refactor(DatePicker): Break up, extract handlers, consolidate state

[m7kvqbe1]

Overview

Refactor DatePicker.

This is a boy scout step change, I'm not aiming for perfection (other things to move on to).

I'm also not fully convinced this is better. I feel like i've added more code and indirection.

Reason

#3955 (comment)

Work carried out

• Break up the DatePicker into Input and FloatingCalendar sub components
• Extract handlers from JSX
• Consolidate state within the reducer (calendarTableVariant, isOpen)
• Expose reducer via context
• Memoize where appropriate (note impact on speed of test suites)

Developer notes

I'm using context to expose the reducer, which is naughty with mutable state but performance impact is limited:

1. State updates are naturally bounded to user interactions
2. Most state changes (like paging the calendar) require child components to re-render anyway
3. Context scope is limited to the relatively shallow DatePicker component tree only
4. Refactoring all of the state and introducing Zustand felt like overkill given the above

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[jpveooys]

I think it looks okay generally. Would've been useful to split this into multiple commits though 😄

(Main negative I can see is probably that it's added a fair bit to the line count...)

[thyhjwb6]

👍

I think it looks good and also gets me thinking about custom hooks - whether 1-2 more could be introduced or whether the existing ones need rework/adding to, but this is far enough for now.

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
87.7% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud