/*
 * Copyright 2017 Google Inc. All Rights Reserved.
 *
 * 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.errorprone.bugpatterns;

import static com.google.errorprone.BugPattern.Category.PROTOBUF;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.matchers.Matchers.instanceMethod;

import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
import com.google.errorprone.fixes.Fix;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.MethodInvocationTree;

/**
 * Points out if #ordinal() is called on a Protocol Buffer Enum.
 *
 * @author bhagwani@google.com (Sumit Bhagwani)
 */
@BugPattern(
  name = "ProtocolBufferOrdinal",
  summary = "#ordinal() value on Protocol Buffer Enum can change if enumeration order of changed",
  explanation =
      "Shuffling of values in a Protocol Buffer enum can change the ordinal value of the enum "
          + "member. Since changing tag number isn't advisable in protos, use #getNumber() "
          + "instead which gives the tag number.",
  category = PROTOBUF,
  severity = WARNING
)
public class ProtocolBufferOrdinal extends BugChecker implements MethodInvocationTreeMatcher {

  private static final String PROTO_SUPER_CLASS = "com.google.protobuf.ProtocolMessageEnum";

  private static final Matcher<ExpressionTree> PROTO_MSG_ORDINAL_MATCHER =
      instanceMethod().onDescendantOf(PROTO_SUPER_CLASS).named("ordinal");

  @Override
  public Description matchMethodInvocation(
      MethodInvocationTree methodInvocationTree, VisitorState state) {
    if (!PROTO_MSG_ORDINAL_MATCHER.matches(methodInvocationTree, state)) {
      return Description.NO_MATCH;
    }
    ExpressionTree rec = ASTHelpers.getReceiver(methodInvocationTree);
    if (rec != null) {
      Fix fix =
          SuggestedFix.replace(
              state.getEndPosition(rec),
              state.getEndPosition(methodInvocationTree),
              ".getNumber()");
      return describeMatch(methodInvocationTree, fix);
    }
    return Description.NO_MATCH;
  }
}

@@ -1536,17 +1536,16 @@
 mary = %22
-#
 ordinal(
@@ -1553,17 +1553,17 @@
  value o
-n
+f
  Protoco
@@ -1608,18 +1608,18 @@
 n order 
-of
+is
  changed

Fix description of ProtocolBufferOrdinal