// Real-socket tests for the HSMS T-timer family (E37 §10).
//
// Drives a real `hsms::Connection` over a loopback socket pair with
// deliberately tiny timer budgets and asserts:
//
//   T3 — reply timeout fires S9F9 with the original MHEAD and surfaces
//        Timeout to the caller.
//   T6 — control-transaction timeout (Select.rsp dropped) closes the
//        connection.
//   T7 — not-selected timeout (passive waiting for Select.req) closes
//        the connection.
//   T8 — intercharacter timeout (peer sends length prefix then stalls)
//        closes the connection.
//
// Plus S9F11 emission for an over-length frame.

#include <doctest/doctest.h>

#include <asio.hpp>
#include <array>
#include <atomic>
#include <chrono>
#include <cstdint>
#include <memory>
#include <optional>
#include <string>
#include <thread>
#include <utility>
#include <vector>

#include "secsgem/hsms/connection.hpp"
#include "secsgem/hsms/header.hpp"
#include "secsgem/secs2/message.hpp"

using namespace secsgem::hsms;
using namespace std::chrono_literals;

namespace {

// Identical pattern to test_hsms_connection.cpp's SocketPair, modulo the
// shared `io` pump.  Kept local so the two test files stay independent.
struct SocketPair {
  asio::io_context io;
  asio::ip::tcp::socket a{io};
  asio::ip::tcp::socket b{io};

  SocketPair() {
    asio::ip::tcp::acceptor acc(io, asio::ip::tcp::endpoint(
                                        asio::ip::address_v4::loopback(), 0));
    const auto port = acc.local_endpoint().port();
    std::error_code ec_accept, ec_connect;
    bool accepted = false, connected = false;
    acc.async_accept(a, [&](std::error_code ec) { ec_accept = ec; accepted = true; });
    b.async_connect(asio::ip::tcp::endpoint(asio::ip::address_v4::loopback(), port),
                    [&](std::error_code ec) { ec_connect = ec; connected = true; });
    while (!(accepted && connected)) {
      if (io.stopped()) io.restart();
      if (io.poll() == 0) std::this_thread::sleep_for(1ms);
    }
    REQUIRE_FALSE(ec_accept);
    REQUIRE_FALSE(ec_connect);
  }
};

template <typename Pred>
void pump_until(asio::io_context& io, Pred pred,
                std::chrono::milliseconds budget = 3s) {
  const auto deadline = std::chrono::steady_clock::now() + budget;
  while (!pred()) {
    if (std::chrono::steady_clock::now() > deadline) FAIL("pump_until budget exceeded");
    if (io.stopped()) io.restart();
    if (io.poll() == 0) std::this_thread::sleep_for(1ms);
  }
}

void send_bytes(SocketPair& sp, std::vector<uint8_t> bytes) {
  auto buf = std::make_shared<std::vector<uint8_t>>(std::move(bytes));
  bool done = false;
  asio::async_write(sp.b, asio::buffer(*buf),
                    [buf, &done](std::error_code ec, std::size_t) {
                      REQUIRE_FALSE(ec);
                      done = true;
                    });
  pump_until(sp.io, [&] { return done; });
}

std::optional<Frame> try_recv_frame(SocketPair& sp,
                                     std::chrono::milliseconds budget = 2s) {
  auto lenbuf = std::make_shared<std::array<uint8_t, 4>>();
  std::error_code rec_ec;
  bool len_done = false;
  asio::async_read(sp.b, asio::buffer(*lenbuf),
                   [lenbuf, &len_done, &rec_ec](std::error_code ec, std::size_t) {
                     rec_ec = ec;
                     len_done = true;
                   });
  const auto deadline = std::chrono::steady_clock::now() + budget;
  while (!len_done) {
    if (std::chrono::steady_clock::now() > deadline) return std::nullopt;
    if (sp.io.stopped()) sp.io.restart();
    if (sp.io.poll() == 0) std::this_thread::sleep_for(1ms);
  }
  if (rec_ec) return std::nullopt;
  const uint32_t len = (uint32_t((*lenbuf)[0]) << 24) | (uint32_t((*lenbuf)[1]) << 16) |
                       (uint32_t((*lenbuf)[2]) << 8) | uint32_t((*lenbuf)[3]);
  auto payload = std::make_shared<std::vector<uint8_t>>(len);
  bool payload_done = false;
  asio::async_read(sp.b, asio::buffer(*payload),
                   [payload, &payload_done](std::error_code, std::size_t) {
                     payload_done = true;
                   });
  pump_until(sp.io, [&] { return payload_done; });
  return Frame::decode(payload->data(), payload->size());
}

// Drive the passive Connection into SELECTED so we can exercise data-path
// timers (T3) cleanly.  Tiny T3, T6, T7, T8 so tests stay fast.
struct Selected {
  SocketPair sp;
  std::shared_ptr<Connection> conn;

  explicit Selected(Timers t) {
    conn = std::make_shared<Connection>(std::move(sp.a),
                                         Connection::Mode::Passive,
                                         /*device_id=*/0, t);
    bool selected = false;
    conn->set_selected_handler([&] { selected = true; });
    conn->start();
    send_bytes(sp, Frame(Header::control(SType::SelectReq, 1)).encode());
    auto rsp = try_recv_frame(sp);
    REQUIRE(rsp.has_value());
    REQUIRE(rsp->header.stype == SType::SelectRsp);
    pump_until(sp.io, [&] { return selected; });
  }
};

// Timer profiles tuned per test so the timer of interest is the FIRST to
// fire.  Without this, e.g. T7 (armed on passive start) wins over T8
// because they're both 150ms and T7 was armed first.
Timers profile_for_t3() {
  Timers t;
  t.t3 = 150ms; t.t6 = 5s; t.t7 = 5s; t.t8 = 5s; t.linktest = 0ms;
  return t;
}
Timers profile_for_t6() {
  Timers t;
  t.t3 = 5s; t.t6 = 150ms; t.t7 = 5s; t.t8 = 5s; t.linktest = 0ms;
  return t;
}
Timers profile_for_t7() {
  Timers t;
  t.t3 = 5s; t.t6 = 5s; t.t7 = 150ms; t.t8 = 5s; t.linktest = 0ms;
  return t;
}
Timers profile_for_t8() {
  Timers t;
  // T7 must outlast T8 here, otherwise T7 wins and closes first.
  t.t3 = 5s; t.t6 = 5s; t.t7 = 5s; t.t8 = 150ms; t.linktest = 0ms;
  return t;
}

}  // namespace

TEST_CASE("T3: reply timeout emits S9F9 and surfaces Timeout to caller") {
  Selected s(profile_for_t3());

  // Driver sends a primary message expecting a reply.  The peer doesn't
  // reply at all — only consumes the frame.
  std::optional<std::error_code> got_ec;
  s.conn->send_request(secsgem::secs2::Message(1, 1, true),
                       [&](std::error_code ec, const secsgem::secs2::Message&) {
                         got_ec = ec;
                       });

  // First frame on the peer is the primary S1F1 itself.
  auto primary = try_recv_frame(s.sp);
  REQUIRE(primary.has_value());
  CHECK(primary->header.stream() == 1);
  CHECK(primary->header.function() == 1);
  const uint32_t primary_sys = primary->header.system_bytes;

  // Pump past T3.  The reply callback should fire with Timeout AND an
  // S9F9 frame should land on the peer carrying the original MHEAD.
  pump_until(s.sp.io, [&] { return got_ec.has_value(); }, 2s);
  REQUIRE(got_ec.has_value());
  CHECK(got_ec->value() == static_cast<int>(Error::Timeout));

  auto s9 = try_recv_frame(s.sp);
  REQUIRE(s9.has_value());
  CHECK(s9->header.stream() == 9);
  CHECK(s9->header.function() == 9);
  // S9F9 body is the failed primary's MHEAD as <B 10>; the formatcode
  // byte for binary is 0x21 followed by length-byte then 10 payload bytes.
  REQUIRE(s9->body.size() >= 12);
  CHECK(s9->body[0] == 0x21);
  CHECK(s9->body[1] == 10);
  // Bytes 6..9 of the MHEAD are the system_bytes (big-endian).
  const uint32_t echoed_sys =
      (uint32_t(s9->body[2 + 6]) << 24) | (uint32_t(s9->body[2 + 7]) << 16) |
      (uint32_t(s9->body[2 + 8]) << 8) | uint32_t(s9->body[2 + 9]);
  CHECK(echoed_sys == primary_sys);

  s.conn->close("test done");
}

TEST_CASE("T6: dropped Select.rsp closes the active connection") {
  SocketPair sp;
  bool closed = false;
  std::string close_reason;
  auto conn = std::make_shared<Connection>(std::move(sp.a),
                                            Connection::Mode::Active,
                                            /*device_id=*/0, profile_for_t6());
  conn->set_closed_handler([&](const std::string& r) {
    closed = true;
    close_reason = r;
  });
  conn->start();

  // Active mode emits Select.req on start.  We deliberately do NOT reply.
  auto sel = try_recv_frame(sp);
  REQUIRE(sel.has_value());
  CHECK(sel->header.stype == SType::SelectReq);

  // Drain the io_context past T6; the connection should self-close.
  pump_until(sp.io, [&] { return closed; }, 2s);
  CHECK(closed);
  CHECK(close_reason.find("T6") != std::string::npos);
}

TEST_CASE("T7: passive connection with no Select.req self-closes") {
  SocketPair sp;
  bool closed = false;
  std::string close_reason;
  auto conn = std::make_shared<Connection>(std::move(sp.a),
                                            Connection::Mode::Passive,
                                            /*device_id=*/0, profile_for_t7());
  conn->set_closed_handler([&](const std::string& r) {
    closed = true;
    close_reason = r;
  });
  conn->start();
  // Peer sends nothing — T7 should fire.
  pump_until(sp.io, [&] { return closed; }, 2s);
  CHECK(closed);
  CHECK(close_reason.find("T7") != std::string::npos);
}

TEST_CASE("T8: length-prefix-then-stall closes the connection") {
  SocketPair sp;
  bool closed = false;
  std::string close_reason;
  auto conn = std::make_shared<Connection>(std::move(sp.a),
                                            Connection::Mode::Passive,
                                            /*device_id=*/0, profile_for_t8());
  conn->set_closed_handler([&](const std::string& r) {
    closed = true;
    close_reason = r;
  });
  conn->start();

  // Send only the 4-byte length prefix.  Connection will allocate the
  // body buffer and arm T8 — when no bytes follow, T8 fires.
  send_bytes(sp, {0x00, 0x00, 0x00, 0x0A});

  pump_until(sp.io, [&] { return closed; }, 2s);
  CHECK(closed);
  CHECK(close_reason.find("T8") != std::string::npos);
}

TEST_CASE("S9F11: over-length frame triggers emission + close") {
  SocketPair sp;
  bool closed = false;
  // T7 long so the close reason isn't ambiguously T7.
  auto conn = std::make_shared<Connection>(std::move(sp.a),
                                            Connection::Mode::Passive,
                                            /*device_id=*/0, profile_for_t8());
  conn->set_closed_handler([&](const std::string&) { closed = true; });
  conn->start();

  // Length prefix of 0x40000001 = 1 GiB + 1, well above kMaxFrameLength.
  send_bytes(sp, {0x40, 0x00, 0x00, 0x01});

  auto s9 = try_recv_frame(sp);
  REQUIRE(s9.has_value());
  CHECK(s9->header.stream() == 9);
  CHECK(s9->header.function() == 11);
  // Body's <B 10> starts with the offending length prefix bytes.
  REQUIRE(s9->body.size() >= 12);
  CHECK(s9->body[0] == 0x21);
  CHECK(s9->body[1] == 10);
  CHECK(s9->body[2] == 0x40);
  CHECK(s9->body[3] == 0x00);
  CHECK(s9->body[4] == 0x00);
  CHECK(s9->body[5] == 0x01);

  pump_until(sp.io, [&] { return closed; }, 2s);
  CHECK(closed);
}