/**
 * Copyright 2010 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 org.waveprotocol.wave.client.common.webdriver;

import com.google.common.base.Preconditions;
import com.google.gwt.dom.client.Element;
import com.google.gwt.user.client.ui.UIObject;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

/**
 * Helper methods for adding debugclasses to the DOM Elements.
 *
 */
public class DebugClassHelper {

  /** The name of the debug-class attribute. */
  private static final String DEBUG_CLASS_ATTRIBUTE = "dc";
  /** Whether debug class should be set (e.g. for testing purposes). */
  private static boolean debugClassEnabled = false;

  /** Disallow construction. */
  private DebugClassHelper() {}

  /**
   * Adds a debug class to a UIObject.
   *
   * @param uiObject the object to modify
   * @param debugClass to be added
   */
  public static final void addDebugClass(UIObject uiObject, String debugClass) {
    Preconditions.checkNotNull(uiObject, "uiObject cannot be null");
    addDebugClass(uiObject.getElement(), debugClass);
  }

  /**
   * Adds a debug class to an Element.
   *
   * @param elem the object to modify
   * @param debugClass to be added
   */
  public static final void addDebugClass(Element elem, String debugClass) {
    Preconditions.checkNotNull(elem, "addDebugClass: Element must not be null");
    if (debugClassEnabled) {
      Set<String> debugClasses = getDebugClasses(elem);
      if (debugClasses.add(debugClass)) {
        elem.setAttribute(DEBUG_CLASS_ATTRIBUTE, joinDebugClasses(debugClasses));
      }
    }
  }

  /**
   * Replaces a debug class name from an Element with another one.
   *
   * @param elem the object to modify
   * @param oldClassName previous class name to be removed
   * @param newClassName new class name to be added
   */
  public static final void replaceDebugClass(
      Element elem, String oldClassName, String newClassName) {
    Preconditions.checkNotNull(elem, "replaceDebugClass: Element must not be null");
    if (debugClassEnabled) {
      Set<String> debugClasses = getDebugClasses(elem);
      boolean removed = debugClasses.remove(oldClassName);
      // if no change happened in the debugClasses, do nothing
      if (debugClasses.add(newClassName) || removed) {
        elem.setAttribute(DEBUG_CLASS_ATTRIBUTE, joinDebugClasses(debugClasses));
      }
    }
  }

  /**
   * Removes a debug class from a UIObject.
   *
   * @param uiObject the object to modify
   * @param debugClass to be removed
   */
  public static final void removeDebugClass(UIObject uiObject, String debugClass) {
    Preconditions.checkNotNull(uiObject, "uiObject cannot be null");
    removeDebugClass(uiObject.getElement(), debugClass);
  }

  /**
   * Remove a debug class from an Element.
   *
   * @param elem the object to modify
   * @param debugClass to be removed
   */
  public static final void removeDebugClass(Element elem, String debugClass) {
    if (debugClassEnabled && null != elem) {
      Set<String> debugClasses = getDebugClasses(elem);
      if (debugClasses.remove(debugClass)) {
        elem.setAttribute(DEBUG_CLASS_ATTRIBUTE, joinDebugClasses(debugClasses));
      }
    }
  }

  /**
   * Removes all debug classes from a UIObject.
   * @param uiObject The UIObject to remove debug classes from.
   */
  public static void clearDebugClasses(UIObject uiObject) {
    clearDebugClasses(uiObject.getElement());
  }

  /**
   * Removes all debug classes from an Element.
   * @param elem The element to remove debug classes from.
   */
  public static void clearDebugClasses(Element elem) {
    elem.removeAttribute(DEBUG_CLASS_ATTRIBUTE);
  }

  /**
   * Join a set of Strings into a space-separated String.
   * @param debugClasses to be joined
   * @return a String of debug classes
   */
  private static final String joinDebugClasses(Set<String> debugClasses) {
    StringBuilder result = new StringBuilder();
    for (String debugClass : debugClasses) {
      result.append(debugClass);
      result.append(" ");
    }
    return result.toString().trim();
  }

  /**
   * Get a set of debug classes present in an element.
   * @param elem from which debug classes will be read from
   * @return the set of debug classes
   */
  private static final Set<String> getDebugClasses(Element elem) {
    Set<String> result = new HashSet<String>();
    String debugClasses = elem.getAttribute(DEBUG_CLASS_ATTRIBUTE);
    result.addAll(Arrays.asList(debugClasses.split(" ")));
    return result;
  }

  /**
   * Set whether to enable debug classes (for testing purposes).
   *
   * @param enableDebugClass the new value
   */
  public static void setDebugClassEnabled(boolean enableDebugClass) {
    debugClassEnabled = enableDebugClass;
  }
}