To implement a router you need to write a JSON metadata file, a Python file that implements the route function and one QML file. The route function should given two points return a dictionary of route properties with keys x, y, locations, location_indexes, maneuvers, mode and language, example below. The location points (2 or more) are given as an argument in the form of a list. List elements can be strings (addresses, landmarks, etc.), two-element tuples or lists of (x, y) coordinates, or dictionaries with the keys x, y (coordinates), and optional text (can be used by router to describe location). If returning multiple alternative routes for the user to choose from, the return value should be a list of dictionaries of route properties.

{
    "x": [24.943464, 24.943294, 24.94318, ...],
    "y": [60.166938, 60.167053, 60.16705, ...],
    "locations": as_supplied_to_the_route_function_call,
    "location_indexes": [0, 122, ...],
    "maneuvers": [
        {
            "x": 24.943464,
            "y": 60.166938,
            "icon": "depart",
            "narrative": "Drive northwest.",
            "duration": 29.0,
        },
        ...
    ],
    "mode": "car",
    "language": "en_US",
    "traffic": 120,
}

Here, location_indexes designate the index of the point on the route (xi,yi) which is considered as the closest to the location.

A QML file, the settings file (*_settings.qml) is optional; it can be used to provide a column of router-specific settings, which are shown in Pure's routing page below the endpoint selectors. To pass settings to your router, you have two options. If those settings are to be saved across sessions, define a CONF_DEFAULTS attribute in your Python code; it will be automatically passed to and available at poor.conf. For settings which shouldn't be saved across sessions, you can use page.params in your QML.

If you provide settings file, you will have to ensure that QML object has full property. When this property is set to false, only minimal settings (if any) are expected. Show all settings when full is true.

If your router supports multiple languages, provide the list of languages in *_settings.qml and use the user-given selection in the Python route function. When returning the narration language as a part of the return dictionary of route, make sure to use the standard locale format xx[_YY]. See the OSM Scout router for an example on how to implement language settings in QML and Python.

To display a route on the map, you'll want to call navigator.setRoute. See the implementation of these functions in qml/Navigator.qml to understand which fields are expected in their arguments.

To download data you should always use poor.http.get or poor.http.get_json in order to use Pure's user-agent and default timeout and error handling. You might also find poor.AttrDict, a dictionary with attribute access to keys, convenient when working with JSON data.

Use ~/.local/share/harbour-pure-maps/routers as a local installation directory in which to place your files. Since routers require QML files and include "../qml" in their source, add a symbolic link ~/.local/share/harbour-pure-maps/qml pointing to /usr/share/harbour-pure-maps/qml. Restart Pure Maps, and your router should be loaded, listed and available for use. During development, consider keeping your files under the Pure Maps source tree and using the Python interpreter or a test script, e.g.

>>> import poor
>>> router = poor.Router("my_router")
>>> router.route(["erottaja, helsinki", "tapiola, espoo"])

for testing.