1 files changed, 175 insertions, 0 deletions
diff --git a/java/com/google/gerrit/server/restapi/change/DeleteChangeMessage.java b/java/com/google/gerrit/server/restapi/change/DeleteChangeMessage.java
new file mode 100644
index 0000000000..881d106366
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+++ b/java/com/google/gerrit/server/restapi/change/DeleteChangeMessage.java
@@ -0,0 +1,175 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.restapi.change;
+
+import static com.google.gerrit.server.ChangeMessagesUtil.createChangeMessageInfo;
+import static java.util.Objects.requireNonNull;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Strings;
+import com.google.gerrit.common.Nullable;
+import com.google.gerrit.extensions.api.changes.DeleteChangeMessageInput;
+import com.google.gerrit.extensions.common.ChangeMessageInfo;
+import com.google.gerrit.extensions.common.Input;
+import com.google.gerrit.extensions.restapi.Response;
+import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.ChangeMessage;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.ChangeMessagesUtil;
+import com.google.gerrit.server.CurrentUser;
+import com.google.gerrit.server.account.AccountLoader;
+import com.google.gerrit.server.change.ChangeMessageResource;
+import com.google.gerrit.server.notedb.ChangeNotes;
+import com.google.gerrit.server.permissions.GlobalPermission;
+import com.google.gerrit.server.permissions.PermissionBackend;
+import com.google.gerrit.server.permissions.PermissionBackendException;
+import com.google.gerrit.server.update.BatchUpdate;
+import com.google.gerrit.server.update.BatchUpdateOp;
+import com.google.gerrit.server.update.ChangeContext;
+import com.google.gerrit.server.update.RetryHelper;
+import com.google.gerrit.server.update.RetryingRestModifyView;
+import com.google.gerrit.server.update.UpdateException;
+import com.google.gerrit.server.util.time.TimeUtil;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.Singleton;
+import java.io.IOException;
+import java.util.List;
+
+/** Deletes a change message by rewriting history. */
+@Singleton
+public class DeleteChangeMessage
+    extends RetryingRestModifyView<
+        ChangeMessageResource, DeleteChangeMessageInput, Response<ChangeMessageInfo>> {
+
+  private final Provider<CurrentUser> userProvider;
+  private final Provider<ReviewDb> dbProvider;
+  private final PermissionBackend permissionBackend;
+  private final ChangeMessagesUtil changeMessagesUtil;
+  private final AccountLoader.Factory accountLoaderFactory;
+  private final ChangeNotes.Factory notesFactory;
+
+  @Inject
+  public DeleteChangeMessage(
+      Provider<CurrentUser> userProvider,
+      Provider<ReviewDb> dbProvider,
+      PermissionBackend permissionBackend,
+      ChangeMessagesUtil changeMessagesUtil,
+      AccountLoader.Factory accountLoaderFactory,
+      ChangeNotes.Factory notesFactory,
+      RetryHelper retryHelper) {
+    super(retryHelper);
+    this.userProvider = userProvider;
+    this.dbProvider = dbProvider;
+    this.permissionBackend = permissionBackend;
+    this.changeMessagesUtil = changeMessagesUtil;
+    this.accountLoaderFactory = accountLoaderFactory;
+    this.notesFactory = notesFactory;
+  }
+
+  @Override
+  public Response<ChangeMessageInfo> applyImpl(
+      BatchUpdate.Factory updateFactory,
+      ChangeMessageResource resource,
+      DeleteChangeMessageInput input)
+      throws RestApiException, PermissionBackendException, OrmException, UpdateException,
+          IOException {
+    CurrentUser user = userProvider.get();
+    permissionBackend.user(user).check(GlobalPermission.ADMINISTRATE_SERVER);
+
+    String newChangeMessage =
+        createNewChangeMessage(user.asIdentifiedUser().getName(), input.reason);
+    DeleteChangeMessageOp deleteChangeMessageOp =
+        new DeleteChangeMessageOp(resource.getChangeMessageIndex(), newChangeMessage);
+    try (BatchUpdate batchUpdate =
+        updateFactory.create(
+            dbProvider.get(), resource.getChangeResource().getProject(), user, TimeUtil.nowTs())) {
+      batchUpdate.addOp(resource.getChangeId(), deleteChangeMessageOp).execute();
+    }
+
+    ChangeMessageInfo updatedMessageInfo =
+        createUpdatedChangeMessageInfo(resource.getChangeId(), resource.getChangeMessageIndex());
+    return Response.created(updatedMessageInfo);
+  }
+
+  private ChangeMessageInfo createUpdatedChangeMessageInfo(Change.Id id, int targetIdx)
+      throws OrmException, PermissionBackendException {
+    List<ChangeMessage> messages =
+        changeMessagesUtil.byChange(dbProvider.get(), notesFactory.createChecked(id));
+    ChangeMessage updatedChangeMessage = messages.get(targetIdx);
+    AccountLoader accountLoader = accountLoaderFactory.create(true);
+    ChangeMessageInfo info = createChangeMessageInfo(updatedChangeMessage, accountLoader);
+    accountLoader.fill();
+    return info;
+  }
+
+  @VisibleForTesting
+  public static String createNewChangeMessage(String deletedBy, @Nullable String deletedReason) {
+    requireNonNull(deletedBy, "user name must not be null");
+
+    if (Strings.isNullOrEmpty(deletedReason)) {
+      return createNewChangeMessage(deletedBy);
+    }
+    return String.format("Change message removed by: %s\nReason: %s", deletedBy, deletedReason);
+  }
+
+  @VisibleForTesting
+  public static String createNewChangeMessage(String deletedBy) {
+    requireNonNull(deletedBy, "user name must not be null");
+
+    return "Change message removed by: " + deletedBy;
+  }
+
+  private class DeleteChangeMessageOp implements BatchUpdateOp {
+    private final int targetMessageIdx;
+    private final String newMessage;
+
+    DeleteChangeMessageOp(int targetMessageIdx, String newMessage) {
+      this.targetMessageIdx = targetMessageIdx;
+      this.newMessage = newMessage;
+    }
+
+    @Override
+    public boolean updateChange(ChangeContext ctx) throws OrmException {
+      PatchSet.Id psId = ctx.getChange().currentPatchSetId();
+      changeMessagesUtil.replaceChangeMessage(
+          ctx.getDb(), ctx.getUpdate(psId), targetMessageIdx, newMessage);
+      return true;
+    }
+  }
+
+  @Singleton
+  public static class DefaultDeleteChangeMessage
+      extends RetryingRestModifyView<ChangeMessageResource, Input, Response<ChangeMessageInfo>> {
+    private final DeleteChangeMessage deleteChangeMessage;
+
+    @Inject
+    public DefaultDeleteChangeMessage(
+        DeleteChangeMessage deleteChangeMessage, RetryHelper retryHelper) {
+      super(retryHelper);
+      this.deleteChangeMessage = deleteChangeMessage;
+    }
+
+    @Override
+    protected Response<ChangeMessageInfo> applyImpl(
+        BatchUpdate.Factory updateFactory, ChangeMessageResource resource, Input input)
+        throws Exception {
+      return deleteChangeMessage.applyImpl(updateFactory, resource, new DeleteChangeMessageInput());
+    }
+  }
+}