Write new routing plugin

[taylor.smock]

Problem:
Mappers attempting to debug why a routing engine does stupid things or takes poor routes.

Solution:
Show mappers a route with route instructions as they edit live.

Goals:

1. Use production routing engines
   • ​valhalla
   • ​OsmAnd
   • ​OSRM
   • ​Organic Maps
2. Show routing instructions in JOSM for given modes (pedestrian, biking, vehicle, and possibly public transport)
3. [Stretch goal] If routing engine supports it, show weights for ways in given mode; this should allow debugging why a different route was not chosen.

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MVP will use one of the specified routing engines and show routing instructions in JOSM.
I am currently investigating using valhalla for the initial routing engine. This will most likely require Java 22 for ​FFI support without JVM flags. Alternatively, I can use JNI or a derivative thereof. As an additional alternative, if the routing engine exposes a web interface or a command line interface, we can use those for routing support.

Possible implementation details:
Valhalla (MIT):

• Provides a C++ library (libvalhalla)
• Provides a web interface
• Provides a ​CLI

OSRM (BSD 2-clause):

• Provides a C++ library
• Provides a ​web interface

OSMAnd (GPLv3):

• Java library and bindings already written (thanks to Android)
• Has some kind of web interface (see comment:2)

Organic Maps (Apache 2):

• Java library and bindings already written (thanks to Android)

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Most likely, I will have to write the current edit layer to pbf in order to load it into a routing engine. There may be additional steps, such as converting the pbf to the engine specific format.

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This plugin should completely replace the routing plugin which uses custom Java code for routing.

[IreuN]

FYI OsmAnd also provides web interface at ​https://osmand.net/map/navigate/ and ​https://test.osmand.net/map/navigate/

[taylor.smock]

I probably can't send the website arbitrary OSM data (AKA whatever the editor has changed); at a minimum, I'd have to spin up an instance on-device.

I could use it as a "status as of whenever OsmAnd updated their backend routing db".

Thanks for the information.