The Sun Tribe Code Challenge

You are challenged to implement a date-interval difference function. The arguments to the function difference will be clojure sets, each of which contains zero or more LocalDateRange objects. The function must return a set of LocalDateRange objects that represent the interval difference of the first set and all additional sets of the input. This English sentence represents an example of the operation:

"Remove the second week in January and New Years Day from the month of January 2024."

Context

At Sun Tribe Trading we gather the energy production of solar generators from various sources (typically APIs from the manufacturers of solar energy equipment) and submit the data to regulatory authorities. It's important that we accurately determine the energy data we need to gather based on the data we already have on hand and the current reporting period. Date interval operations are central to this computation.

Evaluation

Your solution will be evaluated as follows, in decreasing order of importance:

• Correctness. Do all the tests pass?
• Readability. Can we understand your code? Is it well organized? Is it well documented? Is it idiomatic?
• Performance. How long does it take to run the test suite?

Correctness and performance will be evaluated by running this command in the root of your submitted repository:

time clojure -X:test

Readability will be evaluated by your potential future colleagues looking at the entire contents of the repository. You may organize the code of your implementation in any way you deem appropriate, but you must not modify the challenge-test namespace. You may add additional tests in separate namespaces. You may introduce additional dependencies and make other modifications to the deps.edn file, but you must not modify the :test alias.

Scale of the Challenge

We believe that a performance-optimized solution to the problem is difficult and we have not attempted to implement it. We have implemented a correct solution in less than fifty lines of documented Clojure code with no additional dependencies. It takes ~15 seconds to complete the test suite on a 2023 MacBook Pro with an Apple M2 Pro processor and 32G of RAM.

Hints, maybe helpful

Our solution evolved from the observation that a LocalDateRange object can be represented (inefficiently) by a sequence of LocalDate objects. That representation can be input into a set difference operation, but the result must be "compressed" back into the minimal set of LocalDateRange objects.

The LocalDateRange class has some useful methods (class and instance).

Before coding, you should be comfortable with the concept of a time interval, and more specifically a (local) date interval as implemented by the backing Java library we use.

Submitting your response

This git repository is the entire input you will need for the Sun Tribe code challenge. Your submission should be a modified version of this repository (including our initial commits and the commit(s) of your solution). You may submit either:

• a link to a public http(s) repository that can be cloned by git clone <url>.

-or-

• a repository compressed into a standard zip file that can be opened with unzip <file>.