refactor(editor): extract database block (#9435)

Part of: [BS-2269](https://linear.app/affine-design/issue/BS-2269/%E8%BF%81%E7%A7%BB-database-block-%E5%88%B0-affine-%E6%96%87%E4%BB%B6%E5%A4%B9%E4%B8%8B%E5%B9%B6%E5%BC%80%E5%90%AF-nouncheckedindexedaccess)

blocksuite/affine/block-database/src/utils/title-doc.ts

@@ -0,0 +1,30 @@
+import type { AffineTextAttributes } from '@blocksuite/affine-shared/types';
+import type { DeltaOperation, Text } from '@blocksuite/store';
+
+export const getSingleDocIdFromText = (text?: Text) => {
+  const deltas = text?.deltas$.value;
+  if (!deltas) return;
+  let linkedDocId: string | undefined = undefined;
+  for (const delta of deltas) {
+    if (isLinkedDoc(delta)) {
+      if (linkedDocId) {
+        return;
+      }
+      linkedDocId = delta.attributes?.reference?.pageId as string;
+    } else if (delta.insert) {
+      return;
+    }
+  }
+  return linkedDocId;
+};
+
+export const isLinkedDoc = (delta: DeltaOperation) => {
+  const attributes: AffineTextAttributes | undefined = delta.attributes;
+  return attributes?.reference?.type === 'LinkedPage';
+};
+
+export const isPureText = (text?: Text): boolean => {
+  const deltas = text?.deltas$.value;
+  if (!deltas) return true;
+  return deltas.every(v => !isLinkedDoc(v));
+};