mapcomplete/Logic/ExtraFunction.ts

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import {GeoOperations} from "./GeoOperations";
import {UIElement} from "../UI/UIElement";
import Combine from "../UI/Base/Combine";
export class ExtraFunction {
private static DistanceToFunc = new ExtraFunction(
"distanceTo",
"Calculates the distance between the feature and a specified point",
["longitude", "latitude"],
(feature) => {
return (lon, lat) => {
// Feature._lon and ._lat is conveniently place by one of the other metatags
return GeoOperations.distanceBetween([lon, lat], [feature._lon, feature._lat]);
}
}
)
private static readonly allFuncs: ExtraFunction[] = [ExtraFunction.DistanceToFunc];
private readonly _name: string;
private readonly _args: string[];
private readonly _doc: string;
private readonly _f: (feat: any) => any;
constructor(name: string, doc: string, args: string[], f: ((feat: any) => any)) {
this._name = name;
this._doc = doc;
this._args = args;
this._f = f;
}
public static FullPatchFeature(feature) {
for (const func of ExtraFunction.allFuncs) {
func.PatchFeature(feature);
}
}
public static HelpText(): UIElement {
return new Combine([
ExtraFunction.intro,
...ExtraFunction.allFuncs.map(func =>
new Combine([
"<h3>" + func._name + "</h3>",
func._doc,
"<ul>",
...func._args.map(arg => "<li>" + arg + "</li>"),
"</ul>"
])
)
]);
}
public PatchFeature(feature: any) {
feature[this._name] = this._f(feature);
}
static readonly intro = `<h2>Calculating tags with Javascript</h2>
<p>In some cases, it is useful to have some tags calculated based on other properties. Some useful tags are available by default (e.g. <b>_lat</b>, <b>lon</b>, <b>_country</b>), as detailed above.</p>
<p>It is also possible to calculate your own tags - but this requires some javascript knowledge. </p>
Before proceeding, some warnings:
<ul>
<li> DO NOT DO THIS AS BEGINNER</li>
<li> <b>Only do this if all other techniques fail</b>. This should <i>not</i> be done to create a rendering effect, only to calculate a specific value</li>
<li> <b>THIS MIGHT BE DISABLED WITHOUT ANY NOTICE ON UNOFFICIAL THEMES</b>. As unofficial themes might be loaded from the internet, this is the equivalent of injecting arbitrary code into the client. It'll be disabled if abuse occurs.</li>
</ul>
In the layer object, add a field <b>calculatedTags</b>, e.g.:
<div class="code">
"calculatedTags": {
"_someKey": "javascript-expression",
"name": "feat.properties.name ?? feat.properties.ref ?? feat.properties.operator",
"_distanceCloserThen3Km": "feat.distanceTo( some_lon, some_lat) < 3 ? 'yes' : 'no'"
}
</div>
`
}