This is an exercise I did during a job interview process. Part of that process was to meet with a couple of other developers and discuss what I would do to improve the code if I had a chance to do it again. Long story short, I got the job. :)

This code will display a table of rows listing a train line, route, route number, and operator ID, based on data uploaded by a user in the form of a .CSV file. While it is assumed that the user will upload a CSV file that is fully compliant to this format, it does not assume that the file has a header row: it checks for a header row based on the first cell containing the text "TRAIN_LINE."

By default, the table is sorted by run number. The user can sort by train line, route, route number, or operator ID by clicking the corresponding header. If there are more than five rows, the table will be paginated in groups of five, allowing the user to click directly to a specific page, or to advance to the next or previous page, assuming there's one available.

All rows will be unique; should the user upload a file that contains identical rows, the duplicates will be filtered out.

Unit tests are included in the "tests" folder, and the appropriate vendor files should be present in the "vendor" folder as well. The testing assumes using PHPUnit 9.5 and PHP version 8.1. To run the unit tests, use the command line to navigate to the root of the project folder and enter "phpunit tests".

The "data" folder contains three example CSV files to show the functionality:

• trains.csv - the original data file provided
• trains-dupes.csv - contains duplicate entries, made to demonstrate how the code filters out non-unique entries
• trains-multipage.csv - contains enough entries to trigger pagination for three pages