Rewrite the whole IID usage

IRC users and channels are now distinguished by the separator used in the
IID (% or !).

ref #2468

7 files changed, 253 insertions, 89 deletions

diff --git a/src/bridge/bridge.cpp b/src/bridge/bridge.cpp
index 3377135..6d864c0 100644
--- a/src/bridge/bridge.cpp
+++ b/src/bridge/bridge.cpp
@@ -106,8 +106,8 @@ IrcClient* Bridge::get_irc_client(const std::string& hostname)
 
 bool Bridge::join_irc_channel(const Iid& iid, const std::string& username)
 {
-  IrcClient* irc = this->get_irc_client(iid.server, username);
-  if (iid.chan.empty())
+  IrcClient* irc = this->get_irc_client(iid.get_server(), username);
+  if (iid.get_local().empty())
     { // Join the dummy channel
       if (irc->is_welcomed())
         {
@@ -117,7 +117,7 @@ bool Bridge::join_irc_channel(const Iid& iid, const std::string& username)
           // joined the channel
           const IrcMessage join_message(irc->get_nick(), "JOIN", {""});
           irc->on_channel_join(join_message);
-          const IrcMessage end_join_message(std::string(iid.server), "366",
+          const IrcMessage end_join_message(std::string(iid.get_server()), "366",
                                             {irc->get_nick(),
                                                 "", "End of NAMES list"});
           irc->on_channel_completely_joined(end_join_message);
@@ -129,9 +129,9 @@ bool Bridge::join_irc_channel(const Iid& iid, const std::string& username)
         }
       return true;
     }
-  if (irc->is_channel_joined(iid.chan) == false)
+  if (irc->is_channel_joined(iid.get_local()) == false)
     {
-      irc->send_join_command(iid.chan);
+      irc->send_join_command(iid.get_local());
       return true;
     }
   return false;
@@ -139,15 +139,15 @@ bool Bridge::join_irc_channel(const Iid& iid, const std::string& username)
 
 void Bridge::send_channel_message(const Iid& iid, const std::string& body)
 {
-  if (iid.chan.empty() || iid.server.empty())
+  if (iid.get_local().empty() || iid.get_server().empty())
     {
-      log_warning("Cannot send message to channel: [" << iid.chan << "] on server [" << iid.server << "]");
+      log_warning("Cannot send message to channel: [" << iid.get_local() << "] on server [" << iid.get_server() << "]");
       return;
     }
-  IrcClient* irc = this->get_irc_client(iid.server);
+  IrcClient* irc = this->get_irc_client(iid.get_server());
   if (!irc)
     {
-      log_warning("Cannot send message: no client exist for server " << iid.server);
+      log_warning("Cannot send message: no client exist for server " << iid.get_server());
       return;
     }
   // Because an IRC message cannot contain \n, we need to convert each line
@@ -166,27 +166,27 @@ void Bridge::send_channel_message(const Iid& iid, const std::string& body)
       if (line.substr(0, 6) == "/mode ")
         {
           std::vector<std::string> args = utils::split(line.substr(6), ' ', false);
-          irc->send_mode_command(iid.chan, args);
+          irc->send_mode_command(iid.get_local(), args);
           continue;             // We do not want to send that back to the
                                 // XMPP user, that’s not a textual message.
         }
       else if (line.substr(0, 4) == "/me ")
-        irc->send_channel_message(iid.chan, action_prefix + line.substr(4) + "\01");
+        irc->send_channel_message(iid.get_local(), action_prefix + line.substr(4) + "\01");
       else
-        irc->send_channel_message(iid.chan, line);
-      this->xmpp->send_muc_message(iid.chan + "%" + iid.server, irc->get_own_nick(),
+        irc->send_channel_message(iid.get_local(), line);
+      this->xmpp->send_muc_message(std::to_string(iid), irc->get_own_nick(),
                                    this->make_xmpp_body(line), this->user_jid);
     }
 }
 
 void Bridge::send_private_message(const Iid& iid, const std::string& body, const std::string& type)
 {
-  if (iid.chan.empty() || iid.server.empty())
+  if (iid.get_local().empty() || iid.get_server().empty())
     return ;
-  IrcClient* irc = this->get_irc_client(iid.server);
+  IrcClient* irc = this->get_irc_client(iid.get_server());
   if (!irc)
     {
-      log_warning("Cannot send message: no client exist for server " << iid.server);
+      log_warning("Cannot send message: no client exist for server " << iid.get_server());
       return;
     }
   std::vector<std::string> lines = utils::split(body, '\n', true);
@@ -195,38 +195,38 @@ void Bridge::send_private_message(const Iid& iid, const std::string& body, const
   for (const std::string& line: lines)
     {
       if (line.substr(0, 4) == "/me ")
-        irc->send_private_message(iid.chan, action_prefix + line.substr(4) + "\01", type);
+        irc->send_private_message(iid.get_local(), action_prefix + line.substr(4) + "\01", type);
       else
-        irc->send_private_message(iid.chan, line, type);
+        irc->send_private_message(iid.get_local(), line, type);
     }
 }
 
 void Bridge::leave_irc_channel(Iid&& iid, std::string&& status_message)
 {
-  IrcClient* irc = this->get_irc_client(iid.server);
+  IrcClient* irc = this->get_irc_client(iid.get_server());
   if (irc)
-    irc->send_part_command(iid.chan, status_message);
+    irc->send_part_command(iid.get_local(), status_message);
 }
 
 void Bridge::send_irc_nick_change(const Iid& iid, const std::string& new_nick)
 {
-  IrcClient* irc = this->get_irc_client(iid.server);
+  IrcClient* irc = this->get_irc_client(iid.get_server());
   if (irc)
     irc->send_nick_command(new_nick);
 }
 
 void Bridge::send_irc_kick(const Iid& iid, const std::string& target, const std::string& reason)
 {
-  IrcClient* irc = this->get_irc_client(iid.server);
+  IrcClient* irc = this->get_irc_client(iid.get_server());
   if (irc)
-    irc->send_kick_command(iid.chan, target, reason);
+    irc->send_kick_command(iid.get_local(), target, reason);
 }
 
 void Bridge::set_channel_topic(const Iid& iid, const std::string& subject)
 {
-  IrcClient* irc = this->get_irc_client(iid.server);
+  IrcClient* irc = this->get_irc_client(iid.get_server());
   if (irc)
-    irc->send_topic_command(iid.chan, subject);
+    irc->send_topic_command(iid.get_local(), subject);
 }
 
 void Bridge::send_xmpp_version_to_irc(const Iid& iid, const std::string& name, const std::string& version, const std::string& os)
@@ -239,22 +239,22 @@ void Bridge::send_xmpp_version_to_irc(const Iid& iid, const std::string& name, c
 void Bridge::send_message(const Iid& iid, const std::string& nick, const std::string& body, const bool muc)
 {
   if (muc)
-    this->xmpp->send_muc_message(iid.chan + "%" + iid.server, nick,
+    this->xmpp->send_muc_message(std::to_string(iid), nick,
                                  this->make_xmpp_body(body), this->user_jid);
   else
-    this->xmpp->send_message(iid.chan + "%" + iid.server,
+    this->xmpp->send_message(std::to_string(iid),
                              this->make_xmpp_body(body), this->user_jid, "chat");
 }
 
 void Bridge::send_join_failed(const Iid& iid, const std::string& nick, const std::string& type, const std::string& condition, const std::string& text)
 {
-  this->xmpp->send_presence_error(iid.chan + "%" + iid.server, nick, this->user_jid, type, condition, text);
+  this->xmpp->send_presence_error(std::to_string(iid), nick, this->user_jid, type, condition, text);
 }
 
 void Bridge::send_muc_leave(Iid&& iid, std::string&& nick, const std::string& message, const bool self)
 {
-  this->xmpp->send_muc_leave(std::move(iid.chan) + "%" + std::move(iid.server), std::move(nick), this->make_xmpp_body(message), this->user_jid, self);
-  IrcClient* irc = this->get_irc_client(iid.server);
+  this->xmpp->send_muc_leave(std::to_string(iid), std::move(nick), this->make_xmpp_body(message), this->user_jid, self);
+  IrcClient* irc = this->get_irc_client(iid.get_server());
   if (irc && irc->number_of_joined_channels() == 0)
     irc->send_quit_command("");
 }
@@ -269,7 +269,7 @@ void Bridge::send_nick_change(Iid&& iid,
   std::string role;
   std::tie(role, affiliation) = get_role_affiliation_from_irc_mode(user_mode);
 
-  this->xmpp->send_nick_change(std::move(iid.chan) + "%" + std::move(iid.server),
+  this->xmpp->send_nick_change(std::to_string(iid),
                                old_nick, new_nick, affiliation, role, this->user_jid, self);
 }
 
@@ -309,7 +309,7 @@ void Bridge::send_topic(const std::string& hostname, const std::string& chan_nam
 
 std::string Bridge::get_own_nick(const Iid& iid)
 {
-  IrcClient* irc = this->get_irc_client(iid.server);
+  IrcClient* irc = this->get_irc_client(iid.get_server());
   if (irc)
     return irc->get_own_nick();
   return "";
@@ -322,12 +322,12 @@ size_t Bridge::active_clients() const
 
 void Bridge::kick_muc_user(Iid&& iid, const std::string& target, const std::string& reason, const std::string& author)
 {
-  this->xmpp->kick_user(iid.chan + "%" + iid.server, target, reason, author, this->user_jid);
+  this->xmpp->kick_user(std::to_string(iid), target, reason, author, this->user_jid);
 }
 
 void Bridge::send_nickname_conflict_error(const Iid& iid, const std::string& nickname)
 {
-  this->xmpp->send_nickname_conflict_error(iid.chan + "%" + iid.server, nickname, this->user_jid);
+  this->xmpp->send_nickname_conflict_error(std::to_string(iid), nickname, this->user_jid);
 }
 
 void Bridge::send_affiliation_role_change(const Iid& iid, const std::string& target, const char mode)
@@ -336,10 +336,10 @@ void Bridge::send_affiliation_role_change(const Iid& iid, const std::string& tar
   std::string affiliation;
 
   std::tie(role, affiliation) = get_role_affiliation_from_irc_mode(mode);
-  this->xmpp->send_affiliation_role_change(iid.chan + "%" + iid.server, target, affiliation, role, this->user_jid);
+  this->xmpp->send_affiliation_role_change(std::to_string(iid), target, affiliation, role, this->user_jid);
 }
 
 void Bridge::send_iq_version_request(const std::string& nick, const std::string& hostname)
 {
-  this->xmpp->send_iq_version_request(nick + "%" + hostname, this->user_jid);
+  this->xmpp->send_iq_version_request(nick + "!" + hostname, this->user_jid);
 }
diff --git a/src/irc/iid.cpp b/src/irc/iid.cpp
index 4694c0c..4893e9e 100644
--- a/src/irc/iid.cpp
+++ b/src/irc/iid.cpp
@@ -1,21 +1,63 @@
+#include <utils/tolower.hpp>
+
 #include <irc/iid.hpp>
 
-Iid::Iid(const std::string& iid)
+Iid::Iid(const std::string& iid):
+  is_channel(false),
+  is_user(false)
 {
-  std::string::size_type sep = iid.find("%");
+  const std::string::size_type sep = iid.find_first_of("%!");
   if (sep != std::string::npos)
     {
-      this->chan = iid.substr(0, sep);
-      sep++;
+      if (iid[sep] == '%')
+        this->is_channel = true;
+      else
+        this->is_user = true;
+      this->set_local(iid.substr(0, sep));
+      this->set_server(iid.substr(sep + 1));
     }
   else
-    {
-      this->chan = iid;
-      return;
-    }
-  this->server = iid.substr(sep);
+    this->set_server(iid);
+}
+
+Iid::Iid():
+  is_channel(false),
+  is_user(false)
+{
+}
+
+void Iid::set_local(const std::string& loc)
+{
+  this->local = utils::tolower(loc);
+}
+
+void Iid::set_server(const std::string& serv)
+{
+  this->server = utils::tolower(serv);
+}
+
+const std::string& Iid::get_local() const
+{
+  return this->local;
 }
 
-Iid::Iid()
+const std::string& Iid::get_server() const
 {
+  return this->server;
+}
+
+std::string Iid::get_sep() const
+{
+  if (this->is_channel)
+    return "%";
+  else if (this->is_user)
+    return "!";
+  return "";
+}
+
+namespace std {
+  const std::string to_string(const Iid& iid)
+  {
+    return iid.get_local() + iid.get_sep() + iid.get_server();
+  }
 }
diff --git a/src/irc/iid.hpp b/src/irc/iid.hpp
index a62ac71..2302a18 100644
--- a/src/irc/iid.hpp
+++ b/src/irc/iid.hpp
@@ -4,17 +4,40 @@
 #include <string>
 
 /**
- * A name representing an IRC channel, on the same model than the XMPP JIDs (but much simpler).
- * The separator between the server and the channel name is '%'
- * #test%irc.freenode.org has :
- * - chan: "#test" (the # is part of the name, it could very well be absent, or & instead
- * - server: "irc.freenode.org"
- * #test has:
- * - chan: "#test"
- * - server: ""
- * %irc.freenode.org:
- * - chan: ""
- * - server: "irc.freenode.org"
+ * A name representing an IRC channel on an IRC server, or an IRC user on an
+ * IRC server, or just an IRC server.
+ *
+ * The separator for an user is '!', for a channel it's '%'. If no separator
+ * is present, it's just an irc server.
+ * It’s possible to have an empty-string server, but it makes no sense in
+ * the biboumi context.
+ *
+ * #test%irc.example.org has :
+ * - local: "#test" (the # is part of the name, it could very well be absent, or & (for example) instead)
+ * - server: "irc.example.org"
+ * - is_channel: true
+ * - is_user: false
+ *
+ * %irc.example.org:
+ * - local: ""
+ * - server: "irc.example.org"
+ * - is_channel: true
+ * - is_user: false
+ * Note: this is the special empty-string channel, used internal in biboumi
+ * but has no meaning on IRC.
+ *
+ * foo!irc.example.org
+ * - local: "foo"
+ * - server: "irc.example.org"
+ * - is_channel: false
+ * - is_user: true
+ * Note: the empty-string user (!irc.example.org) has no special meaning in biboumi
+ *
+ * irc.example.org:
+ * - local: ""
+ * - server: "irc.example.org"
+ * - is_channel: false
+ * - is_user: false
  */
 class Iid
 {
@@ -22,14 +45,28 @@ public:
   explicit Iid(const std::string& iid);
   explicit Iid();
 
-  std::string chan;
-  std::string server;
+  void set_local(const std::string& loc);
+  void set_server(const std::string& serv);
+  const std::string& get_local() const;
+  const std::string& get_server() const;
+
+  bool is_channel;
+  bool is_user;
+
+  std::string get_sep() const;
 
 private:
+  std::string local;
+  std::string server;
+
   Iid(const Iid&) = delete;
   Iid(Iid&&) = delete;
   Iid& operator=(const Iid&) = delete;
   Iid& operator=(Iid&&) = delete;
 };
 
+namespace std {
+  const std::string to_string(const Iid& iid);
+}
+
 #endif // IID_INCLUDED
diff --git a/src/irc/irc_client.cpp b/src/irc/irc_client.cpp
index c3765a6..6e22980 100644
--- a/src/irc/irc_client.cpp
+++ b/src/irc/irc_client.cpp
@@ -102,10 +102,11 @@ void IrcClient::on_connection_close()
   log_warning(message);
 }
 
-IrcChannel* IrcClient::get_channel(const std::string& name)
+IrcChannel* IrcClient::get_channel(const std::string& n)
 {
-  if (name.empty())
+  if (n.empty())
     return &this->dummy_channel;
+  const std::string name = utils::tolower(n);
   try
     {
       return this->channels.at(name).get();
@@ -382,15 +383,18 @@ void IrcClient::on_channel_message(const IrcMessage& message)
   const IrcUser user(message.prefix);
   const std::string nick = user.nick;
   Iid iid;
-  iid.chan = utils::tolower(message.arguments[0]);
-  iid.server = this->hostname;
+  iid.set_local(message.arguments[0]);
+  iid.set_server(this->hostname);
   const std::string body = message.arguments[1];
   bool muc = true;
-  if (!this->get_channel(iid.chan)->joined)
+  if (!this->get_channel(iid.get_local())->joined)
     {
-      iid.chan = nick;
+      iid.is_user = true;
+      iid.set_local(nick);
       muc = false;
     }
+  else
+    iid.is_channel = true;
   if (!body.empty() && body[0] == '\01')
     {
       if (body.substr(1, 6) == "ACTION")
@@ -460,8 +464,9 @@ void IrcClient::on_nickname_conflict(const IrcMessage& message)
   for (auto it = this->channels.begin(); it != this->channels.end(); ++it)
   {
     Iid iid;
-    iid.chan = it->first;
-    iid.server = this->hostname;
+    iid.set_local(it->first);
+    iid.set_server(this->hostname);
+    iid.is_channel = true;
     this->bridge->send_nickname_conflict_error(iid, nickname);
   }
 }
@@ -499,7 +504,7 @@ void IrcClient::on_welcome_message(const IrcMessage& message)
 
 void IrcClient::on_part(const IrcMessage& message)
 {
-  const std::string chan_name = utils::tolower(message.arguments[0]);
+  const std::string chan_name = message.arguments[0];
   IrcChannel* channel = this->get_channel(chan_name);
   if (!channel->joined)
     return ;
@@ -512,13 +517,14 @@ void IrcClient::on_part(const IrcMessage& message)
       std::string nick = user->nick;
       channel->remove_user(user);
       Iid iid;
-      iid.chan = chan_name;
-      iid.server = this->hostname;
+      iid.set_local(chan_name);
+      iid.set_server(this->hostname);
+      iid.is_channel = true;
       bool self = channel->get_self()->nick == nick;
       if (self)
       {
         channel->joined = false;
-        this->channels.erase(chan_name);
+        this->channels.erase(utils::tolower(chan_name));
         // channel pointer is now invalid
         channel = nullptr;
       }
@@ -533,8 +539,9 @@ void IrcClient::on_error(const IrcMessage& message)
   for (auto it = this->channels.begin(); it != this->channels.end(); ++it)
   {
     Iid iid;
-    iid.chan = it->first;
-    iid.server = this->hostname;
+    iid.set_local(it->first);
+    iid.set_server(this->hostname);
+    iid.is_channel = true;
     IrcChannel* channel = it->second.get();
     if (!channel->joined)
       continue;
@@ -560,8 +567,9 @@ void IrcClient::on_quit(const IrcMessage& message)
           std::string nick = user->nick;
           channel->remove_user(user);
           Iid iid;
-          iid.chan = chan_name;
-          iid.server = this->hostname;
+          iid.set_local(chan_name);
+          iid.set_server(this->hostname);
+          iid.is_channel = true;
           this->bridge->send_muc_leave(std::move(iid), std::move(nick), txt, false);
         }
     }
@@ -579,8 +587,9 @@ void IrcClient::on_nick(const IrcMessage& message)
         {
           std::string old_nick = user->nick;
           Iid iid;
-          iid.chan = chan_name;
-          iid.server = this->hostname;
+          iid.set_local(chan_name);
+          iid.set_server(this->hostname);
+          iid.is_channel = true;
           const bool self = channel->get_self()->nick == old_nick;
           const char user_mode = user->get_most_significant_mode(this->sorted_user_modes);
           this->bridge->send_nick_change(std::move(iid), old_nick, new_nick, user_mode, self);
@@ -606,8 +615,9 @@ void IrcClient::on_kick(const IrcMessage& message)
     channel->joined = false;
   IrcUser author(message.prefix);
   Iid iid;
-  iid.chan = chan_name;
-  iid.server = this->hostname;
+  iid.set_local(chan_name);
+  iid.set_server(this->hostname);
+  iid.is_channel = true;
   this->bridge->kick_muc_user(std::move(iid), target, reason, author.nick);
 }
 
@@ -625,8 +635,9 @@ void IrcClient::on_channel_mode(const IrcMessage& message)
   // For now, just transmit the modes so the user can know what happens
   // TODO, actually interprete the mode.
   Iid iid;
-  iid.chan = utils::tolower(message.arguments[0]);
-  iid.server = this->hostname;
+  iid.set_local(message.arguments[0]);
+  iid.set_server(this->hostname);
+  iid.is_channel = true;
   IrcUser user(message.prefix);
   std::string mode_arguments;
   for (size_t i = 1; i < message.arguments.size(); ++i)
@@ -638,10 +649,10 @@ void IrcClient::on_channel_mode(const IrcMessage& message)
           mode_arguments += message.arguments[i];
         }
     }
-  this->bridge->send_message(iid, "", "Mode "s + iid.chan +
+  this->bridge->send_message(iid, "", "Mode "s + iid.get_local() +
                                       " [" + mode_arguments + "] by " + user.nick,
                              true);
-  const IrcChannel* channel = this->get_channel(iid.chan);
+  const IrcChannel* channel = this->get_channel(iid.get_local());
   if (!channel)
     return;
 
@@ -695,7 +706,7 @@ void IrcClient::on_channel_mode(const IrcMessage& message)
               if (!user)
                 {
                   log_warning("Trying to set mode for non-existing user '" << target
-                              << "' in channel" << iid.chan);
+                              << "' in channel" << iid.get_local());
                   return;
                 }
               if (add)
diff --git a/src/test.cpp b/src/test.cpp
index 216608a..87ab49c 100644
--- a/src/test.cpp
+++ b/src/test.cpp
@@ -290,5 +290,41 @@ int main()
   std::cout << correctjid2 << std::endl;
   assert(correctjid2 == "zigougou@poez.io");
 
+  /**
+   * IID parsing
+   */
+  std::cout << color << "Testing IID parsing…" << reset << std::endl;
+  Iid iid1("foo!irc.example.org");
+  std::cout << std::to_string(iid1) << std::endl;
+  assert(std::to_string(iid1) == "foo!irc.example.org");
+  assert(iid1.get_local() == "foo");
+  assert(iid1.get_server() == "irc.example.org");
+  assert(!iid1.is_channel);
+  assert(iid1.is_user);
+
+  Iid iid2("#test%irc.example.org");
+  std::cout << std::to_string(iid2) << std::endl;
+  assert(std::to_string(iid2) == "#test%irc.example.org");
+  assert(iid2.get_local() == "#test");
+  assert(iid2.get_server() == "irc.example.org");
+  assert(iid2.is_channel);
+  assert(!iid2.is_user);
+
+  Iid iid3("%irc.example.org");
+  std::cout << std::to_string(iid3) << std::endl;
+  assert(std::to_string(iid3) == "%irc.example.org");
+  assert(iid3.get_local() == "");
+  assert(iid3.get_server() == "irc.example.org");
+  assert(iid3.is_channel);
+  assert(!iid3.is_user);
+
+  Iid iid4("irc.example.org");
+  std::cout << std::to_string(iid4) << std::endl;
+  assert(std::to_string(iid4) == "irc.example.org");
+  assert(iid4.get_local() == "");
+  assert(iid4.get_server() == "irc.example.org");
+  assert(!iid4.is_channel);
+  assert(!iid4.is_user);
+
   return 0;
 }
diff --git a/src/xmpp/xmpp_component.cpp b/src/xmpp/xmpp_component.cpp
index 4c9c8ff..ec8517c 100644
--- a/src/xmpp/xmpp_component.cpp
+++ b/src/xmpp/xmpp_component.cpp
@@ -306,7 +306,7 @@ void XmppComponent::handle_presence(const Stanza& stanza)
                               error_type, error_name, "");
         });
 
-  if (!iid.server.empty())
+  if (iid.is_channel && !iid.get_server().empty())
     { // presence toward a MUC that corresponds to an irc channel, or a
       // dummy channel if iid.chan is empty
       if (type.empty())
@@ -353,7 +353,7 @@ void XmppComponent::handle_message(const Stanza& stanza)
                               error_type, error_name, "");
         });
   XmlNode* body = stanza.get_child("body", COMPONENT_NS);
-  if (type == "groupchat")
+  if (type == "groupchat" && iid.is_channel)
     {
       if (to.resource.empty())
         if (body && !body->get_inner().empty())
@@ -379,11 +379,13 @@ void XmppComponent::handle_message(const Stanza& stanza)
       if (kickable_error)
         bridge->shutdown("Error from remote client");
     }
-  else if (type == "chat")
+  else if (type == "chat" && iid.is_user && !iid.get_local().empty())
     {
       if (body && !body->get_inner().empty())
         bridge->send_private_message(iid, body->get_inner());
     }
+  else if (iid.is_user)
+    this->send_invalid_user_error(to.local, from);
   stanza_error.disable();
 }
 
@@ -671,6 +673,36 @@ void XmppComponent::send_invalid_room_error(const std::string& muc_name,
   this->send_stanza(presence);
 }
 
+void XmppComponent::send_invalid_user_error(const std::string& user_name, const std::string& to)
+{
+  Stanza message("message");
+  message["from"] = user_name + "@" + this->served_hostname;
+  message["to"] = to;
+  message["type"] = "error";
+  XmlNode x("x");
+  x["xmlns"] = MUC_NS;
+  x.close();
+  message.add_child(std::move(x));
+  XmlNode error("error");
+  error["type"] = "cancel";
+  XmlNode item_not_found("item-not-found");
+  item_not_found["xmlns"] = STANZA_NS;
+  item_not_found.close();
+  error.add_child(std::move(item_not_found));
+  XmlNode text("text");
+  text["xmlns"] = STANZA_NS;
+  text["xml:lang"] = "en";
+  text.set_inner(user_name +
+                 " is not a valid IRC user name. A correct user jid is of the form: <nick>!<server>@" +
+                 this->served_hostname);
+  text.close();
+  error.add_child(std::move(text));
+  error.close();
+  message.add_child(std::move(error));
+  message.close();
+  this->send_stanza(message);
+}
+
 void XmppComponent::send_topic(const std::string& from, Xmpp::body&& topic, const std::string& to)
 {
   XmlNode message("message");
@@ -711,7 +743,7 @@ void XmppComponent::send_muc_message(const std::string& muc_name, const std::str
   this->send_stanza(message);
 }
 
-void XmppComponent::send_muc_leave(std::string&& muc_name, std::string&& nick, Xmpp::body&& message, const std::string& jid_to, const bool self)
+void XmppComponent::send_muc_leave(const std::string& muc_name, std::string&& nick, Xmpp::body&& message, const std::string& jid_to, const bool self)
 {
   Stanza presence("presence");
   presence["to"] = jid_to;
diff --git a/src/xmpp/xmpp_component.hpp b/src/xmpp/xmpp_component.hpp
index 5de471c..f1806de 100644
--- a/src/xmpp/xmpp_component.hpp
+++ b/src/xmpp/xmpp_component.hpp
@@ -131,6 +131,12 @@ public:
                                const std::string& nick,
                                const std::string& to);
   /**
+   * Send an error to indicate that the user tried to send a message to an
+   * invalid user.
+   */
+  void send_invalid_user_error(const std::string& user_name,
+                               const std::string& to);
+  /**
    * Send the MUC topic to the user
    */
   void send_topic(const std::string& from, Xmpp::body&& xmpp_topic, const std::string& to);
@@ -141,7 +147,7 @@ public:
   /**
    * Send an unavailable presence for this nick
    */
-  void send_muc_leave(std::string&& muc_name, std::string&& nick, Xmpp::body&& message, const std::string& jid_to, const bool self);
+  void send_muc_leave(const std::string& muc_name, std::string&& nick, Xmpp::body&& message, const std::string& jid_to, const bool self);
   /**
    * Indicate that a participant changed his nick
    */