Add `Attachment.migrateDataToFileSystem`

js/modules/types/attachment.js

@@ -3,6 +3,7 @@ const isString = require('lodash/isString');
 const MIME = require('./mime');
 const { arrayBufferToBlob, blobToArrayBuffer, dataURLToBlob } = require('blob-util');
 const { autoOrientImage } = require('../auto_orient_image');
+const { migrateDataToFileSystem } = require('./attachment/migrate_data_to_file_system');
 
 // // Incoming message attachment fields
 // {
@@ -107,3 +108,5 @@ exports.removeSchemaVersion = (attachment) => {
   delete attachmentWithoutSchemaVersion.schemaVersion;
   return attachmentWithoutSchemaVersion;
 };
+
+exports.migrateDataToFileSystem = migrateDataToFileSystem;

js/modules/types/attachment/migrate_data_to_file_system.js

@@ -0,0 +1,37 @@
+const isArrayBuffer = require('lodash/isArrayBuffer');
+const isFunction = require('lodash/isFunction');
+const isUndefined = require('lodash/isUndefined');
+
+
+// type Context :: {
+//   writeAttachmentData :: ArrayBuffer -> Promise (IO Path)
+// }
+//
+//      migrateDataToFileSystem :: Attachment ->
+//                                 Context ->
+//                                 Promise Attachment
+exports.migrateDataToFileSystem = async (attachment, { writeAttachmentData } = {}) => {
+  if (!isFunction(writeAttachmentData)) {
+    throw new TypeError('`writeAttachmentData` must be a function');
+  }
+
+  const { data } = attachment;
+  const hasData = !isUndefined(data);
+  const shouldSkipSchemaUpgrade = !hasData;
+  if (shouldSkipSchemaUpgrade) {
+    console.log('WARNING: `attachment.data` is `undefined`');
+    return attachment;
+  }
+
+  const isValidData = isArrayBuffer(data);
+  if (!isValidData) {
+    throw new TypeError('Expected `attachment.data` to be an array buffer;' +
+      ` got: ${typeof attachment.data}`);
+  }
+
+  const path = await writeAttachmentData(data);
+
+  const attachmentWithoutData = Object.assign({}, attachment, { path });
+  delete attachmentWithoutData.data;
+  return attachmentWithoutData;
+};

test/modules/types/attachment_test.js

@@ -1,5 +1,6 @@
 require('mocha-testcheck').install();
 
+const stringToArrayBuffer = require('string-to-arraybuffer');
 const { assert } = require('chai');
 
 const Attachment = require('../../../js/modules/types/attachment');
@@ -101,4 +102,81 @@ describe('Attachment', () => {
       assert.deepEqual(actual, expected);
     });
   });
+
+  describe('migrateDataToFileSystem', () => {
+    it('should write data to disk and store relative path to it', async () => {
+      const input = {
+        contentType: 'image/jpeg',
+        data: stringToArrayBuffer('Above us only sky'),
+        fileName: 'foo.jpg',
+        size: 1111,
+      };
+
+      const expected = {
+        contentType: 'image/jpeg',
+        path: 'abc/abcdefgh123456789',
+        fileName: 'foo.jpg',
+        size: 1111,
+      };
+
+      const expectedAttachmentData = stringToArrayBuffer('Above us only sky');
+      const writeAttachmentData = async (attachmentData) => {
+        assert.deepEqual(attachmentData, expectedAttachmentData);
+        return 'abc/abcdefgh123456789';
+      };
+
+      const actual = await Attachment.migrateDataToFileSystem(
+        input,
+        { writeAttachmentData }
+      );
+      assert.deepEqual(actual, expected);
+    });
+
+    it('should skip over (invalid) attachments without data', async () => {
+      const input = {
+        contentType: 'image/jpeg',
+        fileName: 'foo.jpg',
+        size: 1111,
+      };
+
+      const expected = {
+        contentType: 'image/jpeg',
+        fileName: 'foo.jpg',
+        size: 1111,
+      };
+
+      const writeAttachmentData = async () =>
+        'abc/abcdefgh123456789';
+
+      const actual = await Attachment.migrateDataToFileSystem(
+        input,
+        { writeAttachmentData }
+      );
+      assert.deepEqual(actual, expected);
+    });
+
+    it('should throw error if data is not valid', async () => {
+      const input = {
+        contentType: 'image/jpeg',
+        data: 42,
+        fileName: 'foo.jpg',
+        size: 1111,
+      };
+
+      const writeAttachmentData = async () =>
+        'abc/abcdefgh123456789';
+
+      try {
+        await Attachment.migrateDataToFileSystem(input, { writeAttachmentData });
+      } catch (error) {
+        assert.strictEqual(
+          error.message,
+          'Expected `attachment.data` to be an array buffer; got: number'
+        );
+        return;
+      }
+
+      assert.fail('Unreachable');
+    });
+  });
 });