1 files changed, 106 insertions, 0 deletions
diff --git a/modules/ircv3_msgid.cpp b/modules/ircv3_msgid.cpp
new file mode 100644
index 000000000..9212941f2
--- /dev/null
+++ b/modules/ircv3_msgid.cpp
@@ -0,0 +1,106 @@
+/*
+ * InspIRCd -- Internet Relay Chat Daemon
+ *
+ *   Copyright (C) 2019-2023 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 "inspircd.h"
+#include "modules/ctctags.h"
+
+class MsgIdTag final
+	: public CTCTags::TagProvider
+{
+public:
+	MsgIdTag(Module* mod)
+		: CTCTags::TagProvider(mod)
+	{
+	}
+
+	ModResult OnProcessTag(User* user, const std::string& tagname, std::string& tagvalue) override
+	{
+		if (!irc::equals(tagname, "msgid"))
+			return MOD_RES_PASSTHRU;
+
+		// We should only allow this tag if it is added by a remote server.
+		return IS_LOCAL(user) ? MOD_RES_DENY : MOD_RES_ALLOW;
+	}
+};
+
+class MsgIdGenerator final
+{
+	uint64_t counter = 0;
+	std::string strid;
+	const std::string::size_type baselen;
+
+public:
+	MsgIdGenerator()
+		: strid(fmt::format("{}~{}~", ServerInstance->Config->ServerId, ServerInstance->startup_time))
+		, baselen(strid.length())
+	{
+	}
+
+	const std::string& GetNext()
+	{
+		strid.erase(baselen);
+		strid.append(ConvToStr(counter++));
+		return strid;
+	}
+};
+
+class ModuleMsgId final
+	: public Module
+	, public CTCTags::EventListener
+{
+private:
+	MsgIdTag tag;
+	MsgIdGenerator generator;
+
+	ModResult CopyMessageId(const ClientProtocol::TagMap& tags_in, ClientProtocol::TagMap& tags_out)
+	{
+		ClientProtocol::TagMap::const_iterator iter = tags_in.find("msgid");
+		if (iter != tags_in.end())
+		{
+			// If the remote server has sent a message identifier we should use that as
+			// identifiers need to be the same on all sides of the network.
+			tags_out.insert(*iter);
+			return MOD_RES_PASSTHRU;
+		}
+
+		// Otherwise, we can just create a new message identifier.
+		tags_out.emplace("msgid", ClientProtocol::MessageTagData(&tag, generator.GetNext()));
+		return MOD_RES_PASSTHRU;
+	}
+
+public:
+	ModuleMsgId()
+		: Module(VF_VENDOR, "Provides support for the IRCv3 Message IDs specification.")
+		, CTCTags::EventListener(this)
+		, tag(this)
+	{
+	}
+
+	ModResult OnUserPreMessage(User* user, MessageTarget& target, MessageDetails& details) override
+	{
+		return CopyMessageId(details.tags_in, details.tags_out);
+	}
+
+	ModResult OnUserPreTagMessage(User* user, MessageTarget& target, CTCTags::TagMessageDetails& details) override
+	{
+		return CopyMessageId(details.tags_in, details.tags_out);
+	}
+};
+
+MODULE_INIT(ModuleMsgId)