/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at
 * trunk/opends/resource/legal-notices/OpenDS.LICENSE
 * or https://OpenDS.dev.java.net/OpenDS.LICENSE.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at
 * trunk/opends/resource/legal-notices/OpenDS.LICENSE.  If applicable,
 * add the following below this CDDL HEADER, with the fields enclosed
 * by brackets "[]" replaced with your own identifying information:
 *      Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 *
 *
 *      Copyright 2009-2010 Sun Microsystems, Inc.
 */

package org.opends.sdk;



import java.util.*;

import com.sun.opends.sdk.util.Validator;



/**
 * An implementation of the {@code Attribute} interface with predictable
 * iteration order.
 * <p>
 * Internally, attribute values are stored in a linked list and it's this list
 * which defines the iteration ordering, which is the order in which elements
 * were inserted into the set (insertion-order). This ordering is particularly
 * useful in LDAP where clients generally appreciate having things returned in
 * the same order they were presented.
 * <p>
 * All operations are supported by this implementation.
 */
public final class LinkedAttribute extends AbstractAttribute
{

  private static abstract class Impl
  {

    abstract boolean add(LinkedAttribute attribute, ByteString value);



    abstract void clear(LinkedAttribute attribute);



    abstract boolean contains(LinkedAttribute attribute, ByteString value);



    boolean containsAll(final LinkedAttribute attribute,
        final Collection<?> values)
    {
      // TODO: could optimize if objects is a LinkedAttribute having the same
      // equality matching rule.
      for (final Object value : values)
      {
        if (!contains(attribute, ByteString.valueOf(value)))
        {
          return false;
        }
      }
      return true;
    }



    abstract ByteString firstValue(LinkedAttribute attribute)
        throws NoSuchElementException;



    abstract Iterator<ByteString> iterator(LinkedAttribute attribute);



    abstract boolean remove(LinkedAttribute attribute, ByteString value);



    abstract <T> boolean retainAll(LinkedAttribute attribute,
        Collection<T> values, Collection<? super T> missingValues);



    abstract int size(LinkedAttribute attribute);
  }



  private static final class MultiValueImpl extends Impl
  {

    @Override
    boolean add(final LinkedAttribute attribute, final ByteString value)
    {
      final ByteString normalizedValue = normalizeValue(attribute, value);
      if (attribute.multipleValues.put(normalizedValue, value) == null)
      {
        return true;
      }
      else
      {
        return false;
      }
    }



    @Override
    void clear(final LinkedAttribute attribute)
    {
      attribute.multipleValues = null;
      attribute.pimpl = ZERO_VALUE_IMPL;
    }



    @Override
    boolean contains(final LinkedAttribute attribute, final ByteString value)
    {
      return attribute.multipleValues.containsKey(normalizeValue(attribute,
          value));
    }



    @Override
    ByteString firstValue(final LinkedAttribute attribute)
        throws NoSuchElementException
    {
      return attribute.multipleValues.values().iterator().next();
    }



    @Override
    Iterator<ByteString> iterator(final LinkedAttribute attribute)
    {
      return new Iterator<ByteString>()
      {
        private Impl expectedImpl = MULTI_VALUE_IMPL;

        private Iterator<ByteString> iterator = attribute.multipleValues
            .values().iterator();



        @Override
        public boolean hasNext()
        {
          return iterator.hasNext();
        }



        @Override
        public ByteString next()
        {
          if (attribute.pimpl != expectedImpl)
          {
            throw new ConcurrentModificationException();
          }
          else
          {
            return iterator.next();
          }
        }



        @Override
        public void remove()
        {
          if (attribute.pimpl != expectedImpl)
          {
            throw new ConcurrentModificationException();
          }
          else
          {
            iterator.remove();

            // Resize if we have removed the second to last value.
            if (attribute.multipleValues != null
                && attribute.multipleValues.size() == 1)
            {
              resize(attribute);
              iterator = attribute.pimpl.iterator(attribute);
            }

            // Always update since we may change to single or zero value
            // impl.
            expectedImpl = attribute.pimpl;
          }
        }

      };
    }



    @Override
    boolean remove(final LinkedAttribute attribute, final ByteString value)
    {
      final ByteString normalizedValue = normalizeValue(attribute, value);
      if (attribute.multipleValues.remove(normalizedValue) != null)
      {
        resize(attribute);
        return true;
      }
      else
      {
        return false;
      }
    }



    @Override
    <T> boolean retainAll(final LinkedAttribute attribute,
        final Collection<T> values, final Collection<? super T> missingValues)
    {
      // TODO: could optimize if objects is a LinkedAttribute having the same
      // equality matching rule.
      if (values.isEmpty())
      {
        clear(attribute);
        return true;
      }

      final Map<ByteString, T> valuesToRetain = new HashMap<ByteString, T>(
          values.size());
      for (final T value : values)
      {
        valuesToRetain.put(
            normalizeValue(attribute, ByteString.valueOf(value)), value);
      }

      boolean modified = false;
      final Iterator<ByteString> iterator = attribute.multipleValues.keySet()
          .iterator();
      while (iterator.hasNext())
      {
        final ByteString normalizedValue = iterator.next();
        if (valuesToRetain.remove(normalizedValue) == null)
        {
          modified = true;
          iterator.remove();
        }
      }

      if (missingValues != null)
      {
        missingValues.addAll(valuesToRetain.values());
      }

      resize(attribute);

      return modified;
    }



    @Override
    int size(final LinkedAttribute attribute)
    {
      return attribute.multipleValues.size();
    }



    private void resize(final LinkedAttribute attribute)
    {
      // May need to resize if initial size estimate was wrong (e.g. all
      // values in added collection were the same).
      switch (attribute.multipleValues.size())
      {
      case 0:
        attribute.multipleValues = null;
        attribute.pimpl = ZERO_VALUE_IMPL;
        break;
      case 1:
        final Map.Entry<ByteString, ByteString> e = attribute.multipleValues
            .entrySet().iterator().next();
        attribute.singleValue = e.getValue();
        attribute.normalizedSingleValue = e.getKey();
        attribute.multipleValues = null;
        attribute.pimpl = SINGLE_VALUE_IMPL;
        break;
      default:
        // Nothing to do.
        break;
      }
    }
  }



  private static final class SingleValueImpl extends Impl
  {

    @Override
    boolean add(final LinkedAttribute attribute, final ByteString value)
    {
      final ByteString normalizedValue = normalizeValue(attribute, value);
      if (attribute.normalizedSingleValue().equals(normalizedValue))
      {
        return false;
      }

      attribute.multipleValues = new LinkedHashMap<ByteString, ByteString>(2);
      attribute.multipleValues.put(attribute.normalizedSingleValue,
          attribute.singleValue);
      attribute.multipleValues.put(normalizedValue, value);
      attribute.singleValue = null;
      attribute.normalizedSingleValue = null;
      attribute.pimpl = MULTI_VALUE_IMPL;

      return true;
    }



    @Override
    void clear(final LinkedAttribute attribute)
    {
      attribute.singleValue = null;
      attribute.normalizedSingleValue = null;
      attribute.pimpl = ZERO_VALUE_IMPL;
    }



    @Override
    boolean contains(final LinkedAttribute attribute, final ByteString value)
    {
      final ByteString normalizedValue = normalizeValue(attribute, value);
      return attribute.normalizedSingleValue().equals(normalizedValue);
    }



    @Override
    ByteString firstValue(final LinkedAttribute attribute)
        throws NoSuchElementException
    {
      if (attribute.singleValue != null)
      {
        return attribute.singleValue;
      }
      else
      {
        throw new NoSuchElementException();
      }
    }



    @Override
    Iterator<ByteString> iterator(final LinkedAttribute attribute)
    {
      return new Iterator<ByteString>()
      {
        private Impl expectedImpl = SINGLE_VALUE_IMPL;

        private boolean hasNext = true;



        @Override
        public boolean hasNext()
        {
          return hasNext;
        }



        @Override
        public ByteString next()
        {
          if (attribute.pimpl != expectedImpl)
          {
            throw new ConcurrentModificationException();
          }
          else if (hasNext)
          {
            hasNext = false;
            return attribute.singleValue;
          }
          else
          {
            throw new NoSuchElementException();
          }
        }



        @Override
        public void remove()
        {
          if (attribute.pimpl != expectedImpl)
          {
            throw new ConcurrentModificationException();
          }
          else if (hasNext || attribute.singleValue == null)
          {
            throw new IllegalStateException();
          }
          else
          {
            clear(attribute);
            expectedImpl = attribute.pimpl;
          }
        }

      };
    }



    @Override
    boolean remove(final LinkedAttribute attribute, final ByteString value)
    {
      if (contains(attribute, value))
      {
        clear(attribute);
        return true;
      }
      else
      {
        return false;
      }
    }



    @Override
    <T> boolean retainAll(final LinkedAttribute attribute,
        final Collection<T> values, final Collection<? super T> missingValues)
    {
      // TODO: could optimize if objects is a LinkedAttribute having the same
      // equality matching rule.
      if (values.isEmpty())
      {
        clear(attribute);
        return true;
      }

      final ByteString normalizedSingleValue = attribute
          .normalizedSingleValue();
      boolean retained = false;
      for (final T value : values)
      {
        final ByteString normalizedValue = normalizeValue(attribute,
            ByteString.valueOf(value));
        if (normalizedSingleValue.equals(normalizedValue))
        {
          if (missingValues == null)
          {
            // We can stop now.
            return false;
          }
          retained = true;
        }
        else if (missingValues != null)
        {
          missingValues.add(value);
        }
      }

      if (!retained)
      {
        clear(attribute);
        return true;
      }
      else
      {
        return false;
      }
    }



    @Override
    int size(final LinkedAttribute attribute)
    {
      return 1;
    }
  }



  private static final class ZeroValueImpl extends Impl
  {

    @Override
    boolean add(final LinkedAttribute attribute, final ByteString value)
    {
      attribute.singleValue = value;
      attribute.pimpl = SINGLE_VALUE_IMPL;
      return true;
    }



    @Override
    void clear(final LinkedAttribute attribute)
    {
      // Nothing to do.
    }



    @Override
    boolean contains(final LinkedAttribute attribute, final ByteString value)
    {
      return false;
    }



    @Override
    boolean containsAll(final LinkedAttribute attribute,
        final Collection<?> values)
    {
      return values.isEmpty();
    }



    @Override
    ByteString firstValue(final LinkedAttribute attribute)
        throws NoSuchElementException
    {
      throw new NoSuchElementException();
    }



    @Override
    Iterator<ByteString> iterator(final LinkedAttribute attribute)
    {
      return new Iterator<ByteString>()
      {
        @Override
        public boolean hasNext()
        {
          return false;
        }



        @Override
        public ByteString next()
        {
          if (attribute.pimpl != ZERO_VALUE_IMPL)
          {
            throw new ConcurrentModificationException();
          }
          else
          {
            throw new NoSuchElementException();
          }
        }



        @Override
        public void remove()
        {
          if (attribute.pimpl != ZERO_VALUE_IMPL)
          {
            throw new ConcurrentModificationException();
          }
          else
          {
            throw new IllegalStateException();
          }
        }

      };
    }



    @Override
    boolean remove(final LinkedAttribute attribute, final ByteString value)
    {
      return false;
    }



    @Override
    <T> boolean retainAll(final LinkedAttribute attribute,
        final Collection<T> values, final Collection<? super T> missingValues)
    {
      if (missingValues != null)
      {
        missingValues.addAll(values);
      }
      return false;
    }



    @Override
    int size(final LinkedAttribute attribute)
    {
      return 0;
    }

  }



  /**
   * An attribute factory which can be used to create new linked attributes.
   */
  public static final AttributeFactory FACTORY = new AttributeFactory()
  {
    @Override
    public Attribute newAttribute(
        final AttributeDescription attributeDescription)
        throws NullPointerException
    {
      return new LinkedAttribute(attributeDescription);
    }
  };

  private static final MultiValueImpl MULTI_VALUE_IMPL = new MultiValueImpl();

  private static final SingleValueImpl SINGLE_VALUE_IMPL = new SingleValueImpl();

  private static final ZeroValueImpl ZERO_VALUE_IMPL = new ZeroValueImpl();

  private final AttributeDescription attributeDescription;

  private Map<ByteString, ByteString> multipleValues = null;

  private ByteString normalizedSingleValue = null;

  private Impl pimpl = ZERO_VALUE_IMPL;

  private ByteString singleValue = null;



  /**
   * Creates a new attribute having the same attribute description and attribute
   * values as {@code attribute}.
   *
   * @param attribute
   *          The attribute to be copied.
   * @throws NullPointerException
   *           If {@code attribute} was {@code null}.
   */
  public LinkedAttribute(final Attribute attribute) throws NullPointerException
  {
    this.attributeDescription = attribute.getAttributeDescription();

    if (attribute instanceof LinkedAttribute)
    {
      final LinkedAttribute other = (LinkedAttribute) attribute;
      this.pimpl = other.pimpl;
      this.singleValue = other.singleValue;
      this.normalizedSingleValue = other.normalizedSingleValue;
      if (other.multipleValues != null)
      {
        this.multipleValues = new LinkedHashMap<ByteString, ByteString>(
            other.multipleValues);
      }
    }
    else
    {
      addAll(attribute);
    }
  }



  /**
   * Creates a new attribute having the specified attribute description and no
   * attribute values.
   *
   * @param attributeDescription
   *          The attribute description.
   * @throws NullPointerException
   *           If {@code attributeDescription} was {@code null}.
   */
  public LinkedAttribute(final AttributeDescription attributeDescription)
      throws NullPointerException
  {
    Validator.ensureNotNull(attributeDescription);
    this.attributeDescription = attributeDescription;
  }



  /**
   * Creates a new attribute having the specified attribute description and
   * single attribute value.
   *
   * @param attributeDescription
   *          The attribute description.
   * @param value
   *          The single attribute value.
   * @throws NullPointerException
   *           If {@code attributeDescription} or {@code value} was {@code null}
   *           .
   */
  public LinkedAttribute(final AttributeDescription attributeDescription,
      final ByteString value) throws NullPointerException
  {
    this(attributeDescription);
    add(value);
  }



  /**
   * Creates a new attribute having the specified attribute description and
   * attribute values.
   *
   * @param attributeDescription
   *          The attribute description.
   * @param values
   *          The attribute values.
   * @throws NullPointerException
   *           If {@code attributeDescription} or {@code values} was
   *           {@code null}.
   */
  public LinkedAttribute(final AttributeDescription attributeDescription,
      final ByteString... values) throws NullPointerException
  {
    this(attributeDescription);
    addAll(Arrays.asList(values));
  }



  /**
   * Creates a new attribute having the specified attribute description and
   * attribute values.
   *
   * @param attributeDescription
   *          The attribute description.
   * @param values
   *          The attribute values.
   * @throws NullPointerException
   *           If {@code attributeDescription} or {@code values} was
   *           {@code null}.
   */
  public LinkedAttribute(final AttributeDescription attributeDescription,
      final Collection<ByteString> values) throws NullPointerException
  {
    this(attributeDescription);
    addAll(values);
  }



  /**
   * Creates a new attribute having the specified attribute description and no
   * attribute values. The attribute description will be decoded using the
   * default schema.
   *
   * @param attributeDescription
   *          The attribute description.
   * @throws LocalizedIllegalArgumentException
   *           If {@code attributeDescription} could not be decoded using the
   *           default schema.
   * @throws NullPointerException
   *           If {@code attributeDescription} was {@code null}.
   */
  public LinkedAttribute(final String attributeDescription)
      throws LocalizedIllegalArgumentException, NullPointerException
  {
    this(AttributeDescription.valueOf(attributeDescription));
  }



  /**
   * Creates a new attribute having the specified attribute description and
   * single attribute value. The attribute description will be decoded using the
   * default schema.
   * <p>
   * If {@code value} is not an instance of {@code ByteString} then it will be
   * converted using the {@link ByteString#valueOf(Object)} method.
   *
   * @param attributeDescription
   *          The attribute description.
   * @param value
   *          The single attribute value.
   * @throws LocalizedIllegalArgumentException
   *           If {@code attributeDescription} could not be decoded using the
   *           default schema.
   * @throws NullPointerException
   *           If {@code attributeDescription} or {@code value} was {@code null}
   *           .
   */
  public LinkedAttribute(final String attributeDescription, final Object value)
      throws LocalizedIllegalArgumentException, NullPointerException
  {
    this(attributeDescription);
    add(ByteString.valueOf(value));
  }



  /**
   * Creates a new attribute having the specified attribute description and
   * attribute values. The attribute description will be decoded using the
   * default schema.
   * <p>
   * Any attribute values which are not instances of {@code ByteString} will be
   * converted using the {@link ByteString#valueOf(Object)} method.
   *
   * @param attributeDescription
   *          The attribute description.
   * @param values
   *          The attribute values.
   * @throws LocalizedIllegalArgumentException
   *           If {@code attributeDescription} could not be decoded using the
   *           default schema.
   * @throws NullPointerException
   *           If {@code attributeDescription} or {@code values} was
   *           {@code null}.
   */
  public LinkedAttribute(final String attributeDescription,
      final Object... values) throws LocalizedIllegalArgumentException,
      NullPointerException
  {
    this(attributeDescription);
    for (final Object value : values)
    {
      add(ByteString.valueOf(value));
    }
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public boolean add(final ByteString value) throws NullPointerException
  {
    Validator.ensureNotNull(value);
    return pimpl.add(this, value);
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public boolean addAll(final Collection<? extends ByteString> values,
      final Collection<? super ByteString> duplicateValues)
      throws NullPointerException
  {
    Validator.ensureNotNull(values);

    // TODO: could optimize if objects is a LinkedAttribute having the same
    // equality matching rule.
    boolean modified = false;
    for (final ByteString value : values)
    {
      if (add(value))
      {
        modified = true;
      }
      else if (duplicateValues != null)
      {
        duplicateValues.add(value);
      }
    }
    return modified;
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public void clear()
  {
    pimpl.clear(this);
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public boolean contains(final Object value) throws NullPointerException
  {
    Validator.ensureNotNull(value);
    return pimpl.contains(this, ByteString.valueOf(value));
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public boolean containsAll(final Collection<?> values)
      throws NullPointerException
  {
    Validator.ensureNotNull(values);
    return pimpl.containsAll(this, values);
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public ByteString firstValue() throws NoSuchElementException
  {
    return pimpl.firstValue(this);
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public AttributeDescription getAttributeDescription()
  {
    return attributeDescription;
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public Iterator<ByteString> iterator()
  {
    return pimpl.iterator(this);
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public boolean remove(final Object value) throws NullPointerException
  {
    Validator.ensureNotNull(value);
    return pimpl.remove(this, ByteString.valueOf(value));
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public <T> boolean removeAll(final Collection<T> values,
      final Collection<? super T> missingValues) throws NullPointerException
  {
    Validator.ensureNotNull(values);

    // TODO: could optimize if objects is a LinkedAttribute having the same
    // equality matching rule.
    boolean modified = false;
    for (final T value : values)
    {
      if (remove(ByteString.valueOf(value)))
      {
        modified = true;
      }
      else if (missingValues != null)
      {
        missingValues.add(value);
      }
    }
    return modified;
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public <T> boolean retainAll(final Collection<T> values,
      final Collection<? super T> missingValues) throws NullPointerException
  {
    Validator.ensureNotNull(values);
    return pimpl.retainAll(this, values, missingValues);
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public int size()
  {
    return pimpl.size(this);
  }



  // Lazily computes the normalized single value.
  private ByteString normalizedSingleValue()
  {
    if (normalizedSingleValue == null)
    {
      normalizedSingleValue = normalizeValue(this, singleValue);
    }
    return normalizedSingleValue;
  }

}