Initial support for edited messages (receive only)

5 files changed, 180 insertions, 26 deletions

diff --git a/lib/events/roomevent.cpp b/lib/events/roomevent.cpp
index f1e563ff..0143826a 100644
--- a/lib/events/roomevent.cpp
+++ b/lib/events/roomevent.cpp
@@ -66,6 +66,20 @@ QString RoomEvent::senderId() const
     return fullJson()["sender"_ls].toString();
 }
 
+bool RoomEvent::isReplaced() const
+{
+    return unsignedJson()["m.relations"_ls].toObject().contains("m.replace");
+}
+
+QString RoomEvent::replacedBy() const
+{
+    // clang-format off
+    return unsignedJson()["m.relations"_ls].toObject()
+            .value("m.replace").toObject()
+            .value(EventIdKeyL).toString();
+    // clang-format on
+}
+
 QString RoomEvent::redactionReason() const
 {
     return isRedacted() ? _redactedBecause->reason() : QString{};
diff --git a/lib/events/roomevent.h b/lib/events/roomevent.h
index e26a7135..0e6f730d 100644
--- a/lib/events/roomevent.h
+++ b/lib/events/roomevent.h
@@ -51,6 +51,8 @@ namespace QMatrixClient
             QDateTime timestamp() const;
             QString roomId() const;
             QString senderId() const;
+            bool isReplaced() const;
+            QString replacedBy() const;
             bool isRedacted() const { return bool(_redactedBecause); }
             const event_ptr_tt<RedactionEvent>& redactedBecause() const
             {
diff --git a/lib/events/roommessageevent.cpp b/lib/events/roommessageevent.cpp
index 8f4e0ebc..d4b0d812 100644
--- a/lib/events/roommessageevent.cpp
+++ b/lib/events/roommessageevent.cpp
@@ -36,6 +36,7 @@ static const auto BodyKey = "body"_ls;
 static const auto FormattedBodyKey = "formatted_body"_ls;
 
 static const auto TextTypeKey = "m.text";
+static const auto EmoteTypeKey = "m.emote";
 static const auto NoticeTypeKey = "m.notice";
 
 static const auto HtmlContentTypeId = QStringLiteral("org.matrix.custom.html");
@@ -62,7 +63,7 @@ struct MsgTypeDesc
 
 const std::vector<MsgTypeDesc> msgTypes =
     { { TextTypeKey, MsgType::Text, make<TextContent> }
-    , { QStringLiteral("m.emote"), MsgType::Emote, make<TextContent> }
+    , { EmoteTypeKey, MsgType::Emote, make<TextContent> }
     , { NoticeTypeKey, MsgType::Notice, make<TextContent> }
     , { QStringLiteral("m.image"), MsgType::Image, make<ImageContent> }
     , { QStringLiteral("m.file"), MsgType::File, make<FileContent> }
@@ -95,12 +96,25 @@ QJsonObject RoomMessageEvent::assembleContentJson(const QString& plainBody,
                 const QString& jsonMsgType, TypedBase* content)
 {
     auto json = content ? content->toJson() : QJsonObject();
-    if (jsonMsgType != TextTypeKey && jsonMsgType != NoticeTypeKey &&
-            json.contains(RelatesToKey))
-    {
-        json.remove(RelatesToKey);
-        qCWarning(EVENTS) << RelatesToKey << "cannot be used in" << jsonMsgType
-                          << "messages; the relation has been stripped off";
+    if (json.contains(RelatesToKey)) {
+        if (jsonMsgType != TextTypeKey && jsonMsgType != NoticeTypeKey
+            && jsonMsgType != EmoteTypeKey) {
+            json.remove(RelatesToKey);
+            qCWarning(EVENTS)
+                << RelatesToKey << "cannot be used in" << jsonMsgType
+                << "messages; the relation has been stripped off";
+        } else {
+            // After the above, we know for sure that the content is TextContent
+            // and that its RelatesTo structure is not omitted
+            auto* textContent = static_cast<const TextContent*>(content);
+            if (textContent->relatesTo->type == RelatesTo::ReplacementTypeId()) {
+                auto newContentJson = json.take("m.new_content"_ls).toObject();
+                newContentJson.insert(BodyKey, plainBody);
+                newContentJson.insert(TypeKey, jsonMsgType);
+                json.insert(QStringLiteral("m.new_content"), newContentJson);
+                json[BodyKey] = "* " + plainBody;
+            }
+        }
     }
     json.insert(QStringLiteral("msgtype"), jsonMsgType);
     json.insert(QStringLiteral("body"), plainBody);
@@ -223,6 +237,16 @@ bool RoomMessageEvent::hasThumbnail() const
     return content() && content()->thumbnailInfo();
 }
 
+QString RoomMessageEvent::replacedEvent() const
+{
+    if (!content() || !hasTextContent())
+        return {};
+
+    const auto& rel = static_cast<const TextContent*>(content())->relatesTo;
+    return !rel.omitted() && rel->type == RelatesTo::ReplacementTypeId()
+               ? rel->eventId : QString();
+}
+
 QString rawMsgTypeForMimeType(const QMimeType& mimeType)
 {
     auto name = mimeType.name();
@@ -251,41 +275,72 @@ TextContent::TextContent(const QString& text, const QString& contentType,
         mimeType = QMimeDatabase().mimeTypeForName("text/html");
 }
 
+namespace QMatrixClient
+{
+// Overload the default fromJson<> logic that defined in converters.h
+// as we want
+template <>
+Omittable<RelatesTo> fromJson(const QJsonValue& jv)
+{
+    const auto jo = jv.toObject();
+    if (jo.isEmpty())
+        return none;
+    const auto replyJson = jo.value(RelatesTo::ReplyTypeId()).toObject();
+    if (!replyJson.isEmpty())
+        return replyTo(fromJson<QString>(replyJson[EventIdKeyL]));
+
+    return RelatesTo { jo.value("rel_type"_ls).toString(),
+                       jo.value(EventIdKeyL).toString() };
+}
+}
+
 TextContent::TextContent(const QJsonObject& json)
+    : relatesTo(fromJson<Omittable<RelatesTo>>(json[RelatesToKey]))
 {
     QMimeDatabase db;
     static const auto PlainTextMimeType = db.mimeTypeForName("text/plain");
     static const auto HtmlMimeType = db.mimeTypeForName("text/html");
 
+    const auto actualJson =
+        relatesTo.omitted() || relatesTo->type != RelatesTo::ReplacementTypeId()
+        ? json : json.value("m.new_content"_ls).toObject();
     // Special-casing the custom matrix.org's (actually, Riot's) way
     // of sending HTML messages.
-    if (json["format"_ls].toString() == HtmlContentTypeId)
+    if (actualJson["format"_ls].toString() == HtmlContentTypeId)
     {
         mimeType = HtmlMimeType;
-        body = json[FormattedBodyKey].toString();
+        body = actualJson[FormattedBodyKey].toString();
     } else {
         // Falling back to plain text, as there's no standard way to describe
         // rich text in messages.
         mimeType = PlainTextMimeType;
-        body = json[BodyKey].toString();
+        body = actualJson[BodyKey].toString();
     }
-    const auto replyJson = json[RelatesToKey].toObject()
-                           .value(RelatesTo::ReplyTypeId()).toObject();
-    if (!replyJson.isEmpty())
-        relatesTo = replyTo(fromJson<QString>(replyJson[EventIdKeyL]));
 }
 
 void TextContent::fillJson(QJsonObject* json) const
 {
+    static const auto FormatKey = QStringLiteral("format");
+    static const auto RichBodyKey = QStringLiteral("formatted_body");
+
     Q_ASSERT(json);
     if (mimeType.inherits("text/html"))
     {
-        json->insert(QStringLiteral("format"), HtmlContentTypeId);
-        json->insert(QStringLiteral("formatted_body"), body);
+        json->insert(FormatKey, HtmlContentTypeId);
+        json->insert(RichBodyKey, body);
     }
-    if (!relatesTo.omitted())
+    if (!relatesTo.omitted()) {
         json->insert(QStringLiteral("m.relates_to"),
-            QJsonObject { { relatesTo->type, relatesTo->eventId } });
+                     QJsonObject { { relatesTo->type, relatesTo->eventId } });
+        if (relatesTo->type == RelatesTo::ReplacementTypeId()) {
+            QJsonObject newContentJson;
+            if (mimeType.inherits("text/html")) {
+                json->insert(FormatKey, HtmlContentTypeId);
+                json->insert(RichBodyKey, body);
+            }
+            json->insert(QStringLiteral("m.new_content"), newContentJson);
+        }
+    }
 }
 
 LocationContent::LocationContent(const QString& geoUri,
diff --git a/lib/events/roommessageevent.h b/lib/events/roommessageevent.h
index c2e075eb..7320e4ea 100644
--- a/lib/events/roommessageevent.h
+++ b/lib/events/roommessageevent.h
@@ -72,6 +72,7 @@ namespace QMatrixClient
             bool hasTextContent() const;
             bool hasFileContent() const;
             bool hasThumbnail() const;
+            QString replacedEvent() const;
 
             static QString rawMsgTypeForUrl(const QUrl& url);
             static QString rawMsgTypeForFile(const QFileInfo& fi);
@@ -79,6 +80,7 @@ namespace QMatrixClient
         private:
             QScopedPointer<EventContent::TypedBase> _content;
 
+            // FIXME: should it really be static?
             static QJsonObject assembleContentJson(const QString& plainBody,
                 const QString& jsonMsgType, EventContent::TypedBase* content);
 
@@ -95,6 +97,7 @@ namespace QMatrixClient
         struct RelatesTo
         {
             static constexpr const char* ReplyTypeId() { return "m.in_reply_to"; }
+            static constexpr const char* ReplacementTypeId() { return "m.replace"; }
             QString type; // The only supported relation so far
             QString eventId;
         };
diff --git a/lib/room.cpp b/lib/room.cpp
index cb368d9e..958991b7 100644
--- a/lib/room.cpp
+++ b/lib/room.cpp
@@ -307,14 +307,22 @@ class Room::Private
             return requestSetState(EvT(std::forward<ArgTs>(args)...));
         }
 
-  /**
-         * @brief Apply redaction to the timeline
+        /*! Apply redaction to the timeline
          *
          * Tries to find an event in the timeline and redact it; deletes the
          * redaction event whether the redacted event was found or not.
+         * \return true if the event has been found and redacted; false otherwise
          */
         bool processRedaction(const RedactionEvent& redaction);
 
+        /*! Apply a new revision of the event to the timeline
+         *
+         * Tries to find an event in the timeline and replace it with the new
+         * content passed in \p newMessage.
+         * \return true if the event has been found and replaced; false otherwise
+         */
+        bool processReplacement(const RoomMessageEvent& newMessage);
+
         void setTags(TagsMap newTags);
 
         QJsonObject toJson() const;
@@ -2041,6 +2049,52 @@ bool Room::Private::processRedaction(const RedactionEvent& redaction)
     return true;
 }
 
+/** Make a replaced event
+ *
+ * Takes \p target and returns a copy of it with content taken from
+ * \p replacement. Disposal of the original event after that is on the caller.
+ */
+RoomEventPtr makeReplaced(const RoomEvent& target,
+                          const RoomMessageEvent& replacement)
+{
+    auto originalJson = target.originalJsonObject();
+    originalJson[ContentKeyL] = replacement.contentJson();
+
+    auto unsignedData = originalJson.take(UnsignedKeyL).toObject();
+    auto relations = unsignedData.take("m.relations"_ls).toObject();
+    relations["m.replace"_ls] = replacement.id();
+    unsignedData.insert(QStringLiteral("m.relations"), relations);
+    originalJson.insert(UnsignedKey, unsignedData);
+
+    return loadEvent<RoomEvent>(originalJson);
+}
+
+bool Room::Private::processReplacement(const RoomMessageEvent& newEvent)
+{
+    // Can't use findInTimeline because it returns a const iterator, and
+    // we need to change the underlying TimelineItem.
+    const auto pIdx = eventsIndex.find(newEvent.replacedEvent());
+    if (pIdx == eventsIndex.end())
+        return false;
+
+    Q_ASSERT(q->isValidIndex(*pIdx));
+
+    auto& ti = timeline[Timeline::size_type(*pIdx - q->minTimelineIndex())];
+    if (ti->replacedBy() == newEvent.id())
+    {
+        qCDebug(MAIN) << "Event" << ti->id() << "is already replaced with"
+                      << newEvent.id();
+        return true;
+    }
+
+    // Make a new event from the redacted JSON and put it in the timeline
+    // instead of the redacted one. oldEvent will be deleted on return.
+    auto oldEvent = ti.replaceEvent(makeReplaced(*ti, newEvent));
+    qCDebug(MAIN) << "Replaced" << oldEvent->id() << "with" << newEvent.id();
+    emit q->replacedEvent(ti.event(), rawPtr(oldEvent));
+    return true;
+}
+
 Connection* Room::connection() const
 {
     Q_ASSERT(d->connection);
@@ -2052,10 +2106,16 @@ User* Room::localUser() const
     return connection()->user();
 }
 
-inline bool isRedaction(const RoomEventPtr& ep)
+/// Whether the event is a redaction or a replacement
+inline bool isEditing(const RoomEventPtr& ep)
 {
     Q_ASSERT(ep);
-    return is<RedactionEvent>(*ep);
+    if (is<RedactionEvent>(*ep))
+        return true;
+    if (auto* msgEvent = eventCast<RoomMessageEvent>(ep))
+        return msgEvent->replacedEvent().isEmpty();
+
+    return false;
 }
 
 Room::Changes Room::Private::addNewMessageEvents(RoomEvents&& events)
@@ -2067,18 +2127,19 @@ Room::Changes Room::Private::addNewMessageEvents(RoomEvents&& events)
     // Pre-process redactions so that events that get redacted in the same
     // batch landed in the timeline already redacted.
     // NB: We have to store redaction events to the timeline too - see #220.
-    auto redactionIt = std::find_if(events.begin(), events.end(), isRedaction);
-    for(const auto& eptr: RoomEventsRange(redactionIt, events.end()))
+    auto it = std::find_if(events.begin(), events.end(), isEditing);
+    for(const auto& eptr: RoomEventsRange(it, events.end()))
+    {
         if (auto* r = eventCast<RedactionEvent>(eptr))
         {
             // Try to find the target in the timeline, then in the batch.
             if (processRedaction(*r))
                 continue;
-            auto targetIt = std::find_if(events.begin(), redactionIt,
+            auto targetIt = std::find_if(events.begin(), it,
                 [id=r->redactedEvent()] (const RoomEventPtr& ep) {
                     return ep->id() == id;
                 });
-            if (targetIt != redactionIt)
+            if (targetIt != it)
                 *targetIt = makeRedacted(**targetIt, *r);
             else
                 qCDebug(MAIN) << "Redaction" << r->id()
@@ -2086,6 +2147,25 @@ Room::Changes Room::Private::addNewMessageEvents(RoomEvents&& events)
                               << "is not found";
             // If the target event comes later, it comes already redacted.
         }
+        if (auto* msg = eventCast<RoomMessageEvent>(eptr)) {
+            if (!msg->replacedEvent().isEmpty()) {
+                if (processReplacement(*msg))
+                    continue;
+                auto targetIt = std::find_if(events.begin(), it,
+                    [id=msg->replacedEvent()] (const RoomEventPtr& ep) {
+                        return ep->id() == id;
+                    });
+                if (targetIt != it)
+                    *targetIt = makeReplaced(**targetIt, *msg);
+                else // FIXME: don't ignore, just show it wherever it arrived
+                    qCDebug(MAIN) << "Replacing event" << msg->id()
+                                  << "ignored: replaced event" << msg->replacedEvent()
+                                  << "is not found";
+                // Same as with redactions above, the replaced event coming
+                // later will come already with the new content.
+            }
+        }
+    }
 
     // State changes arrive as a part of timeline; the current room state gets
     // updated before merging events to the timeline because that's what