/*
 * The contents of this file are subject to the terms of the Common Development and
 * Distribution License (the License). You may not use this file except in compliance with the
 * License.
 *
 * You can obtain a copy of the License at legal/CDDLv1.0.txt. See the License for the
 * specific language governing permission and limitations under the License.
 *
 * When distributing Covered Software, include this CDDL Header Notice in each file and include
 * the License file at legal/CDDLv1.0.txt. If applicable, add the following below the CDDL
 * Header, with the fields enclosed by brackets [] replaced by your own identifying
 * information: "Portions Copyright [year] [name of copyright owner]".
 *
 * Copyright 2012-2013 ForgeRock AS.
 */
package org.forgerock.opendj.rest2ldap;

import static java.util.Collections.emptyList;
import static java.util.Collections.emptySet;
import static java.util.Collections.singleton;
import static java.util.Collections.singletonList;
import static org.forgerock.opendj.ldap.Filter.alwaysFalse;
import static org.forgerock.opendj.ldap.Functions.fixedFunction;
import static org.forgerock.opendj.rest2ldap.Utils.base64ToByteString;
import static org.forgerock.opendj.rest2ldap.Utils.byteStringToBase64;
import static org.forgerock.opendj.rest2ldap.Utils.byteStringToJson;
import static org.forgerock.opendj.rest2ldap.Utils.jsonToAttribute;
import static org.forgerock.opendj.rest2ldap.Utils.jsonToByteString;
import static org.forgerock.opendj.rest2ldap.Utils.toFilter;
import static org.forgerock.opendj.rest2ldap.WritabilityPolicy.READ_WRITE;

import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Set;

import org.forgerock.json.fluent.JsonPointer;
import org.forgerock.json.fluent.JsonValue;
import org.forgerock.json.resource.BadRequestException;
import org.forgerock.json.resource.ResourceException;
import org.forgerock.json.resource.ResultHandler;
import org.forgerock.opendj.ldap.Attribute;
import org.forgerock.opendj.ldap.AttributeDescription;
import org.forgerock.opendj.ldap.ByteString;
import org.forgerock.opendj.ldap.Entry;
import org.forgerock.opendj.ldap.Filter;
import org.forgerock.opendj.ldap.Function;
import org.forgerock.opendj.ldap.LinkedAttribute;

/**
 * An attribute mapper which provides a simple mapping from a JSON value to a
 * single LDAP attribute.
 */
public final class SimpleAttributeMapper extends AttributeMapper {
    private Function<ByteString, ?, Void> decoder = null;
    private Object defaultJSONValue = null;
    private Collection<Object> defaultJSONValues = Collections.emptySet();
    private ByteString defaultLDAPValue = null;
    private Function<Object, ByteString, Void> encoder = null;
    private boolean isRequired = false;
    private boolean isSingleValued = false;
    private final AttributeDescription ldapAttributeName;
    private WritabilityPolicy writabilityPolicy = READ_WRITE;

    SimpleAttributeMapper(final AttributeDescription ldapAttributeName) {
        this.ldapAttributeName = ldapAttributeName;
    }

    /**
     * Sets the decoder which will be used for converting LDAP attribute values
     * to JSON values.
     *
     * @param f
     *            The function to use for decoding LDAP attribute values.
     * @return This attribute mapper.
     */
    public SimpleAttributeMapper decoder(final Function<ByteString, ?, Void> f) {
        this.decoder = f;
        return this;
    }

    /**
     * Sets the default JSON value which should be substituted when the LDAP
     * attribute is not found in the LDAP entry.
     *
     * @param defaultValue
     *            The default JSON value.
     * @return This attribute mapper.
     */
    public SimpleAttributeMapper defaultJSONValue(final Object defaultValue) {
        this.defaultJSONValue = defaultValue;
        this.defaultJSONValues = defaultValue != null ? singleton(defaultValue) : emptySet();
        return this;
    }

    /**
     * Sets the default LDAP value which should be substituted when the JSON
     * attribute is not found in the JSON value.
     *
     * @param defaultValue
     *            The default LDAP value.
     * @return This attribute mapper.
     */
    public SimpleAttributeMapper defaultLDAPValue(final Object defaultValue) {
        this.defaultLDAPValue = defaultValue != null ? ByteString.valueOf(defaultValue) : null;
        return this;
    }

    /**
     * Sets the encoder which will be used for converting JSON values to LDAP
     * attribute values.
     *
     * @param f
     *            The function to use for encoding LDAP attribute values.
     * @return This attribute mapper.
     */
    public SimpleAttributeMapper encoder(final Function<Object, ByteString, Void> f) {
        this.encoder = f;
        return this;
    }

    /**
     * Indicates that JSON values are base 64 encodings of binary data. Calling
     * this method is equivalent to the following:
     *
     * <pre>
     * mapper.decoder(...); // function that converts binary data to base 64
     * mapper.encoder(...); // function that converts base 64 to binary data
     * </pre>
     *
     * @return This attribute mapper.
     */
    public SimpleAttributeMapper isBinary() {
        decoder = byteStringToBase64();
        encoder = base64ToByteString();
        return this;
    }

    /**
     * Indicates that the LDAP attribute is mandatory and must be provided
     * during create requests.
     *
     * @return This attribute mapper.
     */
    public SimpleAttributeMapper isRequired() {
        this.isRequired = true;
        return this;
    }

    /**
     * Indicates that multi-valued LDAP attribute should be represented as a
     * single-valued JSON value, rather than an array of values.
     *
     * @return This attribute mapper.
     */
    public SimpleAttributeMapper isSingleValued() {
        this.isSingleValued = true;
        return this;
    }

    /**
     * Indicates whether or not the LDAP attribute supports updates. The default
     * is {@link WritabilityPolicy#READ_WRITE}.
     *
     * @param policy
     *            The writability policy.
     * @return This attribute mapper.
     */
    public SimpleAttributeMapper writability(final WritabilityPolicy policy) {
        this.writabilityPolicy = policy;
        return this;
    }

    @Override
    void getLDAPAttributes(final Context c, final JsonPointer jsonAttribute,
            final Set<String> ldapAttributes) {
        ldapAttributes.add(ldapAttributeName.toString());
    }

    @Override
    void getLDAPFilter(final Context c, final FilterType type, final JsonPointer jsonAttribute,
            final String operator, final Object valueAssertion, final ResultHandler<Filter> h) {
        if (jsonAttribute.isEmpty()) {
            h.handleResult(toFilter(c, type, ldapAttributeName.toString(), valueAssertion));
        } else {
            // This attribute mapper does not support partial filtering.
            h.handleResult(alwaysFalse());
        }
    }

    @Override
    void toJSON(final Context c, final Entry e, final ResultHandler<JsonValue> h) {
        final Function<ByteString, ?, Void> f =
                decoder == null ? fixedFunction(byteStringToJson(), ldapAttributeName) : decoder;
        final Object value;
        if (isSingleValued || ldapAttributeName.getAttributeType().isSingleValue()) {
            value = e.parseAttribute(ldapAttributeName).as(f, defaultJSONValue);
        } else {
            value = e.parseAttribute(ldapAttributeName).asSetOf(f, defaultJSONValues);
        }
        h.handleResult(new JsonValue(value));
    }

    @Override
    void toLDAP(final Context c, final JsonValue v, final ResultHandler<List<Attribute>> h) {
        try {
            final List<Attribute> result;
            if (v == null || v.isNull()) {
                if (attributeIsRequired()) {
                    // FIXME: improve error message.
                    throw new BadRequestException("no value provided");
                } else if (defaultLDAPValue != null) {
                    result =
                            singletonList((Attribute) new LinkedAttribute(ldapAttributeName,
                                    defaultLDAPValue));
                } else {
                    result = emptyList();
                }
            } else if (v.isList() && attributeIsSingleValued()) {
                // FIXME: improve error message.
                throw new BadRequestException("expected single value, but got multiple values");
            } else if (!writabilityPolicy.canCreate(ldapAttributeName)) {
                if (writabilityPolicy.discardWrites()) {
                    result = emptyList();
                } else {
                    // FIXME: improve error message.
                    throw new BadRequestException("attempted to create a read-only value");
                }
            } else {
                final Object value = v.getObject();
                if (value != null) {
                    final Function<Object, ByteString, Void> f =
                            encoder != null ? encoder : fixedFunction(jsonToByteString(),
                                    ldapAttributeName);
                    result = singletonList(jsonToAttribute(value, ldapAttributeName, f));
                } else if (defaultLDAPValue != null) {
                    result =
                            singletonList((Attribute) new LinkedAttribute(ldapAttributeName,
                                    defaultLDAPValue));
                } else {
                    result = emptyList();
                }
            }
            h.handleResult(result);
        } catch (final ResourceException e) {
            h.handleError(e);
        } catch (final Exception e) {
            // FIXME: improve error message.
            h.handleError(new BadRequestException(e.getMessage()));
        }
    }

    private boolean attributeIsRequired() {
        return isRequired && defaultJSONValue == null;
    }

    private boolean attributeIsSingleValued() {
        return isSingleValued || ldapAttributeName.getAttributeType().isSingleValue();
    }

}