refactor: simplify uses of getMessageSnapshot (#6607)

Reviewed-by: pajlada <rasmus.karlsson@pajlada.com>

src/common/Channel.cpp

@@ -81,6 +81,16 @@ std::vector<MessagePtr> Channel::getMessageSnapshot(size_t nItems) const
     return this->messages_.lastN(nItems);
 }
 
+MessagePtr Channel::getLastMessage() const
+{
+    auto last = this->messages_.last();
+    if (last)
+    {
+        return *std::move(last);
+    }
+    return nullptr;
+}
+
 void Channel::addMessage(MessagePtr message, MessageContext context,
                          std::optional<MessageFlags> overridingFlags)
 {
@@ -146,19 +156,15 @@ void Channel::addOrReplaceClearChat(MessagePtr message, const QDateTime &now)
 
 void Channel::disableAllMessages()
 {
-    std::vector<MessagePtr> snapshot = this->getMessageSnapshot();
-    int snapshotLength = snapshot.size();
-    for (int i = 0; i < snapshotLength; i++)
+    for (const auto &message : this->getMessageSnapshot())
     {
-        const auto &message = snapshot[i];
         if (message->flags.hasAny({MessageFlag::System, MessageFlag::Timeout,
                                    MessageFlag::Whisper}))
         {
             continue;
         }
 
-        // FOURTF: disabled for now
-        const_cast<Message *>(message.get())->flags.set(MessageFlag::Disabled);
+        message->flags.set(MessageFlag::Disabled);
     }
 }
 

src/common/Channel.hpp

@@ -79,9 +79,14 @@ public:
     virtual const QString &getLocalizedName() const;
     bool isTwitchChannel() const;
     virtual bool isEmpty() const;
+
     std::vector<MessagePtr> getMessageSnapshot() const;
     std::vector<MessagePtr> getMessageSnapshot(size_t nItems) const;
 
+    /// Returns the last message (the one at the bottom). If the channel has no
+    /// messages, this will return an empty shared pointer.
+    MessagePtr getLastMessage() const;
+
     // MESSAGES
     // overridingFlags can be filled in with flags that should be used instead
     // of the message's flags. This is useful in case a flag is specific to a