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/**
 * Sencha GXT 3.1.0 - Sencha for GWT
 * Copyright(c) 2007-2014, Sencha, Inc.
 * [email protected]
 *
 * http://www.sencha.com/products/gxt/license/
 */
package com.sencha.gxt.data.shared.loader;

import java.util.HashSet;
import java.util.List;
import java.util.Set;

/**
 * Default implementation of the TreeLoader interface.
 * 
 * 
 * Events:
 * {@link BeforeLoadEvent}
 * {@link LoadEvent}
 * {@link LoadExceptionEvent}
 * 
 * 
 * 
 * @param  the model data type
 */
public class TreeLoader extends Loader> {

  private Set children = new HashSet();

  /**
   * Creates a new tree loader instance.
   * 
   * @param proxy the data reader
   */
  public TreeLoader(DataProxy> proxy) {
    super(proxy);
  }

  /**
   * Creates a new tree loader instance.
   * 
   * @param proxy the data proxy
   * @param reader the data reader
   */
  public  TreeLoader(DataProxy proxy, DataReader, T> reader) {
    super(proxy, reader);
  }

  /**
   * Returns true if the model has children. This method allows tree based
   * components to determine if the expand icon should be displayed next to a
   * node.
   * 
   * @param parent the parent model
   * @return true if the model has children, otherwise false
   */
  public boolean hasChildren(M parent) {
    return false;
  }

  /**
   * Initiates a load request for the parent's children.
   * 
   * @param parent the parent
   * @return true if the load was requested
   */
  public boolean loadChildren(M parent) {
    if (children.contains(parent)) {
      return false;
    }
    children.add(parent);
    return load(parent);
  }

  @Override
  protected void onLoadFailure(M loadConfig, Throwable t) {
    children.remove(loadConfig);
    fireEvent(new LoadExceptionEvent(loadConfig, t));
  }

  @Override
  protected void onLoadSuccess(M loadConfig, List result) {
    children.remove(loadConfig);
    fireEvent(new LoadEvent>(loadConfig, result));
  }

}