Provide a JID for IRC users, and add a stringprep dependency for this

src/xmpp/jid.cpp

@@ -1,4 +1,12 @@
 #include <xmpp/jid.hpp>
+#include <config.h>
+#include <cstring>
+
+#ifdef LIBIDN_FOUND
+ #include <stringprep.h>
+#endif
+
+#include <logger/logger.hpp>
 
 Jid::Jid(const std::string& jid)
 {
@@ -19,3 +27,41 @@ Jid::Jid(const std::string& jid)
 
   this->domain = jid.substr(at, slash - at);
 }
+
+#include <iostream>
+
+static constexpr size_t max_jid_part_len = 1023;
+
+std::string jidprep(const std::string& original)
+{
+#ifdef LIBIDN_FOUND
+  // TODO: cache the result
+  const std::string error_msg("Failed to convert " + original + " into a valid JID:");
+  Jid jid(original);
+
+  char local[max_jid_part_len] = {};
+  memcpy(local, jid.local.data(), jid.local.size());
+  Stringprep_rc rc = static_cast<Stringprep_rc>(::stringprep(local, max_jid_part_len,
+                     static_cast<Stringprep_profile_flags>(0), stringprep_xmpp_nodeprep));
+  if (rc != STRINGPREP_OK)
+  {
+    log_error(error_msg + stringprep_strerror(rc));
+    return "";
+  }
+
+  char domain[max_jid_part_len] = {};
+  memcpy(domain, jid.domain.data(), jid.domain.size());
+  rc = static_cast<Stringprep_rc>(::stringprep(domain, max_jid_part_len,
+       static_cast<Stringprep_profile_flags>(0), stringprep_nameprep));
+  if (rc != STRINGPREP_OK)
+  {
+    log_error(error_msg + stringprep_strerror(rc));
+    return "";
+  }
+
+  return std::string(local) + "@" + domain;
+#else
+  (void)original;
+  return "";
+#endif
+}

src/xmpp/jid.hpp

@@ -22,5 +22,15 @@ private:
   Jid& operator=(Jid&&) = delete;
 };
 
+/**
+ * Prepare the given UTF-8 string according to the XMPP node stringprep
+ * identifier profile.  This is used to send properly-formed JID to the XMPP
+ * server.
+ *
+ * If the stringprep library is not found, we return an empty string.  When
+ * this function is used, the result must always be checked for an empty
+ * value, and if this is the case it must not be used as a JID.
+ */
+std::string jidprep(const std::string& original);
 
 #endif // JID_INCLUDED

src/xmpp/xmpp_component.cpp

@@ -267,7 +267,10 @@ void XmppComponent::send_message(const std::string& from, Xmpp::body&& body, con
   this->send_stanza(node);
 }
 
-void XmppComponent::send_user_join(const std::string& from, const std::string& nick, const std::string& to)
+void XmppComponent::send_user_join(const std::string& from,
+                                   const std::string& nick,
+                                   const std::string& realjid,
+                                   const std::string& to)
 {
   XmlNode node("presence");
   node["to"] = to;
@@ -280,6 +283,12 @@ void XmppComponent::send_user_join(const std::string& from, const std::string& n
   XmlNode item("item");
   item["affiliation"] = "member";
   item["role"] = "participant";
+  if (!realjid.empty())
+    {
+      const std::string preped_jid = jidprep(realjid);
+      if (!preped_jid.empty())
+        item["jid"] = preped_jid;
+    }
   item.close();
   x.add_child(std::move(item));
   x.close();
@@ -408,7 +417,7 @@ void XmppComponent::send_nick_change(const std::string& muc_name, const std::str
   if (self)
     this->send_self_join(muc_name, new_nick, jid_to);
   else
-    this->send_user_join(muc_name, new_nick, jid_to);
+    this->send_user_join(muc_name, new_nick, "", jid_to);
 }
 
 void XmppComponent::kick_user(const std::string& muc_name,

src/xmpp/xmpp_component.hpp

@@ -62,7 +62,10 @@ public:
   /**
    * Send a join from a new participant
    */
-  void send_user_join(const std::string& from, const std::string& nick, const std::string& to);
+  void send_user_join(const std::string& from,
+                      const std::string& nick,
+                      const std::string& realjid,
+                      const std::string& to);
   /**
    * Send the self join to the user
    */