/**
 * Copyright 2008 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.editor.impl;

import com.google.gwt.core.client.GWT;
import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.SpanElement;
import com.google.gwt.dom.client.StyleInjector;
import org.waveprotocol.wave.client.editor.content.TransparentManager;
import org.waveprotocol.wave.model.document.util.FilteredView.Skip;

import java.util.ArrayList;
import java.util.List;

/**
 * Transparent node manager for diff annotations
 * Keeps track of all diff annotation nodes for a given document
 *
 * @author danilatos@google.com (Daniel Danilatos)
 */
public class DiffManager implements TransparentManager<Element> {

  private static final DiffManagerResources resources = GWT.create(DiffManagerResources.class);
  static {
    StyleInjector.inject(resources.css().getText(), true);
  }

  private static final String DIFF_KEY = NodeManager.getNextMarkerName("dt");

  /**
   * Type of diff annotation
   */
  public enum DiffType {
    /** insert/insertxml op */
    INSERT,
    /** delete op */
    DELETE,
  }

  /**
   * Annotation element we're keeping track of
   */
  private final List<Element> elements = new ArrayList<Element>();

  /**
   * @param element
   * @return The annotation type of the given element, or null if it is not
   *   an element managed by this instance
   */
  public DiffType getDiffType(Element element) {
    return element == null || NodeManager.getTransparentManager(element) != this
        ? null : (DiffType) element.getPropertyObject(DIFF_KEY);
  }

  /**
   * Create a diff annotation element
   * @param type The type of change it will be annotating
   * @return The newly created element
   */
  public Element createElement(DiffType type) {
    SpanElement element = Document.get().createSpanElement();
    element.setPropertyObject(DIFF_KEY, type);
    NodeManager.setTransparentBackref(element, this);

    // HACK(danilatos): Demo looms, no time for learning how to use resource bundle etc.
    // or adding accessors to stylebase
    switch (type) {
      case INSERT:
        NodeManager.setTransparency(element, Skip.SHALLOW);
        break;
      case DELETE:
        NodeManager.setTransparency(element, Skip.DEEP);
        break;
    }

    styleElement(element, type);

    elements.add(element);

    return element;
  }

  /**
   * Apply styles and other rendering properties to an element to make it look
   * and behave like a diff marker, without actually registering it as such.
   *
   * @param element
   * @param type
   */
  public static void styleElement(Element element, DiffType type) {
    switch (type) {
      case INSERT:
        element.addClassName(resources.css().insert());
        break;
      case DELETE:
        element.addClassName(resources.css().delete());
        NodeManager.setTransparency(element, Skip.DEEP);
        element.setAttribute("contentEditable", "false");
        break;
    }
  }

  /**
   * Clear diffs from the document
   */
  public void clear() {
    TransparencyUtil.clear(elements);
  }

  /**
   * Clear diffs from a document that is being discarded
   * (All it does is clean up backreferences to assist garbage collection)
   */
  public void clearFast() {
    for (Element e : elements) {
      // Break circular references in browsers with poor gc
      e.setPropertyObject(DIFF_KEY, null);
    }

    elements.clear();
  }

  /**
   * {@inheritDoc}
   */
  public Element needToSplit(Element transparentNode) {
    DiffType type = (DiffType) transparentNode.getPropertyObject(DIFF_KEY);
    if (type == null) {
      throw new IllegalArgumentException("No diff type known for given node");
    }

    return createElement(type);
  }

}