chore: Move editor into codebase (#2930)

shared/editor/commands/splitHeading.ts

@@ -0,0 +1,54 @@
+import { NodeType } from "prosemirror-model";
+import { EditorState, TextSelection, Transaction } from "prosemirror-state";
+import { findBlockNodes } from "prosemirror-utils";
+import findCollapsedNodes from "../queries/findCollapsedNodes";
+
+export default function splitHeading(type: NodeType) {
+  return (state: EditorState, dispatch: (tr: Transaction) => void): boolean => {
+    const { $from, from, $to, to } = state.selection;
+
+    // check we're in a matching heading node
+    if ($from.parent.type !== type) return false;
+
+    // check that the caret is at the end of the content, if it isn't then
+    // standard node splitting behaviour applies
+    const endPos = $to.after() - 1;
+    if (endPos !== to) return false;
+
+    // If the node isn't collapsed standard behavior applies
+    if (!$from.parent.attrs.collapsed) return false;
+
+    // Find the next visible block after this one. It takes into account nested
+    // collapsed headings and reaching the end of the document
+    const allBlocks = findBlockNodes(state.doc);
+    const collapsedBlocks = findCollapsedNodes(state.doc);
+    const visibleBlocks = allBlocks.filter(
+      (a) => !collapsedBlocks.find((b) => b.pos === a.pos)
+    );
+    const nextVisibleBlock = visibleBlocks.find((a) => a.pos > from);
+    const pos = nextVisibleBlock
+      ? nextVisibleBlock.pos
+      : state.doc.content.size;
+
+    // Insert our new heading directly before the next visible block
+    const transaction = state.tr.insert(
+      pos,
+      type.create({ ...$from.parent.attrs, collapsed: false })
+    );
+
+    // Move the selection into the new heading node and make sure it's on screen
+    dispatch(
+      transaction
+        .setSelection(
+          TextSelection.near(
+            transaction.doc.resolve(
+              Math.min(pos + 1, transaction.doc.content.size)
+            )
+          )
+        )
+        .scrollIntoView()
+    );
+
+    return true;
+  };
+}