From ca28bd01af7a1a3321c6770a070f9ff4b093dd10 Mon Sep 17 00:00:00 2001
From: Thomas SharedInbox <sharedinbox@thomas-guettler.de>
Date: Thu, 14 May 2026 19:44:09 +0200
Subject: [PATCH] fix(imap): fetch full message for attachment download to fix
 base64 decoding
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

A partial BODY.PEEK[n] fetch omits the section's MIME headers, so
enough_mail's decodeContentBinary() has no Content-Transfer-Encoding
and returns the raw base64 string instead of the decoded bytes.
Fetching BODY.PEEK[] gives enough_mail the full MIME structure and
getPart(fetchPartId) correctly decodes the attachment.

Also adds an integration test that creates an email with a binary
attachment, syncs it, and asserts the downloaded bytes match the
original — this test failed before the fix.

Closes #70

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 .../repositories/email_repository_impl.dart   |  6 +-
 .../email_repository_imap_test.dart           | 57 +++++++++++++++++++
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/lib/data/repositories/email_repository_impl.dart b/lib/data/repositories/email_repository_impl.dart
index 09b6ed1..3bb546e 100644
--- a/lib/data/repositories/email_repository_impl.dart
+++ b/lib/data/repositories/email_repository_impl.dart
@@ -2509,9 +2509,13 @@ class EmailRepositoryImpl implements EmailRepository {
     );
     try {
       await client.selectMailboxByPath(emailRow.mailboxPath);
+      // Fetch the full message so enough_mail has MIME headers (including
+      // Content-Transfer-Encoding) and getPart() can decode the part correctly.
+      // A partial BODY.PEEK[n] fetch omits those headers, causing
+      // decodeContentBinary() to return raw base64 instead of decoded bytes.
       final fetch = await client.uidFetchMessage(
         emailRow.uid,
-        'BODY.PEEK[${attachment.fetchPartId}]',
+        'BODY.PEEK[]',
       );
       final msg = fetch.messages.first;
       final part = msg.getPart(attachment.fetchPartId) ?? msg;
diff --git a/test/integration/email_repository_imap_test.dart b/test/integration/email_repository_imap_test.dart
index c2b3f96..c83421b 100644
--- a/test/integration/email_repository_imap_test.dart
+++ b/test/integration/email_repository_imap_test.dart
@@ -8,6 +8,7 @@
 
 import 'dart:convert';
 import 'dart:io';
+import 'dart:typed_data';
 
 import 'package:drift/drift.dart' show Value;
 import 'package:enough_mail/enough_mail.dart';
@@ -564,4 +565,60 @@ void main() {
     expect(pending, hasLength(1));
     expect(pending.first.changeType, 'delete');
   });
+
+  test('downloadAttachment fetches binary attachment bytes from IMAP',
+      () async {
+    final attachmentBytes = Uint8List.fromList(
+      List.generate(32, (i) => i + 1),
+    );
+    const attachmentName = 'hello.bin';
+    const attachmentMime = 'application/octet-stream';
+
+    // Build a multipart email with a binary attachment and append it.
+    final client = await _imapConnect(
+      host: imapHost,
+      port: imapPort,
+      user: userEmail,
+      pass: userPass,
+    );
+    try {
+      final builder = MessageBuilder()
+        ..from = [MailAddress('Alice', userEmail)]
+        ..to = [MailAddress('Alice', userEmail)]
+        ..subject = 'attach-${DateTime.now().millisecondsSinceEpoch}'
+        ..text = 'See attachment.';
+      builder.addBinary(
+        attachmentBytes,
+        MediaType.fromText(attachmentMime),
+        filename: attachmentName,
+      );
+      await client.appendMessage(
+        builder.buildMimeMessage(),
+        targetMailboxPath: 'INBOX',
+      );
+    } finally {
+      await client.logout();
+    }
+
+    final r = makeRepo();
+    await r.accounts.addAccount(account, userPass);
+    await r.emails.syncEmails('test', 'INBOX');
+
+    final emails = await r.emails.observeEmails('test', 'INBOX').first;
+    expect(emails, hasLength(1));
+    expect(emails.first.hasAttachment, isTrue);
+
+    final body = await r.emails.getEmailBody(emails.first.id);
+    expect(body.attachments, hasLength(1));
+    expect(body.attachments.first.filename, attachmentName);
+    expect(body.attachments.first.contentType, attachmentMime);
+    expect(body.attachments.first.fetchPartId, isNotEmpty);
+
+    final path = await r.emails.downloadAttachment(
+      emails.first.id,
+      body.attachments.first,
+    );
+    final downloaded = await File(path).readAsBytes();
+    expect(downloaded, equals(attachmentBytes));
+  });
 }