Add dummy REST API endpoint for preview Fix

This commit adds dummy endpoint for preview Fix. Endpoint always returns empty map

Change-Id: I64d7e2f46085275ff3f5e2aea397d5ce18da2741
diff --git a/java/com/google/gerrit/extensions/api/changes/RevisionApi.java b/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
index f8404ce..7d4f555 100644
--- a/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
+++ b/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
@@ -22,6 +22,7 @@
 import com.google.gerrit.extensions.common.CherryPickChangeInfo;
 import com.google.gerrit.extensions.common.CommentInfo;
 import com.google.gerrit.extensions.common.CommitInfo;
+import com.google.gerrit.extensions.common.DiffInfo;
 import com.google.gerrit.extensions.common.EditInfo;
 import com.google.gerrit.extensions.common.FileInfo;
 import com.google.gerrit.extensions.common.MergeableInfo;
@@ -125,6 +126,8 @@
    */
   EditInfo applyFix(String fixId) throws RestApiException;
 
+  Map<String, DiffInfo> getFixPreview(String fixId) throws RestApiException;
+
   DraftApi createDraft(DraftInput in) throws RestApiException;
 
   DraftApi draft(String id) throws RestApiException;
@@ -296,6 +299,11 @@
     }
 
     @Override
+    public Map<String, DiffInfo> getFixPreview(String fixId) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
     public Map<String, List<CommentInfo>> drafts() throws RestApiException {
       throw new NotImplementedException();
     }
diff --git a/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java b/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
index 01dfe36..1a4cbb8 100644
--- a/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
+++ b/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
@@ -44,6 +44,7 @@
 import com.google.gerrit.extensions.common.CommentInfo;
 import com.google.gerrit.extensions.common.CommitInfo;
 import com.google.gerrit.extensions.common.DescriptionInput;
+import com.google.gerrit.extensions.common.DiffInfo;
 import com.google.gerrit.extensions.common.EditInfo;
 import com.google.gerrit.extensions.common.FileInfo;
 import com.google.gerrit.extensions.common.Input;
@@ -71,6 +72,7 @@
 import com.google.gerrit.server.restapi.change.Fixes;
 import com.google.gerrit.server.restapi.change.GetCommit;
 import com.google.gerrit.server.restapi.change.GetDescription;
+import com.google.gerrit.server.restapi.change.GetFixPreview;
 import com.google.gerrit.server.restapi.change.GetMergeList;
 import com.google.gerrit.server.restapi.change.GetPatch;
 import com.google.gerrit.server.restapi.change.GetRelated;
@@ -126,6 +128,7 @@
   private final ListRevisionComments listComments;
   private final ListRobotComments listRobotComments;
   private final ApplyFix applyFix;
+  private final GetFixPreview getFixPreview;
   private final Fixes fixes;
   private final ListRevisionDrafts listDrafts;
   private final CreateDraftComment createDraft;
@@ -169,6 +172,7 @@
       ListRevisionComments listComments,
       ListRobotComments listRobotComments,
       ApplyFix applyFix,
+      GetFixPreview getFixPreview,
       Fixes fixes,
       ListRevisionDrafts listDrafts,
       CreateDraftComment createDraft,
@@ -211,6 +215,7 @@
     this.robotComments = robotComments;
     this.listRobotComments = listRobotComments;
     this.applyFix = applyFix;
+    this.getFixPreview = getFixPreview;
     this.fixes = fixes;
     this.listDrafts = listDrafts;
     this.createDraft = createDraft;
@@ -452,6 +457,15 @@
   }
 
   @Override
+  public Map<String, DiffInfo> getFixPreview(String fixId) throws RestApiException {
+    try {
+      return getFixPreview.apply(fixes.parse(revision, IdString.fromDecoded(fixId))).value();
+    } catch (Exception e) {
+      throw asRestApiException("Cannot get fix preview", e);
+    }
+  }
+
+  @Override
   public List<CommentInfo> draftsAsList() throws RestApiException {
     try {
       return listDrafts.getComments(revision);
diff --git a/java/com/google/gerrit/server/restapi/change/GetFixPreview.java b/java/com/google/gerrit/server/restapi/change/GetFixPreview.java
new file mode 100644
index 0000000..db89819
--- /dev/null
+++ b/java/com/google/gerrit/server/restapi/change/GetFixPreview.java
@@ -0,0 +1,33 @@
+// Copyright (C) 2019 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 com.google.gerrit.extensions.common.DiffInfo;
+import com.google.gerrit.extensions.restapi.Response;
+import com.google.gerrit.extensions.restapi.RestReadView;
+import com.google.gerrit.server.change.FixResource;
+import com.google.inject.Singleton;
+import java.util.HashMap;
+import java.util.Map;
+
+@Singleton
+public class GetFixPreview implements RestReadView<FixResource> {
+
+  @Override
+  public Response<Map<String, DiffInfo>> apply(FixResource resource) {
+    Map<String, DiffInfo> result = new HashMap<>();
+    return Response.ok(result);
+  }
+}
diff --git a/java/com/google/gerrit/server/restapi/change/Module.java b/java/com/google/gerrit/server/restapi/change/Module.java
index 539463f..4409c6a 100644
--- a/java/com/google/gerrit/server/restapi/change/Module.java
+++ b/java/com/google/gerrit/server/restapi/change/Module.java
@@ -160,6 +160,7 @@
     get(ROBOT_COMMENT_KIND).to(GetRobotComment.class);
     child(REVISION_KIND, "fixes").to(Fixes.class);
     post(FIX_KIND, "apply").to(ApplyFix.class);
+    get(FIX_KIND, "preview").to(GetFixPreview.class);
 
     child(REVISION_KIND, "files").to(Files.class);
     put(FILE_KIND, "reviewed").to(PutReviewed.class);
diff --git a/javatests/com/google/gerrit/acceptance/api/revision/RobotCommentsIT.java b/javatests/com/google/gerrit/acceptance/api/revision/RobotCommentsIT.java
index e3b7456..db1e99b7 100644
--- a/javatests/com/google/gerrit/acceptance/api/revision/RobotCommentsIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/revision/RobotCommentsIT.java
@@ -31,6 +31,7 @@
 import com.google.gerrit.extensions.api.changes.ReviewInput.RobotCommentInput;
 import com.google.gerrit.extensions.client.Comment;
 import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.common.DiffInfo;
 import com.google.gerrit.extensions.common.EditInfo;
 import com.google.gerrit.extensions.common.FixReplacementInfo;
 import com.google.gerrit.extensions.common.FixSuggestionInfo;
@@ -960,6 +961,27 @@
     }
   }
 
+  @Test
+  public void getFixPreviewWithNonexistingFixId() throws Exception {
+    addRobotComment(changeId, withFixRobotCommentInput);
+
+    assertThrows(
+        ResourceNotFoundException.class,
+        () -> gApi.changes().id(changeId).current().getFixPreview("Non existing fixId"));
+  }
+
+  @Test
+  public void getFixPreview() throws Exception {
+    addRobotComment(changeId, withFixRobotCommentInput);
+    List<RobotCommentInfo> robotCommentInfos = getRobotComments();
+
+    List<String> fixIds = getFixIds(robotCommentInfos);
+    String fixId = Iterables.getOnlyElement(fixIds);
+
+    Map<String, DiffInfo> result = gApi.changes().id(changeId).current().getFixPreview(fixId);
+    assertThat(result).isEmpty();
+  }
+
   private static RobotCommentInput createRobotCommentInputWithMandatoryFields() {
     RobotCommentInput in = new RobotCommentInput();
     in.robotId = "happyRobot";