#include "net.hpp"

#include "net_if.hpp"
#include <stdexcept>
#include <llarp/constants/platform.hpp>

#include "ip.hpp"
#include "ip_range.hpp"
#include <llarp/util/logging.hpp>
#include <llarp/util/str.hpp>

#include <iphlpapi.h>
#include <llarp/win32/exception.hpp>

#include <cstdio>
#include <list>
#include <type_traits>

namespace llarp::net
{
  class Platform_Impl : public Platform
  {
    /// visit all adapters (not addresses). windows serves net info per adapter unlink posix which
    /// gives a list of all distinct addresses.
    template <typename Visit_t>
    void
    iter_adapters(Visit_t&& visit, int af = AF_UNSPEC) const
    {
      ULONG sz{};
      GetAdaptersAddresses(af, 0, nullptr, nullptr, &sz);
      auto ptr = std::make_unique<byte_t[]>(sz);
      auto* addrs = reinterpret_cast<PIP_ADAPTER_ADDRESSES>(ptr.get());

      if (auto err = GetAdaptersAddresses(af, 0, nullptr, addrs, &sz); err != ERROR_SUCCESS)
        throw llarp::win32::error{err, "GetAdaptersAddresses()"};

      for (auto* addr = addrs; addr->Next; addr = addr->Next)
        visit(addr);
    }

    template <typename adapter_t>
    bool
    adapter_has_ip(adapter_t* a, ipaddr_t ip) const
    {
      for (auto* addr = a->FirstUnicastAddress; addr->Next; addr = addr->Next)
      {
        SockAddr saddr{*addr->Address.lpSockaddr};
        LogDebug(fmt::format("'{}' has address '{}'", a->AdapterName, saddr));
        if (saddr.getIP() == ip)
          return true;
      }
      return false;
    }

    template <typename adapter_t>
    bool
    adapter_has_fam(adapter_t* a, int af) const
    {
      for (auto* addr = a->FirstUnicastAddress; addr->Next; addr = addr->Next)
      {
        SockAddr saddr{*addr->Address.lpSockaddr};
        if (saddr.Family() == af)
          return true;
      }
      return false;
    }

   public:
    std::optional<int>
    GetInterfaceIndex(ipaddr_t ip) const override
    {
      std::optional<int> found;
      int af{AF_INET};
      if (std::holds_alternative<ipv6addr_t>(ip))
        af = AF_INET6;
      iter_adapters(
          [&found, ip, this](auto* adapter) {
            if (found)
              return;

            LogDebug(fmt::format(
                "visit adapter looking for '{}': '{}' idx={}",
                ip,
                adapter->AdapterName,
                adapter->IfIndex));
            if (adapter_has_ip(adapter, ip))
            {
              found = adapter->IfIndex;
            }
          },
          af);
      return found;
    }

    std::optional<llarp::SockAddr>
    GetInterfaceAddr(std::string_view name, int af) const override
    {
      std::optional<SockAddr> found;
      iter_adapters([name = std::string{name}, af, &found, this](auto* a) {
        if (found)
          return;
        if (std::string{a->AdapterName} != name)
          return;

        if (adapter_has_fam(a, af))
          found = SockAddr{*a->FirstUnicastAddress->Address.lpSockaddr};
      });
      return found;
    }

    std::optional<SockAddr>
    AllInterfaces(SockAddr fallback) const override
    {
      // windows seems to not give a shit about source address
      return fallback.isIPv6() ? SockAddr{"[::]"} : SockAddr{"0.0.0.0"};
    }

    std::optional<std::string>
    FindFreeTun() const override
    {
      return "lokitun0";
    }

    std::optional<std::string>
    GetBestNetIF(int) const override
    {
      // TODO: implement me ?
      return std::nullopt;
    }

    std::optional<IPRange>
    FindFreeRange() const override
    {
      std::list<IPRange> currentRanges;
      iter_adapters([&currentRanges](auto* i) {
        for (auto* addr = i->FirstUnicastAddress; addr and addr->Next; addr = addr->Next)
        {
          SockAddr saddr{*addr->Address.lpSockaddr};
          currentRanges.emplace_back(
              saddr.asIPv6(),
              ipaddr_netmask_bits(addr->OnLinkPrefixLength, addr->Address.lpSockaddr->sa_family));
        }
      });

      auto ownsRange = [&currentRanges](const IPRange& range) -> bool {
        for (const auto& ownRange : currentRanges)
        {
          if (ownRange * range)
            return true;
        }
        return false;
      };
      // generate possible ranges to in order of attempts
      std::list<IPRange> possibleRanges;
      for (byte_t oct = 16; oct < 32; ++oct)
      {
        possibleRanges.emplace_back(IPRange::FromIPv4(172, oct, 0, 1, 16));
      }
      for (byte_t oct = 0; oct < 255; ++oct)
      {
        possibleRanges.emplace_back(IPRange::FromIPv4(10, oct, 0, 1, 16));
      }
      for (byte_t oct = 0; oct < 255; ++oct)
      {
        possibleRanges.emplace_back(IPRange::FromIPv4(192, 168, oct, 1, 24));
      }
      // for each possible range pick the first one we don't own
      for (const auto& range : possibleRanges)
      {
        if (not ownsRange(range))
          return range;
      }
      return std::nullopt;
    }

    std::string
    LoopbackInterfaceName() const override
    {
      // todo: implement me? does windows even have a loopback?
      return "";
    }

    bool
    HasInterfaceAddress(ipaddr_t ip) const override
    {
      return GetInterfaceIndex(ip) != std::nullopt;
    }

    std::vector<InterfaceInfo>
    AllNetworkInterfaces() const override
    {
      std::vector<InterfaceInfo> all;
      iter_adapters([&all](auto* a) {
        auto& cur = all.emplace_back();
        cur.index = a->IfIndex;
        cur.name = a->AdapterName;
        for (auto* addr = a->FirstUnicastAddress; addr and addr->Next; addr = addr->Next)
        {
          SockAddr saddr{*addr->Address.lpSockaddr};
          cur.addrs.emplace_back(
              saddr.asIPv6(),
              ipaddr_netmask_bits(addr->OnLinkPrefixLength, addr->Address.lpSockaddr->sa_family));
        }
      });
      return all;
    }
  };

  const Platform_Impl g_plat{};

  const Platform*
  Platform::Default_ptr()
  {
    return &g_plat;
  }
}  // namespace llarp::net