ConstantOnLHSOfComparisonInspection.java

/*
 * Copyright 2003-2011 Dave Griffith, Bas Leijdekkers
 *
 * 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.siyeh.ig.style;

import com.intellij.codeInspection.ProblemDescriptor;
import com.intellij.openapi.project.Project;
import com.intellij.psi.PsiBinaryExpression;
import com.intellij.psi.PsiExpression;
import com.intellij.psi.util.PsiUtil;
import com.intellij.util.IncorrectOperationException;
import com.siyeh.InspectionGadgetsBundle;
import com.siyeh.ig.BaseInspection;
import com.siyeh.ig.BaseInspectionVisitor;
import com.siyeh.ig.InspectionGadgetsFix;
import com.siyeh.ig.PsiReplacementUtil;
import com.siyeh.ig.psiutils.ComparisonUtils;
import com.siyeh.ig.psiutils.ExpressionUtils;
import org.jetbrains.annotations.NotNull;

public class ConstantOnLHSOfComparisonInspection extends BaseInspection {

  @Override
  @NotNull
  public String getID() {
    return "ConstantOnLeftSideOfComparison";
  }

  @Override
  @NotNull
  public String getDisplayName() {
    return InspectionGadgetsBundle.message("constant.on.lhs.of.comparison.display.name");
  }

  @Override
  @NotNull
  public String buildErrorString(Object... infos) {
    return InspectionGadgetsBundle.message("constant.on.lhs.of.comparison.problem.descriptor");
  }

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

  @Override
  public InspectionGadgetsFix buildFix(Object... infos) {
    return new SwapComparisonFix();
  }

  private static class SwapComparisonFix extends InspectionGadgetsFix {

    @Override
    @NotNull
    public String getFamilyName() {
      return InspectionGadgetsBundle.message("flip.comparison.quickfix");
    }

    @Override
    public void doFix(Project project, ProblemDescriptor descriptor) throws IncorrectOperationException {
      final PsiBinaryExpression expression = (PsiBinaryExpression)descriptor.getPsiElement();
      final PsiExpression rhs = expression.getROperand();
      if (rhs == null) {
        return;
      }
      final String flippedComparison = ComparisonUtils.getFlippedComparison(expression.getOperationTokenType());
      if (flippedComparison == null) {
        return;
      }
      final PsiExpression lhs = expression.getLOperand();
      final String rhsText = rhs.getText();
      final String lhsText = lhs.getText();
      PsiReplacementUtil.replaceExpression(expression, rhsText + ' ' + flippedComparison + ' ' + lhsText);
    }
  }

  private static class ConstantOnLHSOfComparisonVisitor extends BaseInspectionVisitor {

    @Override
    public void visitBinaryExpression(@NotNull PsiBinaryExpression expression) {
      super.visitBinaryExpression(expression);
      if (!ComparisonUtils.isComparison(expression)) {
        return;
      }
      final PsiExpression lhs = expression.getLOperand();
      final PsiExpression rhs = expression.getROperand();
      if (rhs == null || !isConstantExpression(lhs) || isConstantExpression(rhs)) {
        return;
      }
      registerError(expression);
    }

    private static boolean isConstantExpression(PsiExpression expression) {
      return ExpressionUtils.isNullLiteral(expression) || PsiUtil.isConstantExpression(expression);
    }
  }
}