/**
    * This file Copyright (c) 2003-2017 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.virtualuri.mapping;
  
  import info.magnolia.context.MgnlContext;
  import info.magnolia.context.WebContext;
  
  import java.net.URI;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.List;
  import java.util.Optional;
  
  import org.apache.commons.lang3.StringUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Virtual Uri mapping that can forward to a different url depending on the request host name. The "mappings" node
   * contains a list of nodes with "host" and "toUri" properties.
   * See below for a sample configuration:
   *
   * <pre>
   * # [module]/virtualUriMappings/[mapping-name].yaml
   * ---
   * class: info.magnolia.virtualuri.mapping.HostBasedVirtualUriMapping
   * fromUri: /
   * toUri: redirect:/.magnolia/admincentral
   * mappings:
   *   - host: www.acme.com
   *     toUri: forward:/acme/en/index.html
   *   - host: www.acme.de
   *     toUri: forward:/acme/de/index.html
   * </pre>
   */
  public class HostBasedVirtualUriMapping extends DefaultVirtualUriMapping {
      private static final Logger log = LoggerFactory.getLogger(HostBasedVirtualUriMapping.class);
  
      private List<HostUriMapping> hostMappings = new ArrayList<>();
  
      public List<HostUriMapping> getMappings() {
          return Collections.unmodifiableList(hostMappings);
      }
  
      public void setMappings(List<HostUriMapping> hostMappings) {
          this.hostMappings = hostMappings;
      }
  
      /**
       * Choose shortest HostMapping matching request host, with the least number of additional characters.
       *
       * @return The URI to map to.
       */
      @Override
      public Optional<Result> mapUri(URI uri) {
          Optional<Result> fallbackResult = super.mapUri(uri);
          if (!fallbackResult.isPresent()) {
              // fromUri pattern didn't match
              return Optional.empty();
          }
  
          Optional<String> hostResult = tryToMapHost();
          if (!hostResult.isPresent()) {
              return fallbackResult;
          }
  
          return Optional.of(new Result(hostResult.get(), getPattern().getLength(), this));
     }
 
     @Override
     public boolean isValid() {
         return StringUtils.isNotEmpty(getFromUri()) && hostMappings.stream()
                 .anyMatch(HostUriMapping::isValid);
     }
 
     /**
      * Choose the longest host-mapping matching the request host from its end (most specific).
      */
     protected Optional<String> tryToMapHost() {
         if (hostMappings == null || hostMappings.isEmpty()) {
             log.warn("No configured hosts to evaluate");
             return Optional.empty();
         }
 
         // URI mappings consume a relativized URI, so we historically resort to other means to get the host name.
         // This may be revisited if we generalize relative URIs into a domain abstraction of a magnolia request (superseding most of agg-state).
         String requestHost = ((WebContext) MgnlContext.getInstance()).getRequest().getServerName();
         Comparator<HostUriMapping> hostLengthComparator = (hm1, hm2) -> Integer.compare(hm1.getHost().length(), hm2.getHost().length());
 
         return hostMappings.stream()
                 .filter(hostMapping -> hostMapping.isValid() && requestHost.endsWith(hostMapping.getHost()))
                 .max(hostLengthComparator)
                 .map(HostUriMapping::getToUri);
     }
 
     @Override
     public String toString() {
         return "[" + super.toString() + "[hosts:" + hostMappings.toString() + "]]";
     }
 
     /**
      * HostUriMapping object to receive "mapping" nodes in configuration.
      */
     public static class HostUriMapping {
         private String host;
         private String toUri;
 
         public String getHost() {
             return host;
         }
 
         public void setHost(String host) {
             this.host = host;
         }
 
         public String getToUri() {
             return toUri;
         }
 
         public void setToUri(String toUri) {
             this.toUri = toUri;
         }
 
         public boolean isValid() {
             return StringUtils.isNotEmpty(host) && StringUtils.isNotEmpty(toUri);
         }
 
         @Override
         public String toString() {
             return String.format("[%s --> %s]", host, toUri);
         }
     }
 }