Make nonces unique

Send every message with a unique nonce saving and saving it in a
hashtable making sure we don't echo back our own messages.

Commit is based on a patch contributed by Trecourt Nicolas, thank you!

Fixes: #182

src/discord-handlers.c

@@ -615,7 +615,7 @@ static gboolean discord_prepare_message(struct im_connection *ic,
   time_t tstamp = use_tstamp ? parse_iso_8601(json_o_str(minfo, "timestamp")) : 0;
 
   // Don't echo self messages that we sent in this session
-  if (is_self && nonce != NULL && g_strcmp0(nonce, dd->nonce) == 0) {
+  if (is_self && nonce != NULL && g_hash_table_remove(dd->sent_message_ids, nonce)) {
     g_free(author);
     g_free(msg);
     return FALSE;

src/discord-http.c

@@ -527,8 +527,15 @@ void discord_http_send_msg(struct im_connection *ic, const char *id,
     emsg = nmsg;
   }
 
+  gchar *nonce;
+  guchar nonce_bytes[16];
+
+  random_bytes(nonce_bytes, sizeof(nonce_bytes));
+  nonce = g_base64_encode(nonce_bytes, sizeof(nonce_bytes));
+  g_hash_table_insert(dd->sent_message_ids, nonce,
+      GUINT_TO_POINTER((guint)time(NULL)));
   g_string_printf(content, "{\"content\":\"%s\", \"nonce\":\"%s\"}",
-                  emsg, dd->nonce);
+                  emsg, nonce);
   g_free(emsg);
   g_string_printf(request, "POST /api/channels/%s/messages HTTP/1.1\r\n"
                   "Host: %s\r\n"

src/discord-util.c

@@ -113,6 +113,7 @@ static void free_pending_ev(gpointer *ev)
 
 void free_discord_data(discord_data *dd)
 {
+  g_hash_table_destroy(dd->sent_message_ids);
   g_slist_free_full(dd->pending_events, (GDestroyNotify)free_pending_ev);
   g_slist_free_full(dd->pending_reqs, (GDestroyNotify)free_pending_req);
   g_slist_free_full(dd->pchannels, (GDestroyNotify)free_channel_info);

src/discord.c

@@ -133,6 +133,8 @@ static void discord_login(account_t *acc)
   struct im_connection *ic = imcb_new(acc);
 
   discord_data *dd = g_new0(discord_data, 1);
+  dd->sent_message_ids = g_hash_table_new_full(g_str_hash, g_str_equal,
+                            g_free, NULL);
   dd->keepalive_interval = DEFAULT_KEEPALIVE_INTERVAL;
   ic->proto_data = dd;
 

src/discord.h

@@ -54,30 +54,31 @@ typedef struct _gw_data {
 } gw_data;
 
 typedef struct _discord_data {
-  char     *token;
-  char     *id;
-  char     *session_id;
-  char     *uname;
-  char     *nonce;
-  gw_data  *gateway;
-  GSList   *servers;
-  GSList   *pchannels;
-  gint     main_loop_id;
-  GString  *ws_buf;
-  ws_state state;
-  gint     keepalive_interval;
-  gint     keepalive_loop_id;
-  gint     heartbeat_timeout_id;
-  gint     status_timeout_id;
-  void     *ssl;
-  int      sslfd;
-  gint     inpa;
-  gint     wsid;
-  guint64  seq;
-  guint    pending_sync;
-  GSList   *pending_reqs;
-  GSList   *pending_events;
-  gboolean reconnecting;
+  char       *token;
+  char       *id;
+  char       *session_id;
+  char       *uname;
+  char       *nonce;
+  gw_data    *gateway;
+  GSList     *servers;
+  GSList     *pchannels;
+  gint       main_loop_id;
+  GString    *ws_buf;
+  ws_state   state;
+  gint       keepalive_interval;
+  gint       keepalive_loop_id;
+  gint       heartbeat_timeout_id;
+  gint       status_timeout_id;
+  void       *ssl;
+  int        sslfd;
+  gint       inpa;
+  gint       wsid;
+  guint64    seq;
+  guint      pending_sync;
+  GSList     *pending_reqs;
+  GSList     *pending_events;
+  gboolean   reconnecting;
+  GHashTable *sent_message_ids;
 } discord_data;
 
 typedef struct _server_info {