chore: Move editor into codebase (#2930)

shared/editor/lib/headingToSlug.ts

@@ -0,0 +1,28 @@
+import { escape } from "lodash";
+import { Node } from "prosemirror-model";
+import slugify from "slugify";
+
+// Slugify, escape, and remove periods from headings so that they are
+// compatible with both url hashes AND dom ID's (querySelector does not like
+// ID's that begin with a number or a period, for example).
+function safeSlugify(text: string) {
+  return `h-${escape(
+    slugify(text, {
+      remove: /[!"#$%&'\.()*+,\/:;<=>?@\[\]\\^_`{|}~]/g,
+      lower: true,
+    })
+  )}`;
+}
+
+// calculates a unique slug for this heading based on it's text and position
+// in the document that is as stable as possible
+export default function headingToSlug(node: Node, index = 0) {
+  const slugified = safeSlugify(node.textContent);
+  if (index === 0) return slugified;
+  return `${slugified}-${index}`;
+}
+
+export function headingToPersistenceKey(node: Node, id?: string) {
+  const slug = headingToSlug(node);
+  return `rme-${id || window?.location.pathname}–${slug}`;
+}