/*
    * Licensed to The Apereo Foundation under one or more contributor license
    * agreements. See the NOTICE file distributed with this work for additional
    * information regarding copyright ownership.
    *
    *
    * The Apereo Foundation licenses this file to you under the Educational
    * Community 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://opensource.org/licenses/ecl2.txt
   *
   * 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.opencastproject.oaipmh.server;
  
  import static org.opencastproject.oaipmh.OaiPmhConstants.OAI_2_0_SCHEMA_LOCATION;
  import static org.opencastproject.oaipmh.OaiPmhConstants.OAI_2_0_XML_NS;
  import static org.opencastproject.oaipmh.OaiPmhUtil.toUtcSecond;
  import static org.opencastproject.util.data.Option.none;
  import static org.opencastproject.util.data.Option.some;
  
  import org.opencastproject.mediapackage.EName;
  import org.opencastproject.metadata.dublincore.DublinCore;
  import org.opencastproject.metadata.dublincore.DublinCoreCatalog;
  import org.opencastproject.metadata.dublincore.DublinCoreValue;
  import org.opencastproject.oaipmh.OaiPmhConstants;
  import org.opencastproject.oaipmh.persistence.OaiPmhDatabaseException;
  import org.opencastproject.oaipmh.persistence.SearchResult;
  import org.opencastproject.oaipmh.persistence.SearchResultItem;
  import org.opencastproject.oaipmh.util.XmlGen;
  import org.opencastproject.util.data.Function;
  import org.opencastproject.util.data.Option;
  
  import org.w3c.dom.Element;
  import org.w3c.dom.Node;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Date;
  import java.util.List;
  
  import javax.xml.XMLConstants;
  
  /**
   * OAI-PMH specific XML generator.
   */
  public abstract class OaiXmlGen extends XmlGen {
  
    protected OaiPmhRepository repository;
  
    /**
     * Create a new OaiXmlGen for a certain repository.
     */
    public OaiXmlGen(OaiPmhRepository repository) {
      super(some(OaiPmhConstants.OAI_2_0_XML_NS));
      this.repository = repository;
    }
  
    /**
     * Create the OAI-PMH tag.
     */
    Element oai(Node... nodes) {
      final List<Node> combined = new ArrayList<>();
      combined.add(schemaLocation(OAI_2_0_SCHEMA_LOCATION));
      combined.add($eTxt("responseDate", OAI_2_0_XML_NS, toUtcSecond(new Date())));
      Collections.addAll(combined, nodes);
      return $e("OAI-PMH",
                Collections.singletonList(ns("xsi", XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI)),
                combined);
    }
  
    /**
     * Create the dublin core tag from single nodes.
     */
    Element dc(Node... nodes) {
      List<Node> combined = new ArrayList<Node>(Arrays.asList(nodes));
      combined.add(schemaLocation(OaiPmhConstants.OAI_DC_SCHEMA_LOCATION));
      return $e("oai_dc:dc", OaiPmhConstants.OAI_DC_XML_NS,
                Arrays.asList(ns("dc", "http://purl.org/dc/elements/1.1/"),
                     ns("xsi", XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI)),
                combined);
    }
  
    /**
     * Create the dublin core tag from a search result item. Note: Sets are currently not supported.
     */
    @SuppressWarnings("unchecked") Element dc(final SearchResultItem item, Option<String> set) {
      try {
        return getDublincoreElement(item.getEpisodeDublinCore());
      } catch (OaiPmhDatabaseException ex) {
        return dc($e("dc:identifier", $txtBlank(item.getId())));
     }
   }
 
   // <dcterms:description xml:lang="en">
   // Introduction lecture from the Institute for Atmospheric and Climate Science.
   // </dcterms:description>
   private Element getDublincoreElement(DublinCoreCatalog dc) {
     List<Node> nodes = new ArrayList<Node>();
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_TITLE));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_CREATOR));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_SUBJECT));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_DESCRIPTION));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_PUBLISHER));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_CONTRIBUTOR));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_TYPE));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_FORMAT));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_IDENTIFIER));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_SOURCE));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_LANGUAGE));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_RELATION));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_COVERAGE));
     nodes.addAll(getDublinCoreNodes(dc, DublinCore.PROPERTY_LICENSE));
     return dc(nodes.toArray(new Node[nodes.size()]));
   }
 
   private List<Node> getDublinCoreNodes(DublinCoreCatalog dc, EName eName) {
     List<Node> nodes = new ArrayList<Node>();
 
     List<DublinCoreValue> values = dc.get(eName);
     for (DublinCoreValue dcValue : values) {
       Element element = $e("dc:" + eName.getLocalName(), $langNode(dcValue.getLanguage()), $txt(dcValue.getValue()));
       nodes.add(element);
     }
     return nodes;
   }
 
   /**
    * Create the resumption token and store the query.
    */
   Node resumptionToken(final Option<String> resumptionToken, final String metadataPrefix, final SearchResult result,
                        Date until, Option<String> set) {
     // compute the token value...
     final Option<Option<String>> token;
     if (result.size() == result.getLimit()) {
       SearchResultItem lastResult = result.getItems().get((int) (result.size() - 1));
       // more to come...
       token = some(some(repository.saveQuery(new ResumableQuery(metadataPrefix, lastResult.getModificationDate(),
                                                                 until, set))));
     } else if (resumptionToken.isSome()) {
       // last page reached
       token = some(Option.<String>none());
     } else {
       token = none();
     }
     // ... then transform it into a node
     return token.map(new Function<Option<String>, Node>() {
       @Override
       public Node apply(Option<String> token) {
         return $e("resumptionToken",
                   // $a("completeListSize", Long.toString(result.getTotalSize())),
                   // $a("cursor", Integer.toString(offset)),
                   token.map(mkText).getOrElse(nodeZero));
       }
     }).getOrElse(nodeZero);
   }
 
   /**
    * Create a record element.
    */
   Element record(final SearchResultItem item, final Node metadata) {
     if (item.isDeleted()) {
       return $e("record", header(item));
     } else {
       return $e("record", header(item), $e("metadata", metadata));
     }
   }
 
   /**
    * Create a metadata format element.
    */
   Element metadataFormat(MetadataFormat f) {
     return $e("metadataFormat", $eTxt("metadataPrefix", f.getPrefix()), $eTxt("schema", f.getSchema().toString()),
               $eTxt("metadataNamespace", f.getNamespace().toString()));
   }
 
   /**
    * Create a metadata prefix attribute if one is requested in the params.
    */
   Node metadataPrefixAttr(Params p) {
     return $aSome("metadataPrefix", p.getMetadataPrefix());
   }
 
   /**
    * Create the header element for a result item.
    */
   Element header(final SearchResultItem item) {
     // How to determine the media type?
     // There is a field oc_mediatype in the index but this one distinguishes
     // only audioVisual and series.
     Element header = $e("header",
                         $eTxt("identifier", item.getId()),
                         $eTxt("datestamp", repository.toSupportedGranularity(item.getModificationDate())));
     if (item.isDeleted()) {
       header.setAttribute("status", "deleted");
     }
     for (String setSpec: item.getSetSpecs()) {
       header.appendChild($eTxt("setSpec", setSpec));
     }
     return header;
   }
 
   /**
    * Merge two node arrays into a list.
    */
   protected List<Node> merge(Node[] a, Node... b) {
     List<Node> merge = new ArrayList<Node>(a.length + b.length);
     java.util.Collections.addAll(merge, a);
     java.util.Collections.addAll(merge, b);
     return merge;
   }
 }