Improve /mode behavior

This fixes /mode using the name of invalid contexts
and also adds some documentation to what is happening.

In the end though it still must guess between modes
and nicks if ran in a valid context.

Fixes #1470

src/common/outbound.c

@@ -2679,17 +2679,26 @@ cmd_me (struct session *sess, char *tbuf, char *word[], char *word_eol[])
 static int
 cmd_mode (struct session *sess, char *tbuf, char *word[], char *word_eol[])
 {
-	/* +channel channels are dying, let those servers whine about modes.
-	 * return info about current channel if available and no info is given */
-	if ((*word[2] == '+') || (*word[2] == 0) || (!is_channel(sess->server, word[2]) &&
-				!(rfc_casecmp(sess->server->nick, word[2]) == 0)))
+	/* We allow omitting the target, so we have to figure it out:
+	 * - Can only use info from channels or dialogs
+	 * - Empty arg is always sess info
+	 * - Assume + is mode not channel
+	 * - We know valid channels and our nick
+	 * - We cannot easily know if other nick or valid mode (Need to store 004)
+	 */
+	if ((sess->type != SESS_CHANNEL && sess->type != SESS_DIALOG)
+	    || (!(*word[2] == '-' || *word[2] == '+' || *word[2] == '\0')
+	        && (is_channel (sess->server, word[2]) || !rfc_casecmp (sess->server->nick, word[2])))
+	   )
+	{
+		sess->server->p_mode (sess->server, word[2], word_eol[3]);
+	}
+	else
 	{
 		if(sess->channel[0] == 0)
 			return FALSE;
 		sess->server->p_mode (sess->server, sess->channel, word_eol[2]);
 	}
-	else
-		sess->server->p_mode (sess->server, word[2], word_eol[3]);
 	return TRUE;
 }