integrating with valhalla

[farfromrefug]

I would like to use your plugin but i would like to use valhalla as routing backend instead of the integrated ones.
Any guide/advise on how to do that?

[smellyshovel]

@farfromrefug Hello! I'd say that you have 2 major options here:

1. Translate Valhall's responses into OSRM-compatible format. I'm pretty much sure that some open source tools for that should exist, though personally I'm not familiar with any of them
2. Subclass the plugin's main class and alter its fetch/buildRoutelines implementations to handle Valhalla data instead of OSRM compatible

The good part is that it's definitely been done before, though not for Valhalla, but for graphhopper. So I'm sure that it's possible to achieve (moreover, should be pretty painless).

[smellyshovel]

@farfromrefug you don't "switch" between Mapbox and OSRM. They are (almost) the same, with the only difference that Mapbox provides some additional configuration parameters. So in order to "switch" from OSRM to Mapbox (or vice-versa), you just give it a correct API URL.

As long as your own backend is also OSRM-compatible, you can use it without any changes in the plugin as well. But this means that your server would actually have to be just a "translator" (adapter, if you wish), rather than an actual routing engine.

[smellyshovel]

In other words, in order to decide which backend to use, you provide different values for the api configuration parameter. For example, compare the 1st and the 3rd examples' sources here: https://maplibre.org/maplibre-gl-directions/:

1st example: no API specified (it falls back to OSRM)

maplibre-gl-directions/demo/src/examples/1 User Interaction.svelte

Line 48 in f000a69

directions = new MapLibreGlDirections(map, {

3rd example: use Mapbox

maplibre-gl-directions/demo/src/examples/3 Mapbox Directions API and Congestions.svelte

Line 43 in f000a69

api: "https://api.mapbox.com/directions/v5",

[smellyshovel]

In your case it would be something like

       api: "https://my.custom.directions.com/routing", 

where this server would expect OSRM-like input and respond with OSRM-like responses, but internally use Valhalla for the actual routing.

[farfromrefug]

@smellyshovel awesome thank for the detailed explanation!
Will look at it and try that

[smellyshovel]

Good luck. Feel free to post any useful findings here!