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/*
 * 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.myfaces.trinidad.context;

import java.util.ArrayDeque;
import java.util.Collections;
import java.util.Deque;
import java.util.Iterator;
import java.util.Queue;

import javax.faces.context.FacesContext;

import org.apache.myfaces.trinidad.logging.TrinidadLogger;


/**
 * Default, internal, implementation of the {@link ComponentContextManager} for use from the
 * {@link RequestContext} class.
 */
final class ComponentContextManagerImpl
  extends ComponentContextManager
{
  public void pushChange(ComponentContextChange change)
  {
    if (_stack == null)
    {
      _stack = Collections.asLifoQueue(new ArrayDeque());
    }

    _stack.offer(change);

    if (_LOG.isFine())
    {
      _LOG.fine("Component context change pushed onto the stack. Change: {0}. New stack size: {1}",
        new Object[] { change, _stack.size() });
    }
  }

  public ComponentContextChange popChange()
    throws IllegalStateException
  {
    if (_stack == null)
    {
      throw new IllegalStateException("No changes to pop");
    }

    ComponentContextChange change = _stack.poll();

    if (_LOG.isFine())
    {
      _LOG.fine("Component context change popped from the stack. Popped change: {0}. " +
                "New head of stack: {1}. New stack size: {2}",
        new Object[] { change, _stack.peek(), _stack.size() });
    }

    if (_stack.isEmpty())
    {
      _stack = null;
    }

    return change;
  }

  public ComponentContextChange peekChange()
  {
    return _stack == null ? null : _stack.peek();
  }

  public SuspendedContextChanges suspend(FacesContext facesContext)
  {
    if (_stack == null)
    {
      _LOG.fine("Stack with no changes has been suspended");
      return new SuspendedContextChangesImpl(new ArrayDeque(0));
    }

    ArrayDeque q = new ArrayDeque(_stack.size());
    for (ComponentContextChange change : _stack)
    {
      change.suspend(facesContext);
      q.offer(change);
    }

    _stack = null;

    if (_LOG.isFine())
    {
      _LOG.fine("Component change stack has been suspended. Number of suspended changes: {0}",
        new Object[] { q.size() });
    }

    return new SuspendedContextChangesImpl(q);
  }

  public SuspendedContextChanges partialSuspend(
    FacesContext    facesContext,
    SuspendCallback callback)
  {
    if (_stack == null)
    {
      _LOG.fine("Stack with no changes has been partially suspended");
      return new SuspendedContextChangesImpl(new ArrayDeque(0));
    }

    ArrayDeque q = new ArrayDeque(_stack.size());
    for (Iterator iter = _stack.iterator();
         iter.hasNext(); )
    {
      ComponentContextChange change = iter.next();
      SuspendCallback.SuspendResult result = callback.getSuspendResult(change);

      if (result == SuspendCallback.SuspendResult.STOP)
      {
        break;
      }

      iter.remove();
      change.suspend(facesContext);
      q.offer(change);

      if (result == SuspendCallback.SuspendResult.STOP_AFTER_CURRENT)
      {
        break;
      }
    }

    if (_LOG.isFine())
    {
      _LOG.fine("Component change stack has been partially suspended. " +
                "Number of suspended changes: {0}. New stack size: {1}",
        new Object[] { q.size(), _stack.size() });
    }

    if (_stack.isEmpty())
    {
      _stack = null;
    }

    return new SuspendedContextChangesImpl(q);
  }

  public Iterator resume(
    FacesContext            facesContext,
    SuspendedContextChanges suspendedChanges)
  {
    assert suspendedChanges instanceof SuspendedContextChangesImpl :
      "Invalid suspend changes";

    SuspendedContextChangesImpl suspendedChangesImpl =
      (SuspendedContextChangesImpl)suspendedChanges;

    if (_stack == null)
    {
      _stack = Collections.asLifoQueue(new ArrayDeque());
    }

    for (Iterator iter =
           suspendedChangesImpl._suspendedStack.descendingIterator();
         iter.hasNext(); )
    {
      ComponentContextChange change = iter.next();
      change.resume(facesContext);
      _stack.offer(change);
    }

    if (_LOG.isFine())
    {
      _LOG.fine("Component change stack has been resumed. " +
                "Number of resumed changes: {0}. New stack size: {1}",
        new Object[] { suspendedChangesImpl._suspendedStack.size(), _stack.size() });
    }

    return suspendedChangesImpl._suspendedStack.descendingIterator();
  }

  private static class SuspendedContextChangesImpl
    extends SuspendedContextChanges
  {
    SuspendedContextChangesImpl(
      Deque suspendedStack)
    {
      _suspendedStack = suspendedStack;
    }

    private Deque _suspendedStack;
  }

  private Queue _stack;

  private static final TrinidadLogger _LOG = TrinidadLogger.createTrinidadLogger(
                                               ComponentContextManagerImpl.class);
}