Implement reviewer access via REST

This change enables users to request details about a reviewer given a
change and a reviewer id.  The returned result is a map including the
reviewers:
* kind (gerritcodereview#reviewer)
* id
* email
* name (if provided)

Example:
curl -s localhost:8080/
    changes/blah~master~I2933f24c1fc0d7f44a34bb1dc7a3242fdfd29028/
    reviewers/1000000

{
  "kind": "gerritcodereview#reviewer",
  "id": "1000000",
  "email": "cco3%40android.com"
}

Change-Id: I3e164527d5e4cc5707577b31a8618a7ae9f7b098

gerrit-server/src/main/java/com/google/gerrit/server/change/GetReviewer.java

@@ -14,13 +14,20 @@
 
 package com.google.gerrit.server.change;
 
-import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.RestReadView;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
 
 public class GetReviewer implements RestReadView<ReviewerResource> {
+  private final ReviewerJson json;
+
+  @Inject
+  GetReviewer(ReviewerJson json) {
+    this.json = json;
+  }
+
   @Override
-  public Object apply(ReviewerResource resource)
-      throws BadRequestException, Exception {
-    throw new BadRequestException("Not yet implemented");
+  public Object apply(ReviewerResource reviewerResource) throws OrmException {
+    return json.format(reviewerResource);
   }
 }

gerrit-server/src/main/java/com/google/gerrit/server/change/ReviewerJson.java

@@ -0,0 +1,38 @@
+// Copyright (C) 2012 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.change;
+
+import com.google.gerrit.reviewdb.client.Account;
+
+public class ReviewerJson {
+  ReviewerJson() {
+  }
+
+  public ReviewerInfo format(ReviewerResource reviewerResource) {
+    ReviewerInfo reviewerInfo = new ReviewerInfo();
+    Account account = reviewerResource.getAccount();
+    reviewerInfo.id = account.getId().toString();
+    reviewerInfo.email = account.getPreferredEmail();
+    reviewerInfo.name = account.getFullName();
+    return reviewerInfo;
+  }
+
+  public static class ReviewerInfo {
+    final String kind = "gerritcodereview#reviewer";
+    String id;
+    String email;
+    String name;
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/change/ReviewerResource.java

@@ -22,14 +22,14 @@ public class ReviewerResource extends ChangeResource {
   public static final TypeLiteral<RestView<ReviewerResource>> REVIEWER_KIND =
       new TypeLiteral<RestView<ReviewerResource>>() {};
 
-  private final Account.Id id;
+  private final Account account;
 
-  public ReviewerResource(ChangeResource rsrc, Account.Id id) {
-    super(rsrc);
-    this.id = id;
+  public ReviewerResource(ChangeResource changeResource, Account account) {
+    super(changeResource);
+    this.account = account;
   }
 
-  public Account.Id getAccountId() {
-    return id;
+  public Account getAccount() {
+    return account;
   }
 }

gerrit-server/src/main/java/com/google/gerrit/server/change/Reviewers.java

@@ -19,15 +19,30 @@ import com.google.gerrit.extensions.restapi.ChildCollection;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.RestView;
 import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.PatchSetApproval;
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.account.AccountCache;
+import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Provider;
+
+import java.util.HashSet;
+import java.util.Set;
 
 public class Reviewers implements
     ChildCollection<ChangeResource, ReviewerResource> {
   private final DynamicMap<RestView<ReviewerResource>> views;
+  private final Provider<ReviewDb> dbProvider;
+  private final AccountCache accountCache;
 
   @Inject
-  Reviewers(DynamicMap<RestView<ReviewerResource>> views) {
+  Reviewers(Provider<ReviewDb> dbProvider,
+            DynamicMap<RestView<ReviewerResource>> views,
+            AccountCache accountCache) {
+    this.dbProvider = dbProvider;
     this.views = views;
+    this.accountCache = accountCache;
   }
 
   @Override
@@ -41,11 +56,31 @@ public class Reviewers implements
   }
 
   @Override
-  public ReviewerResource parse(ChangeResource change, String id)
-      throws ResourceNotFoundException, Exception {
-    if (id.matches("^[0-9]+$")) {
-      return new ReviewerResource(change, Account.Id.parse(id));
+  public ReviewerResource parse(ChangeResource changeResource, String id)
+      throws OrmException, ResourceNotFoundException {
+    // Get the account id
+    if (!id.matches("^[0-9]+$")) {
+      throw new ResourceNotFoundException(id);
+    }
+    Account.Id accountId = Account.Id.parse(id);
+
+    // See if the id exists as a reviewer for this change
+    if (fetchAccountIds(changeResource).contains(accountId)) {
+      Account account = accountCache.get(accountId).getAccount();
+      return new ReviewerResource(changeResource, account);
     }
     throw new ResourceNotFoundException(id);
   }
+
+  private Set<Account.Id> fetchAccountIds(ChangeResource changeResource)
+      throws OrmException {
+    ReviewDb db = dbProvider.get();
+    Change.Id changeId = changeResource.getChange().getId();
+    Set<Account.Id> accountIds = new HashSet<Account.Id>();
+    for (PatchSetApproval patchSetApproval
+         : db.patchSetApprovals().byChange(changeId)) {
+      accountIds.add(patchSetApproval.getAccountId());
+    }
+    return accountIds;
+  }
 }