/*
 * Copyright 2003-2010 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.ipp.psiutils;

import com.intellij.psi.*;
import com.intellij.psi.tree.IElementType;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.util.Collection;

class VariableAssignedVisitor extends JavaRecursiveElementVisitor {

  @NotNull private final Collection<PsiVariable> variables;
  private final boolean recurseIntoClasses;
  private boolean assigned = false;

  public VariableAssignedVisitor(@NotNull Collection<PsiVariable> variables,
                                 boolean recurseIntoClasses) {
    this.variables = variables;
    this.recurseIntoClasses = recurseIntoClasses;
  }

  @Override
  public void visitElement(@NotNull PsiElement element) {
    if (assigned) {
      return;
    }
    super.visitElement(element);
  }

  @Override
  public void visitAssignmentExpression(
    @NotNull PsiAssignmentExpression assignment) {
    if (assigned) {
      return;
    }
    super.visitAssignmentExpression(assignment);
    final PsiExpression lhs = assignment.getLExpression();
    for (PsiVariable variable : variables) {
      if (mayEvaluateToVariable(lhs, variable)) {
        assigned = true;
      }
    }
  }

  @Override
  public void visitClass(PsiClass aClass) {
    if (!recurseIntoClasses) {
      return;
    }
    if (assigned) {
      return;
    }
    super.visitClass(aClass);
  }

  @Override
  public void visitPrefixExpression(
    @NotNull PsiPrefixExpression prefixExpression) {
    if (assigned) {
      return;
    }
    super.visitPrefixExpression(prefixExpression);
    final IElementType tokenType = prefixExpression.getOperationTokenType();
    if (!tokenType.equals(JavaTokenType.PLUSPLUS) &&
        !tokenType.equals(JavaTokenType.MINUSMINUS)) {
      return;
    }
    final PsiExpression operand = prefixExpression.getOperand();
    for (PsiVariable variable : variables) {
      if (mayEvaluateToVariable(operand, variable)) {
        assigned = true;
      }
    }
  }

  @Override
  public void visitPostfixExpression(
    @NotNull PsiPostfixExpression postfixExpression) {
    if (assigned) {
      return;
    }
    super.visitPostfixExpression(postfixExpression);
    final IElementType tokenType = postfixExpression.getOperationTokenType();
    if (!tokenType.equals(JavaTokenType.PLUSPLUS) &&
        !tokenType.equals(JavaTokenType.MINUSMINUS)) {
      return;
    }
    final PsiExpression operand = postfixExpression.getOperand();
    for (PsiVariable variable : variables) {
      if (mayEvaluateToVariable(operand, variable)) {
        assigned = true;
      }
    }
  }

  public static boolean mayEvaluateToVariable(
    @Nullable PsiExpression expression,
    @NotNull PsiVariable variable) {
    if (expression == null) {
      return false;
    }
    if (expression instanceof PsiBinaryExpression) {
      final PsiBinaryExpression binaryExpression =
        (PsiBinaryExpression)expression;
      final PsiExpression lOperand = binaryExpression.getLOperand();
      final PsiExpression rOperand = binaryExpression.getROperand();
      return mayEvaluateToVariable(lOperand, variable) ||
             mayEvaluateToVariable(rOperand, variable);
    }
    if (expression instanceof PsiParenthesizedExpression) {
      final PsiParenthesizedExpression parenthesizedExpression =
        (PsiParenthesizedExpression)expression;
      final PsiExpression containedExpression =
        parenthesizedExpression.getExpression();
      return mayEvaluateToVariable(containedExpression, variable);
    }
    if (expression instanceof PsiTypeCastExpression) {
      final PsiTypeCastExpression typeCastExpression =
        (PsiTypeCastExpression)expression;
      final PsiExpression containedExpression =
        typeCastExpression.getOperand();
      return mayEvaluateToVariable(containedExpression, variable);
    }
    if (expression instanceof PsiConditionalExpression) {
      final PsiConditionalExpression conditional =
        (PsiConditionalExpression)expression;
      final PsiExpression thenExpression = conditional.getThenExpression();
      final PsiExpression elseExpression = conditional.getElseExpression();
      return mayEvaluateToVariable(thenExpression, variable) ||
             mayEvaluateToVariable(elseExpression, variable);
    }
    if (expression instanceof PsiArrayAccessExpression) {
      final PsiElement parent = expression.getParent();
      if (parent instanceof PsiArrayAccessExpression) {
        return false;
      }
      final PsiType type = variable.getType();
      if (!(type instanceof PsiArrayType)) {
        return false;
      }
      final PsiArrayType arrayType = (PsiArrayType)type;
      final int dimensions = arrayType.getArrayDimensions();
      if (dimensions <= 1) {
        return false;
      }
      PsiArrayAccessExpression arrayAccessExpression =
        (PsiArrayAccessExpression)expression;
      PsiExpression arrayExpression =
        arrayAccessExpression.getArrayExpression();
      int count = 1;
      while (arrayExpression instanceof PsiArrayAccessExpression) {
        arrayAccessExpression =
          (PsiArrayAccessExpression)arrayExpression;
        arrayExpression = arrayAccessExpression.getArrayExpression();
        count++;
      }
      return count != dimensions &&
             mayEvaluateToVariable(arrayExpression, variable);
    }
    return evaluatesToVariable(expression, variable);
  }

  public static boolean evaluatesToVariable(
    @Nullable PsiExpression expression,
    @NotNull PsiVariable variable) {
    final PsiExpression strippedExpression =
      ParenthesesUtils.stripParentheses(expression);
    if (strippedExpression == null) {
      return false;
    }
    if (!(expression instanceof PsiReferenceExpression)) {
      return false;
    }
    final PsiReferenceExpression referenceExpression =
      (PsiReferenceExpression)expression;
    final PsiElement referent = referenceExpression.resolve();
    return variable.equals(referent);
  }

  public boolean isAssigned() {
    return assigned;
  }
}