/*
 * 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/applications-module.h"
#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("SocketBoundTcpRoutingExample");

static const uint32_t totalTxBytes = 20000;
static uint32_t currentTxBytes = 0;
static const uint32_t writeSize = 1040;
uint8_t data[writeSize];

void StartFlow(Ptr<Socket>, Ipv4Address, uint16_t);
void WriteUntilBufferFull(Ptr<Socket>, uint32_t);

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);

    staticRoutingDst->AddHostRouteTo(Ipv4Address("10.1.2.1"), Ipv4Address("10.20.1.1"), 1);
    staticRoutingDstRtr->AddHostRouteTo(Ipv4Address("10.1.2.1"), Ipv4Address("10.10.2.1"), 2);
    staticRoutingRtr2->AddHostRouteTo(Ipv4Address("10.1.2.1"), 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> srcSocket1 =
        Socket::CreateSocket(nSrc, TypeId::LookupByName("ns3::TcpSocketFactory"));
    Ptr<Socket> srcSocket2 =
        Socket::CreateSocket(nSrc, TypeId::LookupByName("ns3::TcpSocketFactory"));
    Ptr<Socket> srcSocket3 =
        Socket::CreateSocket(nSrc, TypeId::LookupByName("ns3::TcpSocketFactory"));
    Ptr<Socket> srcSocket4 =
        Socket::CreateSocket(nSrc, TypeId::LookupByName("ns3::TcpSocketFactory"));

    uint16_t dstport = 12345;
    Ipv4Address dstaddr("10.20.1.2");

    PacketSinkHelper sink("ns3::TcpSocketFactory",
                          InetSocketAddress(Ipv4Address::GetAny(), dstport));
    ApplicationContainer apps = sink.Install(nDst);
    apps.Start(Seconds(0));
    apps.Stop(Seconds(10));

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

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

    // First packet as normal (goes via Rtr1)
    Simulator::Schedule(Seconds(0.1), &StartFlow, srcSocket1, dstaddr, dstport);
    // Second via Rtr1 explicitly
    Simulator::Schedule(Seconds(1), &BindSock, srcSocket2, SrcToRtr1);
    Simulator::Schedule(Seconds(1.1), &StartFlow, srcSocket2, dstaddr, dstport);
    // Third via Rtr2 explicitly
    Simulator::Schedule(Seconds(2), &BindSock, srcSocket3, SrcToRtr2);
    Simulator::Schedule(Seconds(2.1), &StartFlow, srcSocket3, dstaddr, dstport);
    // Fourth again as normal (goes via Rtr1)
    Simulator::Schedule(Seconds(3), &BindSock, srcSocket4, Ptr<NetDevice>(nullptr));
    Simulator::Schedule(Seconds(3.1), &StartFlow, srcSocket4, 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
BindSock(Ptr<Socket> sock, Ptr<NetDevice> netdev)
{
    sock->BindToNetDevice(netdev);
}

void
StartFlow(Ptr<Socket> localSocket, Ipv4Address servAddress, uint16_t servPort)
{
    NS_LOG_INFO("Starting flow at time " << Simulator::Now().GetSeconds());
    currentTxBytes = 0;
    localSocket->Bind();
    localSocket->Connect(InetSocketAddress(servAddress, servPort)); // connect

    // tell the tcp implementation to call WriteUntilBufferFull again
    // if we blocked and new tx buffer space becomes available
    localSocket->SetSendCallback(MakeCallback(&WriteUntilBufferFull));
    WriteUntilBufferFull(localSocket, localSocket->GetTxAvailable());
}

void
WriteUntilBufferFull(Ptr<Socket> localSocket, uint32_t txSpace)
{
    while (currentTxBytes < totalTxBytes && localSocket->GetTxAvailable() > 0)
    {
        uint32_t left = totalTxBytes - currentTxBytes;
        uint32_t dataOffset = currentTxBytes % writeSize;
        uint32_t toWrite = writeSize - dataOffset;
        toWrite = std::min(toWrite, left);
        toWrite = std::min(toWrite, localSocket->GetTxAvailable());
        int amountSent = localSocket->Send(&data[dataOffset], toWrite, 0);
        if (amountSent < 0)
        {
            // we will be called again when new tx space becomes available.
            return;
        }
        currentTxBytes += amountSent;
    }
    localSocket->Close();
}
