Rework sending server protocol messages.

- Replace CmdBuilder with MessageBuilder. This has a less footgun
  API. All message building has to go through this now so we can
  implement other message formats in the future.

- Replace the message parsing in WriteLine with an analogue to
  PreProcessOldProtocolMessage. This should be much faster.

- Move parameter translation from the core to spanningtree.

- Change EncodeParameter to return the value instead of updating
  in place.

- Replace the OnBuild*Message events with one OnServerMessage that
  can now access all parts of the message and change them.

1 files changed, 114 insertions, 0 deletions

diff --git a/modules/spanningtree/msgbuilder.cpp b/modules/spanningtree/msgbuilder.cpp
new file mode 100644
index 000000000..4b7b73301
--- /dev/null
+++ b/modules/spanningtree/msgbuilder.cpp
@@ -0,0 +1,114 @@
+/*
+ * InspIRCd -- Internet Relay Chat Daemon
+ *
+ *   Copyright (C) 2026 Sadie Powell <sadie@witchery.services>
+ *
+ * This file is part of InspIRCd.  InspIRCd is free software: you can
+ * redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation, version 2.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <sstream>
+
+#include "main.h"
+#include "msgbuilder.h"
+
+void MessageBuilder::Broadcast(const TreeServer* omit)
+{
+	for (const auto* server : Utils->TreeRoot->GetChildren())
+	{
+		if (!omit || omit != server)
+			Unicast(server->GetSocket());
+	}
+}
+
+MessageBuilder& MessageBuilder::PushParams(const CommandBase::Params& newparams)
+{
+	for (const auto& param : newparams)
+		Push(param);
+	PushTags(newparams.GetTags());
+	return *this;
+}
+
+MessageBuilder& MessageBuilder::PushTags(ClientProtocol::TagMap newtags)
+{
+	auto& oldtags = this->parameters.GetTags();
+	newtags.insert(oldtags.begin(), oldtags.end());
+	std::swap(oldtags, newtags);
+	return *this;
+}
+
+void MessageBuilder::Finalize()
+{
+	if (!Utils || this->finalized)
+		return; // Should never happen
+
+	Utils->Creator->messageeventprov.Call(&ServerProtocol::MessageEventListener::OnServerMessage,
+		this->source, this->command, this->parameters);
+
+	finalized = true;
+}
+
+std::string MessageBuilder::ToRFC1459() const
+{
+	std::stringstream buffer;
+
+	const auto& tags = this->parameters.GetTags();
+	if (!tags.empty())
+	{
+		auto separator = '@';
+		for (const auto &[tname, tinfo] : tags)
+		{
+			buffer << separator << tname;
+			if (!tinfo.value.empty())
+				buffer << '=' << tinfo.value;
+			separator = ';';
+		}
+		if (separator != '@')
+			buffer << ' ';
+	}
+
+	if (this->source)
+		buffer << ':' << source->uuid << ' ';
+
+	buffer << command;
+	if (!this->parameters.empty())
+	{
+		buffer << ' ';
+		for (auto it = this->parameters.begin(); it != this->parameters.end() - 1; ++it)
+			buffer << *it << ' ';
+
+		const auto &last = this->parameters.back();
+		if (last.empty() || last[0] == ':' || last.find(' ') != std::string::npos)
+			buffer << ':';
+		buffer << last;
+	}
+
+	return buffer.str();
+}
+
+void MessageBuilder::Unicast(TreeServer* server)
+{
+	if (server->GetSocket())
+		Unicast(server->GetSocket());
+}
+
+void MessageBuilder::Unicast(TreeSocket* socket)
+{
+	this->Finalize();
+	socket->SendMessage(*this);
+}
+
+void MessageBuilder::Unicast(const User* user)
+{
+	if (user->server)
+		Unicast(static_cast<TreeServer*>(user->server));
+}