/*
 * 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.sling.api.resource;

import java.util.Iterator;

import org.jetbrains.annotations.Nullable;
import org.jetbrains.annotations.NotNull;
import javax.servlet.http.HttpServletRequest;

import org.osgi.annotation.versioning.ConsumerType;

/**
 * API for providers of resources. Used by the {@link ResourceResolver} to
 * transparently access resources from different locations such as a JCR
 * repository (the default) or OSGi bundles.
 * <p>
 * This interface is intended to be implemented by providers of resource
 * instances on behalf of the {@link ResourceResolver}. It
 * is not intended to be used by client applications directly. A resource
 * provider can either directly implement this service interface, e.g.
 * when no user authentication is provided (like for bundle resources)
 * or a {@link ResourceProviderFactory} service can be implemented which
 * upon successful authentication returns a resource provider with the
 * given user credentials.
 *
 * @deprecated Use the {@link org.apache.sling.spi.resource.provider.ResourceProvider}
 */
@ConsumerType
@Deprecated
public interface ResourceProvider {

    /**
     * The service name to use when registering implementations of this
     * interface as services (value is
     * "org.apache.sling.api.resource.ResourceProvider").
     */
    String SERVICE_NAME = ResourceProvider.class.getName();

    /**
     * The name of the service registration property containing the root paths
     * of the resources provided by this provider (value is "provider.roots").
     */
    String ROOTS = "provider.roots";

    /**
     * The name of the service registration property containing the a boolean
     * flag whether this provider owns the tree registered by the roots. The
     * default for this value is {@code false}. If a provider owns a root
     * no other providers are asked for resources under this root if this
     * provider does not have a resource. (value is "provider.ownsRoots").
     *
     * @since 2.2 (Sling API Bundle 2.2.0)
     */
    String OWNS_ROOTS = "provider.ownsRoots";

    /**
     * The name of the service registration property containing the a boolean
     * flag indicating if the ResourceAccessSecurity service should be used for
     * this provider or not. ResourceProvider implementations are encouraged
     * to use the ResourceAccessSecurity service for access control unless
     * the underlying storage already provides it.
     * The default for this value is {@code false}.
     * (value is "provider.useResourceAccessSecurity")
     * @since 2.4 (Sling API Bundle 2.5.0)
     */
    String USE_RESOURCE_ACCESS_SECURITY = "provider.useResourceAccessSecurity";

    /**
     * The resource type be set on resources returned by the
     * {@link #listChildren(Resource)} method to enable traversing the
     * resource
     * tree down to a deeply nested provided resource which has no concrete
     * parent hierarchy (value is"sling:syntheticResourceProviderResource").
     *
     * @see #listChildren(Resource)
     */
    String RESOURCE_TYPE_SYNTHETIC = "sling:syntheticResourceProviderResource";

    /**
     * Returns a resource from this resource provider or {@code null} if
     * the resource provider cannot find it. The path should have one of the
     * {@link #ROOTS} strings as its prefix.
     * <p>
     * This method is called to resolve a resource for the given request.
     * The properties of the request, such as request
     * parameters, may be use to parameterize the resource resolution. An
     * example of such parameterization is support for a JSR-311
     * style resource provider to support the parameterized URL patterns.
     *
     * @param resourceResolver
     *            The {@link ResourceResolver} to which the returned
     *            {@link Resource} is attached.
     * @param request The request
     * @param path The resource path
     * @return {@code null} If this provider does not have a resource for
     *         the path.
     * @throws org.apache.sling.api.SlingException
     *             may be thrown in case of any problem creating the {@code Resource} instance.
     * @deprecated since 2.2.0 (and JCR Resource 2.1.0), this method will not be invoked.
     */
    @Deprecated
    @Nullable Resource getResource(@NotNull ResourceResolver resourceResolver, @NotNull HttpServletRequest request, @NotNull String path);

    /**
     * Returns a resource from this resource provider or {@code null} if
     * the resource provider cannot find it. The path should have one of the {@link #ROOTS}
     * strings as its prefix.
     *
     * The resource provider must not return cached instances for a resource as
     * the resource resolver will update the resource metadata of the resource
     * at the end of the resolution process and this metadata might be different
     * depending on the full path of resource resolution passed into the
     * resource resolver.
     *
     * @param resourceResolver
     *            The {@link ResourceResolver} to which the returned {@link Resource} is attached.
     * @param path The full path of the resource.
     * @return {@code null} If this provider does not have a resource for
     *         the path.
     * @throws org.apache.sling.api.SlingException
     *             may be thrown in case of any problem creating the {@code Resource} instance.
     */
    @Nullable Resource getResource(@NotNull ResourceResolver resourceResolver, @NotNull String path);

    /**
     * Returns an {@code Iterator} of {@link Resource} objects loaded from
     * the children of the given {@code Resource}. The returned {@link Resource} instances
     *  are attached to the same
     * {@link ResourceResolver} as the given {@code parent} resource.
     * <p>
     * This method may be called for resource providers whose root path list contains a path such
     * that the resource path is a
     * prefix of the list entry. This allows for the enumeration of deeply nested provided resources
     * for which no actual parent
     * hierarchy exists.
     * <p>
     * The returned iterator may in turn contain resources which do not actually exist but are required
     *  to traverse the resource
     * tree. Such resources SHOULD be {@link SyntheticResource} objects whose resource type MUST be set to
     * {@link #RESOURCE_TYPE_SYNTHETIC}.
     *
     * As with {@link #getResource(ResourceResolver, String)} the returned Resource objects must
     * not be cached objects.
     *
     * @param parent
     *            The {@link Resource Resource} whose children are requested.
     * @return An {@code Iterator} of {@link Resource} objects or {@code null} if the resource
     *         provider has no children for the given resource.
     * @throws NullPointerException
     *             If {@code parent} is {@code null}.
     * @throws org.apache.sling.api.SlingException
     *             If any error occurs acquiring the child resource iterator.
     */
    @Nullable Iterator<Resource> listChildren(@NotNull Resource parent);
}