.

If the classifier doesn't know how to categorize a given transaction description it will return null. In this case this transaction should appear in the report under NO_CATEGORY.

Server

We have implemented a server that has two endpoints you need to use in order to generate the report. This code is already implemented and you just need to use it without changing it.

To start the server run npm install && npm run startServer.

This will start a server on http://localhost:4000 with the following endpoints:

1. Graphql

   http://localhost:4000/graphql

   A graphql endpoint that exposes one query called transactions that fetches transactions by username and transaction dates. When the server is running you can go to the url in the browser and see the schema and run queries in the graphql playground.

   (A good source about graphql is this intro and in this page about queries, the relevant parts are fields, arguments and variables)

2. Transaction classification

   POST http://localhost:4000/transaction/classification

   This endpoint receives a description of a transaction and returns the category of that transaction.

   Example of the request post body:

   {
    "transactionDescription": "Star taxies"
   }

   Example of the response body:

   {
       "transactionCategory": "PUBLIC_TRANSPORTATION"
   }

Your code

What you need to do, is implement the generateReport function in test-code/solution/expenseReportGenerator.js

The function receives a username, startDate and endDate parameters which you should use to:

• Fetch the relevant transactions from graphql
• For each of those transactions call the transaction classification endpoint to get the expense category
• Process the data and return the report.

Bonus

If you finish the requirements above and still have time, here is a bonus task:

Assume that the classification endpoint has a rate limit of at most 10 concurrent request and will block you if you exceed this rate.

Write your code in a way that limits the concurrent calls you are making to this endpoint to 10.

Notes

• The date format in the test is always DD/MM/YYYY (for example 01/10/2017 or 15/08/2018)

• All transactions are in the date range between 01/01/2017 to 31/12/2018

• All of the code you write should be under the solution directory. The rest of the code outside that directory should be considered an api that you use without changing it.

• Please work according to the following priorities:

  • Make it work
  • Write clean code
  • Write tests

  A basic test that works is better that a fully implemented, tested and beautifully coded test that doesn't work.

  But of course, if you have the time, submit clean and tested code.