feat(editor): content block getter command (#10720)

### TL;DR
Added new commands to retrieve the first and last content blocks in a document.

### What changed?
- Created `getFirstContentBlockCommand` to find the first content block in a document
- Created `getLastContentBlockCommand` to find the last content block in a document
- Added `getFirstNoteBlock` utility function to find the first note block in a document

blocksuite/affine/shared/src/commands/block-crud/get-first-content-block.ts

@@ -0,0 +1,43 @@
+import type { Command } from '@blocksuite/block-std';
+import type { BlockModel } from '@blocksuite/store';
+
+import { getFirstNoteBlock } from '../../utils';
+
+/**
+ * Get the first content block in the document
+ *
+ * @param ctx - Command context
+ * @param ctx.root - The root note block model
+ * @param next - Next handler function
+ * @returns The first content block model or null
+ */
+export const getFirstContentBlockCommand: Command<
+  {
+    root?: BlockModel;
+  },
+  {
+    firstBlock: BlockModel | null;
+  }
+> = (ctx, next) => {
+  const doc = ctx.std.host.doc;
+  const noteBlock = ctx.root ?? getFirstNoteBlock(doc);
+  if (!noteBlock) {
+    next({
+      firstBlock: null,
+    });
+    return;
+  }
+
+  for (const child of noteBlock.children) {
+    if (child.role === 'content') {
+      next({
+        firstBlock: child,
+      });
+      return;
+    }
+  }
+
+  next({
+    firstBlock: null,
+  });
+};

blocksuite/affine/shared/src/commands/block-crud/get-last-content-block.ts

@@ -0,0 +1,43 @@
+import type { Command } from '@blocksuite/block-std';
+import type { BlockModel } from '@blocksuite/store';
+
+import { getLastNoteBlock } from '../../utils';
+
+/**
+ * Get the last content block in the document
+ *
+ * @param ctx - Command context
+ * @param ctx.root - The root note block model
+ * @param next - Next handler function
+ * @returns The last content block model or null
+ */
+export const getLastContentBlockCommand: Command<
+  {
+    root?: BlockModel;
+  },
+  {
+    lastBlock: BlockModel | null;
+  }
+> = (ctx, next) => {
+  const noteBlock = ctx.root ?? getLastNoteBlock(ctx.std.host.doc);
+  if (!noteBlock) {
+    next({
+      lastBlock: null,
+    });
+    return;
+  }
+
+  const children = noteBlock.children;
+  for (let i = children.length - 1; i >= 0; i--) {
+    if (children[i].role === 'content') {
+      next({
+        lastBlock: children[i],
+      });
+      return;
+    }
+  }
+
+  next({
+    lastBlock: null,
+  });
+};

blocksuite/affine/shared/src/commands/block-crud/index.ts

@@ -1,4 +1,6 @@
 export { getBlockIndexCommand } from './get-block-index.js';
+export { getFirstContentBlockCommand } from './get-first-content-block.js';
+export { getLastContentBlockCommand } from './get-last-content-block.js';
 export { getNextBlockCommand } from './get-next-block.js';
 export { getPrevBlockCommand } from './get-prev-block.js';
 export { getSelectedBlocksCommand } from './get-selected-blocks.js';

blocksuite/affine/shared/src/utils/model/getter.ts

@@ -57,3 +57,19 @@ export function getLastNoteBlock(doc: Store) {
   }
   return note;
 }
+
+export function getFirstNoteBlock(doc: Store) {
+  let note: NoteBlockModel | null = null;
+  if (!doc.root) return null;
+  const { children } = doc.root;
+  for (const child of children) {
+    if (
+      matchModels(child, [NoteBlockModel]) &&
+      child.displayMode !== NoteDisplayMode.EdgelessOnly
+    ) {
+      note = child as NoteBlockModel;
+      break;
+    }
+  }
+  return note;
+}