/*
 * 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 com.google.gwt.user.client.ui;

import com.google.gwt.core.client.GWT;
import com.google.gwt.core.client.JavaScriptObject;
import com.google.gwt.dom.client.IFrameElement;
import com.google.gwt.safehtml.client.SafeHtmlTemplates;
import com.google.gwt.safehtml.shared.SafeHtml;
import com.google.gwt.uibinder.client.UiConstructor;
import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Element;

/**
 * A {@link com.google.gwt.user.client.ui.Frame} that has a 'name' associated
 * with it. This allows the frame to be the target of a
 * {@link com.google.gwt.user.client.ui.FormPanel}
 * 
 * <h3>CSS Style Rules</h3>
 * <ul class='css'>
 * <li>.gwt-Frame { }</li>
 * </ul>
 */
public class NamedFrame extends Frame {
  interface IFrameTemplate extends SafeHtmlTemplates {
    static final IFrameTemplate INSTANCE = GWT.create(IFrameTemplate.class);

    // Setting a src prevents mixed-content warnings.
    // http://weblogs.asp.net/bleroy/archive/2005/08/09/how-to-put-a-div-over-a-select-in-ie.aspx
    @Template("<iframe src=\"javascript:''\" name='{0}'>")
    SafeHtml get(String name);
  }

  // Used inside JSNI, so please don't delete this field just because
  // your compiler or IDE says it's unused.
  private static JavaScriptObject PATTERN_NAME;

  static {
    if (GWT.isClient()) {
      initStatics();
    }
  }

  /**
   * Creates an HTML IFRAME element with a name.
   * 
   * @param name the name of the frame, which must contain at least one
   *          non-whitespace character and must not contain reserved HTML markup
   *          characters such as '<code>&lt;</code>', '<code>&gt;</code>',
   *          or '<code>&amp;</code>'
   * @return the newly-created element
   * @throws IllegalArgumentException if the supplied name is not allowed 
   */
  private static IFrameElement createIFrame(String name) {
    if (name == null || !isValidName(name.trim())) {
      throw new IllegalArgumentException(
          "expecting one or more non-whitespace chars with no '<', '>', or '&'");
    }

    // Use innerHTML to implicitly create the <iframe>. This is necessary
    // because most browsers will not respect a dynamically-set iframe name.
    Element div = DOM.createDiv();
    div.setInnerSafeHtml(IFrameTemplate.INSTANCE.get(name));
    return div.getFirstChild().cast();
  }

  private static native void initStatics() /*-{
    @com.google.gwt.user.client.ui.NamedFrame::PATTERN_NAME = /^[^<>&\'\"]+$/;
  }-*/;

  /**
   * @param name the specified frame name to be checked
   * @return <code>true</code> if the name is valid, <code>false</code> if
   *         not
   */
  private static native boolean isValidName(String name) /*-{
    return @com.google.gwt.user.client.ui.NamedFrame::PATTERN_NAME.test(name);
  }-*/;

  /**
   * Constructs a frame with the given name.
   * 
   * @param name the name of the frame, which must contain at least one
   *          non-whitespace character and must not contain reserved HTML markup
   *          characters such as '<code>&lt;</code>', '<code>&gt;</code>',
   *          or '<code>&amp;</code>'
   *          
   * @throws IllegalArgumentException if the supplied name is not allowed 
   */
  @UiConstructor
  public NamedFrame(String name) {
    super(createIFrame(name));
    setStyleName(DEFAULT_STYLENAME);
  }

  /**
   * Gets the name associated with this frame.
   * 
   * @return the frame's name
   */
  public String getName() {
    return DOM.getElementProperty(getElement(), "name");
  }
}