#pragma once

#include "llarp/iwp.h"
#include "llarp/iwp/establish_job.hpp"
#include "router.hpp"
#include "session.hpp"
#include "str.hpp"

#include <algorithm>
#include <fstream>
#include <mutex>

struct llarp_link
{
  typedef std::mutex mtx_t;
  typedef std::lock_guard< mtx_t > lock_t;

  llarp_router *router;
  llarp_crypto *crypto;
  llarp_logic *logic;
  llarp_ev_loop *netloop;
  llarp_async_iwp *iwp;
  llarp_threadpool *worker;
  llarp_link *parent = nullptr;
  llarp_udp_io udp;
  llarp::Addr addr;
  char keyfile[255];
  uint32_t timeout_job_id;

  const char *
  name() const
  {
    return m_name;
  }
  const char *m_name;

  typedef std::unordered_map< llarp::Addr, llarp_link_session *,
                              llarp::addrhash >
      LinkMap_t;

  LinkMap_t m_sessions;
  mtx_t m_sessions_Mutex;

  typedef std::unordered_map< llarp::PubKey, llarp::Addr, llarp::PubKeyHash >
      SessionMap_t;

  SessionMap_t m_Connected;
  mtx_t m_Connected_Mutex;

  typedef std::unordered_map< llarp::Addr, llarp_link_session *,
                              llarp::addrhash >
      PendingSessionMap_t;
  PendingSessionMap_t m_PendingSessions;
  mtx_t m_PendingSessions_Mutex;

  llarp::SecretKey seckey;

  llarp_link(const llarp_iwp_args &args)
      : router(args.router)
      , crypto(args.crypto)
      , logic(args.logic)
      , worker(args.cryptoworker)
      , m_name("IWP")
  {
    strncpy(keyfile, args.keyfile, sizeof(keyfile));
    iwp = llarp_async_iwp_new(crypto, logic, worker);
  }

  ~llarp_link()
  {
    llarp_async_iwp_free(iwp);
  }

  bool
  has_intro_from(const llarp::Addr &from)
  {
    std::unique_lock< std::mutex > lock(m_PendingSessions_Mutex);
    return m_PendingSessions.find(from) != m_PendingSessions.end();
  }

  void
  put_intro_from(llarp_link_session *s)
  {
    std::unique_lock< std::mutex > lock(m_PendingSessions_Mutex);
    m_PendingSessions[s->addr] = s;
  }

  void
  remove_intro_from(const llarp::Addr &from)
  {
    std::unique_lock< std::mutex > lock(m_PendingSessions_Mutex);
    m_PendingSessions.erase(from);
  }

  // set that src address has identity pubkey
  void
  MapAddr(const llarp::Addr &src, const llarp::PubKey &identity)
  {
    lock_t lock(m_Connected_Mutex);
    m_Connected[identity] = src;
  }

  static bool
  has_session_to(llarp_link *serv, const byte_t *pubkey)
  {
    llarp::PubKey pk(pubkey);
    lock_t lock(serv->m_Connected_Mutex);
    return serv->m_Connected.find(pk) != serv->m_Connected.end();
  }

  void
  TickSessions()
  {
    auto now = llarp_time_now_ms();
    {
      lock_t lock(m_sessions_Mutex);
      std::set< llarp::Addr > remove;
      for(auto &itr : m_sessions)
      {
        llarp_link_session *s = itr.second;
        if(s && s->Tick(now))
          remove.insert(itr.first);
      }

      for(const auto &addr : remove)
        RemoveSessionByAddr(addr);
    }
  }

  static bool
  sendto(llarp_link *serv, const byte_t *pubkey, llarp_buffer_t buf)
  {
    // lock_t lock(serv->m_Connected_Mutex);
    auto itr = serv->m_Connected.find(pubkey);
    if(itr != serv->m_Connected.end())
    {
      // lock_t innerlock(serv->m_sessions_Mutex);
      auto inner_itr = serv->m_sessions.find(itr->second);
      if(inner_itr != serv->m_sessions.end())
      {
        llarp_link_session *link = inner_itr->second;
        return link->sendto(buf);
      }
    }

    return false;
  }

  void
  UnmapAddr(const llarp::Addr &src)
  {
    lock_t lock(m_Connected_Mutex);
    // std::unordered_map< llarp::pubkey, llarp::Addr, llarp::pubkeyhash >
    auto itr = std::find_if(
        m_Connected.begin(), m_Connected.end(),
        [src](const std::pair< llarp::PubKey, llarp::Addr > &item) -> bool {
          return src == item.second;
        });
    if(itr == std::end(m_Connected))
      return;

    // tell router we are done with this session
    router->SessionClosed(itr->first);

    m_Connected.erase(itr);
  }

  llarp_link_session *
  create_session(llarp::Addr src)
  {
    return new llarp_link_session(this, seckey, src);
  }

  bool
  has_session_to(const llarp::Addr &dst)
  {
    lock_t lock(m_sessions_Mutex);
    return m_sessions.find(dst) != m_sessions.end();
  }

  llarp_link_session *
  find_session(const llarp::Addr &addr)
  {
    lock_t lock(m_sessions_Mutex);
    auto itr = m_sessions.find(addr);
    if(itr == m_sessions.end())
      return nullptr;
    else
      return itr->second;
  }

  void
  put_session(const llarp::Addr &src, llarp_link_session *impl)
  {
    lock_t lock(m_sessions_Mutex);
    m_sessions.emplace(src, impl);
    impl->our_router = &router->rc;
  }

  void
  clear_sessions()
  {
    lock_t lock(m_sessions_Mutex);
    auto itr = m_sessions.begin();
    while(itr != m_sessions.end())
    {
      delete itr->second;
      itr = m_sessions.erase(itr);
    }
  }

  static void
  handle_logic_pump(void *user)
  {
    llarp_link *self = static_cast< llarp_link * >(user);
    lock_t lock(self->m_sessions_Mutex);
    auto itr = self->m_sessions.begin();
    while(itr != self->m_sessions.end())
    {
      itr->second->TickLogic();
      ++itr;
    }
  }

  void
  PumpLogic()
  {
    llarp_logic_queue_job(logic, {this, &handle_logic_pump});
  }

  void
  RemoveSessionByAddr(const llarp::Addr &addr)
  {
    auto itr = m_sessions.find(addr);
    if(itr != m_sessions.end())
    {
      llarp::LogDebug("removing session ", addr);
      UnmapAddr(addr);
      llarp_link_session *s = itr->second;
      s->done();
      m_sessions.erase(itr);
      delete s;
    }
  }

  uint8_t *
  pubkey()
  {
    return llarp::seckey_topublic(seckey);
  }

  bool
  ensure_privkey()
  {
    llarp::LogDebug("ensure transport private key at ", keyfile);
    std::error_code ec;
    if(!fs::exists(keyfile, ec))
    {
      if(!keygen(keyfile))
        return false;
    }
    std::ifstream f(keyfile);
    if(f.is_open())
    {
      f.read((char *)seckey.data(), seckey.size());
      return true;
    }
    return false;
  }

  bool
  keygen(const char *fname)
  {
    crypto->encryption_keygen(seckey);
    llarp::LogInfo("new transport key generated");
    std::ofstream f(fname);
    if(f.is_open())
    {
      f.write((char *)seckey.data(), seckey.size());
      return true;
    }
    return false;
  }

  static void
  handle_cleanup_timer(void *l, uint64_t orig, uint64_t left)
  {
    if(left)
      return;
    llarp_link *link     = static_cast< llarp_link * >(l);
    link->timeout_job_id = 0;
    link->TickSessions();
    link->issue_cleanup_timer(orig);
  }

  // this is called in net threadpool
  static void
  handle_recvfrom(struct llarp_udp_io *udp, const struct sockaddr *saddr,
                  const void *buf, ssize_t sz)
  {
    llarp_link *link = static_cast< llarp_link * >(udp->user);

    llarp_link_session *s = link->find_session(*saddr);
    if(s == nullptr)
    {
      // new inbound session
      s = link->create_session(*saddr);
    }
    s->recv(buf, sz);
  }

  void
  cancel_timer()
  {
    if(timeout_job_id)
    {
      llarp_logic_cancel_call(logic, timeout_job_id);
    }
    timeout_job_id = 0;
  }

  void
  issue_cleanup_timer(uint64_t timeout)
  {
    timeout_job_id = llarp_logic_call_later(
        logic, {timeout, this, &llarp_link::handle_cleanup_timer});
  }

  void
  get_our_address(struct llarp_ai *addr)
  {
    addr->rank = 1;
    strncpy(addr->dialect, "IWP", sizeof(addr->dialect));
    memcpy(addr->enc_key, pubkey(), 32);
    memcpy(addr->ip.s6_addr, this->addr.addr6(), 16);
    addr->port = this->addr.port();
  }

  static void
  after_recv(llarp_udp_io *udp)
  {
    llarp_link *self = static_cast< llarp_link * >(udp->user);
    self->PumpLogic();
  }

  bool
  configure(struct llarp_ev_loop *netloop, const char *ifname, int af,
            uint16_t port)
  {
    if(!ensure_privkey())
    {
      llarp::LogError("failed to ensure private key");
      return false;
    }

    llarp::LogDebug("configure link ifname=", ifname, " af=", af,
                    " port=", port);
    // bind
    sockaddr_in ip4addr;
    sockaddr_in6 ip6addr;
    sockaddr *addr = nullptr;
    switch(af)
    {
      case AF_INET:
        addr = (sockaddr *)&ip4addr;
        llarp::Zero(addr, sizeof(ip4addr));
        break;
      case AF_INET6:
        addr = (sockaddr *)&ip6addr;
        llarp::Zero(addr, sizeof(ip6addr));
        break;
        // TODO: AF_PACKET
      default:
        llarp::LogError(__FILE__, "unsupported address family", af);
        return false;
    }

    addr->sa_family = af;

    if(!llarp::StrEq(ifname, "*"))
    {
      if(!llarp_getifaddr(ifname, af, addr))
      {
        llarp::LogError("failed to get address of network interface ", ifname);
        return false;
      }
    }
    else
      m_name = "OWP";  // outboundLink_name;

    switch(af)
    {
      case AF_INET:
        ip4addr.sin_port = htons(port);
        break;
      case AF_INET6:
        ip6addr.sin6_port = htons(port);
        break;
        // TODO: AF_PACKET
      default:
        return false;
    }

    this->addr    = *addr;
    this->netloop = netloop;
    udp.recvfrom  = &llarp_link::handle_recvfrom;
    udp.user      = this;
    udp.tick      = &llarp_link::after_recv;
    llarp::LogDebug("bind IWP link to ", addr);
    if(llarp_ev_add_udp(netloop, &udp, addr) == -1)
    {
      llarp::LogError("failed to bind to ", addr);
      return false;
    }
    return true;
  }

  bool
  start_link(struct llarp_logic *pLogic)
  {
    // give link implementations
    // link->parent         = l;
    timeout_job_id = 0;
    this->logic          = pLogic;
    // start cleanup timer
    issue_cleanup_timer(500);
    return true;
  }

  bool
  stop_link()
  {
    cancel_timer();
    llarp_ev_close_udp(&udp);
    clear_sessions();
    return true;
  }

  void
  iter_sessions(llarp_link_session_iter iter)
  {
    auto sz = m_sessions.size();
    if(sz)
    {
      llarp::LogDebug("we have ", sz, "sessions");
      iter.link = this;
      // TODO: race condition with cleanup timer
      for(auto &item : m_sessions)
        if(item.second)
          if(!iter.visit(&iter, item.second))
            return;
    }
  }

  bool
  try_establish(struct llarp_link_establish_job *job)
  {
    llarp::Addr dst(job->ai);
    llarp::LogDebug("establish session to ", dst);
    llarp_link_session *s = find_session(dst);
    if(s == nullptr)
    {
      s = create_session(dst);
      put_session(dst, s);
    }
    else
      return false;
    s->establish_job = job;
    s->frame.alive();  // mark it alive
    s->introduce(job->ai.enc_key);

    return true;
  }

  void
  mark_session_active(llarp_link_session *s)
  {
    s->frame.alive();
  }
};