/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache 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://www.apache.org/licenses/LICENSE-2.0
   *
   * 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.apache.chemistry.opencmis.client.runtime.util;
  
  import java.util.Iterator;
  import java.util.List;
  
  import org.apache.chemistry.opencmis.client.runtime.util.AbstractPageFetcher.Page;
  
  /**
   * Abstract {@code Iterator} implementation.
   *
   * @param <T>
   *            the type returned by the iterator
   */
  public abstract class AbstractIterator<T> implements Iterator<T> {
  
      private long skipCount;
      private int skipOffset;
      private final AbstractPageFetcher<T> pageFetcher;
  
      private Page<T> page;
      private Long totalNumItems;
      private Boolean hasMoreItems;
  
      /**
       * Constructor.
       */
      protected AbstractIterator(long skipCount, AbstractPageFetcher<T> pageFetcher) {
          this.skipCount = skipCount;
          this.pageFetcher = pageFetcher;
      }
  
      public long getPosition() {
          return skipCount + skipOffset;
      }
  
      public long getPageNumItems() {
          Page<T> currentPage = getCurrentPage();
          if (currentPage != null) {
              List<T> items = currentPage.getItems();
              if (items != null) {
                  return items.size();
              }
          }
          return 0L;
      }
  
      public long getTotalNumItems() {
          if (totalNumItems == null) {
              totalNumItems = Long.valueOf(-1);
              Page<T> currentPage = getCurrentPage();
              if (currentPage != null) {
                  // set number of items
                  if (currentPage.getTotalNumItems() != null) {
                      totalNumItems = currentPage.getTotalNumItems();
                  }
              }
          }
          return totalNumItems.longValue();
      }
  
      public boolean getHasMoreItems() {
          if (hasMoreItems == null) {
              hasMoreItems = Boolean.FALSE;
              Page<T> currentPage = getCurrentPage();
              if (currentPage != null) {
                  if (currentPage.getHasMoreItems() != null) {
                      hasMoreItems = currentPage.getHasMoreItems();
                  }
              }
          }
          return hasMoreItems.booleanValue();
      }
  
      @Override
      public void remove() {
          throw new UnsupportedOperationException();
      }
  
      /**
       * Gets current skip count
       *
      * @return skip count
      */
     protected long getSkipCount() {
         return skipCount;
     }
 
     /**
      * Gets current skip offset (from skip count)
      *
      * @return skip offset
      */
     protected int getSkipOffset() {
         return skipOffset;
     }
 
     /**
      * Increment the skip offset by one
      *
      * @return incremented skip offset
      */
     protected int incrementSkipOffset() {
         return skipOffset++;
     }
 
     /**
      * Gets the current page of items within collection
      *
      * @return current page
      */
     protected Page<T> getCurrentPage() {
         if (page == null) {
             page = pageFetcher.fetchPage(skipCount);
         }
         return page;
     }
 
     /**
      * Skip to the next page of items within collection
      *
      * @return next page
      */
     protected Page<T> incrementPage() {
         skipCount += skipOffset;
         skipOffset = 0;
         totalNumItems = null;
         hasMoreItems = null;
         page = pageFetcher.fetchPage(skipCount);
         return page;
     }
 
 }