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/**
 * Copyright (c) 2014 SQUARESPACE, 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.squarespace.less.model;

import static com.squarespace.less.core.LessUtils.safeEquals;

import java.util.List;

import com.squarespace.less.LessException;
import com.squarespace.less.core.Buffer;
import com.squarespace.less.core.LessUtils;
import com.squarespace.less.exec.ExecEnv;
import com.squarespace.less.exec.SelectorUtils;


/**
 * Represents one selector in a selector set.
 */
public class Selector implements Node {

  private static final byte FLAG_EVALUATE = 0x01;
  private static final byte FLAG_HAS_WILDCARD = 0x02;
  private static final byte FLAG_MIXIN_PATH_BUILT = 0x04;

  /**
   * Default capacity for the selector's element list.
   */
  private static final int DEFAULT_CAPACITY = 4;

  /**
   * List of elements in this selector.
   */
  protected List elements;

  /**
   * {@link Mixin} path this selector maps to.
   */
  protected List mixinPath;

  /**
   * Flags set on this selector.
   */
  protected byte flags;

  /**
   * Indicates whether the selector list contains a wildcard element.
   */
  public boolean hasWildcard() {
    return (flags & FLAG_HAS_WILDCARD) != 0;
  }

  /**
   * Adds an element to the selector.
   */
  public void add(Element element) {
    elements = LessUtils.initList(elements, DEFAULT_CAPACITY);
    elements.add(element);
    if (element.needsEval()) {
      flags |= FLAG_EVALUATE;
    }
    if (element.isWildcard()) {
      flags |= FLAG_HAS_WILDCARD;
    }
  }

  /**
   * Returns the list of elements in this selector.
   */
  public List elements() {
    return LessUtils.safeList(elements);
  }

  /**
   * Indicates this selector has a "mixin-friendly" path.
   */
  public boolean hasMixinPath() {
    buildMixinPath();
    return mixinPath != null;
  }

  /**
   * Returns the segmented {@link Mixin} path corresponding to this selector.
   */
  public List mixinPath() {
    buildMixinPath();
    return mixinPath;
  }

  /**
   * Number of elements in the selector.
   */
  public int size() {
    return (elements == null) ? 0 : elements.size();
  }

  /**
   * Indicates whether the selector has no elements.
   */
  public boolean isEmpty() {
    return elements == null || elements.isEmpty();
  }

  /**
   * See {@link Node#needsEval()}
   */
  @Override
  public boolean needsEval() {
    return (flags & FLAG_EVALUATE) != 0;
  }

  /**
   * See {@link Node#eval(ExecEnv)}
   */
  @Override
  public Node eval(ExecEnv env) throws LessException {
    if (!needsEval()) {
      return this;
    }
    Selector result = new Selector();
    int size = elements.size();
    for (int i = 0; i < size; i++) {
      Element elem = elements.get(i);
      result.add((Element)elem.eval(env));
    }

    result.mixinPath = SelectorUtils.renderSelector(result, env.context());
    result.flags |= FLAG_MIXIN_PATH_BUILT;
    return result;
  }

  /**
   * See {@link Node#type()}
   */
  @Override
  public NodeType type() {
    return NodeType.SELECTOR;
  }

  /**
   * See {@link Node#repr(Buffer)}
   */
  @Override
  public void repr(Buffer buf) {
    Selectors.reprSelector(buf, this);
  }

  /**
   * See {@link Node#modelRepr(Buffer)}
   */
  @Override
  public void modelRepr(Buffer buf) {
    typeRepr(buf);
    posRepr(buf);
    buf.append('\n');
    buf.incrIndent();
    ReprUtils.modelRepr(buf, "\n", true, elements);
    buf.decrIndent();
  }

  @Override
  public boolean equals(Object obj) {
    return (obj instanceof Selector) ? safeEquals(elements, ((Selector)obj).elements) : false;
  }

  @Override
  public String toString() {
    return ModelUtils.toString(this);
  }

  @Override
  public int hashCode() {
    return ModelUtils.notHashable();
  }

  /**
   * Builds the mixin path on demand.
   */
  private void buildMixinPath() {
    if ((flags & FLAG_MIXIN_PATH_BUILT) == 0) {
      this.mixinPath = SelectorUtils.renderSelector(this);
      flags |= FLAG_MIXIN_PATH_BUILT;
    }
  }

}