/*
 * Copyright 2012 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.JDK;
import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
import static com.google.errorprone.matchers.Matchers.instanceMethod;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.MemberSelectTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.tools.javac.code.Symbol.TypeSymbol;
import java.lang.annotation.Retention;

/** @author scottjohnson@google.com (Scott Johnson) */
@BugPattern(
  name = "NonRuntimeAnnotation",
  summary = "Calling getAnnotation on an annotation that is not retained at runtime.",
  explanation =
      "Calling getAnnotation on an annotation that does not have its Retention set to "
          + "RetentionPolicy.RUNTIME will always return null.",
  category = JDK,
  severity = ERROR
)
public class NonRuntimeAnnotation extends BugChecker implements MethodInvocationTreeMatcher {

  @Override
  public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
    if (!instanceMethod().onDescendantOf("java.lang.Class").named("getAnnotation")
        .matches(tree, state)) {
      return Description.NO_MATCH;
    }
    MemberSelectTree memTree = (MemberSelectTree) tree.getArguments().get(0);
    TypeSymbol annotation = ASTHelpers.getSymbol(memTree.getExpression()).type.tsym;

    Retention retention = ASTHelpers.getAnnotation(annotation, Retention.class);
    if (retention != null && retention.value().equals(RUNTIME)) {
      return Description.NO_MATCH;
    }

    return describeMatch(tree, SuggestedFix.replace(tree, "null"));
  }
}