Add source for video files (#698)

build.gradle

@@ -230,6 +230,7 @@ project(":core") {
         compile group: 'org.bytedeco.javacpp-presets', name: 'opencv', version: '3.0.0-1.1', classifier: os
         compile group: 'org.bytedeco.javacpp-presets', name: 'opencv-3.0.0-1.1', classifier: 'linux-frc'
         compile group: 'org.bytedeco.javacpp-presets', name: 'videoinput', version: '0.200-1.1', classifier: os
+        compile group: 'org.bytedeco.javacpp-presets', name: 'ffmpeg', version: '0.200-1.1', classifier: os
         compile group: 'org.python', name: 'jython', version: '2.7.0'
         compile group: 'com.thoughtworks.xstream', name: 'xstream', version: '1.4.9'
         compile group: 'org.apache.commons', name: 'commons-lang3', version: '3.5'

core/src/main/java/edu/wpi/grip/core/GripCoreModule.java

@@ -16,6 +16,7 @@
 import edu.wpi.grip.core.sources.ImageFileSource;
 import edu.wpi.grip.core.sources.MultiImageFileSource;
 import edu.wpi.grip.core.sources.NetworkTableEntrySource;
+import edu.wpi.grip.core.sources.VideoFileSource;
 import edu.wpi.grip.core.util.ExceptionWitness;
 import edu.wpi.grip.core.util.GripMode;
 
@@ -157,6 +158,9 @@ public <I> void hear(TypeLiteral<I> type, TypeEncounter<I> encounter) {
     install(new FactoryModuleBuilder()
         .implement(ClassifierSource.class, ClassifierSource.class)
         .build(ClassifierSource.Factory.class));
+    install(new FactoryModuleBuilder()
+        .implement(VideoFileSource.class, VideoFileSource.class)
+        .build(VideoFileSource.Factory.class));
 
     install(new FactoryModuleBuilder().build(ExceptionWitness.Factory.class));
     install(new FactoryModuleBuilder().build(Timer.Factory.class));

core/src/main/java/edu/wpi/grip/core/Source.java

@@ -7,6 +7,7 @@
 import edu.wpi.grip.core.sources.ImageFileSource;
 import edu.wpi.grip.core.sources.MultiImageFileSource;
 import edu.wpi.grip.core.sources.NetworkTableEntrySource;
+import edu.wpi.grip.core.sources.VideoFileSource;
 import edu.wpi.grip.core.util.ExceptionWitness;
 
 import com.google.common.base.MoreObjects;
@@ -125,6 +126,8 @@ public static class SourceFactoryImpl implements SourceFactory {
     NetworkTableEntrySource.Factory networkTableEntryFactory;
     @Inject
     ClassifierSource.Factory fileSourceFactory;
+    @Inject
+    VideoFileSource.Factory videoFileSourceFactory;
 
     @Override
     public Source create(Class<?> type, Properties properties) throws IOException {
@@ -140,6 +143,8 @@ public Source create(Class<?> type, Properties properties) throws IOException {
         return networkTableEntryFactory.create(properties);
       } else if (type.isAssignableFrom(ClassifierSource.class)) {
         return fileSourceFactory.create(properties);
+      } else if (type.isAssignableFrom(VideoFileSource.class)) {
+        return videoFileSourceFactory.create(properties);
       } else {
         throw new IllegalArgumentException(type + " was not a valid type");
       }

core/src/main/java/edu/wpi/grip/core/observables/Observable.java

@@ -0,0 +1,56 @@
+package edu.wpi.grip.core.observables;
+
+/**
+ * An observable wraps a value that, when changed, will notify listeners of the change.
+ *
+ * @param <T> the type of value to observe
+ */
+public interface Observable<T> {
+
+  /**
+   * Add an observer to this observable. It will be notified of any future changes to the value
+   * of this observable. Listeners will be fired in the order in which they were added, and on the
+   * thread that updates the observed value. Because of this, listeners should take as little time
+   * as possible to run (unless submitting a long-running task to a worker thread).
+   */
+  void addObserver(Observer<? super T> observer);
+
+  /**
+   * Removes an observer from this observable. The observer will not be updated with future changes
+   * to the value of this observable.
+   */
+  void removeObserver(Observer<? super T> observer);
+
+  /**
+   * Gets the current value of this observable.
+   */
+  T get();
+
+  /**
+   * Sets the value of this observable. If it's not {@link Object#equals(Object) equal} to the
+   * current value, all observers will be notified of the change.
+   */
+  void set(T value);
+
+  /**
+   * Creates an observable initialized to the given value. This observable is <i>not</i>
+   * thread-safe; for a thread-safe observable, use {@link #synchronizedOf(Object) synchronizedOf}.
+   *
+   * @param value the initial value of the observable
+   * @param <T>   the type of value in the observable
+   */
+  static <T> Observable<T> of(T value) {
+    return new SimpleObservable<>(value);
+  }
+
+  /**
+   * Creates a thread-safe observable initialized to the given value.
+   *
+   * @param value the initial value of the observable
+   * @param <T>   the type of value in the observable
+   */
+  static <T> Observable<T> synchronizedOf(T value) {
+    return new SynchronizedObservable<>(value);
+  }
+
+}

core/src/main/java/edu/wpi/grip/core/observables/Observer.java

@@ -0,0 +1,19 @@
+package edu.wpi.grip.core.observables;
+
+/**
+ * Observes changes to the value of an {@link Observable}.
+ *
+ * @param <T> the type of the value to observe
+ */
+@FunctionalInterface
+public interface Observer<T> {
+
+  /**
+   * Called when the value of the observable changes.
+   *
+   * @param previous the previous value of the observable
+   * @param current  the current value of the observable
+   */
+  void onChange(T previous, T current);
+
+}

core/src/main/java/edu/wpi/grip/core/observables/SimpleObservable.java

@@ -0,0 +1,59 @@
+package edu.wpi.grip.core.observables;
+
+import java.util.LinkedHashSet;
+import java.util.Objects;
+import java.util.Set;
+
+/**
+ * Default thread-unsafe implementation of {@link Observable}. For a thread-safe solution, see
+ * {@link SynchronizedObservable}.
+ *
+ * @param <T> the type of the values to observe
+ */
+public class SimpleObservable<T> implements Observable<T> {
+
+  private final Set<Observer<? super T>> observers = new LinkedHashSet<>();
+  private T value;
+
+  /**
+   * Creates an observable value with no initial value.
+   */
+  SimpleObservable() {
+    this(null);
+  }
+
+  /**
+   * Creates an observable value with the given initial value.
+   *
+   * @param initialValue the initial value
+   */
+  SimpleObservable(T initialValue) {
+    this.value = initialValue;
+  }
+
+  @Override
+  public void addObserver(Observer<? super T> observer) {
+    Objects.requireNonNull(observer, "Listener cannot be null");
+    observers.add(observer);
+  }
+
+  @Override
+  public void removeObserver(Observer<? super T> observer) {
+    observers.remove(observer);
+  }
+
+  @Override
+  public T get() {
+    return value;
+  }
+
+  @Override
+  public void set(T value) {
+    T previous = this.value;
+    if (!Objects.equals(previous, value)) {
+      this.value = value;
+      observers.forEach(l -> l.onChange(previous, value));
+    }
+  }
+
+}

core/src/main/java/edu/wpi/grip/core/observables/SynchronizedObservable.java

@@ -0,0 +1,53 @@
+package edu.wpi.grip.core.observables;
+
+/**
+ * A thread-safe implementation of {@link Observable}. This should only be used in situations where
+ * observers are <i>very likely</i> to run in multiple threads. Otherwise, {@link SimpleObservable}
+ * should be used to avoid the penalties of {@code synchronized} and lock contention.
+ *
+ * @param <T> the type of the values to observe
+ */
+public class SynchronizedObservable<T> extends SimpleObservable<T> {
+
+  private final Object observersLock = new Object();
+  private final Object valueLock = new Object();
+
+  SynchronizedObservable() {
+    super();
+  }
+
+  SynchronizedObservable(T initialValue) {
+    super(initialValue);
+  }
+
+  @Override
+  public void addObserver(Observer<? super T> observer) {
+    synchronized (observersLock) {
+      super.addObserver(observer);
+    }
+  }
+
+  @Override
+  public void removeObserver(Observer<? super T> observer) {
+    synchronized (observersLock) {
+      super.addObserver(observer);
+    }
+  }
+
+  @Override
+  public T get() {
+    synchronized (valueLock) {
+      return super.get();
+    }
+  }
+
+  @Override
+  public void set(T value) {
+    synchronized (valueLock) {
+      synchronized (observersLock) {
+        super.set(value);
+      }
+    }
+  }
+
+}