Add plaintext hash to existing message attachments

ts/util/attachments/migrateDataToFilesystem.ts

@@ -0,0 +1,46 @@
+// Copyright 2023 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { isFunction, isTypedArray, isUndefined, omit } from 'lodash';
+import type { AttachmentType } from '../../types/Attachment';
+import type { LoggerType } from '../../types/Logging';
+import { getPlaintextHashForInMemoryAttachment } from '../../AttachmentCrypto';
+
+export async function migrateDataToFileSystem(
+  attachment: AttachmentType,
+  {
+    writeNewAttachmentData,
+    logger,
+  }: {
+    writeNewAttachmentData: (data: Uint8Array) => Promise<string>;
+    logger: LoggerType;
+  }
+): Promise<AttachmentType> {
+  if (!isFunction(writeNewAttachmentData)) {
+    throw new TypeError("'writeNewAttachmentData' must be a function");
+  }
+
+  const { data } = attachment;
+  const attachmentHasData = !isUndefined(data);
+  const shouldSkipSchemaUpgrade = !attachmentHasData;
+
+  if (shouldSkipSchemaUpgrade) {
+    return attachment;
+  }
+
+  // This attachment was already broken by a roundtrip to the database - repair it now
+  if (!isTypedArray(data)) {
+    logger.warn(
+      'migrateDataToFileSystem: Attachment had non-array `data` field; deleting.'
+    );
+    return omit({ ...attachment }, ['data']);
+  }
+
+  const plaintextHash = getPlaintextHashForInMemoryAttachment(data);
+  const path = await writeNewAttachmentData(data);
+
+  const attachmentWithoutData = omit({ ...attachment, path, plaintextHash }, [
+    'data',
+  ]);
+  return attachmentWithoutData;
+}