Add ActorTimer and related (#51)

* Add ActorTimer and related

* cr

sdk/src/main/java/io/dapr/actors/runtime/ActorTimer.java

@@ -0,0 +1,41 @@
+package io.dapr.actors.runtime;
+
+import java.time.Duration;
+import java.util.function.Function;
+
+/**
+ *  Represents the timer set on an Actor.
+ */
+public interface ActorTimer {
+
+  /**
+   * Gets the time when timer is first due.
+   * @return Time as Duration when timer is first due.
+   */
+  Duration getDueTime();
+
+  /**
+   * Gets the periodic time when timer will be invoked.
+   * @return Periodic time as Duration when timer will be invoked.
+   */
+  Duration getPeriod();
+
+  /**
+   * Gets the name of the Timer. The name is unique per actor.
+   * @return The name of the timer.
+   */
+  String getName();
+
+  /**
+   *
+   * @return Gets a delegate that specifies a method to be called when the timer fires.
+   *     It has one parameter: the state object passed to RegisterTimer.
+   */
+  Function<Object, Void> getAsyncCallback();
+
+  /**
+   *
+   * @return Gets state containing information to be used by the callback method, or null.
+   */
+  Object getState();
+}

sdk/src/main/java/io/dapr/actors/runtime/ActorTimerImpl.java

@@ -0,0 +1,88 @@
+package io.dapr.actors.runtime;
+
+import org.json.JSONObject;
+import java.time.Duration;
+import java.util.function.Function;
+
+/**
+ * Represents the timer set on an Actor.
+ */
+class ActorTimerImpl implements ActorTimer {
+
+  private final AbstractActor owner;
+  private String name;
+  private Function<Object, Void> asyncCallback;
+  private Object state;
+  private Duration dueTime;
+  private Duration period;
+
+  /**
+   *
+   * @param owner  The Actor that owns this timer.  The timer callback will be fired for this Actor.
+   * @param timerName The name of the timer.
+   * @param asyncCallback The callback to invoke when the timer fires.
+   * @param state information to be used by the callback method
+   * @param dueTime the time when timer is first due.
+   * @param period the periodic time when timer will be invoked.
+   */
+  public ActorTimerImpl(AbstractActor owner, String timerName, Function<Object, Void> asyncCallback, Object state, Duration dueTime, Duration period) {
+    this.owner = owner;
+    this.name = timerName;
+    this.asyncCallback = asyncCallback;
+    this.state = state;
+    this.dueTime = dueTime;
+    this.period = period;
+  }
+
+  /**
+   * Gets the name of the Timer. The name is unique per actor.
+   * @return The name of the timer.
+   */
+  public String getName() {
+    return this.name;
+  }
+
+  /**
+   * Gets the time when timer is first due.
+   * @return Time as Duration when timer is first due.
+   */
+  public Duration getDueTime() {
+    return this.dueTime;
+  }
+
+  /**
+   * @return Gets a delegate that specifies a method to be called when the timer fires.
+   *     It has one parameter: the state object passed to RegisterTimer.
+   */
+  public Function<Object, Void> getAsyncCallback() {
+    return this.asyncCallback;
+  }
+
+  /**
+   * Gets the periodic time when timer will be invoked.
+   * @return Periodic time as Duration when timer will be invoked.
+   */
+  public Duration getPeriod() {
+    return this.period;
+  }
+
+  /**
+   *
+   * @return Gets state containing information to be used by the callback method, or null.
+   */
+  public Object getState() {
+    return this.state;
+  }
+
+  /**
+   *
+   * @return
+   */
+  String serialize()
+  {
+    JSONObject j = new JSONObject();
+    j.put("dueTime", ConverterUtils.ConvertDurationToDaprFormat(this.getDueTime()));
+    j.put("period", ConverterUtils.ConvertDurationToDaprFormat(this.getPeriod()));
+    return j.toString();
+  }
+}

sdk/src/test/java/io/dapr/actors/runtime/ActorTimerImplTest.java

@@ -0,0 +1,57 @@
+package io.dapr.actors.runtime;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.time.Duration;
+
+public class ActorTimerImplTest {
+
+  @Test
+  public void serialize() {
+    Duration dueTime = Duration.ZERO
+      .plusMinutes(7)
+      .plusSeconds(17);
+
+    Duration period = Duration.ZERO
+      .plusHours(1)
+      .plusSeconds(3);
+
+    ActorTimerImpl timer = new ActorTimerImpl(
+      null,
+      "testTimer",
+      null,
+      null,
+      dueTime,
+      period);
+    String s = timer.serialize();
+
+    String expected = "{\"period\":\"1h0m3s0ms\",\"dueTime\":\"0h7m17s0ms\"}";
+    Assert.assertEquals(expected, s);
+  }
+
+  @Test
+  public void serializeWithOneTimePeriod() {
+    Duration dueTime = Duration.ZERO
+      .plusMinutes(7)
+      .plusSeconds(17);
+
+    // this is intentionally negative
+    Duration period = Duration.ZERO
+      .minusHours(1)
+      .minusMinutes(3);
+
+    ActorTimerImpl timer = new ActorTimerImpl(
+      null,
+      "testTimer",
+      null,
+      null,
+      dueTime,
+      period);
+    String s = timer.serialize();
+
+    // A negative period will be serialized to an empty string which is interpreted by Dapr to mean fire once only.
+    String expected = "{\"period\":\"\",\"dueTime\":\"0h7m17s0ms\"}";
+    Assert.assertEquals(expected, s);
+  }
+}