feat: Modernize the visual card editor. (#2586)

scripts/svg-path-plugin.js

@@ -0,0 +1,28 @@
+import { readFileSync } from 'node:fs';
+
+/**
+ * Rollup/Vite plugin: importing an SVG yields `{ path, viewBox }` extracted at
+ * build time, the shape a Home Assistant custom iconset serves. The SVG must
+ * be a single-path icon.
+ *
+ * @type {() => import('rollup').Plugin}
+ */
+export const svgPath = () => ({
+  name: 'svg-path',
+
+  // Vite: run before its builtin asset handling.
+  enforce: 'pre',
+
+  load(id) {
+    if (!id.endsWith('.svg')) {
+      return null;
+    }
+    const source = readFileSync(id, 'utf-8');
+    const path = / d="([^"]*)"/.exec(source)?.[1];
+    const viewBox = /viewBox="([^"]*)"/.exec(source)?.[1];
+    if (!path || !viewBox) {
+      throw new Error(`Imported SVG must have a path and viewBox: ${id}`);
+    }
+    return `export default ${JSON.stringify({ path, viewBox })};`;
+  },
+});