/*
 * 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.jena.fuseki.servlets ;

import java.util.concurrent.atomic.AtomicLong ;

import javax.servlet.http.HttpServlet ;
import javax.servlet.http.HttpServletRequest ;
import javax.servlet.http.HttpServletResponse ;

import org.apache.jena.atlas.lib.StrUtils ;
import org.apache.jena.fuseki.Fuseki ;
import org.apache.jena.riot.web.HttpNames ;

/**
 * Addition HTTP Servlet operations. 
 */
public abstract class ServletBase extends HttpServlet {

    private static final long serialVersionUID = -4391231243228221820L;

    public static final String METHOD_DELETE    = "DELETE" ;
    public static final String METHOD_HEAD      = "HEAD" ;
    public static final String METHOD_GET       = "GET" ;
    public static final String METHOD_OPTIONS   = "OPTIONS" ;
    public static final String METHOD_POST      = "POST" ;
    public static final String METHOD_PUT       = "PUT" ;
    public static final String METHOD_TRACE     = "TRACE" ;
    public static final String METHOD_PATCH     = "PATCH" ;
    
    private static AtomicLong     requestIdAlloc = new AtomicLong(0) ;

    protected ServletBase() {}
    
    /**
     * Helper method which gets a unique request ID and appends it as a header
     * to the response
     * 
     * @param request
     *            HTTP Request
     * @param response
     *            HTTP Response
     * @return Request ID
     */
    protected static long allocRequestId(HttpServletRequest request, HttpServletResponse response) {
        long id = requestIdAlloc.incrementAndGet() ;
        addRequestId(response, id) ;
        return id ;
    }

    /**
     * Helper method for attaching a request ID to a response as a header
     * 
     * @param response
     *            Response
     * @param id
     *            Request ID
     */
    protected static void addRequestId(HttpServletResponse response, long id) {
        response.addHeader("Fuseki-Request-ID", Long.toString(id)) ;
    }

    static final String varyHeaderSetting = StrUtils.strjoin(",",
         HttpNames.hAccept,
         HttpNames.hAcceptEncoding,
         HttpNames.hAcceptCharset) ;

    public static void setVaryHeader(HttpServletResponse httpResponse) {
        httpResponse.setHeader(HttpNames.hVary, varyHeaderSetting) ;
    }

    /** Done via web.xml */ 
    public static boolean CORS_ENABLED = false ;
    
    public static void setCommonHeadersForOptions(HttpServletResponse httpResponse) {
        if ( CORS_ENABLED )
            httpResponse.setHeader(HttpNames.hAccessControlAllowHeaders, "X-Requested-With, Content-Type, Authorization") ;
        setCommonHeaders(httpResponse) ;
    }

    public static void setCommonHeaders(HttpServletResponse httpResponse) {
        if ( CORS_ENABLED )
            httpResponse.setHeader(HttpNames.hAccessControlAllowOrigin, "*") ;
        if ( Fuseki.outputFusekiServerHeader )
            httpResponse.setHeader(HttpNames.hServer, Fuseki.serverHttpName) ;
    }
}