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

/* Test program for multi-interface host, static routing

         Destination host (10.20.1.2)
                 |
                 | 10.20.1.0/24
              DSTRTR
  10.10.1.0/24 /   \  10.10.2.0/24
              / \
           Rtr1    Rtr2
 10.1.1.0/24 |      | 10.1.2.0/24
             |      /
              \    /
             Source
*/

#include "ns3/core-module.h"
#include "ns3/internet-module.h"
#include "ns3/ipv4-list-routing-helper.h"
#include "ns3/ipv4-static-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("SocketBoundRoutingExample");

void SendStuff(Ptr<Socket> sock, Ipv4Address dstaddr, uint16_t port);
void BindSock(Ptr<Socket> sock, Ptr<NetDevice> netdev);
void srcSocketRecv(Ptr<Socket> socket);
void dstSocketRecv(Ptr<Socket> socket);

int
main(int argc, char* argv[])
{
    // Allow the user to override any of the defaults and the above
    // DefaultValue::Bind ()s at run-time, via command-line arguments
    CommandLine cmd(__FILE__);
    cmd.Parse(argc, argv);

    Ptr<Node> nSrc = CreateObject<Node>();
    Ptr<Node> nDst = CreateObject<Node>();
    Ptr<Node> nRtr1 = CreateObject<Node>();
    Ptr<Node> nRtr2 = CreateObject<Node>();
    Ptr<Node> nDstRtr = CreateObject<Node>();

    NodeContainer c = NodeContainer(nSrc, nDst, nRtr1, nRtr2, nDstRtr);

    InternetStackHelper internet;
    internet.Install(c);

    // Point-to-point links
    NodeContainer nSrcnRtr1 = NodeContainer(nSrc, nRtr1);
    NodeContainer nSrcnRtr2 = NodeContainer(nSrc, nRtr2);
    NodeContainer nRtr1nDstRtr = NodeContainer(nRtr1, nDstRtr);
    NodeContainer nRtr2nDstRtr = NodeContainer(nRtr2, nDstRtr);
    NodeContainer nDstRtrnDst = NodeContainer(nDstRtr, nDst);

    // We create the channels first without any IP addressing information
    PointToPointHelper p2p;
    p2p.SetDeviceAttribute("DataRate", StringValue("5Mbps"));
    p2p.SetChannelAttribute("Delay", StringValue("2ms"));
    NetDeviceContainer dSrcdRtr1 = p2p.Install(nSrcnRtr1);
    NetDeviceContainer dSrcdRtr2 = p2p.Install(nSrcnRtr2);
    NetDeviceContainer dRtr1dDstRtr = p2p.Install(nRtr1nDstRtr);
    NetDeviceContainer dRtr2dDstRtr = p2p.Install(nRtr2nDstRtr);
    NetDeviceContainer dDstRtrdDst = p2p.Install(nDstRtrnDst);

    Ptr<NetDevice> SrcToRtr1 = dSrcdRtr1.Get(0);
    Ptr<NetDevice> SrcToRtr2 = dSrcdRtr2.Get(0);

    // Later, we add IP addresses.
    Ipv4AddressHelper ipv4;
    ipv4.SetBase("10.1.1.0", "255.255.255.0");
    Ipv4InterfaceContainer iSrciRtr1 = ipv4.Assign(dSrcdRtr1);
    ipv4.SetBase("10.1.2.0", "255.255.255.0");
    Ipv4InterfaceContainer iSrciRtr2 = ipv4.Assign(dSrcdRtr2);
    ipv4.SetBase("10.10.1.0", "255.255.255.0");
    Ipv4InterfaceContainer iRtr1iDstRtr = ipv4.Assign(dRtr1dDstRtr);
    ipv4.SetBase("10.10.2.0", "255.255.255.0");
    Ipv4InterfaceContainer iRtr2iDstRtr = ipv4.Assign(dRtr2dDstRtr);
    ipv4.SetBase("10.20.1.0", "255.255.255.0");
    Ipv4InterfaceContainer iDstRtrDst = ipv4.Assign(dDstRtrdDst);

    Ptr<Ipv4> ipv4Src = nSrc->GetObject<Ipv4>();
    Ptr<Ipv4> ipv4Rtr1 = nRtr1->GetObject<Ipv4>();
    Ptr<Ipv4> ipv4Rtr2 = nRtr2->GetObject<Ipv4>();
    Ptr<Ipv4> ipv4DstRtr = nDstRtr->GetObject<Ipv4>();
    Ptr<Ipv4> ipv4Dst = nDst->GetObject<Ipv4>();

    Ipv4StaticRoutingHelper ipv4RoutingHelper;
    Ptr<Ipv4StaticRouting> staticRoutingSrc = ipv4RoutingHelper.GetStaticRouting(ipv4Src);
    Ptr<Ipv4StaticRouting> staticRoutingRtr1 = ipv4RoutingHelper.GetStaticRouting(ipv4Rtr1);
    Ptr<Ipv4StaticRouting> staticRoutingRtr2 = ipv4RoutingHelper.GetStaticRouting(ipv4Rtr2);
    Ptr<Ipv4StaticRouting> staticRoutingDstRtr = ipv4RoutingHelper.GetStaticRouting(ipv4DstRtr);
    Ptr<Ipv4StaticRouting> staticRoutingDst = ipv4RoutingHelper.GetStaticRouting(ipv4Dst);

    // Create static routes from Src to Dst
    staticRoutingRtr1->AddHostRouteTo(Ipv4Address("10.20.1.2"), Ipv4Address("10.10.1.2"), 2);
    staticRoutingRtr2->AddHostRouteTo(Ipv4Address("10.20.1.2"), Ipv4Address("10.10.2.2"), 2);

    // Two routes to same destination - setting separate metrics.
    // You can switch these to see how traffic gets diverted via different routes
    staticRoutingSrc->AddHostRouteTo(Ipv4Address("10.20.1.2"), Ipv4Address("10.1.1.2"), 1, 5);
    staticRoutingSrc->AddHostRouteTo(Ipv4Address("10.20.1.2"), Ipv4Address("10.1.2.2"), 2, 10);

    // Creating static routes from DST to Source pointing to Rtr1 VIA Rtr2(!)
    staticRoutingDst->AddHostRouteTo(Ipv4Address("10.1.1.1"), Ipv4Address("10.20.1.1"), 1);
    staticRoutingDstRtr->AddHostRouteTo(Ipv4Address("10.1.1.1"), Ipv4Address("10.10.2.1"), 2);
    staticRoutingRtr2->AddHostRouteTo(Ipv4Address("10.1.1.1"), Ipv4Address("10.1.2.1"), 1);

    // There are no apps that can utilize the Socket Option so doing the work directly..
    // Taken from tcp-large-transfer example

    Ptr<Socket> srcSocket =
        Socket::CreateSocket(nSrc, TypeId::LookupByName("ns3::UdpSocketFactory"));
    srcSocket->Bind();
    srcSocket->SetRecvCallback(MakeCallback(&srcSocketRecv));

    Ptr<Socket> dstSocket =
        Socket::CreateSocket(nDst, TypeId::LookupByName("ns3::UdpSocketFactory"));
    uint16_t dstport = 12345;
    Ipv4Address dstaddr("10.20.1.2");
    InetSocketAddress dst = InetSocketAddress(dstaddr, dstport);
    dstSocket->Bind(dst);
    dstSocket->SetRecvCallback(MakeCallback(&dstSocketRecv));

    AsciiTraceHelper ascii;
    p2p.EnableAsciiAll(ascii.CreateFileStream("socket-bound-static-routing.tr"));
    p2p.EnablePcapAll("socket-bound-static-routing");

    LogComponentEnableAll(LOG_PREFIX_TIME);
    LogComponentEnable("SocketBoundRoutingExample", LOG_LEVEL_INFO);

    // First packet as normal (goes via Rtr1)
    Simulator::Schedule(Seconds(0.1), &SendStuff, srcSocket, dstaddr, dstport);
    // Second via Rtr1 explicitly
    Simulator::Schedule(Seconds(1), &BindSock, srcSocket, SrcToRtr1);
    Simulator::Schedule(Seconds(1.1), &SendStuff, srcSocket, dstaddr, dstport);
    // Third via Rtr2 explicitly
    Simulator::Schedule(Seconds(2), &BindSock, srcSocket, SrcToRtr2);
    Simulator::Schedule(Seconds(2.1), &SendStuff, srcSocket, dstaddr, dstport);
    // Fourth again as normal (goes via Rtr1)
    Simulator::Schedule(Seconds(3), &BindSock, srcSocket, Ptr<NetDevice>(nullptr));
    Simulator::Schedule(Seconds(3.1), &SendStuff, srcSocket, dstaddr, dstport);
    // If you uncomment what's below, it results in ASSERT failing since you can't
    // bind to a socket not existing on a node
    // Simulator::Schedule(Seconds(4),&BindSock, srcSocket, dDstRtrdDst.Get(0));
    Simulator::Run();
    Simulator::Destroy();

    return 0;
}

void
SendStuff(Ptr<Socket> sock, Ipv4Address dstaddr, uint16_t port)
{
    Ptr<Packet> p = Create<Packet>();
    p->AddPaddingAtEnd(100);
    sock->SendTo(p, 0, InetSocketAddress(dstaddr, port));
}

void
BindSock(Ptr<Socket> sock, Ptr<NetDevice> netdev)
{
    sock->BindToNetDevice(netdev);
}

void
srcSocketRecv(Ptr<Socket> socket)
{
    Address from;
    Ptr<Packet> packet = socket->RecvFrom(from);
    packet->RemoveAllPacketTags();
    packet->RemoveAllByteTags();
    NS_LOG_INFO("Source Received " << packet->GetSize() << " bytes from "
                                   << InetSocketAddress::ConvertFrom(from).GetIpv4());
    if (socket->GetBoundNetDevice())
    {
        NS_LOG_INFO("Socket was bound");
    }
    else
    {
        NS_LOG_INFO("Socket was not bound");
    }
}

void
dstSocketRecv(Ptr<Socket> socket)
{
    Address from;
    Ptr<Packet> packet = socket->RecvFrom(from);
    packet->RemoveAllPacketTags();
    packet->RemoveAllByteTags();
    InetSocketAddress address = InetSocketAddress::ConvertFrom(from);
    NS_LOG_INFO("Destination Received " << packet->GetSize() << " bytes from "
                                        << address.GetIpv4());
    NS_LOG_INFO("Triggering packet back to source node's interface 1");
    SendStuff(socket, Ipv4Address("10.1.1.1"), address.GetPort());
}
