/*

  * 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.commons.collections.primitives.adapters.io;

 import java.io.IOException;

 import java.io.Reader;

 import java.util.NoSuchElementException;

 import org.apache.commons.collections.primitives.CharIterator;

 /**

  * Adapts a {@link Reader} to the {@link CharIterator} interface.

  * 

  * @version $Revision: 480462 $ $Date: 2006-11-29 03:15:00 -0500 (Wed, 29 Nov 2006) $

  * @author Rodney Waldhoff

  */

 public class ReaderCharIterator implements CharIterator {

     public ReaderCharIterator(Reader in) {

         this.reader = in;

     }

     public static CharIterator adapt(Reader in) {

         return null == in ? null : new ReaderCharIterator(in);

     }

     public boolean hasNext() {

         ensureNextAvailable();

         return (-1 != next);

     }

     public char next() {

         if(!hasNext()) {

             throw new NoSuchElementException("No next element");

         } else {

             nextAvailable = false;

             return (char)next;

         }

     }

     /**

      * Not supported.

      * @throws UnsupportedOperationException

      */

     public void remove() throws UnsupportedOperationException {

         throw new UnsupportedOperationException("remove() is not supported here");

     }

     private void ensureNextAvailable() {

         if(!nextAvailable) {

             readNext();

         }

     }

     private void readNext() {

         try {

             next = reader.read();

             nextAvailable = true;

         } catch(IOException e) {

             // TODO: Use a tunnelled exception instead? 

             // See http://radio.weblogs.com/0122027/2003/04/01.html#a7, for example            

             throw new RuntimeException(e.toString());

         }

     }

     private Reader reader = null;

     private boolean nextAvailable = false;

     private int next;

 }