java/java-analysis-impl/src/com/intellij/codeInspection/AnonymousCanBeMethodReferenceInspection.java

/*
 * Copyright 2000-2012 JetBrains s.r.o.
 *
 * 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.intellij.codeInspection;

import com.intellij.codeInsight.daemon.GroupNames;
import com.intellij.openapi.diagnostic.Logger;
import com.intellij.openapi.project.Project;
import com.intellij.openapi.util.TextRange;
import com.intellij.pom.java.LanguageLevel;
import com.intellij.psi.*;
import com.intellij.psi.codeStyle.JavaCodeStyleManager;
import com.intellij.psi.util.PsiUtil;
import com.intellij.psi.util.RedundantCastUtil;
import org.jetbrains.annotations.Nls;
import org.jetbrains.annotations.NotNull;

/**
 * User: anna
 */
public class AnonymousCanBeMethodReferenceInspection extends BaseJavaBatchLocalInspectionTool {
  public static final Logger LOG = Logger.getInstance("#" + AnonymousCanBeMethodReferenceInspection.class.getName());

  @Nls
  @NotNull
  @Override
  public String getGroupDisplayName() {
    return GroupNames.LANGUAGE_LEVEL_SPECIFIC_GROUP_NAME;
  }

  @Nls
  @NotNull
  @Override
  public String getDisplayName() {
    return "Anonymous type can be replaced with method reference";
  }

  @Override
  public boolean isEnabledByDefault() {
    return true;
  }

  @NotNull
  @Override
  public String getShortName() {
    return "Anonymous2MethodRef";
  }

  @NotNull
  @Override
  public PsiElementVisitor buildVisitor(@NotNull final ProblemsHolder holder, boolean isOnTheFly) {
    return new JavaElementVisitor() {
      @Override
      public void visitAnonymousClass(PsiAnonymousClass aClass) {
        super.visitAnonymousClass(aClass);
        if (PsiUtil.getLanguageLevel(aClass).isAtLeast(LanguageLevel.JDK_1_8)) {
          final PsiClassType baseClassType = aClass.getBaseClassType();
          if (LambdaUtil.isFunctionalType(baseClassType)) {
            final PsiMethod[] methods = aClass.getMethods();
            if (methods.length == 1 && aClass.getFields().length == 0 && !AnonymousCanBeLambdaInspection.hasForbiddenRefsInsideBody(methods[0], aClass)) {
              final PsiCodeBlock body = methods[0].getBody();
              final PsiCallExpression callExpression =
                LambdaCanBeMethodReferenceInspection
                  .canBeMethodReferenceProblem(body, methods[0].getParameterList().getParameters(), baseClassType);
              if (callExpression != null) {
                final PsiMethod resolveMethod = callExpression.resolveMethod();
                if (resolveMethod != methods[0] && !AnonymousCanBeLambdaInspection.functionalInterfaceMethodReferenced(resolveMethod, aClass)) {
                  final PsiElement parent = aClass.getParent();
                  if (parent instanceof PsiNewExpression) {
                    final PsiJavaCodeReferenceElement classReference = ((PsiNewExpression)parent).getClassOrAnonymousClassReference();
                    if (classReference != null) {
                      final PsiElement lBrace = aClass.getLBrace();
                      LOG.assertTrue(lBrace != null);
                      final TextRange rangeInElement = new TextRange(0, aClass.getStartOffsetInParent() + lBrace.getStartOffsetInParent());
                      holder.registerProblem(parent,
                                             "Anonymous #ref #loc can be replaced with method reference", ProblemHighlightType.LIKE_UNUSED_SYMBOL, rangeInElement, new ReplaceWithMethodRefFix());
                    }
                  }
                }
              }
            }
          }
        }
      }
    };
  }

  private static class ReplaceWithMethodRefFix implements LocalQuickFix {
      @NotNull
      @Override
      public String getName() {
        return "Replace with method reference";
      }

      @NotNull
      @Override
      public String getFamilyName() {
        return getName();
      }

      @Override
      public void applyFix(@NotNull Project project, @NotNull ProblemDescriptor descriptor) {
        final PsiElement element = descriptor.getPsiElement();
        if (element instanceof PsiNewExpression) {
          final PsiAnonymousClass anonymousClass = ((PsiNewExpression)element).getAnonymousClass();
          if (anonymousClass == null) return;
          final PsiMethod[] methods = anonymousClass.getMethods();
          if (methods.length != 1) return;

          final PsiParameter[] parameters = methods[0].getParameterList().getParameters();
          final PsiCallExpression callExpression = LambdaCanBeMethodReferenceInspection
            .canBeMethodReferenceProblem(methods[0].getBody(), parameters, anonymousClass.getBaseClassType());
          if (callExpression == null) return;
          final String methodRefText =
            LambdaCanBeMethodReferenceInspection.createMethodReferenceText(callExpression, anonymousClass.getBaseClassType(), parameters);

          if (methodRefText != null) {
            final String canonicalText = anonymousClass.getBaseClassType().getCanonicalText();
            final PsiExpression psiExpression = JavaPsiFacade.getElementFactory(project).createExpressionFromText("(" + canonicalText + ")" + methodRefText, anonymousClass);
  
            PsiElement castExpr = anonymousClass.getParent().replace(psiExpression);
            if (RedundantCastUtil.isCastRedundant((PsiTypeCastExpression)castExpr)) {
              final PsiExpression operand = ((PsiTypeCastExpression)castExpr).getOperand();
              LOG.assertTrue(operand != null);
              castExpr = castExpr.replace(operand);
            }
            JavaCodeStyleManager.getInstance(project).shortenClassReferences(castExpr);
          }
        }
      }
    }
}