fix: keep editor selection stable around media blocks

src/components/blockNoteCursorTarget.ts

@@ -0,0 +1,45 @@
+interface CursorTargetBlockLike {
+  id: string
+  content?: unknown
+}
+
+function blockSupportsTextCursor(block: CursorTargetBlockLike | undefined): block is CursorTargetBlockLike {
+  return Array.isArray(block?.content)
+}
+
+export function findNearestTextCursorBlock(
+  blocks: CursorTargetBlockLike[],
+  targetIndex: number,
+): CursorTargetBlockLike | null {
+  if (blocks.length === 0) return null
+
+  const clampedTargetIndex = Math.min(Math.max(targetIndex, 0), blocks.length - 1)
+  const targetBlock = blocks[clampedTargetIndex]
+  if (blockSupportsTextCursor(targetBlock)) {
+    return targetBlock
+  }
+
+  for (let distance = 1; distance < blocks.length; distance += 1) {
+    const forwardBlock = blocks[clampedTargetIndex + distance]
+    if (blockSupportsTextCursor(forwardBlock)) {
+      return forwardBlock
+    }
+
+    const backwardBlock = blocks[clampedTargetIndex - distance]
+    if (blockSupportsTextCursor(backwardBlock)) {
+      return backwardBlock
+    }
+  }
+
+  return null
+}
+
+export function findNearestTextCursorBlockById(
+  blocks: CursorTargetBlockLike[],
+  targetBlockId: string,
+): CursorTargetBlockLike | null {
+  const targetIndex = blocks.findIndex((block) => block.id === targetBlockId)
+  if (targetIndex === -1) return null
+
+  return findNearestTextCursorBlock(blocks, targetIndex)
+}