plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/control/GroovyConditionalCanBeElvisInspection.java

/*
 * Copyright 2007-2008 Dave Griffith
 *
 * 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 org.jetbrains.plugins.groovy.codeInspection.control;

import com.intellij.codeInsight.PsiEquivalenceUtil;
import com.intellij.codeInspection.ProblemDescriptor;
import com.intellij.openapi.project.Project;
import com.intellij.psi.CommonClassNames;
import com.intellij.psi.PsiElement;
import com.intellij.psi.PsiMethod;
import com.intellij.psi.PsiType;
import com.intellij.psi.util.InheritanceUtil;
import com.intellij.util.IncorrectOperationException;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.plugins.groovy.codeInspection.BaseInspection;
import org.jetbrains.plugins.groovy.codeInspection.BaseInspectionVisitor;
import org.jetbrains.plugins.groovy.codeInspection.GroovyFix;
import org.jetbrains.plugins.groovy.lang.lexer.GroovyTokenTypes;
import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.*;
import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.literals.GrLiteral;
import org.jetbrains.plugins.groovy.lang.psi.impl.PsiImplUtil;

public class GroovyConditionalCanBeElvisInspection extends BaseInspection {

  @Override
  @NotNull
  public String getDisplayName() {
    return "Conditional expression can be elvis";
  }

  @Override
  @NotNull
  public String getGroupDisplayName() {
    return CONTROL_FLOW;
  }

  @Override
  public String buildErrorString(Object... args) {
    return "Conditional expression can be elvis #loc";
  }

  @Override
  public GroovyFix buildFix(@NotNull PsiElement location) {
    return new GroovyFix() {
      @Override
      @NotNull
      public String getName() {
        return "Convert Conditional to Elvis";
      }

      @Override
      public void doFix(Project project, ProblemDescriptor descriptor) throws IncorrectOperationException {
        final GrConditionalExpression expr = (GrConditionalExpression)descriptor.getPsiElement();

        final GrExpression condition = expr.getCondition();
        final GrExpression thenExpression = expr.getThenBranch();
        final GrExpression elseExpression = expr.getElseBranch();
        assert elseExpression != null;
        assert thenExpression != null;

        final String newExpression;
        if (checkForStringIsEmpty(condition, elseExpression) || checkForListIsEmpty(condition, elseExpression) || checkForEqualsNotElse(condition, elseExpression)) {
          newExpression = elseExpression.getText() + " ?: " + thenExpression.getText();
        }
        else {
          newExpression = thenExpression.getText() + " ?: " + elseExpression.getText();
        }
        PsiImplUtil.replaceExpression(newExpression, expr);
      }
    };
  }

  private static boolean checkPsiElement(GrConditionalExpression expr) {
    if (expr instanceof GrElvisExpression) return false;
    GrExpression condition = expr.getCondition();

    final GrExpression then = expr.getThenBranch();
    final GrExpression elseBranch = expr.getElseBranch();
    if (then == null || elseBranch == null) return false;


    return checkForEqualsThen(condition, then) ||
           checkForEqualsNotElse(condition, elseBranch) ||
           checkForNull(condition, then) ||
           checkForStringIsEmpty(condition, elseBranch) ||
           checkForStringIsNotEmpty(condition, then) ||
           checkForListIsEmpty(condition, elseBranch) ||
           checkForListIsNotEmpty(condition, then);
  }

  private static boolean checkForEqualsNotElse(GrExpression condition, GrExpression elseBranch) {
    if (!(condition instanceof GrUnaryExpression)) return false;
    if (((GrUnaryExpression)condition).getOperationTokenType() != GroovyTokenTypes.mLNOT) return false;

    final GrExpression operand = ((GrUnaryExpression)condition).getOperand();
    return operand != null && PsiEquivalenceUtil.areElementsEquivalent(operand, elseBranch);
  }

  private static boolean checkForEqualsThen(GrExpression condition, GrExpression then) {
    return PsiEquivalenceUtil.areElementsEquivalent(condition, then);
  }

  private static boolean checkForListIsNotEmpty(GrExpression condition, GrExpression then) {
    if (!(condition instanceof GrUnaryExpression)) return false;

    if (((GrUnaryExpression)condition).getOperationTokenType() != GroovyTokenTypes.mLNOT) return false;

    return checkForListIsEmpty(((GrUnaryExpression)condition).getOperand(), then);
  }

  private static boolean checkForListIsEmpty(GrExpression condition, GrExpression elseBranch) {
    if (condition instanceof GrMethodCall) condition = ((GrMethodCall)condition).getInvokedExpression();
    if (!(condition instanceof GrReferenceExpression)) return false;

    final GrExpression qualifier = ((GrReferenceExpression)condition).getQualifier();
    if (qualifier == null) return false;

    if (!PsiEquivalenceUtil.areElementsEquivalent(qualifier, elseBranch)) return false;

    final PsiType type = qualifier.getType();
    if (type == null) return false;
    if (!InheritanceUtil.isInheritor(type, CommonClassNames.JAVA_UTIL_LIST)) return false;

    final PsiElement resolved = ((GrReferenceExpression)condition).resolve();

    return resolved instanceof PsiMethod &&
           "isEmpty".equals(((PsiMethod)resolved).getName()) &&
           ((PsiMethod)resolved).getParameterList().getParametersCount() == 0;
  }

  /**
   * checks for the case !string.isEmpty ? string : something_else
   */
  private static boolean checkForStringIsNotEmpty(GrExpression condition, GrExpression then) {
    if (!(condition instanceof GrUnaryExpression)) return false;

    if (((GrUnaryExpression)condition).getOperationTokenType() != GroovyTokenTypes.mLNOT) return false;

    return checkForStringIsEmpty(((GrUnaryExpression)condition).getOperand(), then);
  }

  /**
   * checks for the case string.isEmpty() ? something_else : string
   */
  private static boolean checkForStringIsEmpty(GrExpression condition, GrExpression elseBranch) {
    if (condition instanceof GrMethodCall) condition = ((GrMethodCall)condition).getInvokedExpression();
    if (!(condition instanceof GrReferenceExpression)) return false;

    final GrExpression qualifier = ((GrReferenceExpression)condition).getQualifier();
    if (qualifier == null) return false;

    if (!PsiEquivalenceUtil.areElementsEquivalent(qualifier, elseBranch)) return false;

    final PsiType type = qualifier.getType();
    if (type == null) return false;
    if (!type.equalsToText(CommonClassNames.JAVA_LANG_STRING)) return false;

    final PsiElement resolved = ((GrReferenceExpression)condition).resolve();

    return resolved instanceof PsiMethod &&
           "isEmpty".equals(((PsiMethod)resolved).getName()) &&
           ((PsiMethod)resolved).getParameterList().getParametersCount() == 0;
  }

  private static boolean checkForNull(GrExpression condition, GrExpression then) {
    if (!(condition instanceof GrBinaryExpression)) return false;

    GrBinaryExpression binaryExpression = (GrBinaryExpression)condition;
    if (GroovyTokenTypes.mNOT_EQUAL != binaryExpression.getOperationTokenType()) return false;

    GrExpression left = binaryExpression.getLeftOperand();
    GrExpression right = binaryExpression.getRightOperand();
    if (left instanceof GrLiteral && "null".equals(left.getText()) && right != null) {
      return PsiEquivalenceUtil.areElementsEquivalent(right, then);
    }
    if (right instanceof GrLiteral && "null".equals(right.getText())) {
      return PsiEquivalenceUtil.areElementsEquivalent(left, then);
    }

    return false;
  }

  @NotNull
  @Override
  public BaseInspectionVisitor buildVisitor() {
    return new Visitor();
  }

  private static class Visitor extends BaseInspectionVisitor {
    @Override
    public void visitConditionalExpression(GrConditionalExpression expression) {
      super.visitConditionalExpression(expression);
      if (checkPsiElement(expression)) {
        registerError(expression);
      }
    }
  }
}