97joseph / PropineInterview

Blockchain programming for Contract Transactions

PropineInterview

Blockchain programming for Contract Transactions

Question 1 - Programming

We're looking at your programming ability. It must not only work, it should be maintainable.

Let us assume you are a crypto investor. You have made transactions over a period of time which is logged in a CSV file. Write a command line program that does the following

• Given no parameters, return the latest portfolio value per token in USD
• Given a token, return the latest portfolio value for that token in USD
• Given a date, return the portfolio value per token in USD on that date
• Given a date and a token, return the portfolio value of that token in USD on that date

The CSV file has the following columns

• timestamp: Integer number of seconds since the Epoch
• transaction_type: Either a DEPOSIT or a WITHDRAWAL
• token: The token symbol
• amount: The amount transacted

Portfolio means the balance of the token where you need to add deposits and subtract withdrawals. You may obtain the exchange rates from cryptocompare where the API is free. You should write it in Node.js as our main stack is in Javascript/Typescript and we need to assess your proficiency.

Submission

Please take no more than 7 days to finish. Your answers should comprise of the following

• Source code that you used for deriving the results
• README that explains various design decisions that you took.

Commit your answers in a private Github repository(it's free) and add Zan(liangzan), Ben(BenPropine) as collaborators. Inform us that it is done at [e-mail], [e-mail].

Solution

Condition

Sample CSV file.

• Given no parameters, return the latest portfolio value per token in USD
• Given a token, return the latest portfolio value for that token in USD
• Given a date, return the portfolio value per token in USD on that date
• Given a date and a token, return the portfolio value of that token in USD on that date

The CSV file has the following columns

• timestamp: Integer number of seconds since the Epoch
• transaction_type: Either a DEPOSIT or a WITHDRAWAL
• token: The token symbol
• amount: The amount transacted

Portfolio means the balance of the token where you need to add deposits and subtract withdrawals. You may obtain the exchange rates from cryptocompare where the API is free.

Development

1. Getting started

npm init
npm i express morgan nodemon ejs body-parser dotenv axios csv-parser

• Create Folders and config file.
  • /assets
    • /css
    • /csv
    • /js
  • /server
  • /controller
  • /routes
  • /services
  • /views
    • index.ejs
    • /include
  • config.env
  • server.js
• I used the EJS template engine with ExpressJS.

2. Build the design of this system.

• /views
  • index.ejs
  • /include
    • _header.ejs (Import css, bootstrap, spinner.)
    • _form.ejs (Enter token and date.)
    • _spinner.ejs (loading animation)
    • _footer.ejs (Import js.)
• /assets/css/style.css (fonts : Barlow, PT+Sans), (Resposive design)

3. Get portfolio (/server/controller/controller.js)

• Read and parse /assets/csv/transactions.csv with csv-parser npm.
• The remaining token quantity is calculated based on the transaction history corresponding to the filter condition.
• Get the USD price corresponding to the token using cryptocompare .
• Calculate token`s portfolio.

4. Print the portfolio to the screen.(/assets/js/index.js)

• After sending the filter condition to the controller using ajax, append the return value(portfolio or error) to the screen.

Run

• install packages

npm install

• change /assets/csv/transactions.csv file.

  *The size of the specified csv file is too large to commit to the current repository. *Excuse me. Please test by replacing the csv file in the current repository.

• run script

npm run start