content: /*
   *  Licensed to the Apache Software Foundation (ASF) under one
   *  or more contributor license agreements.  See the NOTICE file
   *  distributed with this work for additional information
   *  regarding copyright ownership.  The ASF licenses this file
   *  to you 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.apache.causeway.viewer.wicket.ui.pages;
  
  import org.apache.wicket.markup.head.IHeaderResponse;
  import org.apache.wicket.markup.head.MetaDataHeaderItem;
  import org.apache.wicket.markup.html.WebPage;
  import org.apache.wicket.model.IModel;
  import org.apache.wicket.request.mapper.parameter.PageParameters;
  
  import org.apache.causeway.commons.internal.base._Strings;
  import org.apache.causeway.core.metamodel.context.HasMetaModelContext;
  
  /**
   * Provides all the system dependencies for sub-classes.
   * @since 2.0
   */
  public abstract class WebPageBase
  extends WebPage
  implements HasMetaModelContext {
  
      private static final long serialVersionUID = 1L;
  
      protected WebPageBase(final PageParameters parameters) {
          super(parameters);
      }
  
      protected WebPageBase(final IModel<?> model) {
          super(model);
      }
  
      @Override
      public void renderHead(final IHeaderResponse response) {
          super.renderHead(response);
          renderFavicon(response);
      }
  
      // -- FAVICON SUPPORT
  
      protected void renderFavicon(final IHeaderResponse response) {
          getApplicationSettings().getFaviconUrl()
          .filter(_Strings::isNotEmpty)
          .map(getWebAppContextPath()::prependContextPathIfLocal)
          .ifPresent(faviconUrl->{
              response.render(MetaDataHeaderItem.forLinkTag("icon", faviconUrl));
          });
      }
  
      // -- DEPENDENCIES
  
      private transient PageClassRegistry pageClassRegistry;
      public PageClassRegistry getPageClassRegistry() {
          return pageClassRegistry = computeIfAbsent(PageClassRegistry.class, pageClassRegistry);
      }
  
      // -- HELPER
  
      private <X> X computeIfAbsent(final Class<X> type, final X existingIfAny) {
          return existingIfAny!=null
                  ? existingIfAny
                  : getMetaModelContext().lookupServiceElseFail(type);
      }
  
  }
  