Propine Assignment

A command line utility to parse a CSV file of transactions and output portfolio value in USD on the command line.

Requirements

• Node.js Runtime v12.22.9
• A CSV file that contains transaction information. The transaction should look like the following:

timestamp,transaction_type,token,amount
1571967208,DEPOSIT,BTC,0.298660

Usage

• Clone this repository and navigate to the root directory and run the following command to install dependencies:

npm i

• Make sure to add the transactions CSV file in the src directory. A sample can be found here. It's not included in this repo because the file is very large.
• Build the project using:

npm run build

• After that install the command line binary as a global package using:

npm i -g .

• Now you should have the propine command line tool in your system.
• To get latest portfolio value per token in USD, use:

propine portfolio

• To get the latest portfolio value for BTC token in USD, use:

propine portfolio --token BTC

• To get the portfolio value per token in USD on 10/19/2019, use:

propine portfolio --date 10/19/2019

• To get the portfolio value for the BTC token in USD on 10/19/2019, use:

propine portfolio --token BTC --date 10/19/2019

Design Decisions

• I used TypeScript for the project to get type safety. The tsc compiler transpiles the TS code to JS.
• I used ESLint for linting the code. Use this command to run linting:

npm run lint

• Since the CSV file that needs to be parsed is really huge (almost 1GB), I have to use a read steam. Then parse each line of the file one by one excluding the header. The implementation of this is found inside this file. The implementation of this file has been tested using the Jest testing framework. The testing can be found inside this file. I have a smaller CSV file for test fixture. The readCSV function returns a promise (Promise<TokenTransaction>).
• I used the nanospinner package to show a spinner while asynchronous operations are under progress. This avoids the illusion the program has frozen while doing operations. Specially while parsing the CSV file it can take some time to finish.
• I used to yargs package to parse command line arguments. It displays a nice usage message automatically without additional work.
• I added a getPortfolioValue function that takes in the parsed transaction data and command line arguments. I also created a getUSDExchangeRate function that gets exchange rate information for cryptocurrencies. I used the axios package to make the HTTP request to the cryptocompare API.

NB: I added the .env that contains API KEY from cryptocompare because this is a demo project. Normally, I wouldn't commit this .env file to a public repository.

• The getPortfolio value will use the reduce function to get a single portfolio value from an array of transactions. We add for deposits and subtract for withdrawals. We then multiply the final reduced value with the exchange rate received from cryptocompare and return the result.
• Finally, output the result on the console, formatted nicely with Intl. A sample output looks like the following:

✔ Parsing CSV file...
✔ Getting exchange rate information...

Portfolio
=================
BTC: $19,806,522,836.46 USD
ETH: $1,103,613,906.20 USD
XRP: $310,385.21 USD