/*
 * 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.http.http11.auth;

import io.milton.http.AuthenticationHandler;
import io.milton.http.Filter;
import io.milton.http.FilterChain;
import io.milton.http.Request;
import io.milton.http.Response;
import io.milton.http.http11.Http11ResponseHandler;
import io.milton.http.SecurityManager;
import java.util.ArrayList;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A filter to perform authentication before resource location.
 *
 * This allows the authenticated context to be available for resource location.
 *
 * Note that this filter contains a list of AuthenticationHandler. However,
 * these handlers MUST be designed to ignore the resource variable as it will
 * always be null when used with this filter. This approach allows these handlers
 * to be used with the post-resource-location approach.
 *
 */
public class PreAuthenticationFilter implements Filter {

    private static final Logger log = LoggerFactory.getLogger( PreAuthenticationFilter.class );
    private static final ThreadLocal<Request> tlRequest = new ThreadLocal<Request>();
    private final Http11ResponseHandler responseHandler;
    private final List<AuthenticationHandler> authenticationHandlers;

    public static Request getCurrentRequest() {
        return tlRequest.get();
    }

    public PreAuthenticationFilter( Http11ResponseHandler responseHandler, List<AuthenticationHandler> authenticationHandlers ) {
        this.responseHandler = responseHandler;
        this.authenticationHandlers = authenticationHandlers;
    }

    public PreAuthenticationFilter( Http11ResponseHandler responseHandler, SecurityManager securityManager ) {
        this.responseHandler = responseHandler;
        this.authenticationHandlers = new ArrayList<AuthenticationHandler>();
        authenticationHandlers.add( new SecurityManagerBasicAuthHandler( securityManager ) );
        authenticationHandlers.add( new SecurityManagerDigestAuthenticationHandler( securityManager ) );
    }

    public PreAuthenticationFilter( Http11ResponseHandler responseHandler, SecurityManager securityManager, NonceProvider np) {
        this.responseHandler = responseHandler;
        this.authenticationHandlers = new ArrayList<AuthenticationHandler>();
        authenticationHandlers.add( new SecurityManagerBasicAuthHandler( securityManager ) );
        authenticationHandlers.add( new SecurityManagerDigestAuthenticationHandler( np, securityManager ) );
    }


	@Override
    public void process( FilterChain chain, Request request, Response response ) {
        log.trace( "process" );
        try {
            tlRequest.set( request );
            Object authTag = authenticate( request );
            if( authTag != null ) {
                request.getAuthorization().setTag( authTag );
                chain.process( request, response );
            } else {
                responseHandler.respondUnauthorised( null, response, request );
            }
        } finally {
            tlRequest.remove();
        }
    }

    /**
     * Looks for an AuthenticationHandler which supports the given resource and
     * authorization header, and then returns the result of that handler's
     * authenticate method.
     *
     * Returns null if no handlers support the request
     *
     * @param request
     * @return
     */
    public Object authenticate( Request request ) {
        for( AuthenticationHandler h : authenticationHandlers ) {
            if( h.supports( null, request ) ) {
                Object o = h.authenticate( null, request );
                if( o == null ) {
                    log.warn( "authentication failed by AuthenticationHandler:" + h.getClass() );
                }
                return o;
            }
        }

        if( request.getAuthorization() == null ) {
            // note that this is completely normal, so just TRACE
            if( log.isTraceEnabled() ) {
                log.trace( "No AuthenticationHandler supports this request - no authorisation given in request" );
            }
        } else {
            // authorisation was present in the request, but no handlers accepted it - probably a config problem
            if( log.isWarnEnabled() ) {
                log.warn( "No AuthenticationHandler supports this request with scheme:" + request.getAuthorization().getScheme() );
            }
        }
        return null;
    }

    /**
     * Generates a list of http authentication challenges, one for each
     * supported authentication method, to be sent to the client.
     *
     * @param request - the current request
     * @return - a list of http challenges
     */
    public List<String> getChallenges( Request request ) {
        List<String> challenges = new ArrayList<String>();

        for( AuthenticationHandler h : authenticationHandlers ) {
            h.appendChallenges(null, request, challenges);            
        }
        return challenges;
    }
}