Creating good habits and breaking bad ones is no easy task. To keep track of certain habits or achieving personal

goals, more and more people rely on so called habit trackers to help them throughout the day. If you check out

any popular app store, you$$ll find no shortage of habit tracking applications in a wide range of quality and prices.

Recently, a client has approached you and wants you to help them build a basic Python backend for a habit track$-$

ing app, which they want to roll out later this year. To make this project feasible, you must focus on the essential

functionality of such an application. You are not asked to provide any sort of graphical user interface, just the

basic functionality of a habit tracker using object$-$oriented and functional programming in Python, according to

the following specifications.

Formally, a habit is a clearly defined task that must be completed periodically $($e$.$g$.,$ brush your teeth every day or

go to the dentist once every year$).$ The basic building blocks of a tracking app are as follows:

o A user can define multiple habits in the application. A habit has a task specification and a periodicity.

o A task can be completed, i$.$e$.,$checked$-$off$,$ by a user at any point in time.

o Each task needs to be checked$-$off at least once during the period the user defined for the respective

habit. If a user misses to complete a habit during the specified period, the user is said to break the habit.

o If a user manages to complete the task of a habit x consecutive periods in a row, I.e$.,$ without breaking

the habit, we say that the user established a streak of x periods. For instance, if a user wants to work out

every day and does so for two full weeks, they establish a $14-$day streak of working out.

o The habits users enter in the app are not only stored but can also be analysed. Users want answers to

several questions like: what$$s my longest habit streak? What's the list of my current daily habits? With

which habits did I struggle most last month?