--- /dev/null
+/*
+ * rhynodge - ComicMerger.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.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import javax.annotation.Nonnull;
+
+import net.pterodactylus.rhynodge.Merger;
+import net.pterodactylus.rhynodge.State;
+import net.pterodactylus.rhynodge.states.ComicState;
+import net.pterodactylus.rhynodge.states.ComicState.Comic;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+/**
+ * {@link Merger} implementation that merger two {@link ComicState}s.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public class ComicMerger implements Merger {
+
+ @Nonnull
+ @Override
+ public State mergeStates(@Nonnull State previousState, @Nonnull State currentState) {
+ checkArgument(previousState instanceof ComicState, "previous state must be a comic state");
+ checkArgument(currentState instanceof ComicState, "current state must be a comic state");
+
+ ComicState previousComicState = (ComicState) previousState;
+ ComicState currentComicState = (ComicState) currentState;
+
+ List<Comic> allComics = new ArrayList<>(previousComicState.comics());
+ Set<Comic> newComics = new HashSet<>();
+
+ for (Comic comic : currentComicState) {
+ if (!allComics.contains(comic)) {
+ allComics.add(comic);
+ newComics.add(comic);
+ }
+ }
+
+ return new ComicState(allComics, newComics);
+ }
+
+}