In the initial commit to this project, you have been provided with files that contain a JavaScript module, mock data, and some associated tests. Currently the JavaScript module is a skeleton and most functionality is completely missing thus causing the tests to fail. Your task is to write the code that will implement the requirements listed below and make the tests pass.
An order book tracks all buy and sell requests from traders for Bitcoin assets at various price levels. When a trader submits a trade it is either fulfilled immediately, if there is a matching order in the book, or it is added to the book to be fulfilled later.
Assume starting with an empty order book, let's walkthrough several scenarios.
Buy 15 BTC at 5800: The order book is empty so this order cannot be fulfilled immediately. This order is added to the book.
Buy 10 BTC at 6000: The order book only has buy orders and no sell ordrs so this order cannot be fulfilled immediately. This order is added to the book.
Sell 5 BTC at 6100: The order book has two buy orders but neither match this as the prices mismatch. This order is added to the book.
Sell 10 BTC at 6000: The order book has a buy order for 10 BTC at 6000 meaning this order can be fulfilled immediately. This order is executed and the corresponding buy is removed from the order book.
Buy 2 BTC at 6100: The order book has a sell order at this price point for more than this order's quantity. This means this order can be fulfilled immediately and the corresponding sell order can be reduced by 2 as it has been partially fulfilled but the remainder stays in the book.
Sell 25 BTC at 5800: The order book has a buy order at this price point but for a smaller quantity. This order can be partially fulfilled, the corresponding buy order is used up and is removed from the order book and the remainder of this order (Sell 10 BTC at 5800) is added to the book.
.eslintrc.js - a config file for eslint
.gitignore - this file sets the project up to ignore the node_modules folder when committing to git
orderBook.js - this file contains the functions for reconciling orders against the orderBook, executing buys and sells when possible
package.json - this file sets up the Node project including all the dev dependencies
tests.js - this file contains tests for the functions in the orderBook module
You should submit your working changes in a pull request to your repo and request a review from the instructor.
No one is ever upset about a good deal. We want to adjust the code so that it will fulfill orders that are not exact matches but would result in both parties benefitting.
For example, assume the book contains an order to buy 15 BTC at 6000. When we receive a sell order for 15 BTC at 5900 we should fulfill this order given that the buyer will pay less (5900 vs 6000) and the seller will receive the amount requested (5900).
The inverse however would not be true. Given a book with a buy 15 BTC at 5900, when we receive a sell order for 15 BTC at 6000 we should not fulfill this order since it would result in the seller getting less (5900 vs 6000).
There are two tests associated with this extra created that are currently being skipped. Remove the .skip on these tests so they run when beginning this work.