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/*
 * 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 io.milton.resource;

import io.milton.http.Auth;
import io.milton.http.Request;
import io.milton.http.exceptions.BadRequestException;
import io.milton.http.exceptions.NotAuthorizedException;

import java.util.Date;


/**
 * Implementations should implement compareTo as an alphabetic comparison
 * on the name property
 *
 * @author Alienware1
 */
public interface Resource {

    /**
     * Returning a null value is allowed, and disables the ETag field.
     * 
     * If a unique id is returned it will be combined with the modified date (if available)
     * to produce an ETag which identifies this version of this resource. Note that this
     * behaviour can be changed by injecting an alternative EtagGenerator instance into
     * the HttpManagerBuilder
     *
     * @return - a string which uniquely identifies this resource. This will be
     * used in the ETag header field, and affects caching of resources.
     */
    String getUniqueId();

    /**
     * Note that this name MUST be consistent with URL resolution in your ResourceFactory
     * 

     * If they aren't consistent Milton will generate a different href in PropFind
     * responses then what clients have request and this will cause either an
     * error or no resources to be displayed
     *
     * @return - the name of this resource. Ie just the local name, within its folder
     */
    String getName();


    /**
     * Check the given credentials, and return a relevant object if accepted.
     * 

     * Returning null indicates credentials were not accepted
     *
     * @param user     - the user name provided by the user's agent
     * @param password - the password provided by the user's agent
     * @return - if credentials are accepted, some object to attach to the Auth object.
     * otherwise null
     */
    Object authenticate(String user, String password);

    /**
     * Return true if the current user is permitted to access this resource using
     * the specified method.
     * 

     * Note that the current user may be determined by the Auth associated with
     * the request, or by a separate, application specific, login mechanism such
     * as a session variable or cookie based system. This method should correctly
     * interpret all such mechanisms
     * 

     * The auth given as a parameter will be null if authentication failed. The
     * auth associated with the request will still exist
     *
     * @param request
     * @param method
     * @param auth
     * @return - true to permit the request
     */
    boolean authorise(Request request, Request.Method method, Auth auth);

    /**
     * Return the security realm for this resource. Just any string identifier.
     * 

     * This will be used to construct authorization challenges and will be used
     * on Digest authentication to construct the expected response.
     *
     * @return - the security realm, for HTTP authentication
     */
    String getRealm();

    /**
     * The date and time that this resource, or any part of this resource, was last
     * modified. For dynamic rendered resources this should consider everything
     * which will influence its output.
     * 

     * Resources for which no such date can be calculated should return null.
     * 

     * This field, if not null, is used to reply to conditional GETs (ie GET with
     * if-modified-since). If the modified-since argument is later then the modified
     * date then we return a 304 - Not Modified.
     * 

     * Although nulls are explicitly allowed by milton, certain client applications
     * might require modified dates for file browsing. For example, the command line
     * client on Vista doesn't work properly if this is null.
     *
     * @return - null if not known, else the last date the resource was modified
     */
    Date getModifiedDate();


    /**
     * Determine if a redirect is required for this request, and if so return
     * the URL to redirect to. May be absolute or relative.
     * 

     * Called after authorization check but before any method specific processing
     * 
     * Return null for no redirect
     *
     * @param request
     * @return - null for no redirect, else the path to redirect to
     * @throws io.milton.http.exceptions.NotAuthorizedException
     * @throws io.milton.http.exceptions.BadRequestException
     */
    String checkRedirect(Request request) throws NotAuthorizedException, BadRequestException;


}