OFUS - Open FreeMap Url Schema v0.1

    let url = origin/map42/?

    let p = Object.fromEntries(new URL(location).searchParams.entries()); // pares the url parameters
    //let p = params / key: value json object.


    p.mapinfo = [zoom, center_lat, center_lng]                  // set the basic map zoom and position.

    p.basefilter=index_of_filter                                // apply css filter to base map layer

    p.server=wms_server_url_to_load_overlayers_of               // wms server to get overlay layers from

    p.rox=[url, p1, p2, p3, opacity]                            // image overlays to render on the client note this is base of prefix ro so x can be anything.

    p.urlayers=[urlayer_spec1, urlayer_spec2, ...]              // json overlays to render on the client

    p.measure=[[lat1, lon1], [lat2,lon2], ...]                  //a measurement in the measure tool to display

    p.h3viewer=[h3cell1, h3cell1, ...]                          // enable h4 hex cell viewer and saved layer. note buggy

    p.gps=1                                                     // draw a marker on you gps location.

    todo  document urls for all finalized mode .
    sorry alpha customers your on your own reach out with questions!

    [email protected]

Note: Almost everything is url encoded and json stringifies.

Normally this gets handled in the decode stage but in upload make sure to use getParam_______() whitch probably does it right.

Embeding Freemap in an ifream on your site:
Note you may want to adjust the site.

You can use this site to preview and genreate  your iframes.

https://html-css-js.com/html/generator/iframe/

If you insist on implementing this yourself il use the mapinfo as an example.

    function getParamMapinfo() {
        let z = map.getZoom()
        let c = map.getCenter()

        let a = [z, c.lat, c.lng] ; // as you can see here we make an array before


        return "mapinfo=" + encodeURIComponent(JSON.stringify(a))
        // then we stringify the array and finally encode it for safe usage in urls.
    }

    /**
    *
    * @param a [zoom, lat, lng]
    * @return {zoom, latlng: {lat, lng}}
    */
    function mapinfoToZoomLatLng(a) {
        return {
        zoom: a[0],
        latlng: L.latLng(a[1], a[2])
        }
    }
    function setMapinfo(params) {

        try {
        let a = JSON.parse(p.mapinfo); // and so finally here we get string already decoded and simply need to parse the json
        if (!Array.isArray(a) || a.length !== 3) {
        console.log("No param or invalid json")
        }
        // let {zoom, latlng} = mapinfoToZoomLatLng(a);
        let zoom = a.shift();

        map.panTo(L.latLng(a))
        map.setZoom(zoom)

        } catch (e) {
        // note error catching invalid encoded json
        console.error("Invaled mapinfo doing nothing [zoom, lat, lon]")
        }

    }

    // we asume this line has ran elsewhere.
    // let p = Object.fromEntries(new URL(location).searchParams.entries());
    if (p && p.mapinfo) {
        setMapinfo(p) ; // in the loading step we assume we have already decodes our params as the URLSearchParams object does that.
    }