Case study

Setting

This case study puts you in the position of a Java backend developer at trivago. There has been a decision at the management level to re-implement the backend from scratch and see whether the new solution can replace the legacy system which has grown over the past several years.

Your task

First take a look at the interface HotelSearchEngine. Your task will be to implement the two given functions in the concrete implementation in HotelSearchEngineImpl:

• initialize: this function is used to read the .csv (comma separated value) files initially. Take a look at the database schema section for further details.
• performSearch: executes the actual search. You are given a concrete search and can use the OfferProvider interface to retrieve offers from the advertisers.

The initialize function will be called one time during startup, whereas the performSearch function will be called multiple times. Make sure to do the initializations in the former function and execute the latter as quickly as possible. Also, every call to OfferProvider.getOffersFromAdvertiser retrieves offers from advertisers via a network request. It is very costly, so don't call it unnecessarily!

Database schema

The data for your search engine is stored in csv files:

• advertisers.csv: contains an id and the name of the advertiser
• cities.csv: contains ten cities with a name and an id
• hotel_advertiser.csv: models the m-n relationship between hotels and advertisers; every advertiser might have offers for m hotels and each hotel might be offered by n advertisers. Contains two columns, referencing the ids of advertisers and hotels
• hotels: the given hotels for your search engine. Contains an id field and the foreign key to the cities table. Next, you have five columns that further describe the hotel: the number of clicks and impressions over the last week, its name, the user rating (0 - 100), and the hotel star rating (1 - 5).

Important Notes

Scope

• Focus on implementing a minimum viable product, that is, implement the class HotelSearchEngineImpl in a way that correct offers and hotels are returned for a given search query.
• We respect your time, and expect the whole case study to only take about 2 hours. Don't spend your whole weekend trying to impress us with anything fancy.
• Add comments in plain text or pseudocode where you can imagine improvements or have some general ideas.

Hints

• You can use the given unit tests, but beware that they are not exhaustive (feel free to add more).
• If necessary, you can extend all classes with additional methods, but you should not change the method signatures in HotelSearchEngine.

Building

We have provided a Gradle build file as well as Eclipse and Idea project files for convenience, but we use Gradle internally. Here are some useful gradle commands for this project:

• gradle/gradle build: compile and test
• gradle clean: delete all of the build artifacts
• gradle classes/gradle testClasses: compile source/test Java classes
• gradle test: run unit tests