🐛 Fix broken change detection

[rhynodge.git] / src / main / java / net / pterodactylus / rhynodge / mergers / TorrentMerger.java

diff --git a/src/main/java/net/pterodactylus/rhynodge/mergers/TorrentMerger.java b/src/main/java/net/pterodactylus/rhynodge/mergers/TorrentMerger.java
new file mode 100644 (file)
index 0000000..f6a75a8
--- /dev/null
+++ b/src/main/java/net/pterodactylus/rhynodge/mergers/TorrentMerger.java
@@ -0,0 +1,60 @@
+/*
+ * Rhynodge - TorrentMerger.java - Copyright © 2013–2021 David Roden
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package net.pterodactylus.rhynodge.mergers;
+
+import java.util.HashSet;
+import java.util.Set;
+import javax.annotation.Nonnull;
+
+import net.pterodactylus.rhynodge.Merger;
+import net.pterodactylus.rhynodge.State;
+import net.pterodactylus.rhynodge.states.TorrentState;
+import net.pterodactylus.rhynodge.states.TorrentState.TorrentFile;
+
+import static com.google.common.base.Preconditions.checkState;
+
+/**
+ * {@link Merger} implementation that merges two {@link TorrentState}s, taking
+ * careful note of which {@link TorrentFile}s appear in the current
+ * {@link TorrentState} but not in the previous one.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public class TorrentMerger implements Merger {
+
+       /**
+        * {@inheritDoc}
+        */
+       @Nonnull
+       @Override
+       public State mergeStates(@Nonnull State previousState, @Nonnull State currentState) {
+               checkState(currentState instanceof TorrentState, "currentState is not a TorrentState but a %s", currentState.getClass().getName());
+               checkState(previousState instanceof TorrentState, "previousState is not a TorrentState but a %s", currentState.getClass().getName());
+
+               Set<TorrentFile> allTorrentFiles = new HashSet<>(((TorrentState) previousState).torrentFiles());
+               Set<TorrentFile> newTorrentFiles = new HashSet<>();
+               for (TorrentFile torrentFile : (TorrentState) currentState) {
+                       if (allTorrentFiles.add(torrentFile)) {
+                               newTorrentFiles.add(torrentFile);
+                       }
+               }
+
+               return new TorrentState(allTorrentFiles, newTorrentFiles);
+       }
+
+}