platform/lang-api/src/com/intellij/psi/util/PsiFilter.java

/*
 * Copyright 2000-2010 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.psi.util;

import com.intellij.psi.PsiElement;
import com.intellij.psi.PsiRecursiveElementVisitor;
import org.jetbrains.annotations.NotNull;

import java.util.List;

/**
 * @author Konstantin Bulenkov
 */
public class PsiFilter<T extends PsiElement> {
  private final Class<T> filter;
  public static final PsiFilter<?>[] EMPTY = {}; 

  public PsiFilter(@NotNull Class<T> filter) {
    this.filter = filter;
  }

  public boolean accept(T element) {
    return true;
  }

  public final Class<T> getParentClass() {
    return filter; 
  }

  public boolean areEquivalent(T e1, T e2) {
    return e1.isEquivalentTo(e2);
  }

  public Visitor<T> createVisitor(List<T> elements) {
    return new Visitor<T>(this, elements);
  }

  public static class Visitor<T extends PsiElement> extends PsiRecursiveElementVisitor {
    private final PsiFilter<T> filter;
    private final List<T> elements;

    protected Visitor(final PsiFilter<T> filter, final List<T> elements) {
      this.filter = filter;
      this.elements = elements;
    }

    @Override
    public void visitElement(PsiElement element) {
      if (filter.getParentClass().isAssignableFrom(element.getClass())) {
        final T e = (T)element;
        if (filter.accept(e)) {
          elements.add(e);
        }
      }
      super.visitElement(element);
    }
  }
}