Introduce a job scheduler and experiment for sending notifications to idle devices

service/src/main/java/org/whispersystems/textsecuregcm/push/IdleDeviceNotificationScheduler.java

@@ -0,0 +1,99 @@
+package org.whispersystems.textsecuregcm.push;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.google.common.annotations.VisibleForTesting;
+import org.whispersystems.textsecuregcm.identity.IdentityType;
+import org.whispersystems.textsecuregcm.scheduler.JobScheduler;
+import org.whispersystems.textsecuregcm.scheduler.SchedulingUtil;
+import org.whispersystems.textsecuregcm.storage.Account;
+import org.whispersystems.textsecuregcm.storage.AccountsManager;
+import org.whispersystems.textsecuregcm.storage.Device;
+import org.whispersystems.textsecuregcm.util.SystemMapper;
+import software.amazon.awssdk.services.dynamodb.DynamoDbAsyncClient;
+import javax.annotation.Nullable;
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.time.LocalTime;
+import java.util.UUID;
+import java.util.concurrent.CompletableFuture;
+
+public class IdleDeviceNotificationScheduler extends JobScheduler {
+
+  private final AccountsManager accountsManager;
+  private final PushNotificationManager pushNotificationManager;
+  private final Clock clock;
+
+  @VisibleForTesting
+  static final Duration MIN_IDLE_DURATION = Duration.ofDays(14);
+
+  @VisibleForTesting
+  record AccountAndDeviceIdentifier(UUID accountIdentifier, byte deviceId) {}
+
+  public IdleDeviceNotificationScheduler(final AccountsManager accountsManager,
+      final PushNotificationManager pushNotificationManager,
+      final DynamoDbAsyncClient dynamoDbAsyncClient,
+      final String tableName,
+      final Duration jobExpiration,
+      final Clock clock) {
+
+    super(dynamoDbAsyncClient, tableName, jobExpiration, clock);
+
+    this.accountsManager = accountsManager;
+    this.pushNotificationManager = pushNotificationManager;
+    this.clock = clock;
+  }
+
+  @Override
+  public String getSchedulerName() {
+    return "IdleDeviceNotification";
+  }
+
+  @Override
+  protected CompletableFuture<String> processJob(@Nullable final byte[] jobData) {
+    final AccountAndDeviceIdentifier accountAndDeviceIdentifier;
+
+    try {
+      accountAndDeviceIdentifier = SystemMapper.jsonMapper().readValue(jobData, AccountAndDeviceIdentifier.class);
+    } catch (final IOException e) {
+      return CompletableFuture.failedFuture(e);
+    }
+
+    return accountsManager.getByAccountIdentifierAsync(accountAndDeviceIdentifier.accountIdentifier())
+        .thenCompose(maybeAccount -> maybeAccount.map(account ->
+                account.getDevice(accountAndDeviceIdentifier.deviceId()).map(device -> {
+                      if (!isIdle(device)) {
+                        return CompletableFuture.completedFuture("deviceSeenRecently");
+                      }
+
+                      try {
+                        return pushNotificationManager
+                            .sendNewMessageNotification(account, accountAndDeviceIdentifier.deviceId(), true)
+                            .thenApply(ignored -> "sent");
+                      } catch (final NotPushRegisteredException e) {
+                        return CompletableFuture.completedFuture("deviceTokenDeleted");
+                      }
+                    })
+                    .orElse(CompletableFuture.completedFuture("deviceDeleted")))
+            .orElse(CompletableFuture.completedFuture("accountDeleted")));
+  }
+
+  public boolean isIdle(final Device device) {
+    final Duration idleDuration = Duration.between(Instant.ofEpochMilli(device.getLastSeen()), clock.instant());
+
+    return idleDuration.compareTo(MIN_IDLE_DURATION) >= 0;
+  }
+
+  public CompletableFuture<Void> scheduleNotification(final Account account, final byte deviceId, final LocalTime preferredDeliveryTime) {
+    final Instant runAt = SchedulingUtil.getNextRecommendedNotificationTime(account, preferredDeliveryTime, clock);
+
+    try {
+      return scheduleJob(runAt, SystemMapper.jsonMapper().writeValueAsBytes(
+          new AccountAndDeviceIdentifier(account.getIdentifier(IdentityType.ACI), deviceId)));
+    } catch (final JsonProcessingException e) {
+      // This should never happen when serializing an `AccountAndDeviceIdentifier`
+      throw new AssertionError(e);
+    }
+  }
+}