feat: Initial clean release of CHM

packages/editor/ProseMirror/utils/clampPointToDocument.ts

@@ -0,0 +1,19 @@
+import { EditorState } from 'prosemirror-state';
+
+const documentMaximumIndex = (state: EditorState) => {
+	// nodeSize is documented to be the size of a node's content plus two (one for the
+	// start marker and one for the end marker). The main document doesn't have start or
+	// end markers, so subtract these to get the document maximum index:
+	return state.doc.nodeSize - 2;
+};
+
+const clampPointToDocument = (state: EditorState, point: number) => {
+	if (point < 0) return 0;
+
+	const maximumIndex = documentMaximumIndex(state);
+	if (point > maximumIndex) return maximumIndex;
+
+	return point;
+};
+
+export default clampPointToDocument;