Automatic key import / export + Expected monad

Summary:
There are many things going on here (perhaps a bit much for a single patch):

- When an attachment is of mime type "application/pgp-keys", a button is added to import the key to GPG
- When sending a mail and crypto is enabled (encryption, signing or both), the public key of the first private key found is sent as an un-encrypted attachment (T6994)
- The `mailcrypto.{h,cpp}` was, for the most part, rewritten
- Introduction of the expected monad, inspired by what was proposed for C++ [here](https://isocpp.org/files/papers/n4015.pdf), but not at all a strict implementation of this specification. We may want to add some more features of this standard later.

The rationale for some of the choices:

- I found mailcrypto a bit hard to edit to add new features, and a great part was commented code to prepare for the support the SMIME crypto format, which would (in my current knowledge) not be used for sending emails.
- One thing I found that may be missing in the code base was a standardized way of handling errors in C++ code. Since exceptions are disabled I think that the functional way is the way to go. After some research I found the Expected monad / tagged union / sum type, which seemed to suit the problem particularly well.

In the long run, I hope we would move the entire code base to use `Expected` to indicate if a function might fail.

Of course every choice made here is to be considered as a proposition for doing things / RFC, critics wholeheartedly accepted.

Reviewers: cmollekopf

Tags: #kube

Maniphest Tasks: T6994, T8147, T6995

Differential Revision: https://phabricator.kde.org/D11158

1 files changed, 35 insertions, 0 deletions

diff --git a/framework/src/domain/mime/attachmentmodel.cpp b/framework/src/domain/mime/attachmentmodel.cpp
index 2eb2cc13..8b12679b 100644
--- a/framework/src/domain/mime/attachmentmodel.cpp
+++ b/framework/src/domain/mime/attachmentmodel.cpp
@@ -32,6 +32,11 @@
 #include <QUrl>
 #include <QMimeDatabase>
 
+#include <QGpgME/ImportJob>
+#include <QGpgME/Protocol>
+
+#include <memory>
+
 QString sizeHuman(float size)
 {
     QStringList list;
@@ -210,6 +215,36 @@ bool AttachmentModel::openAttachment(const QModelIndex &index)
     return false;
 }
 
+bool AttachmentModel::importPublicKey(const QModelIndex &index)
+{
+    Q_ASSERT(index.internalPointer());
+    const auto part = static_cast<MimeTreeParser::MessagePart *>(index.internalPointer());
+    Q_ASSERT(part);
+    auto pkey = part->node()->decodedContent();
+
+    const auto *proto = QGpgME::openpgp();
+    std::unique_ptr<QGpgME::ImportJob> job(proto->importJob());
+    auto result = job->exec(pkey);
+
+    bool success = true;
+
+    QString message;
+    if(result.numConsidered() == 0) {
+        message = tr("No keys were found in this attachment");
+        success = false;
+    } else {
+        message = tr("%n Key(s) imported", "", result.numImported());
+        if(result.numUnchanged() != 0) {
+            message += "\n" + tr("%n Key(s) were already imported", "", result.numUnchanged());
+        }
+    }
+
+    Kube::Fabric::Fabric{}.postMessage("notification",
+        {{"message", message}});
+
+    return success;
+}
+
 QModelIndex AttachmentModel::parent(const QModelIndex &) const
 {
     return QModelIndex();