Don’t connect sources and sinks directly, use a pipeline to move data around.

[sonitus.git] / src / main / java / net / pterodactylus / sonitus / data / filter / PredicateFilter.java

diff --git a/src/main/java/net/pterodactylus/sonitus/data/filter/PredicateFilter.java b/src/main/java/net/pterodactylus/sonitus/data/filter/PredicateFilter.java
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+/*
+ * Sonitus - PredicateFilter.java - Copyright © 2013 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.sonitus.data.filter;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import net.pterodactylus.sonitus.data.Filter;
+import net.pterodactylus.sonitus.data.Metadata;
+
+import com.google.common.base.Predicate;
+
+/**
+ * {@link Filter} implementation that uses a {@link Predicate} to determine
+ * whether a filter will be used or the data will only be passed through.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public class PredicateFilter extends DummyFilter {
+
+       /** The predicate. */
+       private final Predicate<Metadata> metadataPredicate;
+
+       /** The filter to use if the predicate matches. */
+       private final Filter filter;
+
+       /** Whether the predicate currently matches. */
+       private final AtomicBoolean metadataMatches = new AtomicBoolean(false);
+
+       /**
+        * Creates a new predicate filter.
+        *
+        * @param metadataPredicate
+        *              The predicate to evaluate every time the metadata changes
+        * @param filter
+        *              The filter to use if the predicate matches the metadata
+        */
+       public PredicateFilter(Predicate<Metadata> metadataPredicate, Filter filter) {
+               this.metadataPredicate = metadataPredicate;
+               this.filter = filter;
+       }
+
+       //
+       // FILTER METHODS
+       //
+
+       @Override
+       public void open(Metadata metadata) throws IOException {
+               checkNotNull(metadata, "metadata must not be null");
+
+               metadataMatches.set(metadataPredicate.apply(metadata));
+               if (metadataMatches.get()) {
+                       filter.open(metadata);
+               } else {
+                       super.open(metadata);
+               }
+       }
+
+       @Override
+       public void close() {
+               if (metadataMatches.get()) {
+                       filter.close();
+               } else {
+                       super.close();
+               }
+       }
+
+       @Override
+       public void metadataUpdated(Metadata metadata) {
+               metadataMatches.set(metadataPredicate.apply(metadata));
+               if (metadataMatches.get()) {
+                       filter.metadataUpdated(metadata);
+               } else {
+                       super.metadataUpdated(metadata);
+               }
+       }
+
+       @Override
+       public void process(byte[] buffer) throws IOException {
+               if (metadataMatches.get()) {
+                       filter.process(buffer);
+               } else {
+                       super.process(buffer);
+               }
+       }
+
+       @Override
+       public Metadata metadata() {
+               if (metadataMatches.get()) {
+                       return filter.metadata();
+               } else {
+                       return super.metadata();
+               }
+       }
+
+       @Override
+       public byte[] get(int bufferSize) throws IOException {
+               if (metadataMatches.get()) {
+                       return filter.get(bufferSize);
+               } else {
+                       return super.get(bufferSize);
+               }
+       }
+
+}