planning

node_modules/@mapbox/mapbox-gl-style-spec/composite.js

@@ -0,0 +1,50 @@
+
+export default function (style) {
+    const styleIDs = [];
+    const sourceIDs = [];
+    const compositedSourceLayers = [];
+
+    for (const id in style.sources) {
+        const source = style.sources[id];
+
+        if (source.type !== "vector")
+            continue;
+
+        const match = /^mapbox:\/\/(.*)/.exec(source.url);
+        if (!match)
+            continue;
+
+        styleIDs.push(id);
+        sourceIDs.push(match[1]);
+    }
+
+    if (styleIDs.length < 2)
+        return style;
+
+    styleIDs.forEach((id) => {
+        delete style.sources[id];
+    });
+
+    const compositeID = sourceIDs.join(",");
+
+    style.sources[compositeID] = {
+        "type": "vector",
+        "url": `mapbox://${compositeID}`
+    };
+
+    style.layers.forEach((layer) => {
+        if (styleIDs.indexOf(layer.source) >= 0) {
+            layer.source = compositeID;
+
+            if ('source-layer' in layer) {
+                if (compositedSourceLayers.indexOf(layer['source-layer']) >= 0) {
+                    throw new Error('Conflicting source layer names');
+                } else {
+                    compositedSourceLayers.push(layer['source-layer']);
+                }
+            }
+        }
+    });
+
+    return style;
+}