/*
 * 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 legal-notices/CDDLv1_0.txt
 * or http://forgerock.org/license/CDDLv1.0.html.
 * 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 legal-notices/CDDLv1_0.txt.
 * 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 Sun Microsystems, Inc.
 *      Portions copyright 2012 ForgeRock AS.
 */

package org.forgerock.opendj.ldap.controls;

import static com.forgerock.opendj.util.StaticUtils.getExceptionMessage;
import static org.forgerock.opendj.ldap.CoreMessages.ERR_LDAPASSERT_CONTROL_BAD_OID;
import static org.forgerock.opendj.ldap.CoreMessages.ERR_LDAPASSERT_INVALID_CONTROL_VALUE;
import static org.forgerock.opendj.ldap.CoreMessages.ERR_LDAPASSERT_NO_CONTROL_VALUE;

import java.io.IOException;

import org.forgerock.i18n.LocalizableMessage;
import org.forgerock.opendj.asn1.ASN1;
import org.forgerock.opendj.asn1.ASN1Reader;
import org.forgerock.opendj.asn1.ASN1Writer;
import org.forgerock.opendj.ldap.ByteString;
import org.forgerock.opendj.ldap.ByteStringBuilder;
import org.forgerock.opendj.ldap.DecodeException;
import org.forgerock.opendj.ldap.DecodeOptions;
import org.forgerock.opendj.ldap.Filter;

import com.forgerock.opendj.ldap.LDAPUtils;
import com.forgerock.opendj.util.Validator;

/**
 * The assertion request control as defined in RFC 4528. The Assertion control
 * allows a client to specify that a directory operation should only be
 * processed if an assertion applied to the target entry of the operation is
 * true. It can be used to construct "test and set", "test and clear", and other
 * conditional operations.
 * <p>
 * The following excerpt shows how to check that no description exists on an
 * entry before adding a description.
 *
 * <pre>
 * Connection connection = ...;
 * connection.bind(...);
 *
 * String entryDN = ...;
 * ModifyRequest request =
 *         Requests.newModifyRequest(entryDN)
 *             .addControl(AssertionRequestControl.newControl(
 *                     true, Filter.valueOf("!(description=*)")))
 *             .addModification(ModificationType.ADD, "description",
 *                     "Created using LDAP assertion control");
 *
 * connection.modify(request);
 * ...
 * </pre>
 *
 * @see <a href="http://tools.ietf.org/html/rfc4528">RFC 4528 - Lightweight
 *      Directory Access Protocol (LDAP) Assertion Control </a>
 */
public final class AssertionRequestControl implements Control {
    /**
     * The IANA-assigned OID for the LDAP assertion request control.
     */
    public static final String OID = "1.3.6.1.1.12";

    /**
     * A decoder which can be used for decoding the LDAP assertion request
     * control.
     */
    public static final ControlDecoder<AssertionRequestControl> DECODER =
            new ControlDecoder<AssertionRequestControl>() {

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

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

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

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

                    final ASN1Reader reader = ASN1.getReader(control.getValue());
                    Filter filter;
                    try {
                        filter = LDAPUtils.decodeFilter(reader);
                    } catch (final IOException e) {
                        throw DecodeException.error(ERR_LDAPASSERT_INVALID_CONTROL_VALUE
                                .get(getExceptionMessage(e)), e);
                    }

                    return new AssertionRequestControl(control.isCritical(), filter);
                }

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

    /**
     * Creates a new assertion using the provided criticality and assertion
     * filter.
     *
     * @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 filter
     *            The assertion filter.
     * @return The new control.
     * @throws NullPointerException
     *             If {@code filter} was {@code null}.
     */
    public static AssertionRequestControl newControl(final boolean isCritical, final Filter filter) {
        return new AssertionRequestControl(isCritical, filter);
    }

    // The assertion filter.
    private final Filter filter;

    private final boolean isCritical;

    // Prevent direct instantiation.
    private AssertionRequestControl(final boolean isCritical, final Filter filter) {
        Validator.ensureNotNull(filter);
        this.isCritical = isCritical;
        this.filter = filter;
    }

    /**
     * Returns the assertion filter.
     *
     * @return The assertion filter.
     */
    public Filter getFilter() {
        return filter;
    }

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

    /**
     * {@inheritDoc}
     */
    public ByteString getValue() {
        final ByteStringBuilder buffer = new ByteStringBuilder();
        final ASN1Writer writer = ASN1.getWriter(buffer);
        try {
            LDAPUtils.encodeFilter(writer, filter);
            return buffer.toByteString();
        } catch (final IOException ioe) {
            // This should never happen unless there is a bug somewhere.
            throw new RuntimeException(ioe);
        }
    }

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

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

    /**
     * {@inheritDoc}
     */
    @Override
    public String toString() {
        final StringBuilder builder = new StringBuilder();
        builder.append("AssertionRequestControl(oid=");
        builder.append(getOID());
        builder.append(", criticality=");
        builder.append(isCritical());
        builder.append(", filter=\"");
        builder.append(filter.toString());
        builder.append("\")");
        return builder.toString();
    }
}