/*
 * SPDX-License-Identifier: GPL-2.0-only
 *
 */

//
// Network topology
//
//  n0
//     \ 5 Mb/s, 2ms
//      \          1.5Mb/s, 10ms
//       n2 ------------------------n3
//      /                          /
//     / 5 Mb/s, 2ms              /
//   n1--------------------------
//          1.5 Mb/s, 100ms
//
// this is a modification of simple-global-routing to allow for
// a single hop but higher-cost path between n1 and n3
//
// - Tracing of queues and packet receptions to file "simple-rerouting.tr"

#include "ns3/applications-module.h"
#include "ns3/core-module.h"
#include "ns3/internet-module.h"
#include "ns3/ipv4-global-routing-helper.h"
#include "ns3/network-module.h"
#include "ns3/point-to-point-module.h"

#include <cassert>
#include <fstream>
#include <iostream>
#include <string>

using namespace ns3;

NS_LOG_COMPONENT_DEFINE("SimpleAlternateRoutingExample");

int
main(int argc, char* argv[])
{
    // Users may find it convenient to turn on explicit debugging
    // for selected modules; the below lines suggest how to do this
#if 0
  LogComponentEnable ("GlobalRoutingHelper", LOG_LOGIC);
  LogComponentEnable ("GlobalRouter", LOG_LOGIC);
#endif

    Config::SetDefault("ns3::OnOffApplication::PacketSize", UintegerValue(210));
    Config::SetDefault("ns3::OnOffApplication::DataRate", StringValue("300b/s"));

    // The below metric, if set to 3 or higher, will cause packets between
    // n1 and n3 to take the 2-hop route through n2

    CommandLine cmd(__FILE__);
    //
    // Additionally, we plumb this metric into the default value / command
    // line argument system as well, for exemplary purposes.  This means
    // that it can be resettable at the command-line to the program,
    // rather than recompiling
    // e.g. ns3 --run "simple-alternate-routing --AlternateCost=5"
    uint16_t sampleMetric = 1;
    cmd.AddValue("AlternateCost",
                 "This metric is used in the example script between n3 and n1 ",
                 sampleMetric);

    // Allow the user to override any of the defaults and the above
    // DefaultValue::Bind ()s at run-time, via command-line arguments
    cmd.Parse(argc, argv);

    // Here, we will explicitly create four nodes.  In more sophisticated
    // topologies, we could configure a node factory.
    NS_LOG_INFO("Create nodes.");
    NodeContainer c;
    c.Create(4);
    NodeContainer n0n2 = NodeContainer(c.Get(0), c.Get(2));
    NodeContainer n1n2 = NodeContainer(c.Get(1), c.Get(2));
    NodeContainer n3n2 = NodeContainer(c.Get(3), c.Get(2));
    NodeContainer n1n3 = NodeContainer(c.Get(1), c.Get(3));

    // We create the channels first without any IP addressing information
    NS_LOG_INFO("Create channels.");
    PointToPointHelper p2p;
    p2p.SetDeviceAttribute("DataRate", StringValue("5Mbps"));
    p2p.SetChannelAttribute("Delay", StringValue("2ms"));
    NetDeviceContainer d0d2 = p2p.Install(n0n2);

    NetDeviceContainer d1d2 = p2p.Install(n1n2);

    p2p.SetDeviceAttribute("DataRate", StringValue("1500kbps"));
    p2p.SetChannelAttribute("Delay", StringValue("10ms"));
    NetDeviceContainer d3d2 = p2p.Install(n3n2);

    p2p.SetChannelAttribute("Delay", StringValue("100ms"));
    NetDeviceContainer d1d3 = p2p.Install(n1n3);

    InternetStackHelper internet;
    internet.Install(c);

    // Later, we add IP addresses.  The middle two octets correspond to
    // the channel number.
    NS_LOG_INFO("Assign IP Addresses.");
    Ipv4AddressHelper ipv4;
    ipv4.SetBase("10.0.0.0", "255.255.255.0");
    ipv4.Assign(d0d2);

    ipv4.SetBase("10.1.1.0", "255.255.255.0");
    Ipv4InterfaceContainer i1i2 = ipv4.Assign(d1d2);

    ipv4.SetBase("10.2.2.0", "255.255.255.0");
    ipv4.Assign(d3d2);

    ipv4.SetBase("10.3.3.0", "255.255.255.0");
    Ipv4InterfaceContainer i1i3 = ipv4.Assign(d1d3);

    i1i3.SetMetric(0, sampleMetric);
    i1i3.SetMetric(1, sampleMetric);

    // Create router nodes, initialize routing database and set up the routing
    // tables in the nodes.
    Ipv4GlobalRoutingHelper::PopulateRoutingTables();

    // Create the OnOff application to send UDP datagrams
    NS_LOG_INFO("Create Application.");
    uint16_t port = 9; // Discard port (RFC 863)

    // Create a flow from n3 to n1, starting at time 1.1 seconds
    OnOffHelper onoff("ns3::UdpSocketFactory",
                      Address(InetSocketAddress(i1i2.GetAddress(0), port)));
    onoff.SetConstantRate(DataRate("300b/s"));

    ApplicationContainer apps = onoff.Install(c.Get(3));
    apps.Start(Seconds(1.1));
    apps.Stop(Seconds(10));

    // Create a packet sink to receive these packets
    PacketSinkHelper sink("ns3::UdpSocketFactory",
                          Address(InetSocketAddress(Ipv4Address::GetAny(), port)));
    apps = sink.Install(c.Get(1));
    apps.Start(Seconds(1.1));
    apps.Stop(Seconds(10));

    AsciiTraceHelper ascii;
    p2p.EnableAsciiAll(ascii.CreateFileStream("simple-alternate-routing.tr"));
    p2p.EnablePcapAll("simple-alternate-routing");

    NS_LOG_INFO("Run Simulation.");
    Simulator::Run();
    Simulator::Destroy();
    NS_LOG_INFO("Done.");

    return 0;
}
