[ADD/WIP] Bridging Matrix redacts

I'll still need to consider making redacts from other people count as
"moderations", whatever that is to Gajim, instead of a "self-redact".

Also, _please_, support it if you _ever_ wish adoption, XMPP users!

src/MatrixEventHandler.c

@@ -149,6 +149,77 @@ ParseeBotHandler(ParseeData *data, HashMap *event)
     Free(profile);
     CommandFree(cmd);
 }
+
+static const char *
+GetXMPPInformation(ParseeData *data, HashMap *event, char **from, char **to)
+{
+    const char *type = NULL;
+
+    char *room_id = GrabString(event, 1, "room_id");
+    char *matrix_sender = GrabString(event, 1, "sender");
+    char *chat_id = NULL, *muc_id = NULL;
+    char *user;
+
+    DbRef *room_data;
+    HashMap *data_json;
+
+    XMPPComponent *jabber = data ? data->jabber : NULL;
+
+    bool direct = false;
+    if (!data || !event || !from || !to)
+    {
+        return NULL;
+    }
+
+    *from   = NULL;
+    *to     = NULL;
+
+    chat_id = ParseeGetFromRoomID(data, room_id);
+
+    room_data = DbLock(data->db, 3, "rooms", room_id, "data");
+    data_json = DbJson(room_data);
+    direct = GrabBoolean(data_json, 1, "is_direct");
+    type = direct ? "chat" : "groupchat";
+
+    user = GrabString(data_json, 1, "xmpp_user");
+
+    *from = ParseeEncodeMXID(matrix_sender);
+
+    if (direct)
+    {
+        *to = StrDuplicate(user);
+        Free(chat_id);
+    }
+    else
+    {
+        char *matrix_name, *muc_join_as;
+        
+        muc_id = ParseeGetMUCID(data, chat_id);
+        if (!chat_id)
+        {
+            /* muc_id is already implied to be freed by this point */
+
+            Free(*from);
+            *from = NULL;
+            DbUnlock(data->db, room_data);
+            return NULL;
+        }
+
+        matrix_name = ASGetName(data->config, room_id, matrix_sender);
+        muc_join_as = StrConcat(4, muc_id, "/", matrix_name, "[p]");
+
+        XMPPJoinMUC(jabber, *from, muc_join_as);
+
+        *to = muc_id;
+
+        Free(matrix_name);
+        Free(muc_join_as);
+    }
+
+    Free(chat_id);
+    DbUnlock(data->db, room_data);
+    return type;
+}
 static void
 ParseeMessageHandler(ParseeData *data, HashMap *event)
 {
@@ -316,9 +387,37 @@ ParseeEventHandler(ParseeData *data, HashMap *event)
     }
     else if (StrEquals(event_type, "m.room.redaction"))
     {
-        Log(LOG_WARNING, "Unsupported event redaction %s", event_id);
+        char *from, *to;
+        char *redacted = GrabString(event, 1, "redacts");
+        char *redacted_stanza = NULL;
+        char *chat_id;
+        XMPPComponent *jabber = data->jabber;
+
+        const char *type = GetXMPPInformation(data, event, &from, &to);
+
+        chat_id = ParseeGetFromRoomID(data, room_id);
+
+        if (!ParseeGetOrigin(data, chat_id, redacted, &redacted_stanza))
+        {
+            ParseeGetDMOrigin(data, room_id, redacted, &redacted_stanza);
+        }
+
+        /* Some clients don't support retractions *at all*, which smell.
+         * This therefore serves as a fallback, just in case that fails. */
+        XMPPSendPlain(
+            jabber, from, to, 
+            "[EDIT REDACT FROM PARSEE]", 
+            (char *) type, 
+            NULL, NULL, redacted, 
+            NULL, redacted_stanza
+        );
+        XMPPRetract(jabber, from, to, (char *) type, redacted_stanza);
+
+        Free(redacted_stanza);
+        Free(chat_id);
+        Free(from);
+        Free(to);
         /* TODO: Implement Matrix->XMPP redactions. */
     }
-
 }