Added OrderEnforcer class to schedule ordered tasks.

test/unitTest/java/org/thoughtcrime/securesms/camera/OrderEnforcerTest.java

@@ -0,0 +1,104 @@
+package org.thoughtcrime.securesms.camera;
+
+import org.junit.Test;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static junit.framework.Assert.assertEquals;
+
+public class OrderEnforcerTest {
+
+  @Test
+  public void markCompleted_singleEntry() {
+    AtomicInteger counter = new AtomicInteger(0);
+
+    OrderEnforcer<Stage> enforcer = new OrderEnforcer<>(Stage.A, Stage.B, Stage.C, Stage.D);
+    enforcer.run(Stage.A, new CountRunnable(counter));
+    assertEquals(0, counter.get());
+
+    enforcer.markCompleted(Stage.A);
+    assertEquals(1, counter.get());
+  }
+
+  @Test
+  public void markCompleted_singleEntry_waterfall() {
+    AtomicInteger counter = new AtomicInteger(0);
+
+    OrderEnforcer<Stage> enforcer = new OrderEnforcer<>(Stage.A, Stage.B, Stage.C, Stage.D);
+    enforcer.run(Stage.C, new CountRunnable(counter));
+    assertEquals(0, counter.get());
+
+    enforcer.markCompleted(Stage.A);
+    assertEquals(0, counter.get());
+
+    enforcer.markCompleted(Stage.C);
+    assertEquals(0, counter.get());
+
+    enforcer.markCompleted(Stage.B);
+    assertEquals(1, counter.get());
+  }
+
+  @Test
+  public void markCompleted_multipleEntriesPerStage_waterfall() {
+    AtomicInteger counter = new AtomicInteger(0);
+
+    OrderEnforcer<Stage> enforcer = new OrderEnforcer<>(Stage.A, Stage.B, Stage.C, Stage.D);
+
+    enforcer.run(Stage.A, new CountRunnable(counter));
+    enforcer.run(Stage.A, new CountRunnable(counter));
+    assertEquals(0, counter.get());
+
+    enforcer.run(Stage.B, new CountRunnable(counter));
+    enforcer.run(Stage.B, new CountRunnable(counter));
+    assertEquals(0, counter.get());
+
+    enforcer.run(Stage.C, new CountRunnable(counter));
+    enforcer.run(Stage.C, new CountRunnable(counter));
+    assertEquals(0, counter.get());
+
+    enforcer.run(Stage.D, new CountRunnable(counter));
+    enforcer.run(Stage.D, new CountRunnable(counter));
+    assertEquals(0, counter.get());
+
+    enforcer.markCompleted(Stage.A);
+    assertEquals(counter.get(), 2);
+
+    enforcer.markCompleted(Stage.D);
+    assertEquals(counter.get(), 2);
+
+    enforcer.markCompleted(Stage.B);
+    assertEquals(counter.get(), 4);
+
+    enforcer.markCompleted(Stage.C);
+    assertEquals(counter.get(), 8);
+  }
+
+  @Test
+  public void run_alreadyCompleted() {
+    AtomicInteger counter = new AtomicInteger(0);
+
+    OrderEnforcer<Stage> enforcer = new OrderEnforcer<>(Stage.A, Stage.B, Stage.C, Stage.D);
+    enforcer.markCompleted(Stage.A);
+    enforcer.markCompleted(Stage.B);
+
+    enforcer.run(Stage.B, new CountRunnable(counter));
+    assertEquals(1, counter.get());
+  }
+
+  private static class CountRunnable implements Runnable {
+    private final AtomicInteger counter;
+
+    public CountRunnable(AtomicInteger counter) {
+      this.counter = counter;
+    }
+
+    @Override
+    public void run() {
+      counter.incrementAndGet();
+    }
+  }
+
+  private enum Stage {
+    A, B, C, D
+  }
+}