refactor(gateway): share rpc attachment normalization

src/gateway/server-methods/attachment-normalize.ts

@@ -0,0 +1,32 @@
+import type { ChatAttachment } from "../chat-attachments.js";
+
+export type RpcAttachmentInput = {
+  type?: unknown;
+  mimeType?: unknown;
+  fileName?: unknown;
+  content?: unknown;
+};
+
+export function normalizeRpcAttachmentsToChatAttachments(
+  attachments: RpcAttachmentInput[] | undefined,
+): ChatAttachment[] {
+  return (
+    attachments
+      ?.map((a) => ({
+        type: typeof a?.type === "string" ? a.type : undefined,
+        mimeType: typeof a?.mimeType === "string" ? a.mimeType : undefined,
+        fileName: typeof a?.fileName === "string" ? a.fileName : undefined,
+        content:
+          typeof a?.content === "string"
+            ? a.content
+            : ArrayBuffer.isView(a?.content)
+              ? Buffer.from(a.content.buffer, a.content.byteOffset, a.content.byteLength).toString(
+                  "base64",
+                )
+              : a?.content instanceof ArrayBuffer
+                ? Buffer.from(a.content).toString("base64")
+                : undefined,
+      }))
+      .filter((a) => a.content) ?? []
+  );
+}