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

[sonitus.git] / src / main / java / net / pterodactylus / sonitus / data / source / MultiSource.java

diff --git a/src/main/java/net/pterodactylus/sonitus/data/source/MultiSource.java b/src/main/java/net/pterodactylus/sonitus/data/source/MultiSource.java
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+++ b/src/main/java/net/pterodactylus/sonitus/data/source/MultiSource.java
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+/*
+ * Sonitus - MultiSource.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.source;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.io.EOFException;
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.logging.Logger;
+
+import net.pterodactylus.sonitus.data.Metadata;
+import net.pterodactylus.sonitus.data.Source;
+import net.pterodactylus.sonitus.data.event.SourceFinishedEvent;
+
+import com.google.common.eventbus.EventBus;
+import com.google.inject.Inject;
+
+/**
+ * {@link Source} implementation that simply forwards another source and
+ * supports changing the source without letting the {@link
+ * net.pterodactylus.sonitus.data.Sink} know.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public class MultiSource implements Source {
+
+       /** The logger. */
+       private static final Logger logger = Logger.getLogger(MultiSource.class.getName());
+
+       /** The event bus. */
+       private final EventBus eventBus;
+
+       /** The current source. */
+       private final AtomicReference<Source> source = new AtomicReference<Source>();
+
+       /** Whether the source was changed. */
+       private boolean sourceChanged;
+
+       @Inject
+       public MultiSource(EventBus eventBus) {
+               this.eventBus = eventBus;
+       }
+
+       //
+       // ACTIONS
+       //
+
+       /**
+        * Sets the new source to use.
+        *
+        * @param source
+        *              The new source to use
+        */
+       public void setSource(Source source) {
+               checkNotNull(source, "source must not be null");
+
+               Source oldSource = this.source.getAndSet(source);
+               if (oldSource != null) {
+                       synchronized (this.source) {
+                               sourceChanged = true;
+                               this.source.notifyAll();
+                       }
+                       logger.info(String.format("Next Source set: %s", source));
+               }
+       }
+
+       //
+       // SOURCE METHODS
+       //
+
+       @Override
+       public Metadata metadata() {
+               return source.get().metadata();
+       }
+
+       @Override
+       public byte[] get(int bufferSize) throws EOFException, IOException {
+               while (true) {
+                       try {
+                               return source.get().get(bufferSize);
+                       } catch (EOFException eofe1) {
+                               eventBus.post(new SourceFinishedEvent(source.get()));
+                               synchronized (source) {
+                                       while (!sourceChanged) {
+                                               try {
+                                                       logger.info("Waiting for next Source...");
+                                                       source.wait();
+                                                       logger.info("Was notified.");
+                                               } catch (InterruptedException ioe1) {
+                                                       /* ignore: we’ll end up here again if we were interrupted. */
+                                               }
+                                       }
+                               }
+                       } finally {
+                               synchronized (source) {
+                                       sourceChanged = false;
+                               }
+                       }
+               }
+       }
+
+}