Allow write of generic value in global-refdb

Currently it is only possible to write ObjectId. The possibility of
writing, for example, Long is needed to version the repositories.

Feature: Issue 12256
Change-Id: Id782729b8d7e786211ddc95c944dbb7b00c1e027

src/main/java/com/gerritforge/gerrit/globalrefdb/GlobalRefDatabase.java

diff --git a/src/main/java/com/gerritforge/gerrit/globalrefdb/GlobalRefDatabase.java b/src/main/java/com/gerritforge/gerrit/globalrefdb/GlobalRefDatabase.java
index 4217751..24f86a7 100644
--- a/src/main/java/com/gerritforge/gerrit/globalrefdb/GlobalRefDatabase.java
+++ b/src/main/java/com/gerritforge/gerrit/globalrefdb/GlobalRefDatabase.java
@@ -57,6 +57,21 @@
       throws GlobalRefDbSystemError;
 
   /**
+   * Compare a value of generic type T, and put if it is up-to-date with the current.
+   *
+   * <p>Compare and put are executed as an atomic operation.
+   *
+   * @param project project name of the ref.
+   * @param refName to store the value for.
+   * @param currValue current expected value in the DB.
+   * @param newValue new value to store.
+   * @return true if the put was successful; false otherwise.
+   * @throws GlobalRefDbSystemError the reference cannot be put due to a system error.
+   */
+  <T> boolean compareAndPut(Project.NameKey project, String refName, T currValue, T newValue)
+      throws GlobalRefDbSystemError;
+
+  /**
    * Lock a reference.
    *
    * @param project project name

src/test/java/com/gerritforge/gerrit/globalrefdb/FakeGlobalRefDatabase.java

diff --git a/src/test/java/com/gerritforge/gerrit/globalrefdb/FakeGlobalRefDatabase.java b/src/test/java/com/gerritforge/gerrit/globalrefdb/FakeGlobalRefDatabase.java
index d96f532..4d2e0b6 100644
--- a/src/test/java/com/gerritforge/gerrit/globalrefdb/FakeGlobalRefDatabase.java
+++ b/src/test/java/com/gerritforge/gerrit/globalrefdb/FakeGlobalRefDatabase.java
@@ -30,12 +30,14 @@
 
   private ConcurrentMap<Project.NameKey, ConcurrentMap<String, AtomicReference<ObjectId>>>
       keyValueStore;
+  private ConcurrentMap<String, AtomicReference<?>> genericKeyValueStore;
 
   private ConcurrentMap<Project.NameKey, ConcurrentMap<String, AtomicReference<Lock>>> refLockStore;
 
   public FakeGlobalRefDatabase() {
     keyValueStore = new MapMaker().concurrencyLevel(1).makeMap();
     refLockStore = new MapMaker().concurrencyLevel(1).makeMap();
+    genericKeyValueStore = new MapMaker().concurrencyLevel(1).makeMap();
   }
 
   @Override
@@ -61,6 +63,20 @@
   }
 
   @Override
+  @SuppressWarnings("unchecked")
+  public <T> boolean compareAndPut(Project.NameKey project, String refName, T currValue, T newValue)
+      throws GlobalRefDbSystemError {
+    String key = String.format("%s/%s", project.get(), refName);
+    AtomicReference<T> storedValue = (AtomicReference<T>) genericKeyValueStore.get(key);
+    if (storedValue == null) {
+      genericKeyValueStore.put(key, new AtomicReference<>(newValue));
+      return true;
+    }
+
+    return storedValue.compareAndSet(currValue, newValue);
+  }
+
+  @Override
   public AutoCloseable lockRef(Project.NameKey project, String refName)
       throws GlobalRefDbLockException {
     ConcurrentMap<String, AtomicReference<Lock>> projectRefLock = projectRefLock(project);

src/test/java/com/gerritforge/gerrit/globalrefdb/GlobalRefDatabaseTest.java

diff --git a/src/test/java/com/gerritforge/gerrit/globalrefdb/GlobalRefDatabaseTest.java b/src/test/java/com/gerritforge/gerrit/globalrefdb/GlobalRefDatabaseTest.java
index 9e2ee81..02d060b 100644
--- a/src/test/java/com/gerritforge/gerrit/globalrefdb/GlobalRefDatabaseTest.java
+++ b/src/test/java/com/gerritforge/gerrit/globalrefdb/GlobalRefDatabaseTest.java
@@ -167,6 +167,34 @@
     assertThat(o.isPresent()).isFalse();
   }
 
+  @Test
+  public void shouldCreateGenericEntryInTheGlobalRefDBWhenFirstValue() {
+    assertThat(objectUnderTest.compareAndPut(project, refName, null, new Object())).isTrue();
+  }
+
+  @Test
+  public void shouldUpdateGenericEntryWithNewRef() throws Exception {
+    createChange(refName);
+
+    Object object1 = new Object();
+    objectUnderTest.compareAndPut(project, refName, null, object1);
+
+    Object object2 = new Object();
+    assertThat(objectUnderTest.compareAndPut(project, refName, object1, object2)).isTrue();
+  }
+
+  @Test
+  public void shouldRejectGenericUpdateWhenLocalRepoIsOutdated() throws Exception {
+    createChange(refName);
+
+    Object object1 = new Object();
+    objectUnderTest.compareAndPut(project, refName, null, object1);
+
+    Object object2 = new Object();
+    Object object3 = new Object();
+    assertThat(objectUnderTest.compareAndPut(project, refName, object2, object3)).isFalse();
+  }
+
   private Ref ref(String refName, ObjectId objectId) {
     return new ObjectIdRef.Unpeeled(Ref.Storage.NETWORK, refName, objectId);
   }