degesch: better message autosplit

degesch.c

@@ -2722,27 +2722,57 @@ send_message_to_target (struct app_context *ctx,
 		return;
 	}
 
-	int one_message = 0;
+	// We don't always have the full info for message splitting
+	int space_in_one_message = 0;
 	if (ctx->irc_user_host)
 		// :<nick>!<user>@<host> PRIVMSG <target> :<message>
-		one_message = 510 - 1 - (int) strlen (ctx->irc_user->nickname)
+		space_in_one_message = 510
+			- 1 - (int) strlen (ctx->irc_user->nickname)
 			- 1 - (int) strlen (ctx->irc_user_host)
 			- 1 - 7 - 1 - strlen (target) - 1 - 1;
 
-	// FIXME: UTF-8 sequences
-	int left = strlen (message);
-	while (left)
+	// Attempt to split the message if it doesn't completely fit into
+	// a single IRC protocol message while trying not to break UTF-8.
+	// Unicode can still end up being wrong, though.
+	// TODO: at least try to word-wrap if nothing else
+	for (int message_left = strlen (message); message_left; )
 	{
-		int part = MIN (one_message, left);
-		if (!one_message)
-			part = left;
+		struct str m;
+		str_init (&m);
 
-		irc_send (ctx, "PRIVMSG %s :%.*s", target, part, message);
+		int part_left = MIN (space_in_one_message, message_left);
+		if (!space_in_one_message)
+			part_left = message_left;
+
+		bool empty = true;
+		while (true)
+		{
+			const char *next = utf8_next (message, message_left);
+			hard_assert (next);
+
+			int char_len = message - next;
+			if (char_len > part_left)
+				break;
+
+			str_append_data (&m, message, char_len);
+
+			message += char_len;
+			message_left -= char_len;
+			empty = false;
+		}
+		if (empty)
+		{
+			// Well, that's just weird
+			buffer_send_error (ctx, buffer, "%s",
+				"Message splitting was unsuccessful as there was "
+				"too little room for UTF-8 characters");
+			message_left = 0;
+		}
+
+		irc_send (ctx, "PRIVMSG %s :%s", target, m.str);
 		buffer_send (ctx, buffer, BUFFER_LINE_PRIVMSG, 0,
-			ctx->irc_user->nickname, NULL, "%.*s", part, message);
-
-		left -= part;
-		message += part;
+			ctx->irc_user->nickname, NULL, "%s", m.str);
+		str_free (&m);
 	}
 }