2 * Reactor - FileExistenceTrigger.java - Copyright © 2013 David Roden
4 * This program is free software: you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation, either version 3 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 package net.pterodactylus.reactor.triggers;
20 import net.pterodactylus.reactor.State;
21 import net.pterodactylus.reactor.Trigger;
22 import net.pterodactylus.reactor.output.DefaultOutput;
23 import net.pterodactylus.reactor.output.Output;
24 import net.pterodactylus.reactor.states.FileState;
26 import com.google.common.base.Preconditions;
29 * A trigger that detects changes in the existence of a file.
31 * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
33 public class FileExistenceTrigger implements Trigger {
43 public boolean triggers(State previousState, State currentState) {
44 Preconditions.checkState(previousState instanceof FileState, "previousState is not a FileState");
45 Preconditions.checkState(currentState instanceof FileState, "currentState is not a FileState");
46 return ((FileState) previousState).exists() != ((FileState) currentState).exists();
53 public Output output() {
54 return new DefaultOutput("File appeared/disappeared").addText("text/plain", "File appeared/disappeared").addText("text/html", "<div>File appeared/disappeared</div>");