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/*
 * Copyright 2014 Google Inc.
 *
 * 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.google.gwt.resources.gss;

import com.google.gwt.core.ext.typeinfo.JClassType;
import com.google.gwt.resources.rg.GssResourceGenerator;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssClassSelectorNode;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssTree;
import com.google.gwt.thirdparty.common.css.compiler.ast.DefaultTreeVisitor;
import com.google.gwt.thirdparty.guava.common.base.Preconditions;

import java.util.HashSet;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;

/**
 * Collect all CSS class names in a stylesheet.
 */
public class ClassNamesCollector extends DefaultTreeVisitor {
  private Set  classNames;
  private SortedSet excludedPrefixes;

  /**
   * Extract all CSS class names in the provided stylesheet, modulo those
   * imported from another context.
   */
  public Set getClassNames(CssTree tree, Set imports) {
    Preconditions.checkNotNull(tree, "tree cannot be null");
    Preconditions.checkNotNull(imports, "imports set cannot be null");

    classNames = new HashSet();
    excludedPrefixes = new TreeSet();

    for (JClassType importedType : imports) {
      excludedPrefixes.add(GssResourceGenerator.getImportPrefix(importedType));
    }

    tree.getVisitController().startVisit(this);

    return classNames;
  }

  @Override
  public boolean enterClassSelector(CssClassSelectorNode classSelector) {
    String className = classSelector.getRefinerName();

    if (!isImportedClass(className)) {
      classNames.add(className);
    }

    return false;
  }

  private boolean isImportedClass(String className) {
    SortedSet lowerPrefixes = excludedPrefixes.headSet(className);

    return !lowerPrefixes.isEmpty() && className.startsWith(lowerPrefixes.last());
  }
}