Add custom GeoJSON layer functionality

main.js

@@ -11,6 +11,14 @@ import ToggleMenuControl from './ui/controls.js';
 
 import layerCategories from './layers/index.js';
 
+import VectorLayer from 'ol/layer/Vector';
+import {Vector as VectorSource} from 'ol/source.js';
+import GeoJSON from 'ol/format/GeoJSON.js';
+import {Style} from 'ol/style.js';
+import Icon from 'ol/style/Icon.js';
+
+import pin from './generic-pin.svg?url';
+
 // from https://openlayers.org/en/latest/examples/popup.html
 const container = document.getElementById('popup');
 const content = document.getElementById('popup-content');
@@ -140,6 +148,71 @@ for (let category of layerCategories) {
   }
 }
 
+const customLayerDiv = document.createElement("div");
+customLayerDiv.innerHTML = `
+<details>
+  <summary>Custom</summary>
+  <label>Layer Name: <input name="label"></label><br>
+  <label>Layer URL: <input name="source"></label><br>
+  <label>Color (optional): <input name="color"></label><br>
+  <button>Add</button>
+  <small>(must be in GeoJSON format)</small>
+  <ul></ul>
+</details>`;
+const labelInput = customLayerDiv.querySelector('input[name=label]');
+const sourceInput = customLayerDiv.querySelector('input[name=source]');
+const colorInput = customLayerDiv.querySelector('input[name=color]');
+
+customLayerDiv.querySelector("button").addEventListener("click", function(){
+  newCustomLayer(labelInput.value, sourceInput.value, colorInput.value);
+});
+document.querySelector("aside").appendChild(customLayerDiv);
+
+// https://stackoverflow.com/a/64090995
+let hslToRgb = (h,s,l, a=s*Math.min(l,1-l), f= (n,k=(n+h/30)%12) => l - a*Math.max(Math.min(k-3,9-k,1),-1)) => [f(0),f(8),f(4)];
+
+function newCustomLayer(name, sourceURL, colorString) {
+  let color;
+  if (colorString) {
+    color = colorString.split(' ').map(Number);
+    if (color.length != 3 || color.some(Number.isNaN)) {
+      alert("Invalid color provided; using random color instead.");
+      color = null;
+    }
+  }
+  if (!color) {
+    color = hslToRgb(Math.random()*360, 1, 0.5).map(c => c * 255);
+  }
+  const li = document.createElement("li");
+  const layer = new VectorLayer({
+    source: new VectorSource({
+      // In case people put in layers that don't serve proper CORS headers, we
+      // wrap them in this proxy so they Just Work.
+      url: `https://corsproxy.io/?${encodeURIComponent(sourceURL)}`,
+      format: new GeoJSON,
+    }),
+    style: new Style({
+        image: new Icon({
+            anchor: [0.5, 1],
+            src: pin,
+            color: color,
+        }),
+    }),
+  });
+  li.innerHTML = `
+    <label><input type="checkbox" checked> ${name}</label>
+  `;
+  li.querySelector("input").addEventListener("change", function(e){
+    if (e.target.checked) {
+      map.getLayers().push(layer);
+    } else {
+      map.getLayers().remove(layer);
+    }
+  });
+  map.getLayers().push(layer);
+  customLayerDiv.querySelector("ul").appendChild(li);
+}
+
 let location_set = false;
 
 if (urlLayers.length > 0) {