#include <cstdint>
#include <cstring>
#include <cassert>
#include <llarp/net/ip_packet.hpp>
#include <llarp/config/config.hpp>
#include <llarp/util/fs.hpp>
#include <llarp/util/logging/buffer.hpp>
#include <uvw/loop.h>
#include <llarp/util/logging/logger.hpp>
#include <llarp/util/logging/callback_sink.hpp>
#include "vpn_interface.hpp"
#include "context_wrapper.h"
#include "context.hpp"

namespace
{
  // The default 127.0.0.1:53 won't work (because we run unprivileged) so remap it to this (unless
  // specifically overridden to something else in the config):
  const llarp::SockAddr DefaultDNSBind{"127.0.0.1:1153"};

  struct instance_data
  {
    llarp::apple::Context context;
    std::thread runner;
    packet_writer_callback packet_writer;
    start_reading_callback start_reading;

    std::weak_ptr<llarp::apple::VPNInterface> iface;
  };

}  // namespace

const uint16_t dns_trampoline_port = 1053;

void*
llarp_apple_init(llarp_apple_config* appleconf)
{
  llarp::log::ReplaceLogger(std::make_shared<llarp::log::CallbackSink_mt>(
      [](const char* msg, void* nslog) { reinterpret_cast<ns_logger_callback>(nslog)(msg); },
      nullptr,
      appleconf->ns_logger));

  try
  {
    auto config_dir = fs::u8path(appleconf->config_dir);
    auto config = std::make_shared<llarp::Config>(config_dir);
    fs::path config_path = config_dir / "lokinet.ini";
    if (!fs::exists(config_path))
      llarp::ensureConfig(config_dir, config_path, /*overwrite=*/false, /*asRouter=*/false);
    config->Load(config_path);

    // If no range is specified then go look for a free one, set that in the config, and then return
    // it to the caller via the char* parameters.
    auto& range = config->network.m_ifaddr;
    if (!range.addr.h)
    {
      if (auto maybe = llarp::net::Platform::Default_ptr()->FindFreeRange())
        range = *maybe;
      else
        throw std::runtime_error{"Could not find any free IP range"};
    }
    auto addr = llarp::net::TruncateV6(range.addr).ToString();
    auto mask = llarp::net::TruncateV6(range.netmask_bits).ToString();
    if (addr.size() > 15 || mask.size() > 15)
      throw std::runtime_error{"Unexpected non-IPv4 tunnel range configured"};
    std::strncpy(appleconf->tunnel_ipv4_ip, addr.c_str(), sizeof(appleconf->tunnel_ipv4_ip));
    std::strncpy(
        appleconf->tunnel_ipv4_netmask, mask.c_str(), sizeof(appleconf->tunnel_ipv4_netmask));

    // TODO: in the future we want to do this properly with our pubkey (see issue #1705), but that's
    // going to take a bit more work because we currently can't *get* the (usually) ephemeral pubkey
    // at this stage of lokinet configuration.  So for now we just stick our IPv4 address into it
    // until #1705 gets implemented.
    llarp::huint128_t ipv6{
        llarp::uint128_t{0xfd2e'6c6f'6b69'0000, llarp::net::TruncateV6(range.addr).h}};
    std::strncpy(
        appleconf->tunnel_ipv6_ip, ipv6.ToString().c_str(), sizeof(appleconf->tunnel_ipv6_ip));
    appleconf->tunnel_ipv6_prefix = 48;

    appleconf->upstream_dns[0] = '\0';
    for (auto& upstream : config->dns.m_upstreamDNS)
    {
      if (upstream.isIPv4())
      {
        std::strcpy(appleconf->upstream_dns, upstream.hostString().c_str());
        appleconf->upstream_dns_port = upstream.getPort();
        break;
      }
    }

    // The default DNS bind setting just isn't something we can use as a non-root network extension
    // so remap the default value to a high port unless explicitly set to something else.
    if (config->dns.m_bind == llarp::SockAddr{"127.0.0.1:53"})
      config->dns.m_bind = DefaultDNSBind;

    // If no explicit bootstrap then set the system default one included with the app bundle
    if (config->bootstrap.files.empty())
      config->bootstrap.files.push_back(fs::u8path(appleconf->default_bootstrap));

    auto inst = std::make_unique<instance_data>();
    inst->context.Configure(std::move(config));
    inst->context.route_callbacks = appleconf->route_callbacks;

    inst->packet_writer = appleconf->packet_writer;
    inst->start_reading = appleconf->start_reading;

    return inst.release();
  }
  catch (const std::exception& e)
  {
    llarp::LogError("Failed to initialize lokinet from config: ", e.what());
  }
  return nullptr;
}

int
llarp_apple_start(void* lokinet, void* callback_context)
{
  auto* inst = static_cast<instance_data*>(lokinet);

  inst->context.callback_context = callback_context;

  inst->context.m_PacketWriter = [inst, callback_context](int af_family, void* data, size_t size) {
    inst->packet_writer(af_family, data, size, callback_context);
    return true;
  };

  inst->context.m_OnReadable = [inst, callback_context](llarp::apple::VPNInterface& iface) {
    inst->iface = iface.weak_from_this();
    inst->start_reading(callback_context);
  };

  std::promise<void> result;
  inst->runner = std::thread{[inst, &result] {
    const llarp::RuntimeOptions opts{};
    try
    {
      inst->context.Setup(opts);
    }
    catch (...)
    {
      result.set_exception(std::current_exception());
      return;
    }
    result.set_value();
    inst->context.Run(opts);
  }};

  try
  {
    result.get_future().get();
  }
  catch (const std::exception& e)
  {
    llarp::LogError("Failed to initialize lokinet: ", e.what());
    return -1;
  }

  return 0;
}

uv_loop_t*
llarp_apple_get_uv_loop(void* lokinet)
{
  auto& inst = *static_cast<instance_data*>(lokinet);
  auto uvw = inst.context.loop->MaybeGetUVWLoop();
  assert(uvw);
  return uvw->raw();
}

int
llarp_apple_incoming(void* lokinet, const void* bytes, size_t size)
{
  auto& inst = *static_cast<instance_data*>(lokinet);

  auto iface = inst.iface.lock();
  if (!iface)
    return -2;

  llarp_buffer_t buf{static_cast<const uint8_t*>(bytes), size};
  if (iface->OfferReadPacket(buf))
    return 0;

  llarp::LogError("invalid IP packet: ", llarp::buffer_printer(buf));
  return -1;
}

void
llarp_apple_shutdown(void* lokinet)
{
  auto* inst = static_cast<instance_data*>(lokinet);

  inst->context.CloseAsync();
  inst->context.Wait();
  inst->runner.join();
  delete inst;
}