Add interpolate.mjs

src/interpolate.mjs

@@ -1,6 +1,56 @@
+import { visitParents } from 'unist-util-visit-parents';
+import { createContext, runInContext } from 'vm';
 
-export function interpolate () {
+export function interpolate (node, rootData, options = {}) {
+	if (!node.data) {
+		node.data = {};
+	}
 
+	node.data.interp = rootData || {};
+	visitParents(node, interpolateNode);
+
+	return node;
+}
+
+function getMaskedData (node, ancestors) {
+	let masked = { ...node.data };
+
+	for (let i = ancestors.length - 1; i >= 0; i--) {
+		const ancestor = ancestors[i];
+		if (ancestor.data && ancestor.data.interp) {
+			masked.interp = { ...ancestor.data.interp, ...masked.interp };
+		}
+	}
+
+	return masked;
+}
+
+function interpolateNode (node, ancestors) {
+	const data = getMaskedData(node, ancestors);
+
+	if (node.properties && typeof node.properties === 'object') {
+		for (const key in node.properties) {
+			if (typeof node.properties[key] === 'string') {
+				node.properties[key] = interpolateString(
+					node.properties[key],
+					data.interp
+				);
+			} else if (Array.isArray(node.properties[key])) {
+				node.properties[key] = node.properties[key].map(
+					(value) => interpolateString(value, data.interp)
+				);
+			}
+		}
+	}
+
+	return node;
+}
+
+function interpolateString(str, data) {
+	const context = createContext({ ...data, ...global });
+	const interpolatedStr = runInContext(`\`${str}\``, context);
+
+	return interpolatedStr;
 }
 
 export default interpolate;