package api.usage.twodotzero;

 import api.Writer;

 import java.io.IOException;

 import java.util.concurrent.atomic.AtomicInteger;

 import org.junit.Test;

 import static org.junit.Assert.*;

 /** Emulates what goes wrong when one wants to process really large character 

  * sequence.

  *

  * @author Jaroslav Tulach <jaroslav.tulach@apidesign.org>

  */

 public class BufferedWriterOnCDImageTest {

     public BufferedWriterOnCDImageTest() {

     }

     @Test

     public void testBehaviourOfRealBufferInJDKObviouslyThisIsGoingToThrowOutOfMemoryError() throws IOException {

         AtomicInteger cnt = new AtomicInteger();

         Writer writer = CountingWriter.create(cnt);

         CDSequence cdImage = new CDSequence();

         Writer bufferedWriter = Writer.createBuffered(writer);

         bufferedWriter.append(cdImage);

         assertEquals("Correct number of writes delegated", cdImage.length(), cnt.get());

     }

     /** A "lazy" sequence of characters, for example one that can represent

      * content of a CD, read it lazily, do not fit all into memory at once.

      */

     private static final class CDSequence implements CharSequence {

         private final int start;

         private final int end;

         public CDSequence() {

             this(0, 647 * 1024 * 1024);

         }

         private CDSequence(int start, int end) {

             this.start = start;

             this.end = end;

         }

         public int length() {

             return end - start;

         }

         public char charAt(int index) {

             int ch = index % ('Z' - 'A' + 1);

             return (char) ('A' + ch);

         }

         public CharSequence subSequence(int start, int end) {

             return new CDSequence(start, end);

         }

         @Override

         public String toString() {

             char[] arr = new char[length()];

             for (int i = 0; i < length(); i++) {

                 arr[i] = charAt(i);

             }

             return new String(arr);

         }

     } // end of CharSequence

 }