/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.datamodel.common;
  
  import java.io.IOException;
  import java.util.Date;
  import java.util.stream.Stream;
  
  import org.jdom2.JDOMException;
  import org.mycore.common.MCRUsageException;
  import org.mycore.common.content.MCRContent;
  
  import jakarta.xml.bind.annotation.XmlAccessType;
  import jakarta.xml.bind.annotation.XmlAccessorType;
  import jakarta.xml.bind.annotation.XmlAttribute;
  import jakarta.xml.bind.annotation.XmlRootElement;
  import jakarta.xml.bind.annotation.XmlTransient;
  
  /**
   * Provides information about a stored version of metadata and allows to
   * retrieve that version from SVN
   * 
   * @author Frank Lützenkirchen
   */
  @XmlRootElement(name = "revision")
  @XmlAccessorType(XmlAccessType.FIELD)
  public abstract class MCRAbstractMetadataVersion<T> {
  
      protected enum Type {
          created(MCRAbstractMetadataVersion.CREATED),
          modified(MCRAbstractMetadataVersion.UPDATED),
          deleted(MCRAbstractMetadataVersion.DELETED);
  
          private final char charValue;
  
          Type(char a) {
              this.charValue = a;
          }
  
          public static Type fromValue(char a) {
              return Stream.of(values()).filter(t -> t.charValue == a)
                  .findAny()
                  .orElseThrow(IllegalArgumentException::new);
          }
      }
  
      /**
       * The metadata document this version belongs to
       */
      @XmlTransient
      protected T vm;
  
      /**
       * The revision number of this version
       */
      @XmlAttribute(name = "r")
      protected String revision;
  
      /**
       * The user that created this version
       */
      @XmlAttribute
      protected String user;
  
      /**
       * The date this version was created
       */
      @XmlAttribute
      protected Date date;
  
      /**
       * Was this version result of a create, update or delete?
       */
      @XmlAttribute()
      protected Type type;
  
      /**
       * A version that was created in store
       */
      public static final char CREATED = 'A';
  
      /**
       * A version that was updated in store
      */
     public static final char UPDATED = 'M';
 
     /**
      * A version that was deleted in store
      */
     public static final char DELETED = 'D';
 
     //required for JAXB serialization
     @SuppressWarnings("unused")
     private MCRAbstractMetadataVersion() {
     }
 
     /**
      * Creates a new metadata version info object
      * 
      * @param vm
      *            the metadata document this version belongs to
      * @param revision
      *            the revision of this object, serialised as a string
      * @param user
      *            the user that created this revision
      * @param date
      *            the date on which this revision was created
      * @param type
      *            the type of commit
      */
     public MCRAbstractMetadataVersion(T vm, String revision, String user, Date date, char type) {
         this.vm = vm;
         this.revision = revision;
         this.user = user;
         this.date = date;
         this.type = Type.fromValue(type);
     }
 
     /**
      * Returns the metadata object this version belongs to
      * 
      * @return the metadata object this version belongs to
      */
     public T getMetadataObject() {
         return vm;
     }
 
     /**
      * Returns the type of operation this version comes from
      * 
      * @see #CREATED
      * @see #UPDATED
      * @see #DELETED
      */
     public char getType() {
         return type.charValue;
     }
 
     /**
      * Returns the SVN revision number of this version
      * 
      * @return the SVN revision number of this version
      */
     public String getRevision() {
         return revision;
     }
 
     /**
      * Returns the user that created this version
      * 
      * @return the user that created this version
      */
     public String getUser() {
         return user;
     }
 
     /**
      * Returns the date and time this version was created
      * 
      * @return the date and time this version was created
      */
     public Date getDate() {
         return date;
     }
 
     /**
      * Retrieves this version of the metadata
      * 
      * @return the metadata document as it was in this version
      * @throws MCRUsageException
      *             if this is a deleted version, which can not be retrieved
      */
     abstract public MCRContent retrieve() throws IOException;
 
     /**
      * Replaces the current version of the metadata object with this version,
      * which means that a new version is created that is identical to this old
      * version. The stored metadata document is updated to this old version of
      * the metadata.
      */
     abstract public void restore() throws IOException, JDOMException;
 }