[ADD/FIX/WIP] "Fix" concurrency, prepare XEP-0421

I'll need to break down my commits more...

src/XMPPThread/Bridged.c

@@ -1,6 +1,10 @@
 #include "XMPPThread/internal.h"
 
 #include <Cytoplasm/Memory.h>
+#include <Cytoplasm/Str.h>
+#include <Cytoplasm/Log.h>
+
+#include <string.h>
 
 char *
 ParseeGetBridgedRoom(ParseeData *data, XMLElement *stanza)
@@ -111,3 +115,70 @@ ParseeVerifyAllStanza(ParseeData *args, XMLElement *stanza)
 
     return ret;
 }
+
+bool
+ServerHasXEP421(ParseeData *data, char *from)
+{
+    char *server = NULL, *parsee;
+    XMLElement *disco;
+    bool ret;
+    if (!data || !from)
+    {
+        return false;
+    }
+
+    server = strchr(from, '@');
+    if (!server)
+    {
+        server = from;
+    }
+    else
+    {
+        server++;
+    }
+    server = StrDuplicate(server);
+
+    if (strchr(server, '/'))
+    {
+        *(strchr(server, '/')) = '\0';
+    }
+
+    parsee = ParseeJID(data);
+    disco = XMPPSendDisco(data->jabber, parsee, server);
+
+    ret = XMPPDiscoAdvertises(disco, "urn:xmpp:occupant-id:0");
+
+    XMLFreeElement(disco);
+    Free(parsee);
+    Free(server);
+    return ret;
+}
+char *
+ParseeGetBridgedUser(ParseeData *data, XMLElement *stanza)
+{
+    char *user, *xmpp_from, *type;
+    char *decode_from;
+
+    if (!data || !stanza)
+    {
+        return NULL;
+    }
+
+    xmpp_from = HashMapGet(stanza->attrs, "from");
+    type = HashMapGet(stanza->attrs, "type");
+    decode_from = ParseeLookupJID(xmpp_from);
+
+    /* TODO: On semi-anonymous MUCs, it might be preferable to use a 
+     * form of the occupant ID as the base, as it is more unique, and 
+     * less prone to trigger the character limit on Matrix. 
+     * I'll need to detect these first....
+     *
+     * See: https://xmpp.org/extensions/xep-0421.html */
+    user = ParseeEncodeJID(
+        data->config, 
+        decode_from, 
+        StrEquals(type, "chat")
+    );
+    Free(decode_from);
+    return user;
+}