Support for querying PreKey meta-information.

src/main/java/org/whispersystems/textsecuregcm/controllers/KeysController.java

@@ -23,6 +23,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.whispersystems.textsecuregcm.entities.PreKey;
 import org.whispersystems.textsecuregcm.entities.PreKeyList;
+import org.whispersystems.textsecuregcm.entities.PreKeyStatus;
 import org.whispersystems.textsecuregcm.entities.UnstructuredPreKeyList;
 import org.whispersystems.textsecuregcm.federation.FederatedClientManager;
 import org.whispersystems.textsecuregcm.federation.NoSuchPeerException;
@@ -73,6 +74,20 @@ public class KeysController {
     keys.store(account.getNumber(), device.getId(), preKeys.getKeys(), preKeys.getLastResortKey());
   }
 
+  @Timed
+  @GET
+  @Path("/")
+  @Produces(MediaType.APPLICATION_JSON)
+  public PreKeyStatus getStatus(@Auth Account account) {
+    int count = keys.getCount(account.getNumber(), account.getAuthenticatedDevice().get().getId());
+
+    if (count > 0) {
+      count = count - 1;
+    }
+
+    return new PreKeyStatus(count);
+  }
+
   @Timed
   @GET
   @Path("/{number}/{device_id}")

src/main/java/org/whispersystems/textsecuregcm/entities/PreKeyStatus.java

@@ -0,0 +1,20 @@
+package org.whispersystems.textsecuregcm.entities;
+
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+public class PreKeyStatus {
+
+  @JsonProperty
+  private int count;
+
+  public PreKeyStatus(int count) {
+    this.count = count;
+  }
+
+  public PreKeyStatus() {}
+
+  public int getCount() {
+    return count;
+  }
+}

src/main/java/org/whispersystems/textsecuregcm/storage/Keys.java

@@ -40,7 +40,6 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 import java.sql.ResultSet;
 import java.sql.SQLException;
-import java.util.LinkedList;
 import java.util.List;
 
 public abstract class Keys {
@@ -67,6 +66,9 @@ public abstract class Keys {
   @Mapper(PreKeyMapper.class)
   abstract List<PreKey> retrieveFirst(@Bind("number") String number);
 
+  @SqlQuery("SELECT COUNT(*) FROM keys WHERE number = :number AND device_id = :device_id")
+  public abstract int getCount(@Bind("number") String number, @Bind("device_id") long deviceId);
+
   @Transaction(TransactionIsolationLevel.SERIALIZABLE)
   public void store(String number, long deviceId, List<PreKey> keys, PreKey lastResortKey) {
     for (PreKey key : keys) {

src/test/java/org/whispersystems/textsecuregcm/tests/controllers/KeyControllerTest.java

@@ -6,6 +6,7 @@ import com.yammer.dropwizard.testing.ResourceTest;
 import org.junit.Test;
 import org.whispersystems.textsecuregcm.controllers.KeysController;
 import org.whispersystems.textsecuregcm.entities.PreKey;
+import org.whispersystems.textsecuregcm.entities.PreKeyStatus;
 import org.whispersystems.textsecuregcm.entities.UnstructuredPreKeyList;
 import org.whispersystems.textsecuregcm.limits.RateLimiter;
 import org.whispersystems.textsecuregcm.limits.RateLimiters;
@@ -71,11 +72,25 @@ public class KeyControllerTest extends ResourceTest {
     allKeys.add(SAMPLE_KEY);
     allKeys.add(SAMPLE_KEY2);
     allKeys.add(SAMPLE_KEY3);
+
     when(keys.get(EXISTS_NUMBER)).thenReturn(Optional.of(new UnstructuredPreKeyList(allKeys)));
+    when(keys.getCount(eq(AuthHelper.VALID_NUMBER), eq(1L))).thenReturn(5);
 
     addResource(new KeysController(rateLimiters, keys, accounts, null));
   }
 
+  @Test
+  public void validKeyStatusTest() throws Exception {
+    PreKeyStatus result = client().resource("/v1/keys")
+        .header("Authorization",
+                AuthHelper.getAuthHeader(AuthHelper.VALID_NUMBER, AuthHelper.VALID_PASSWORD))
+        .get(PreKeyStatus.class);
+
+    assertThat(result.getCount() == 4);
+
+    verify(keys).getCount(eq(AuthHelper.VALID_NUMBER), eq(1L));
+  }
+
   @Test
   public void validLegacyRequestTest() throws Exception {
     PreKey result = client().resource(String.format("/v1/keys/%s", EXISTS_NUMBER))