From ba8a3b236a84d42c888a93e4e8cf934062c7a7ea Mon Sep 17 00:00:00 2001
From: Peter Powell <petpow@saberuk.com>
Date: Wed, 15 May 2019 10:33:42 +0100
Subject: Add support for the IRCv3 message id specification.

---
 docs/conf/modules.conf.example |   7 +++
 src/modules/m_ircv3_msgid.cpp  | 121 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 128 insertions(+)
 create mode 100644 src/modules/m_ircv3_msgid.cpp

diff --git a/docs/conf/modules.conf.example b/docs/conf/modules.conf.example
index 8dcdd7d3d..bb8a74dbc 100644
--- a/docs/conf/modules.conf.example
+++ b/docs/conf/modules.conf.example
@@ -1167,6 +1167,13 @@
 # another user into a channel. This respects <options:announceinvites>.
 #<module name="ircv3_invitenotify">
 
+#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#
+# IRCv3 message id module: Provides the msgid IRCv3 extension which
+# adds a unique identifier to each message when the message-tags cap
+# has been requested. This enables support for modern features such as
+# reactions and replies.
+#<module name="ircv3_msgid">
+
 #-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#
 # IRCv3 server-time module. Adds the 'time' tag which adds a timestamp
 # to all messages received from the server.
diff --git a/src/modules/m_ircv3_msgid.cpp b/src/modules/m_ircv3_msgid.cpp
new file mode 100644
index 000000000..4d34455b9
--- /dev/null
+++ b/src/modules/m_ircv3_msgid.cpp
@@ -0,0 +1,121 @@
+/*
+ * InspIRCd -- Internet Relay Chat Daemon
+ *
+ *   Copyright (C) 2019 Peter Powell <petpow@saberuk.com>
+ *   Copyright (C) 2016 Attila Molnar <attilamolnar@hush.com>
+ *
+ * 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/cap.h"
+#include "modules/ctctags.h"
+
+class MsgIdTag : public ClientProtocol::MessageTagProvider
+{
+ private:
+	Cap::Reference ctctagcap;
+
+ public:
+	MsgIdTag(Module* mod)
+		: ClientProtocol::MessageTagProvider(mod)
+		, ctctagcap(mod, "message-tags")
+	{
+	}
+
+	ModResult OnProcessTag(User* user, const std::string& tagname, std::string& tagvalue) CXX11_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;
+	}
+
+	bool ShouldSendTag(LocalUser* user, const ClientProtocol::MessageTagData& tagdata) CXX11_OVERRIDE
+	{
+		return ctctagcap.get(user);
+	}
+};
+
+class MsgIdGenerator
+{
+	uint64_t counter;
+	std::string strid;
+	const std::string::size_type baselen;
+
+ public:
+	MsgIdGenerator()
+		: counter(0)
+		, strid(InspIRCd::Format("%s~%lu~", ServerInstance->Config->GetSID().c_str(), ServerInstance->startup_time))
+		, baselen(strid.length())
+	{
+	}
+
+	const std::string& GetNext()
+	{
+		strid.erase(baselen);
+		strid.append(ConvToStr(counter++));
+		return strid;
+	}
+};
+
+class ModuleMsgId
+	: 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.insert(std::make_pair("msgid", ClientProtocol::MessageTagData(&tag, generator.GetNext())));
+		return MOD_RES_PASSTHRU;
+	}
+
+ public:
+	ModuleMsgId()
+		: CTCTags::EventListener(this)
+		, tag(this)
+	{
+	}
+
+	ModResult OnUserPreMessage(User* user, const MessageTarget& target, MessageDetails& details) CXX11_OVERRIDE
+	{
+		return CopyMessageId(details.tags_in, details.tags_out);
+	}
+
+	ModResult OnUserPreTagMessage(User* user, const MessageTarget& target, CTCTags::TagMessageDetails& details) CXX11_OVERRIDE
+	{
+		return CopyMessageId(details.tags_in, details.tags_out);
+	}
+
+	Version GetVersion() CXX11_OVERRIDE
+	{
+		return Version("Provides the msgid IRCv3 tag", VF_VENDOR);
+	}
+};
+
+MODULE_INIT(ModuleMsgId)
-- 
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