planning

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

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+// @flow
+
+import refProperties from './util/ref_properties.js';
+
+import type {LayerSpecification} from './types.js';
+
+function deref(layer: LayerSpecification, parent: LayerSpecification): LayerSpecification {
+    const result = {};
+
+    for (const k in layer) {
+        if (k !== 'ref') {
+            result[k] = layer[k];
+        }
+    }
+
+    refProperties.forEach((k) => {
+        if (k in parent) {
+            result[k] = (parent: any)[k];
+        }
+    });
+
+    return ((result: any): LayerSpecification);
+}
+
+/**
+ * Given an array of layers, some of which may contain `ref` properties
+ * whose value is the `id` of another property, return a new array where
+ * such layers have been augmented with the 'type', 'source', etc. properties
+ * from the parent layer, and the `ref` property has been removed.
+ *
+ * The input is not modified. The output may contain references to portions
+ * of the input.
+ *
+ * @private
+ * @param {Array<Layer>} layers
+ * @returns {Array<Layer>}
+ */
+export default function derefLayers(layers: Array<LayerSpecification>): Array<LayerSpecification> {
+    layers = layers.slice();
+
+    const map = Object.create(null);
+    for (let i = 0; i < layers.length; i++) {
+        map[layers[i].id] = layers[i];
+    }
+
+    for (let i = 0; i < layers.length; i++) {
+        if ('ref' in layers[i]) {
+            layers[i] = deref(layers[i], map[(layers[i]: any).ref]);
+        }
+    }
+
+    return layers;
+}