Default diff preferences PUT REST endpoint

Change-Id: I287e8dcbda4053c1081a9f18719696596e6aa3d3

gerrit-server/src/main/java/com/google/gerrit/server/config/Module.java

@@ -39,6 +39,7 @@ public class Module extends RestApiModule {
     get(CONFIG_KIND, "preferences").to(GetPreferences.class);
     put(CONFIG_KIND, "preferences").to(SetPreferences.class);
     get(CONFIG_KIND, "preferences.diff").to(GetDiffPreferences.class);
+    put(CONFIG_KIND, "preferences.diff").to(SetDiffPreferences.class);
     put(CONFIG_KIND, "email.confirm").to(ConfirmEmail.class);
   }
 }

gerrit-server/src/main/java/com/google/gerrit/server/config/SetDiffPreferences.java

@@ -0,0 +1,105 @@
+// Copyright (C) 2016 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.config;
+
+import static com.google.gerrit.server.config.ConfigUtil.loadSection;
+import static com.google.gerrit.server.config.ConfigUtil.skipField;
+import static com.google.gerrit.server.config.ConfigUtil.storeSection;
+import static com.google.gerrit.server.config.GetDiffPreferences.readFromGit;
+
+import com.google.gerrit.common.data.GlobalCapability;
+import com.google.gerrit.extensions.annotations.RequiresCapability;
+import com.google.gerrit.extensions.client.DiffPreferencesInfo;
+import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.RestModifyView;
+import com.google.gerrit.server.account.VersionedAccountPreferences;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.git.MetaDataUpdate;
+import com.google.gerrit.server.git.UserConfigSections;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.Singleton;
+import org.eclipse.jgit.errors.ConfigInvalidException;
+import org.eclipse.jgit.errors.RepositoryNotFoundException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+
+@RequiresCapability(GlobalCapability.ADMINISTRATE_SERVER)
+@Singleton
+public class SetDiffPreferences implements
+    RestModifyView<ConfigResource, DiffPreferencesInfo> {
+  private static final Logger log =
+      LoggerFactory.getLogger(SetDiffPreferences.class);
+
+  private final Provider<MetaDataUpdate.User> metaDataUpdateFactory;
+  private final AllUsersName allUsersName;
+  private final GitRepositoryManager gitManager;
+
+  @Inject
+  SetDiffPreferences(GitRepositoryManager gitManager,
+      Provider<MetaDataUpdate.User> metaDataUpdateFactory,
+      AllUsersName allUsersName) {
+    this.gitManager = gitManager;
+    this.metaDataUpdateFactory = metaDataUpdateFactory;
+    this.allUsersName = allUsersName;
+  }
+
+  @Override
+  public Object apply(ConfigResource configResource, DiffPreferencesInfo in)
+      throws BadRequestException, Exception {
+    if (in == null) {
+      throw new BadRequestException("input must be provided");
+    }
+    if (!hasSetFields(in)) {
+      throw new BadRequestException("unsupported option");
+    }
+    return writeToGit(readFromGit(gitManager, allUsersName, in));
+  }
+
+  private DiffPreferencesInfo writeToGit(DiffPreferencesInfo in)
+      throws RepositoryNotFoundException, IOException, ConfigInvalidException {
+    DiffPreferencesInfo out = new DiffPreferencesInfo();
+    try (MetaDataUpdate md = metaDataUpdateFactory.get().create(allUsersName)) {
+      VersionedAccountPreferences prefs =
+          VersionedAccountPreferences.forDefault();
+      prefs.load(md);
+      DiffPreferencesInfo defaults = DiffPreferencesInfo.defaults();
+      storeSection(prefs.getConfig(), UserConfigSections.DIFF, null, in,
+          defaults);
+      prefs.commit(md);
+      loadSection(prefs.getConfig(), UserConfigSections.DIFF, null, out,
+          DiffPreferencesInfo.defaults(), null);
+    }
+    return out;
+  }
+
+  private static boolean hasSetFields(DiffPreferencesInfo in) {
+    try {
+      for (Field field : in.getClass().getDeclaredFields()) {
+        if (skipField(field)) {
+          continue;
+        }
+        if (field.get(in) != null) {
+          return true;
+        }
+      }
+    } catch (IllegalAccessException e) {
+      log.warn("Unable to verify input", e);
+    }
+    return false;
+  }
+}