pull out modifications to the itinerary's data structure from React components

[derhuerst]

Currently, the components responsible for rendering itineraries (e.g. ItineraryLegs, WalkLeg, WaitLeg) contain complex logic that transforms each itinerary. For example, they

• insert waiting legs between other legs in some cases
• when to show bicycle and/or walking legs before/after some transit
• interlines legs only in some very specific cases
• calculate transfer/"gap" times between legs
• etc.

IMO a good example of how to move out such complex logic is the compressLegs(), which is being used by ItineraryLegs. There are probably other good examples!

This is a broader topic to discuss, but it seems like digitransit-ui de-facto has a slightly different semantic model of an itinerary than OTP. It might be worth it making this semantic model more explicit, e.g. by documenting it, adding mapping functions like digitransitItineraryFromOtpItinerary(); This potentially reduces the legibility of the code, though.

The following resources explain the problem and possible solutions in a general manner:

• Thinking in React post from the React documentation
• Higher-Order Components