REST endpoints for managing the attention set

Attention set is returned by default in change details.

Background:
https://www.gerritcodereview.com/design-docs/attention-set.html

Upcoming further changes:
- Add to index
- Extend ReviewInput API to add reviewers
- Add invariants (e.g. user must be reviewer)
- Send notifications in *Attention*Op#postUpdate()
- Consider adding NotificationHandling in AttentionInput
- Consider adding validation listeners

Change-Id: I52ae870a94852ac98f731fef63f65cd2a7064742

java/com/google/gerrit/server/api/changes/AttentionSetApiImpl.java

@@ -0,0 +1,51 @@
+// Copyright (C) 2020 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.api.changes;
+
+import static com.google.gerrit.server.api.ApiUtil.asRestApiException;
+
+import com.google.gerrit.extensions.api.changes.AttentionSetApi;
+import com.google.gerrit.extensions.api.changes.RemoveFromAttentionSetInput;
+import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.server.change.AttentionSetEntryResource;
+import com.google.gerrit.server.restapi.change.RemoveFromAttentionSet;
+import com.google.inject.Inject;
+import com.google.inject.assistedinject.Assisted;
+
+public class AttentionSetApiImpl implements AttentionSetApi {
+  interface Factory {
+    AttentionSetApiImpl create(AttentionSetEntryResource attentionSetEntryResource);
+  }
+
+  private final RemoveFromAttentionSet removeFromAttentionSet;
+  private final AttentionSetEntryResource attentionSetEntryResource;
+
+  @Inject
+  AttentionSetApiImpl(
+      RemoveFromAttentionSet removeFromAttentionSet,
+      @Assisted AttentionSetEntryResource attentionSetEntryResource) {
+    this.removeFromAttentionSet = removeFromAttentionSet;
+    this.attentionSetEntryResource = attentionSetEntryResource;
+  }
+
+  @Override
+  public void remove(RemoveFromAttentionSetInput input) throws RestApiException {
+    try {
+      removeFromAttentionSet.apply(attentionSetEntryResource, input);
+    } catch (Exception e) {
+      throw asRestApiException("Cannot remove from attention set", e);
+    }
+  }
+}

java/com/google/gerrit/server/api/changes/ChangeApiImpl.java

@@ -23,7 +23,9 @@ import com.google.gerrit.exceptions.StorageException;
 import com.google.gerrit.extensions.api.changes.AbandonInput;
 import com.google.gerrit.extensions.api.changes.AddReviewerInput;
 import com.google.gerrit.extensions.api.changes.AddReviewerResult;
+import com.google.gerrit.extensions.api.changes.AddToAttentionSetInput;
 import com.google.gerrit.extensions.api.changes.AssigneeInput;
+import com.google.gerrit.extensions.api.changes.AttentionSetApi;
 import com.google.gerrit.extensions.api.changes.ChangeApi;
 import com.google.gerrit.extensions.api.changes.ChangeEditApi;
 import com.google.gerrit.extensions.api.changes.ChangeMessageApi;
@@ -66,6 +68,8 @@ import com.google.gerrit.server.change.ChangeMessageResource;
 import com.google.gerrit.server.change.ChangeResource;
 import com.google.gerrit.server.change.WorkInProgressOp;
 import com.google.gerrit.server.restapi.change.Abandon;
+import com.google.gerrit.server.restapi.change.AddToAttentionSet;
+import com.google.gerrit.server.restapi.change.AttentionSet;
 import com.google.gerrit.server.restapi.change.ChangeIncludedIn;
 import com.google.gerrit.server.restapi.change.ChangeMessages;
 import com.google.gerrit.server.restapi.change.Check;
@@ -147,6 +151,9 @@ class ChangeApiImpl implements ChangeApi {
   private final Provider<GetChange> getChangeProvider;
   private final PostHashtags postHashtags;
   private final GetHashtags getHashtags;
+  private final AttentionSet attentionSet;
+  private final AttentionSetApiImpl.Factory attentionSetApi;
+  private final AddToAttentionSet addToAttentionSet;
   private final PutAssignee putAssignee;
   private final GetAssignee getAssignee;
   private final GetPastAssignees getPastAssignees;
@@ -197,6 +204,9 @@ class ChangeApiImpl implements ChangeApi {
       Provider<GetChange> getChangeProvider,
       PostHashtags postHashtags,
       GetHashtags getHashtags,
+      AttentionSet attentionSet,
+      AttentionSetApiImpl.Factory attentionSetApi,
+      AddToAttentionSet addToAttentionSet,
       PutAssignee putAssignee,
       GetAssignee getAssignee,
       GetPastAssignees getPastAssignees,
@@ -245,6 +255,9 @@ class ChangeApiImpl implements ChangeApi {
     this.getChangeProvider = getChangeProvider;
     this.postHashtags = postHashtags;
     this.getHashtags = getHashtags;
+    this.attentionSet = attentionSet;
+    this.attentionSetApi = attentionSetApi;
+    this.addToAttentionSet = addToAttentionSet;
     this.putAssignee = putAssignee;
     this.getAssignee = getAssignee;
     this.getPastAssignees = getPastAssignees;
@@ -529,6 +542,24 @@ class ChangeApiImpl implements ChangeApi {
     }
   }
 
+  @Override
+  public AccountInfo addToAttentionSet(AddToAttentionSetInput input) throws RestApiException {
+    try {
+      return addToAttentionSet.apply(change, input).value();
+    } catch (Exception e) {
+      throw asRestApiException("Cannot add to attention set", e);
+    }
+  }
+
+  @Override
+  public AttentionSetApi attention(String id) throws RestApiException {
+    try {
+      return attentionSetApi.create(attentionSet.parse(change, IdString.fromDecoded(id)));
+    } catch (Exception e) {
+      throw asRestApiException("Cannot parse account", e);
+    }
+  }
+
   @Override
   public AccountInfo setAssignee(AssigneeInput input) throws RestApiException {
     try {

java/com/google/gerrit/server/api/changes/Module.java

@@ -32,5 +32,6 @@ public class Module extends FactoryModule {
     factory(RevisionReviewerApiImpl.Factory.class);
     factory(ChangeEditApiImpl.Factory.class);
     factory(ChangeMessageApiImpl.Factory.class);
+    factory(AttentionSetApiImpl.Factory.class);
   }
 }