// Copyright (c) 2018-2020, The Monero Project
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//
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//    conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
//    of conditions and the following disclaimer in the documentation and/or other
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#include "client.h"

#include <boost/thread/mutex.hpp>
#include <boost/utility/string_ref.hpp>
#include <cassert>
#include <system_error>

#include "common/error.h"    // monero/contrib/epee/include
#include "error.h"
#include "misc_log_ex.h"     // monero/contrib/epee/include
#include "net/http_client.h" // monero/contrib/epee/include
#include "net/zmq.h"         // monero/src
#include "serialization/json_object.h" // monero/src

namespace lws
{
namespace rpc
{
  namespace http = epee::net_utils::http;

  namespace
  {
    constexpr const char signal_endpoint[] = "inproc://signal";
    constexpr const char abort_scan_signal[] = "SCAN";
    constexpr const char abort_process_signal[] = "PROCESS";
    constexpr const char minimal_chain_topic[] = "json-minimal-chain_main";
    constexpr const int daemon_zmq_linger = 0;
    constexpr const std::chrono::seconds chain_poll_timeout{20};
    constexpr const std::chrono::minutes chain_sub_timeout{2};

    struct terminate
    {
      void operator()(void* ptr) const noexcept
      {
        if (ptr)
        {
          while (zmq_term(ptr))
          {
            if (zmq_errno() != EINTR)
              break;
          }
        }
      }
    };
    using zcontext = std::unique_ptr<void, terminate>;

    expect<void> do_wait(void* daemon, void* signal_sub, short events, std::chrono::milliseconds timeout) noexcept
    {
      if (timeout <= std::chrono::seconds{0})
        return {lws::error::daemon_timeout};

      zmq_pollitem_t items[2] {
        {daemon, 0, short(events | ZMQ_POLLERR), 0},
        {signal_sub, 0, short(ZMQ_POLLIN | ZMQ_POLLERR), 0}
      };

      for (;;)
      {
        const auto start = std::chrono::steady_clock::now();
        const int ready = zmq_poll(items, 2, timeout.count());
        const auto end = std::chrono::steady_clock::now();
        const auto spent = std::chrono::duration_cast<std::chrono::milliseconds>(start - end);
        timeout -= std::min(spent, timeout);

        if (ready == 0)
          return {lws::error::daemon_timeout};
        if (0 < ready)
          break;
        const int err = zmq_errno();
        if (err != EINTR)
          return net::zmq::make_error_code(err);
      }
      if (items[0].revents)
        return success();

      char buf[1];
      MONERO_ZMQ_CHECK(zmq_recv(signal_sub, buf, 1, 0));

      switch (buf[0])
      {
      case 'P':
        return {lws::error::signal_abort_process};
      case 'S':
        return {lws::error::signal_abort_scan};
      default:
        break;
      }
      return {lws::error::signal_unknown};
    }

    template<std::size_t N>
    expect<void> do_signal(void* signal_pub, const char (&signal)[N]) noexcept
    {
      MONERO_ZMQ_CHECK(zmq_send(signal_pub, signal, sizeof(signal) - 1, 0));
      return success();
    }

    template<std::size_t N>
    expect<void> do_subscribe(void* signal_sub, const char (&signal)[N]) noexcept
    {
      MONERO_ZMQ_CHECK(zmq_setsockopt(signal_sub, ZMQ_SUBSCRIBE, signal, sizeof(signal) - 1));
      return success();
    }
  } // anonymous

  namespace detail
  {
    struct context
    {
      explicit context(zcontext comm, socket signal_pub, std::string daemon_addr, std::string sub_addr, std::chrono::minutes interval)
        : comm(std::move(comm))
        , signal_pub(std::move(signal_pub))
        , daemon_addr(std::move(daemon_addr))
        , sub_addr(std::move(sub_addr))
        , rates_conn()
        , cache_time()
        , cache_interval(interval)
        , cached{}
        , sync_rates()
      {
        if (std::chrono::minutes{0} < cache_interval)
          rates_conn.set_server(crypto_compare.host, boost::none, epee::net_utils::ssl_support_t::e_ssl_support_enabled);
      }

      zcontext comm;
      socket signal_pub;
      const std::string daemon_addr;
      const std::string sub_addr;
      http::http_simple_client rates_conn;
      std::chrono::steady_clock::time_point cache_time;
      const std::chrono::minutes cache_interval;
      rates cached;
      boost::mutex sync_rates;
    };
  } // detail

  expect<void> client::get_response(cryptonote::rpc::Message& response, const std::chrono::seconds timeout, const source_location loc)
  {
    expect<std::string> message = get_message(timeout);
    if (!message)
      return message.error();

    try
    {
      cryptonote::rpc::FullMessage fm{std::move(*message)};
      const cryptonote::rpc::error json_error = fm.getError();
      if (!json_error.use)
      {
        response.fromJson(fm.getMessage());
        return success();
      }

      MERROR("Server returned RPC error: " << json_error.message << " with code " << json_error.code << " called from " << loc);
    }
    catch (const cryptonote::json::JSON_ERROR& error)
    {
      MERROR("Failed to parse json response: " << error.what() << " called from " << loc);
    }

    return {lws::error::bad_daemon_response};
  }

  expect<std::string> client::get_message(std::chrono::seconds timeout)
  {
    MONERO_PRECOND(ctx != nullptr);
    assert(daemon != nullptr);
    assert(signal_sub != nullptr);

    expect<std::string> msg{common_error::kInvalidArgument};
    while (!(msg = net::zmq::receive(daemon.get(), ZMQ_DONTWAIT)))
    {
      if (msg != net::zmq::make_error_code(EAGAIN))
        break;

      MONERO_CHECK(do_wait(daemon.get(), signal_sub.get(), ZMQ_POLLIN, timeout));
      timeout = std::chrono::seconds{0};
    }
    // std::string move constructor is noexcept
    return msg;
  }

  expect<client> client::make(std::shared_ptr<detail::context> ctx) noexcept
  {
    MONERO_PRECOND(ctx != nullptr);

    int option = daemon_zmq_linger;
    client out{std::move(ctx)};

    out.daemon.reset(zmq_socket(out.ctx->comm.get(), ZMQ_REQ));
    if (out.daemon.get() == nullptr)
      return net::zmq::get_error_code();
    MONERO_ZMQ_CHECK(zmq_connect(out.daemon.get(), out.ctx->daemon_addr.c_str()));
    MONERO_ZMQ_CHECK(zmq_setsockopt(out.daemon.get(), ZMQ_LINGER, &option, sizeof(option)));

    if (!out.ctx->sub_addr.empty())
    {
      out.daemon_sub.reset(zmq_socket(out.ctx->comm.get(), ZMQ_SUB));
      if (out.daemon_sub.get() == nullptr)
        return net::zmq::get_error_code();

      option = 1; // keep only last pub message from daemon
      MONERO_ZMQ_CHECK(zmq_connect(out.daemon_sub.get(), out.ctx->sub_addr.c_str()));
      MONERO_ZMQ_CHECK(zmq_setsockopt(out.daemon_sub.get(), ZMQ_CONFLATE, &option, sizeof(option)));
      MONERO_CHECK(do_subscribe(out.daemon_sub.get(), minimal_chain_topic));
    }

    out.signal_sub.reset(zmq_socket(out.ctx->comm.get(), ZMQ_SUB));
    if (out.signal_sub.get() == nullptr)
      return net::zmq::get_error_code();
    MONERO_ZMQ_CHECK(zmq_connect(out.signal_sub.get(), signal_endpoint));

    MONERO_CHECK(do_subscribe(out.signal_sub.get(), abort_process_signal));
    return {std::move(out)};
  }

  client::~client() noexcept
  {}

  expect<void> client::watch_scan_signals() noexcept
  {
    MONERO_PRECOND(ctx != nullptr);
    assert(signal_sub != nullptr);
    return do_subscribe(signal_sub.get(), abort_scan_signal);
  }

  expect<minimal_chain_pub> client::wait_for_block()
  {
    MONERO_PRECOND(ctx != nullptr);
    assert(daemon != nullptr);
    assert(signal_sub != nullptr);

    if (daemon_sub == nullptr)
    {
      MONERO_CHECK(do_wait(daemon.get(), signal_sub.get(), 0, chain_poll_timeout));
      return {lws::error::daemon_timeout};
    }

    {
      const expect<void> ready = do_wait(daemon_sub.get(), signal_sub.get(), ZMQ_POLLIN, chain_sub_timeout);
      if (!ready)
      {
        if (ready == lws::error::daemon_timeout)
          MWARNING("ZeroMQ Pub/Sub chain timeout, check connection settings");
        return ready.error();
      }
    }
    expect<std::string> pub = net::zmq::receive(daemon_sub.get(), ZMQ_DONTWAIT);
    if (!pub)
      return pub.error();

    if (!boost::string_ref{*pub}.starts_with(minimal_chain_topic))
      return {lws::error::bad_daemon_response};
    pub->erase(0, sizeof(minimal_chain_topic));
    return minimal_chain_pub::from_json(std::move(*pub));
  }

  expect<void> client::send(epee::byte_slice message, std::chrono::seconds timeout) noexcept
  {
    MONERO_PRECOND(ctx != nullptr);
    assert(daemon != nullptr);
    assert(signal_sub != nullptr);

    expect<void> sent;
    while (!(sent = net::zmq::send(message.clone(), daemon.get(), ZMQ_DONTWAIT)))
    {
      if (sent != net::zmq::make_error_code(EAGAIN))
        return sent.error();

      MONERO_CHECK(do_wait(daemon.get(), signal_sub.get(), ZMQ_POLLOUT, timeout));
      timeout = std::chrono::seconds{0};
    }
    return success();
  }

  expect<rates> client::get_rates() const
  {
    MONERO_PRECOND(ctx != nullptr);
    if (ctx->cache_interval <= std::chrono::minutes{0})
      return {lws::error::exchange_rates_disabled};

    const auto now  = std::chrono::steady_clock::now();
    const boost::unique_lock<boost::mutex> lock{ctx->sync_rates};
    if (now - ctx->cache_time >= ctx->cache_interval + std::chrono::seconds{30})
      return {lws::error::exchange_rates_old};
    return ctx->cached;
  }

  context context::make(std::string daemon_addr, std::string sub_addr, std::chrono::minutes rates_interval)
  {
    zcontext comm{zmq_init(1)};
    if (comm == nullptr)
      MONERO_THROW(net::zmq::get_error_code(), "zmq_init");

    detail::socket pub{zmq_socket(comm.get(), ZMQ_PUB)};
    if (pub == nullptr)
      MONERO_THROW(net::zmq::get_error_code(), "zmq_socket");
    if (zmq_bind(pub.get(), signal_endpoint) < 0)
      MONERO_THROW(net::zmq::get_error_code(), "zmq_bind");

    return context{
      std::make_shared<detail::context>(
        std::move(comm), std::move(pub), std::move(daemon_addr), std::move(sub_addr), rates_interval
      )
    };
  }

  context::~context() noexcept
  {
    if (ctx)
      raise_abort_process();
  }

  std::string const& context::daemon_address() const
  {
    if (ctx == nullptr)
      MONERO_THROW(common_error::kInvalidArgument, "Invalid lws::rpc::context");
    return ctx->daemon_addr;
  }

  expect<void> context::raise_abort_scan() noexcept
  {
    MONERO_PRECOND(ctx != nullptr);
    assert(ctx->signal_pub != nullptr);
    return do_signal(ctx->signal_pub.get(), abort_scan_signal);
  }

  expect<void> context::raise_abort_process() noexcept
  {
    MONERO_PRECOND(ctx != nullptr);
    assert(ctx->signal_pub != nullptr);
    return do_signal(ctx->signal_pub.get(), abort_process_signal);
  }

  expect<boost::optional<lws::rates>> context::retrieve_rates()
  {
    MONERO_PRECOND(ctx != nullptr);

    if (ctx->cache_interval <= std::chrono::minutes{0})
      return boost::make_optional(false, ctx->cached);

    const auto now = std::chrono::steady_clock::now();
    if (now - ctx->cache_time < ctx->cache_interval)
      return boost::make_optional(false, ctx->cached);

    expect<rates> fresh{lws::error::exchange_rates_fetch};

    const http::http_response_info* info = nullptr;
    const bool retrieved =
      ctx->rates_conn.invoke_get(crypto_compare.path, std::chrono::seconds{20}, std::string{}, std::addressof(info)) &&
      info != nullptr &&
      info->m_response_code == 200;

    // \TODO Remove copy below
    if (retrieved)
      fresh = crypto_compare(std::string{info->m_body});

    const boost::unique_lock<boost::mutex> lock{ctx->sync_rates};
    ctx->cache_time = now;
    if (fresh)
    {
      ctx->cached = *fresh;
      return boost::make_optional(*fresh);
    }
    return fresh.error();
  }
} // rpc
} // lws