/*
    * Copyright (C) 2007 The Guava Authors
    *
    * Licensed 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 com.google.common.collect;
  
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.annotations.GwtIncompatible;
  import com.google.common.testing.GcFinalization;
  
  import junit.framework.TestCase;
  
  import java.lang.ref.WeakReference;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  
  /**
   * Unit test for {@code AbstractIterator}.
   *
   * @author Kevin Bourrillion
   */
  @SuppressWarnings("serial") // No serialization is used in this test
  @GwtCompatible(emulated = true)
  // TODO(cpovirk): why is this slow (>1m/test) under GWT when fully optimized?
  public class AbstractIteratorTest extends TestCase {
  
    public void testDefaultBehaviorOfNextAndHasNext() {
  
      // This sample AbstractIterator returns 0 on the first call, 1 on the
      // second, then signals that it's reached the end of the data
      Iterator<Integer> iter = new AbstractIterator<Integer>() {
        private int rep;
        @Override public Integer computeNext() {
          switch (rep++) {
            case 0:
              return 0;
            case 1:
              return 1;
            case 2:
              return endOfData();
            default:
              fail("Should not have been invoked again");
              return null;
          }
        }
      };
  
      assertTrue(iter.hasNext());
      assertEquals(0, (int) iter.next());
  
      // verify idempotence of hasNext()
      assertTrue(iter.hasNext());
      assertTrue(iter.hasNext());
      assertTrue(iter.hasNext());
      assertEquals(1, (int) iter.next());
  
      assertFalse(iter.hasNext());
  
      // Make sure computeNext() doesn't get invoked again
      assertFalse(iter.hasNext());
  
      try {
        iter.next();
        fail("no exception thrown");
      } catch (NoSuchElementException expected) {
      }
    }
  
    public void testDefaultBehaviorOfPeek() {
      /*
       * This sample AbstractIterator returns 0 on the first call, 1 on the
       * second, then signals that it's reached the end of the data
       */
      AbstractIterator<Integer> iter = new AbstractIterator<Integer>() {
        private int rep;
        @Override public Integer computeNext() {
          switch (rep++) {
            case 0:
              return 0;
            case 1:
              return 1;
            case 2:
              return endOfData();
            default:
              fail("Should not have been invoked again");
              return null;
          }
       }
     };
 
     assertEquals(0, (int) iter.peek());
     assertEquals(0, (int) iter.peek());
     assertTrue(iter.hasNext());
     assertEquals(0, (int) iter.peek());
     assertEquals(0, (int) iter.next());
 
     assertEquals(1, (int) iter.peek());
     assertEquals(1, (int) iter.next());
 
     try {
       iter.peek();
       fail("peek() should throw NoSuchElementException at end");
     } catch (NoSuchElementException expected) {
     }
 
     try {
       iter.peek();
       fail("peek() should continue to throw NoSuchElementException at end");
     } catch (NoSuchElementException expected) {
     }
 
     try {
       iter.next();
       fail("next() should throw NoSuchElementException as usual");
     } catch (NoSuchElementException expected) {
     }
 
     try {
       iter.peek();
       fail("peek() should still throw NoSuchElementException after next()");
     } catch (NoSuchElementException expected) {
     }
   }
 
   @GwtIncompatible("weak references")
   public void testFreesNextReference() {
     Iterator<Object> itr = new AbstractIterator<Object>() {
       @Override public Object computeNext() {
         return new Object();
       }
     };
     WeakReference<Object> ref = new WeakReference<Object>(itr.next());
     GcFinalization.awaitClear(ref);
   }
 
   public void testDefaultBehaviorOfPeekForEmptyIteration() {
 
     AbstractIterator<Integer> empty = new AbstractIterator<Integer>() {
       private boolean alreadyCalledEndOfData;
       @Override public Integer computeNext() {
         if (alreadyCalledEndOfData) {
           fail("Should not have been invoked again");
         }
         alreadyCalledEndOfData = true;
         return endOfData();
       }
     };
 
     try {
       empty.peek();
       fail("peek() should throw NoSuchElementException at end");
     } catch (NoSuchElementException expected) {
     }
 
     try {
       empty.peek();
       fail("peek() should continue to throw NoSuchElementException at end");
     } catch (NoSuchElementException expected) {
     }
   }
 
   public void testSneakyThrow() throws Exception {
     Iterator<Integer> iter = new AbstractIterator<Integer>() {
       boolean haveBeenCalled;
       @Override public Integer computeNext() {
         if (haveBeenCalled) {
           fail("Should not have been called again");
         } else {
           haveBeenCalled = true;
           sneakyThrow(new SomeCheckedException());
         }
         return null; // never reached
       }
     };
 
     // The first time, the sneakily-thrown exception comes out
     try {
       iter.hasNext();
       fail("No exception thrown");
     } catch (Exception e) {
       if (!(e instanceof SomeCheckedException)) {
         throw e;
       }
     }
 
     // But the second time, AbstractIterator itself throws an ISE
     try {
       iter.hasNext();
       fail("No exception thrown");
     } catch (IllegalStateException expected) {
     }
   }
 
   public void testException() {
     final SomeUncheckedException exception = new SomeUncheckedException();
     Iterator<Integer> iter = new AbstractIterator<Integer>() {
       @Override public Integer computeNext() {
         throw exception;
       }
     };
 
     // It should pass through untouched
     try {
       iter.hasNext();
       fail("No exception thrown");
     } catch (SomeUncheckedException e) {
       assertSame(exception, e);
     }
   }
 
   public void testExceptionAfterEndOfData() {
     Iterator<Integer> iter = new AbstractIterator<Integer>() {
       @Override public Integer computeNext() {
         endOfData();
         throw new SomeUncheckedException();
       }
     };
     try {
       iter.hasNext();
       fail("No exception thrown");
     } catch (SomeUncheckedException expected) {
     }
   }
 
   public void testCantRemove() {
     Iterator<Integer> iter = new AbstractIterator<Integer>() {
       boolean haveBeenCalled;
       @Override public Integer computeNext() {
         if (haveBeenCalled) {
           endOfData();
         }
         haveBeenCalled = true;
         return 0;
       }
     };
 
     assertEquals(0, (int) iter.next());
 
     try {
       iter.remove();
       fail("No exception thrown");
     } catch (UnsupportedOperationException expected) {
     }
   }
 
   public void testReentrantHasNext() {
     Iterator<Integer> iter = new AbstractIterator<Integer>() {
       @Override protected Integer computeNext() {
         hasNext();
         return null;
       }
     };
     try {
       iter.hasNext();
       fail();
     } catch (IllegalStateException expected) {
     }
   }
 
   // Technically we should test other reentrant scenarios (9 combinations of
   // hasNext/next/peek), but we'll cop out for now, knowing that peek() and
   // next() both start by invoking hasNext() anyway.
 
   /**
    * Throws a undeclared checked exception.
    */
   private static void sneakyThrow(Throwable t) {
     class SneakyThrower<T extends Throwable> {
       @SuppressWarnings("unchecked") // not really safe, but that's the point
       void throwIt(Throwable t) throws T {
         throw (T) t;
       }
     }
     new SneakyThrower<Error>().throwIt(t);
   }
 
   private static class SomeCheckedException extends Exception {
   }
 
   private static class SomeUncheckedException extends RuntimeException {
   }
 }