package yarfraw.io;

 import java.io.File;

 import java.net.URI;

 import java.util.ArrayList;

 import java.util.Arrays;

 import java.util.List;

 import org.apache.commons.collections.CollectionUtils;

 import yarfraw.core.datamodel.ChannelFeed;

 import yarfraw.core.datamodel.FeedFormat;

 import yarfraw.core.datamodel.ItemEntry;

 import yarfraw.core.datamodel.YarfrawException;

 /**

  * Provides a set of function to facilitate modifications to an RSS 2.0 feed.

  * <br/>

  * *Note* This class is not thread safe.

  * @author jliang

  *

  */

 public class FeedAppender{

   private FeedWriter _writer;

   private FeedReader _reader;

   private int _numItemToKeep = -1;

   public FeedAppender(File file, FeedFormat format) {

     _writer = new FeedWriter(file);

     _reader = new FeedReader(file);

     setFormat(format);

   }

   public FeedAppender(String pathName, FeedFormat format){

     this(new File(pathName), format);

   }

   public FeedAppender(URI uri, FeedFormat format){

     this(new File(uri), format);

   }

   public FeedAppender(File file) {

     this(file, FeedFormat.RSS20);

   }

   public FeedAppender(String pathName){

     this(new File(pathName), FeedFormat.RSS20);

   }

   public FeedAppender(URI uri){

     this(new File(uri), FeedFormat.RSS20);

   } 

   /**

    * The {@link FeedFormat} this writer should be using.<br/>

    * if this is not set, the default is RSS 2.0 format. <code>null</code> format is ignored  

    * @return a {@link FeedFormat} enum

    */

   public FeedFormat getFormat() {

     return _reader.getFormat();

   }

   /**

    * The {@link FeedFormat} this writer should be using.<br/>

    * if this is not set, the default is RSS 2.0 format. <code>null</code> format is ignored  

    * @param format a {@link FeedFormat} enum

    */

   public void setFormat(FeedFormat format) {

     if(format != null){

       _reader.setFormat(format);

       _writer.setFormat(format);

     } 

   }

   /**

    * Maximum number of items to keep in a feed. If the number of actual items

    * If <code>numItemToKeep</code> is non-negative and the actual number of {@link ItemEntry} (after appends)

    * in the feed greater than <code>numItemToKeep</code>, the appender will remove items from the END

    * of the feed to ensure there is at most <code>numItemToKeep</code> items in the feed.

    * @return the current <code>numberItemToKepp</code>, -1 if the value has not yet been set or there's no limit.

    */

   public int getNumItemToKeep() {

     return _numItemToKeep;

   }

   /**

    * Maximum number of items to keep in a feed. If the number of actual items

    * If <code>numItemToKeep</code> is non-negative and the actual number of {@link ItemEntry} (after appends)

    * in the feed greater than <code>numItemToKeep</code>, the appender will remove items from the END

    * of the feed to ensure there is at most <code>numItemToKeep</code> items in the feed.   

    * @param numItemToKeep number of items to keep in the current feed. no limit if it's negative.

    * @return this

    */

   public FeedAppender setNumItemToKeep(int numItemToKeep) {

     _numItemToKeep = numItemToKeep < 0 ? -1 : numItemToKeep;

     return this;

   }

   private List<ItemEntry> trimItemsList(List<ItemEntry> items){

     if(_numItemToKeep != -1 && CollectionUtils.isNotEmpty(items)

             && items.size() > _numItemToKeep){

       return items.subList(0, _numItemToKeep);

     }

     return items;

   }

   /**

    * Appends all of the {@link ItemEntry} in the specified collection into the current feed

    * at the specified position (optional operation).  Shifts the

    * {@link ItemEntry} currently at that position (if any) and any subsequent

    * {@link ItemEntry} to the right (increases their indices).

    * <br/>

    * As in  <code>feedItemList.addAll(index, inputlist)</code>

    * <br/>

    * If <code>numItemToKeep</code> is set and the resulting number of {@link ItemEntry} (after the append)

    * in the feed greater than <code>numItemToKeep</code>, the appender will remove items from the END

    * of the feed to ensure there is at most <code>numItemToKeep</code> items in the feed.

    * 

    * @param index index to append to

    * @param items any number of {@link yarfraw.core.datamodel.ItemEntry}

    * @return this

    * @throws YarfrawException if operation failed.

    */

   public FeedAppender appendAllItemsAt(int index, List<ItemEntry> items) throws YarfrawException{

     ChannelFeed ch = readChannel();

     List<ItemEntry> old = ch.getItems();

     if(old == null){

       old = new ArrayList<ItemEntry>();

       ch.setItems(old);

     }

     old.addAll(index, items);

     ch.setItems(trimItemsList(old));

     _writer = new FeedWriter(_reader._file);

     _writer.writeChannel(ch);

     return this;

   }

   /**

    * Appends all of the {@link ItemEntry} to the <b>beginning</b> of the item list in  the current feed.

    * Shifts the {@link ItemEntry} currently at that position (if any) and any subsequent

    * {@link ItemEntry} to the right (increases their indices).

    * <br/>

    * This is equivalent to <code>appendAllItemsAt(0, inputlist)</code>

    * <br/>

    * If <code>numItemToKeep</code> is set and the resulting number of {@link ItemEntry} (after the append)

    * in the feed greater than <code>numItemToKeep</code>, the appender will remove items from the END

    * of the feed to ensure there is at most <code>numItemToKeep</code> items in the feed.

    *

    * @param items

    * @return

    * @throws YarfrawException if the appender failed to read or write the feed file.

    */

   public FeedAppender appendAllItemsToBeginning(List<ItemEntry> items) throws YarfrawException{

     return appendAllItemsAt(0, items);

   }

   /**

    * Appends all of the {@link ItemEntry} to the <b>beginning</b> of the item list in the current feed.

    * Shifts the {@link ItemEntry} currently at that position (if any) and any subsequent

    * {@link ItemEntry} to the right (increases their indices).

    * <br/>

    * This is equivalent to <code>appendAllItemsAt(0, Arrays.asList(item1, item2, item3))</code>

    * <br/>

    * If <code>numItemToKeep</code> is set and the resulting number of {@link ItemEntry} (after the append)

    * in the feed greater than <code>numItemToKeep</code>, the appender will remove items from the END

    * of the feed to ensure there is at most <code>numItemToKeep</code> items in the feed.

    *

    * @param items

    * @return

    * @throws YarfrawException if the appender failed to read or write the feed file.

    */

   public FeedAppender appendAllItemsToBeginning(ItemEntry...items) throws YarfrawException{

     return appendAllItemsToBeginning(Arrays.asList(items));

   }

   /**

    * Appends all of the {@link ItemEntry} to the <b>end</b> of the item list in current feed.

    * Shifts the {@link ItemEntry} currently at that position (if any) and any subsequent

    * {@link ItemEntry} to the right (increases their indices).

    * <br/>

    * If <code>numItemToKeep</code> is set and the resulting number of {@link ItemEntry} (after the append)

    * in the feed greater than <code>numItemToKeep</code>, the appender will remove items from the END

    * of the feed to ensure there is at most <code>numItemToKeep</code> items in the feed.

    *

    * @param items

    * @return

    * @throws YarfrawException if the appender failed to read or write the feed file.

    */

   public FeedAppender appendAllItemsToEnd(List<ItemEntry> items) throws YarfrawException{

     ChannelFeed ch = readChannel();

     List<ItemEntry> old = ch.getItems();

     if(old == null){

       old = new ArrayList<ItemEntry>();

       ch.setItems(old);

     }

     old.addAll(items);

     ch.setItems(trimItemsList(old));

     _writer = new FeedWriter(_reader._file);

     _writer.writeChannel(ch);

     return this;

   }

   /**

    * Appends all of the {@link ItemEntry} to the <b>end</b> of the item list in the current feed.

    * Shifts the {@link ItemEntry} currently at that position (if any) and any subsequent

    * {@link ItemEntry} to the right (increases their indices).

    * <br/>

    * If <code>numItemToKeep</code> is set and the resulting number of {@link ItemEntry} (after the append)

    * in the feed greater than <code>numItemToKeep</code>, the appender will remove items from the END

    * of the feed to ensure there is at most <code>numItemToKeep</code> items in the feed.

    *

    * @param items

    * @return

    * @throws YarfrawException if the appender failed to read or write the feed file.

    */

   public FeedAppender appendAllItemsToEnd(ItemEntry...items) throws YarfrawException{

     return appendAllItemsToEnd(Arrays.asList(items));

   }

   /**

    * * Remove the item at index <code>index</code> from the feed.

    * @param index

    * @return

    * @throws YarfrawException if the appender failed to read or write the feed file.

    */

   public FeedAppender removeItem(int index) throws YarfrawException{

     ChannelFeed ch = readChannel();

     ch.getItems().remove(index);

     ch.setItems(trimItemsList(ch.getItems()));

     _writer.writeChannel(ch);

     return this;

   }

   /**

    * Set the item at index <code>index</code> to be the input <code>item</code>

    * @param index

    * @param item

    * @return

    * @throws YarfrawException if the appender failed to read or write the feed file.

    */

   public FeedAppender setItem(int index, ItemEntry item) throws YarfrawException{

     ChannelFeed ch = readChannel();

     ch.getItems().set(index, item);

     _writer.writeChannel(ch);

     return this;

   }

   private ChannelFeed readChannel() throws YarfrawException{

     ChannelFeed ch = _reader.readChannel(); 

     if(ch.getItems() == null){

       ch.setItems(new ArrayList<ItemEntry>());

     }

     return ch;

   }

 }