/*
    * 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.message.broker.api.assetmanager;
  
  import org.opencastproject.mediapackage.Catalog;
  import org.opencastproject.mediapackage.MediaPackage;
  import org.opencastproject.mediapackage.MediaPackageElements;
  import org.opencastproject.mediapackage.MediaPackageException;
  import org.opencastproject.mediapackage.MediaPackageParser;
  import org.opencastproject.message.broker.api.MessageItem;
  import org.opencastproject.metadata.dublincore.DublinCoreCatalog;
  import org.opencastproject.metadata.dublincore.DublinCores;
  import org.opencastproject.security.api.AccessControlList;
  import org.opencastproject.security.api.AccessControlParser;
  import org.opencastproject.util.RequireUtil;
  import org.opencastproject.workspace.api.Workspace;
  
  import org.apache.commons.io.IOUtils;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.Serializable;
  import java.nio.charset.StandardCharsets;
  import java.util.Date;
  import java.util.Optional;
  import java.util.function.Function;
  
  import javax.annotation.ParametersAreNonnullByDefault;
  
  /**
   * {@link Serializable} class that represents all of the possible messages sent through an AssetManager queue.
   */
  @ParametersAreNonnullByDefault
  public abstract class AssetManagerItem implements MessageItem, Serializable {
    private static final long serialVersionUID = 5440420510139202434L;
  
    public enum Type {
      Update, Delete
    }
  
    // common fields
  
    private final String mediaPackageId;
    private final long date;
  
    private AssetManagerItem(String mediaPackageId, Date date) {
      this.mediaPackageId = RequireUtil.notNull(mediaPackageId, "mediaPackageId");
      this.date = RequireUtil.notNull(date, "date").getTime();
    }
  
    public abstract Type getType();
  
    public abstract <A> A decompose(Function<? super TakeSnapshot, ? extends A> takeSnapshot,
        Function<? super DeleteEpisode, ? extends A> deleteEpisode);
  
    public final Date getDate() {
      return new Date(date);
    }
  
    @Override
    public final String getId() {
      return mediaPackageId;
    }
  
    /*
     * ------------------------------------------------------------------------------------------------------------------
     */
  
    /**
     * An event for taking a snapshot of a media package.
     */
    public static final class TakeSnapshot extends AssetManagerItem {
      private static final long serialVersionUID = 3530625835200867594L;
  
      private final String mediapackage;
      private final String acl;
      private final long version;
      private final String episodeDublincore;
  
      private TakeSnapshot(String mediaPackageId, String mediapackage, String episodeDublincore, String acl, long version,
              Date date) {
       super(mediaPackageId, date);
       this.mediapackage = mediapackage;
       this.episodeDublincore = episodeDublincore;
       this.acl = acl;
       this.version = version;
     }
 
     @Override
     public <A> A decompose(Function<? super TakeSnapshot, ? extends A> takeSnapshot,
         Function<? super DeleteEpisode, ? extends A> deleteEpisode) {
       return takeSnapshot.apply(this);
     }
 
     @Override
     public Type getType() {
       return Type.Update;
     }
 
     public MediaPackage getMediapackage() {
       try {
         return MediaPackageParser.getFromXml(mediapackage);
       } catch (MediaPackageException e) {
         throw new RuntimeException(e);
       }
     }
 
     public AccessControlList getAcl() {
       return AccessControlParser.parseAclSilent(acl);
     }
 
     public Optional<DublinCoreCatalog> getEpisodeDublincore() {
       if (episodeDublincore == null) {
         return Optional.empty();
       }
 
       try (InputStream is = IOUtils.toInputStream(episodeDublincore, "UTF-8")) {
         return Optional.of(DublinCores.read(is));
       } catch (IOException e) {
         throw new RuntimeException(e);
       }
     }
 
     public long getVersion() {
       return version;
     }
 
     //
 
     public static final Function<TakeSnapshot, MediaPackage> getMediaPackage =
         new Function<TakeSnapshot, MediaPackage>() {
       @Override
       public MediaPackage apply(TakeSnapshot a) {
         return a.getMediapackage();
       }
     };
 
     public static final Function<TakeSnapshot, Optional<DublinCoreCatalog>> getEpisodeDublincore
         = new Function<TakeSnapshot, Optional<DublinCoreCatalog>>() {
           @Override
           public Optional<DublinCoreCatalog> apply(TakeSnapshot a) {
             return a.getEpisodeDublincore();
           }
         };
 
     public static final Function<TakeSnapshot, AccessControlList> getAcl =
         new Function<TakeSnapshot, AccessControlList>() {
       @Override
       public AccessControlList apply(TakeSnapshot a) {
         return a.getAcl();
       }
     };
 
   }
 
   /*
    * ------------------------------------------------------------------------------------------------------------------
    */
 
   /*
    * ------------------------------------------------------------------------------------------------------------------
    */
 
   /**
    * A event that will be sent when all versions of a media package (aka the whole episode) have been deleted.
    */
   public static final class DeleteEpisode extends AssetManagerItem {
     private static final long serialVersionUID = -4906056424740181256L;
 
     private DeleteEpisode(String mediaPackageId, Date date) {
       super(mediaPackageId, date);
     }
 
     @Override
     public <A> A decompose(Function<? super TakeSnapshot, ? extends A> takeSnapshot,
         Function<? super DeleteEpisode, ? extends A> deleteEpisode) {
       return deleteEpisode.apply(this);
     }
 
     @Override
     public Type getType() {
       return Type.Delete;
     }
 
     public String getMediaPackageId() {
       return getId();
     }
 
     public static final Function<DeleteEpisode, String> getMediaPackageId = new Function<DeleteEpisode, String>() {
       @Override
       public String apply(DeleteEpisode a) {
         return a.getMediaPackageId();
       }
     };
   }
 
   /*
    * ------------------------------------------------------------------------------------------------------------------
    */
 
   //
   // constructor methods
   //
 
   /**
    * @param workspace
    *          The workspace
    * @param mp
    *          The media package to update.
    * @param acl
    *          The access control list of the media package to update.
    * @param version
    *          The version of the media package.
    * @param date
    *          The modification date.
    * @return Builds a {@link AssetManagerItem} for taking a media package snapshot.
    */
   public static TakeSnapshot add(Workspace workspace, MediaPackage mp, AccessControlList acl, long version, Date date) {
     String dcXml = null;
     for (Catalog catalog: mp.getCatalogs(MediaPackageElements.EPISODE)) {
       try (InputStream in = workspace.read(catalog.getURI())) {
         dcXml = IOUtils.toString(in, StandardCharsets.UTF_8);
       } catch (Exception e) {
         throw new IllegalStateException(String.format("Unable to load dublin core catalog for event '%s'",
                 mp.getIdentifier()), e);
       }
     }
     return new TakeSnapshot(mp.getIdentifier().toString(), MediaPackageParser.getAsXml(mp), dcXml,
             AccessControlParser.toJsonSilent(acl), version, date);
   }
 
   /**
    * @param mediaPackageId
    *          The unique id of the media package to delete.
    * @param date
    *          The modification date.
    * @return Builds {@link AssetManagerItem} for deleting an episode from the asset manager.
    */
   public static AssetManagerItem deleteEpisode(String mediaPackageId, Date date) {
     return new DeleteEpisode(mediaPackageId, date);
   }
 }