//
//  ========================================================================
//  Copyright (c) 1995-2017 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.server.session;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

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

import org.eclipse.jetty.client.HttpClient;
import org.eclipse.jetty.client.api.ContentResponse;
import org.eclipse.jetty.client.api.Request;
import org.junit.Test;


/**
 * AbstractScatterGunLoadTest
 * 
 * This is an unrealistic test. It takes a scatter-gun approach to smearing a
 * single session across 2 different nodes at once. 
 * 
 * In the real world, we must have a load balancer that uses sticky sessions
 * to keep the session pinned to a particular node.
 */
public abstract class AbstractScatterGunLoadTest
{
    protected boolean _stress = Boolean.getBoolean( "STRESS" );

    public abstract AbstractTestServer createServer(int port);

    @Test
    public void testLightLoad()
        throws Exception
    {
        if ( _stress )
        {
            String contextPath = "";
            String servletMapping = "/server";
            AbstractTestServer server1 = createServer( 0 );
            server1.addContext( contextPath ).addServlet( TestServlet.class, servletMapping );

            try
            {
                server1.start();
                int port1 = server1.getPort();
                AbstractTestServer server2 = createServer( 0 );
                server2.addContext( contextPath ).addServlet( TestServlet.class, servletMapping );

                try
                {
                    server2.start();
                    int port2=server2.getPort();
                    HttpClient client = new HttpClient();
                    client.start();
                    try
                    {
                        String[] urls = new String[2];
                        urls[0] = "http://localhost:" + port1 + contextPath + servletMapping;
                        urls[1] = "http://localhost:" + port2 + contextPath + servletMapping;

                        //create session via first server
                        ContentResponse response1 = client.GET(urls[0] + "?action=init");
                        assertEquals(HttpServletResponse.SC_OK,response1.getStatus());
                        String sessionCookie = response1.getHeaders().get( "Set-Cookie" );
                        assertTrue(sessionCookie != null);
                        // Mangle the cookie, replacing Path with $Path, etc.
                        sessionCookie = sessionCookie.replaceFirst("(\\W)(P|p)ath=", "$1\\$Path=");

                        //simulate 50 clients making 100 requests each
                        ExecutorService executor = Executors.newCachedThreadPool();
                        int clientsCount = 50;
                        CyclicBarrier barrier = new CyclicBarrier( clientsCount + 1 );
                        int requestsCount = 100;
                        Worker[] workers = new Worker[clientsCount];
                        for ( int i = 0; i < clientsCount; ++i )
                        {
                            workers[i] = new Worker( barrier, requestsCount, sessionCookie, urls );
                            workers[i].start();
                            executor.execute( workers[i] );
                        }
                        // Wait for all workers to be ready
                        barrier.await();
                        long start = System.nanoTime();

                        // Wait for all workers to be done
                        barrier.await();
                        long end = System.nanoTime();
                        long elapsed = TimeUnit.NANOSECONDS.toMillis( end - start );
                        System.out.println( "elapsed ms: " + elapsed );

                        for ( Worker worker : workers )
                            worker.stop();
                        executor.shutdownNow();

                        // Perform one request to get the result
                        Request request = client.newRequest( urls[0] + "?action=result" );
                        request.header("Cookie", sessionCookie);
                        ContentResponse response2 = request.send();
                        assertEquals(HttpServletResponse.SC_OK,response2.getStatus());
                        String response = response2.getContentAsString();
                        System.out.println( "get = " + response );
                        assertEquals(response.trim(), String.valueOf( clientsCount * requestsCount ) );
                    }
                    finally
                    {
                        client.stop();
                    }
                }
                finally
                {
                    server2.stop();
                }
            }
            finally
            {
                server1.stop();
            }
        }
    }

    public static class Worker
        implements Runnable
    {
        private final HttpClient client;

        private final CyclicBarrier barrier;

        private final int requestsCount;

        private final String sessionCookie;

        private final String[] urls;


        public Worker( CyclicBarrier barrier, int requestsCount, String sessionCookie, String[] urls )
        {
            this.client = new HttpClient();
            this.barrier = barrier;
            this.requestsCount = requestsCount;
            this.sessionCookie = sessionCookie;
            this.urls = urls;
        }

        public void start()
            throws Exception
        {
            client.start();
        }

        public void stop()
            throws Exception
        {
            client.stop();
        }

        public void run()
        {
            try
            {
                // Wait for all workers to be ready
                barrier.await();

                Random random = new Random( System.nanoTime() );

                for ( int i = 0; i < requestsCount; ++i )
                {
                    int urlIndex = random.nextInt( urls.length );
                    Request request = client.newRequest(urls[urlIndex] + "?action=increment");
                    request.header("Cookie", sessionCookie);
                    ContentResponse response = request.send();
                    assertEquals(HttpServletResponse.SC_OK,response.getStatus());
                }

                // Wait for all workers to be done
                barrier.await();
            }
            catch ( Exception x )
            {
                throw new RuntimeException( x );
            }
        }
    }

    public static class TestServlet
        extends HttpServlet
    {
        @Override
        protected void doGet( HttpServletRequest request, HttpServletResponse response )
            throws ServletException, IOException
        {
            String action = request.getParameter( "action" );
            if ( "init".equals( action ) )
            {
                HttpSession session = request.getSession( true );
                session.setAttribute( "value", 0 );
            }
            else if ( "increment".equals( action ) )
            {
                // Without synchronization
                HttpSession session = request.getSession( false );
                int value = (Integer) session.getAttribute( "value" );
                session.setAttribute( "value", value + 1 );
            }
            else if ( "result".equals( action ) )
            {
                HttpSession session = request.getSession( false );
                int value = (Integer) session.getAttribute( "value" );
                PrintWriter writer = response.getWriter();
                writer.println( value );
                writer.flush();
            }
        }
    }
}