/*
 * 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 2010 Sun Microsystems, Inc.
 */
package org.opends.sdk.controls;



import static com.forgerock.opendj.util.StaticUtils.byteToHex;
import static com.forgerock.opendj.util.StaticUtils.getExceptionMessage;
import static org.opends.sdk.CoreMessages.ERR_VLVREQ_CONTROL_BAD_OID;
import static org.opends.sdk.CoreMessages.INFO_VLVREQ_CONTROL_CANNOT_DECODE_VALUE;
import static org.opends.sdk.CoreMessages.INFO_VLVREQ_CONTROL_INVALID_TARGET_TYPE;
import static org.opends.sdk.CoreMessages.INFO_VLVREQ_CONTROL_NO_VALUE;

import java.io.IOException;

import org.forgerock.i18n.LocalizableMessage;
import org.opends.sdk.ByteString;
import org.opends.sdk.ByteStringBuilder;
import org.opends.sdk.DecodeException;
import org.opends.sdk.DecodeOptions;
import org.opends.sdk.asn1.ASN1;
import org.opends.sdk.asn1.ASN1Reader;
import org.opends.sdk.asn1.ASN1Writer;

import com.forgerock.opendj.util.Validator;



/**
 * The virtual list view request control as defined in
 * draft-ietf-ldapext-ldapv3-vlv. This control allows a client to specify that
 * the server return, for a given search request with associated sort keys, a
 * contiguous subset of the search result set. This subset is specified in terms
 * of offsets into the ordered list, or in terms of a greater than or equal
 * assertion value.
 * <p>
 * This control must be used in conjunction with the server-side sort request
 * control in order to ensure that results are returned in a consistent order.
 * <p>
 * This control is similar to the simple paged results request control, except
 * that it allows the client to move backwards and forwards in the result set.
 *
 * @see VirtualListViewResponseControl
 * @see ServerSideSortRequestControl
 * @see <a href="http://tools.ietf.org/html/draft-ietf-ldapext-ldapv3-vlv">
 *         draft-ietf-ldapext-ldapv3-vlv - LDAP Extensions for Scrolling View
 *         Browsing of Search Results </a>
 */
public final class VirtualListViewRequestControl implements Control
{
  /**
   * The OID for the virtual list view request control.
   */
  public static final String OID = "2.16.840.1.113730.3.4.9";

  /**
   * A decoder which can be used for decoding the virtual list view request
   * control.
   */
  public static final ControlDecoder<VirtualListViewRequestControl> DECODER =
    new ControlDecoder<VirtualListViewRequestControl>()
  {

    public VirtualListViewRequestControl decodeControl(final Control control,
        final DecodeOptions options) throws DecodeException
    {
      Validator.ensureNotNull(control);

      if (control instanceof VirtualListViewRequestControl)
      {
        return (VirtualListViewRequestControl) control;
      }

      if (!control.getOID().equals(OID))
      {
        final LocalizableMessage message = ERR_VLVREQ_CONTROL_BAD_OID.get(
            control.getOID(), OID);
        throw DecodeException.error(message);
      }

      if (!control.hasValue())
      {
        // The request control must always have a value.
        final LocalizableMessage message = INFO_VLVREQ_CONTROL_NO_VALUE.get();
        throw DecodeException.error(message);
      }

      final ASN1Reader reader = ASN1.getReader(control.getValue());
      try
      {
        reader.readStartSequence();

        final int beforeCount = (int) reader.readInteger();
        final int afterCount = (int) reader.readInteger();

        int offset = -1;
        int contentCount = -1;
        ByteString assertionValue = null;
        final byte targetType = reader.peekType();
        switch (targetType)
        {
        case TYPE_TARGET_BYOFFSET:
          reader.readStartSequence();
          offset = (int) reader.readInteger();
          contentCount = (int) reader.readInteger();
          reader.readEndSequence();
          break;
        case TYPE_TARGET_GREATERTHANOREQUAL:
          assertionValue = reader.readOctetString();
          break;
        default:
          final LocalizableMessage message = INFO_VLVREQ_CONTROL_INVALID_TARGET_TYPE
              .get(byteToHex(targetType));
          throw DecodeException.error(message);
        }

        ByteString contextID = null;
        if (reader.hasNextElement())
        {
          contextID = reader.readOctetString();
        }

        return new VirtualListViewRequestControl(control.isCritical(),
            beforeCount, afterCount, contentCount, offset, assertionValue,
            contextID);
      }
      catch (final IOException e)
      {
        final LocalizableMessage message = INFO_VLVREQ_CONTROL_CANNOT_DECODE_VALUE
            .get(getExceptionMessage(e));
        throw DecodeException.error(message, e);
      }
    }



    public String getOID()
    {
      return OID;
    }
  };

  /**
   * The BER type to use when encoding the byOffset target element.
   */
  private static final byte TYPE_TARGET_BYOFFSET = (byte) 0xA0;

  /**
   * The BER type to use when encoding the greaterThanOrEqual target element.
   */
  private static final byte TYPE_TARGET_GREATERTHANOREQUAL = (byte) 0x81;



  /**
   * Creates a new virtual list view request control that will identify the
   * target entry by an assertion value. The assertion value is encoded
   * according to the ORDERING matching rule for the attribute description in
   * the sort control. The assertion value is used to determine the target entry
   * by comparison with the values of the attribute specified as the primary
   * sort key. The first list entry who's value is no less than (less than or
   * equal to when the sort order is reversed) the supplied value is the target
   * entry.
   *
   * @param isCritical
   *          {@code true} if it is unacceptable to perform the operation
   *          without applying the semantics of this control, or {@code false}
   *          if it can be ignored.
   * @param assertionValue
   *          The assertion value that will be used to locate the target entry.
   * @param beforeCount
   *          The number of entries before the target entry to be included in
   *          the search results.
   * @param afterCount
   *          The number of entries after the target entry to be included in the
   *          search results.
   * @param contextID
   *          The context ID provided by the server in the last virtual list
   *          view response for the same set of criteria, or {@code null} if
   *          there was no previous virtual list view response or the server did
   *          not include a context ID in the last response.
   * @return The new control.
   * @throws IllegalArgumentException
   *           If {@code beforeCount} or {@code afterCount} were less than
   *           {@code 0}.
   * @throws NullPointerException
   *           If {@code assertionValue} was {@code null}.
   */
  public static VirtualListViewRequestControl newAssertionControl(
      final boolean isCritical, final ByteString assertionValue,
      final int beforeCount, final int afterCount, final ByteString contextID)
      throws IllegalArgumentException, NullPointerException
  {
    Validator.ensureNotNull(assertionValue);
    Validator.ensureTrue(beforeCount >= 0, "beforeCount is less than 0");
    Validator.ensureTrue(afterCount >= 0, "afterCount is less than 0");

    return new VirtualListViewRequestControl(isCritical, beforeCount,
        afterCount, -1, -1, assertionValue, contextID);
  }



  /**
   * Creates a new virtual list view request control that will identify the
   * target entry by a positional offset within the complete result set.
   *
   * @param isCritical
   *          {@code true} if it is unacceptable to perform the operation
   *          without applying the semantics of this control, or {@code false}
   *          if it can be ignored.
   * @param offset
   *          The positional offset of the target entry in the result set, where
   *          {@code 1} is the first entry.
   * @param contentCount
   *          The content count returned by the server in the last virtual list
   *          view response, or {@code 0} if this is the first virtual list view
   *          request.
   * @param beforeCount
   *          The number of entries before the target entry to be included in
   *          the search results.
   * @param afterCount
   *          The number of entries after the target entry to be included in the
   *          search results.
   * @param contextID
   *          The context ID provided by the server in the last virtual list
   *          view response for the same set of criteria, or {@code null} if
   *          there was no previous virtual list view response or the server did
   *          not include a context ID in the last response.
   * @return The new control.
   * @throws IllegalArgumentException
   *           If {@code beforeCount}, {@code afterCount}, or {@code
   *           contentCount} were less than {@code 0}, or if {@code offset} was
   *           less than {@code 1}.
   */
  public static VirtualListViewRequestControl newOffsetControl(
      final boolean isCritical, final int offset, final int contentCount,
      final int beforeCount, final int afterCount, final ByteString contextID)
      throws IllegalArgumentException
  {
    Validator.ensureTrue(beforeCount >= 0, "beforeCount is less than 0");
    Validator.ensureTrue(afterCount >= 0, "afterCount is less than 0");
    Validator.ensureTrue(offset > 0, "beforeCount is less than 1");
    Validator.ensureTrue(contentCount >= 0, "afterCount is less than 0");

    return new VirtualListViewRequestControl(isCritical, beforeCount,
        afterCount, offset, contentCount, null, contextID);
  }



  private final int beforeCount;

  private final int afterCount;

  private final ByteString contextID;

  private final boolean isCritical;

  private final int contentCount;

  private final int offset;

  private final ByteString assertionValue;



  private VirtualListViewRequestControl(final boolean isCritical,
      final int beforeCount, final int afterCount, final int contentCount,
      final int offset, final ByteString assertionValue,
      final ByteString contextID)
  {
    this.isCritical = isCritical;
    this.beforeCount = beforeCount;
    this.afterCount = afterCount;
    this.contentCount = contentCount;
    this.offset = offset;
    this.assertionValue = assertionValue;
    this.contextID = contextID;
  }



  /**
   * Returns the number of entries after the target entry to be included in the
   * search results.
   *
   * @return The number of entries after the target entry to be included in the
   *         search results.
   */
  public int getAfterCount()
  {
    return afterCount;
  }



  /**
   * Returns the assertion value that will be used to locate the target entry,
   * if applicable.
   *
   * @return The assertion value that will be used to locate the target entry,
   *         or {@code null} if this control is using a target offset.
   */
  public ByteString getAssertionValue()
  {
    return assertionValue;
  }



  /**
   * Returns the assertion value that will be used to locate the target entry,
   * if applicable, decoded as a UTF-8 string.
   *
   * @return The assertion value that will be used to locate the target entry
   *         decoded as a UTF-8 string, or {@code null} if this control is using
   *         a target offset.
   */
  public String getAssertionValueAsString()
  {
    return assertionValue != null ? assertionValue.toString() : null;
  }



  /**
   * Returns the number of entries before the target entry to be included in the
   * search results.
   *
   * @return The number of entries before the target entry to be included in the
   *         search results.
   */
  public int getBeforeCount()
  {
    return beforeCount;
  }



  /**
   * Returns the content count returned by the server in the last virtual list
   * view response, if applicable.
   *
   * @return The content count returned by the server in the last virtual list
   *         view response, which may be {@code 0} if this is the first virtual
   *         list view request, or {@code -1} if this control is using a target
   *         assertion.
   */
  public int getContentCount()
  {
    return contentCount;
  }



  /**
   * Returns the context ID provided by the server in the last virtual list view
   * response for the same set of criteria, or {@code null} if there was no
   * previous virtual list view response or the server did not include a context
   * ID in the last response.
   *
   * @return The context ID provided by the server in the last virtual list view
   *         response, or {@code null} if unavailable.
   */
  public ByteString getContextID()
  {
    return contextID;
  }



  /**
   * Returns the positional offset of the target entry in the result set, if
   * applicable, where {@code 1} is the first entry.
   *
   * @return The positional offset of the target entry in the result set, or
   *         {@code -1} if this control is using a target assertion.
   */
  public int getOffset()
  {
    return offset;
  }



  /**
   * {@inheritDoc}
   */
  public String getOID()
  {
    return OID;
  }



  /**
   * {@inheritDoc}
   */
  public ByteString getValue()
  {
    final ByteStringBuilder buffer = new ByteStringBuilder();
    final ASN1Writer writer = ASN1.getWriter(buffer);
    try
    {
      writer.writeStartSequence();
      writer.writeInteger(beforeCount);
      writer.writeInteger(afterCount);
      if (hasTargetOffset())
      {
        writer.writeStartSequence(TYPE_TARGET_BYOFFSET);
        writer.writeInteger(offset);
        writer.writeInteger(contentCount);
        writer.writeEndSequence();
      }
      else
      {
        writer.writeOctetString(TYPE_TARGET_GREATERTHANOREQUAL, assertionValue);
      }
      if (contextID != null)
      {
        writer.writeOctetString(contextID);
      }
      writer.writeEndSequence();
      return buffer.toByteString();
    }
    catch (final IOException ioe)
    {
      // This should never happen unless there is a bug somewhere.
      throw new RuntimeException(ioe);
    }
  }



  /**
   * Returns {@code true} if this control is using a target offset, or {@code
   * false} if this control is using a target assertion.
   *
   * @return {@code true} if this control is using a target offset, or {@code
   *         false} if this control is using a target assertion.
   */
  public boolean hasTargetOffset()
  {
    return assertionValue != null ? false : true;
  }



  /**
   * {@inheritDoc}
   */
  public boolean hasValue()
  {
    return true;
  }



  /**
   * {@inheritDoc}
   */
  public boolean isCritical()
  {
    return isCritical;
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public String toString()
  {
    final StringBuilder builder = new StringBuilder();
    builder.append("VirtualListViewRequestControl(oid=");
    builder.append(getOID());
    builder.append(", criticality=");
    builder.append(isCritical());
    builder.append(", beforeCount=");
    builder.append(beforeCount);
    builder.append(", afterCount=");
    builder.append(afterCount);
    if (hasTargetOffset())
    {
      builder.append(", offset=");
      builder.append(offset);
      builder.append(", contentCount=");
      builder.append(contentCount);
    }
    else
    {
      builder.append(", greaterThanOrEqual=");
      builder.append(assertionValue);
    }
    if (contextID != null)
    {
      builder.append(", contextID=");
      builder.append(contextID);
    }
    builder.append(")");
    return builder.toString();
  }
}