Add support to retrieve the account diff preferences via REST

The diff preferences of a user can now be retrieved by GET on
'/accounts/*/preferences.diff'.

Change-Id: Ica4014496b8ced4d0d0f34804a8dc4efcdd694a1

gerrit-server/src/main/java/com/google/gerrit/server/account/GetDiffPreferences.java

@@ -0,0 +1,78 @@
+// Copyright (C) 2013 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.account;
+
+import com.google.gerrit.extensions.restapi.AuthException;
+import com.google.gerrit.extensions.restapi.RestReadView;
+import com.google.gerrit.reviewdb.client.AccountDiffPreference;
+import com.google.gerrit.reviewdb.client.AccountDiffPreference.Whitespace;
+import com.google.gerrit.server.CurrentUser;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+
+public class GetDiffPreferences implements RestReadView<AccountResource> {
+
+  private final Provider<CurrentUser> self;
+
+  @Inject
+  GetDiffPreferences(Provider<CurrentUser> self) {
+    this.self = self;
+  }
+
+  @Override
+  public DiffPreferencesInfo apply(AccountResource rsrc) throws AuthException {
+    if (self.get() != rsrc.getUser()
+        && !self.get().getCapabilities().canAdministrateServer()) {
+      throw new AuthException("restricted to administrator");
+    }
+    return DiffPreferencesInfo.parse(rsrc.getUser().getAccountDiffPreference());
+  }
+
+  static class DiffPreferencesInfo {
+    static DiffPreferencesInfo parse(AccountDiffPreference p) {
+      DiffPreferencesInfo info = new DiffPreferencesInfo();
+      info.context = p.getContext();
+      info.expandAllComments = p.isExpandAllComments() ? true : null;
+      info.ignoreWhitespace = p.getIgnoreWhitespace();
+      info.intralineDifference = p.isIntralineDifference() ? true : null;
+      info.lineLength = p.getLineLength();
+      info.manualReview = p.isManualReview() ? true : null;
+      info.retainHeader = p.isRetainHeader() ? true : null;
+      info.showLineEndings = p.isShowLineEndings() ? true : null;
+      info.showTabs = p.isShowTabs() ? true : null;
+      info.showWhitespaceErrors = p.isShowWhitespaceErrors() ? true : null;
+      info.skipDeleted = p.isSkipDeleted() ? true : null;
+      info.skipUncommented = p.isSkipUncommented() ? true : null;
+      info.syntaxHighlighting = p.isSyntaxHighlighting() ? true : null;
+      info.tabSize = p.getTabSize();
+      return info;
+    }
+
+    short context;
+    Boolean expandAllComments;
+    Whitespace ignoreWhitespace;
+    Boolean intralineDifference;
+    int lineLength;
+    Boolean manualReview;
+    Boolean retainHeader;
+    Boolean showLineEndings;
+    Boolean showTabs;
+    Boolean showWhitespaceErrors;
+    Boolean skipDeleted;
+    Boolean skipUncommented;
+    Boolean syntaxHighlighting;
+    int tabSize;
+  }
+}