package com.atlassian.plugins.rest.common.expand.entity;
   
   import com.atlassian.plugins.rest.common.expand.parameter.Indexes;
   
   import static javax.xml.bind.annotation.XmlAccessType.FIELD;
   
   import javax.xml.bind.annotation.XmlAccessorType;
   import javax.xml.bind.annotation.XmlAttribute;
   import javax.xml.bind.annotation.XmlRootElement;
  import java.util.List;
  
  /**
   * An abstract list wrapper that provides support for paging information:
   * <ul>
   * <li>size</li>
   * <li>max-results</li>
   * <li>start-index</li>
   * </ul>
   *
   * @param <T> the type of element in the list to wrap.
   */
  @XmlRootElement
  @XmlAccessorType(FIELD)
  public abstract class AbstractPagedListWrapper<T> implements ListWrapper<T> {
      @XmlAttribute
      private final int size;
  
      @XmlAttribute(name = "max-results")
      private final int maxResults;
  
      @XmlAttribute(name = "start-index")
      private Integer startIndex;
  
      // this is for JAXB
      private AbstractPagedListWrapper() {
          size = 0;
          maxResults = 0;
      }
  
      protected AbstractPagedListWrapper(int size, int maxResults) {
          this.size = size;
          this.maxResults = maxResults;
      }
  
      public Integer getStartIndex() {
          return startIndex;
      }
  
      public int getSize() {
          return size;
      }
  
      public int getMaxResults() {
          return maxResults;
      }
  
      public void setStartIndex(int startIndex) {
          this.startIndex = startIndex;
      }
  
      public final ListWrapperCallback<T> getCallback() {
          return new ListWrapperCallback<T>() {
              public List<T> getItems(Indexes indexes) {
                  final int startIndex = indexes.getMinIndex(size);
                  if (startIndex != -1) {
                      setStartIndex(startIndex);
                  }
                  return getPagingCallback().getItems(indexes);
              }
          };
      }
  
      /**
       * Gets the call back that will actually "retrieve" the necessary element to populate the List. Size, index and max
       * result attributes are already set by this abstract class, no need to worry about them.
       *
       * @return the call back that does all the work.
       */
      public abstract ListWrapperCallback<T> getPagingCallback();
  }