fix: support Docker runtime routing config with OSRM_MODES

[DennisOSRM]

Fixes

Resolves #421: environment override support for Docker runtime config.

Summary

This PR moves Docker routing configuration to runtime and keeps the default Docker behavior on a single default profile pointing to http://localhost:5000.

The new preferred runtime interface is OSRM_MODES, while OSRM_BACKEND remains supported as a deprecated single-backend fallback.

Behavior

1. With no runtime routing override, Docker uses one default profile at http://localhost:5000.
2. If only OSRM_BACKEND is set, the frontend configures one backend and emits a deprecation warning.
3. If only OSRM_MODES is set, the frontend parses the JSON and configures the listed modes.
4. If both are set, OSRM_MODES wins and the frontend emits a deprecation warning for OSRM_BACKEND.
5. Local npm start keeps the public demo profiles for driving, bike, and foot.

Changes

• add Docker entrypoint-based config.json generation at container startup
• load runtime config before the frontend bundle initializes
• parse OSRM_MODES JSON in the frontend and preserve deprecated OSRM_BACKEND fallback behavior
• keep Docker default routing on localhost instead of public demo services
• update README and inline comments to document the new configuration model and deprecation
• add Jest coverage for deprecation warnings and direct entrypoint config generation

Docker examples

Recommended multi-profile runtime config:

docker run -p 9966:9966 \
  -e 'OSRM_MODES=[{"name":"car","url":"https://routing.openstreetmap.de/routed-car"},{"name":"foot","url":"https://routing.openstreetmap.de/routed-foot"},{"name":"bike","url":"https://routing.openstreetmap.de/routed-bike"}]' \
  ghcr.io/project-osrm/osrm-frontend:latest

Deprecated single-backend override:

docker run -p 9966:9966 \
  -e OSRM_BACKEND='http://localhost:5001' \
  ghcr.io/project-osrm/osrm-frontend:latest

Validation

• npm run test:lint
• npm run build
• npm test

[Copilot]

Pull request overview

Adds runtime (container startup) configuration for the OSRM frontend Docker image by generating a config.json from OSRM_* environment variables and loading it before the app bundle runs.

Changes:

• Add docker/entrypoint.sh to emit /usr/share/nginx/html/config.json from OSRM_* env vars at startup.
• Update Docker image runtime to use the new entrypoint and provide default OSRM_* ENV values.
• Load config.json in index.html before bundle.js, and read runtime config in src/leaflet_options.js.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 8 comments.

File	Description
src/leaflet_options.js	Reads runtime config from window.osrmConfig and uses it for initial state and backend URL.
index.html	Initializes defaults and attempts to synchronously load config.json before loading bundle.js.
docker/entrypoint.sh	Generates config.json from environment variables and starts nginx.
docker/Dockerfile	Adds runtime ENV defaults and sets the new entrypoint for the nginx stage.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

getZoom() uses config.OSRM_ZOOM || 13, which prevents setting a valid zoom of 0 and can also return NaN if OSRM_ZOOM is non-numeric (which then propagates into defaultState.zoom). Consider checking for undefined/null explicitly and validating the parsed integer before returning it.

Suggested change

	return parseInt(config.OSRM_ZOOM || 13, 10);
	var zoomValue = config.OSRM_ZOOM;
	var parsedZoom;
	if (zoomValue === undefined || zoomValue === null) {
	return 13;
	}
	parsedZoom = parseInt(zoomValue, 10);
	if (isNaN(parsedZoom)) {
	return 13;
	}
	return parsedZoom;