#include <doctest/doctest.h>

#include <vector>

#include "secsgem/gem/control_state.hpp"

using namespace secsgem::gem;

namespace {

struct Recorder {
  std::vector<std::tuple<ControlState, ControlState, ControlEvent>> changes;
  ControlStateMachine::StateChangeHandler handler() {
    return [this](ControlState from, ControlState to, ControlEvent ev) {
      changes.emplace_back(from, to, ev);
    };
  }
};

ControlStateMachine make_sm(ControlState initial) {
  return ControlStateMachine(ControlTransitionTable::default_table(), initial);
}

}  // namespace

TEST_CASE("default initial state is HostOffline") {
  ControlStateMachine sm;
  CHECK(sm.state() == ControlState::HostOffline);
  CHECK_FALSE(sm.online());
}

TEST_CASE("custom initial state") {
  auto sm = make_sm(ControlState::EquipmentOffline);
  CHECK(sm.state() == ControlState::EquipmentOffline);
}

TEST_CASE("host request online from HostOffline -> OnlineRemote") {
  Recorder rec;
  ControlStateMachine sm;
  sm.set_state_change_handler(rec.handler());

  CHECK(sm.on_host_request_online() == OnlineAck::Accept);
  CHECK(sm.state() == ControlState::OnlineRemote);
  CHECK(sm.online());

  REQUIRE(rec.changes.size() == 2);
  CHECK(std::get<1>(rec.changes[0]) == ControlState::AttemptOnline);
  CHECK(std::get<2>(rec.changes[0]) == ControlEvent::HostRequestOnline);
  CHECK(std::get<1>(rec.changes[1]) == ControlState::OnlineRemote);
  CHECK(std::get<2>(rec.changes[1]) == ControlEvent::AttemptComplete);
}

TEST_CASE("host request online when already online -> AlreadyOnline, no transition") {
  ControlStateMachine sm;
  sm.on_host_request_online();
  REQUIRE(sm.state() == ControlState::OnlineRemote);

  Recorder rec;
  sm.set_state_change_handler(rec.handler());
  CHECK(sm.on_host_request_online() == OnlineAck::AlreadyOnline);
  CHECK(sm.state() == ControlState::OnlineRemote);
  CHECK(rec.changes.empty());
}

TEST_CASE("host request online from EquipmentOffline -> NotAccept") {
  auto sm = make_sm(ControlState::EquipmentOffline);
  CHECK(sm.on_host_request_online() == OnlineAck::NotAccept);
  CHECK(sm.state() == ControlState::EquipmentOffline);
}

TEST_CASE("host request offline from OnlineRemote -> HostOffline") {
  ControlStateMachine sm;
  sm.on_host_request_online();
  REQUIRE(sm.state() == ControlState::OnlineRemote);

  Recorder rec;
  sm.set_state_change_handler(rec.handler());
  CHECK(sm.on_host_request_offline() == OfflineAck::Accept);
  CHECK(sm.state() == ControlState::HostOffline);

  REQUIRE(rec.changes.size() == 1);
  CHECK(std::get<1>(rec.changes[0]) == ControlState::HostOffline);
  CHECK(std::get<2>(rec.changes[0]) == ControlEvent::HostRequestOffline);
}

TEST_CASE("host request offline when already offline is idempotent Accept") {
  ControlStateMachine sm;
  Recorder rec;
  sm.set_state_change_handler(rec.handler());
  CHECK(sm.on_host_request_offline() == OfflineAck::Accept);
  CHECK(sm.state() == ControlState::HostOffline);
  CHECK(rec.changes.empty());
}

TEST_CASE("operator online from EquipmentOffline -> OnlineLocal (default table)") {
  auto sm = make_sm(ControlState::EquipmentOffline);
  CHECK(sm.operator_online());
  CHECK(sm.state() == ControlState::OnlineLocal);
}

TEST_CASE("operator online when already online is rejected") {
  auto sm = make_sm(ControlState::OnlineLocal);
  CHECK_FALSE(sm.operator_online());
  CHECK(sm.state() == ControlState::OnlineLocal);
}

TEST_CASE("operator offline from any online state -> HostOffline") {
  auto sm = make_sm(ControlState::OnlineRemote);
  CHECK(sm.operator_offline());
  CHECK(sm.state() == ControlState::HostOffline);
}

TEST_CASE("operator local toggles only from OnlineRemote") {
  auto sm = make_sm(ControlState::OnlineRemote);
  CHECK(sm.operator_local());
  CHECK(sm.state() == ControlState::OnlineLocal);
  CHECK_FALSE(sm.operator_local());
}

TEST_CASE("operator remote toggles only from OnlineLocal") {
  auto sm = make_sm(ControlState::OnlineLocal);
  CHECK(sm.operator_remote());
  CHECK(sm.state() == ControlState::OnlineRemote);
  CHECK_FALSE(sm.operator_remote());
}

TEST_CASE("is_online classifier") {
  CHECK_FALSE(is_online(ControlState::EquipmentOffline));
  CHECK_FALSE(is_online(ControlState::AttemptOnline));
  CHECK_FALSE(is_online(ControlState::HostOffline));
  CHECK(is_online(ControlState::OnlineLocal));
  CHECK(is_online(ControlState::OnlineRemote));
}

TEST_CASE("default table covers all expected (state, event) pairs") {
  auto t = ControlTransitionTable::default_table();
  // Every state must have an entry for each host event.
  for (auto s : {ControlState::EquipmentOffline, ControlState::AttemptOnline,
                 ControlState::HostOffline, ControlState::OnlineLocal,
                 ControlState::OnlineRemote}) {
    CHECK(t.find(s, ControlEvent::HostRequestOnline) != nullptr);
    CHECK(t.find(s, ControlEvent::HostRequestOffline) != nullptr);
  }
}

TEST_CASE("custom table: a row that only sets ack, no transition") {
  ControlTransitionTable t;
  t.add({ControlState::HostOffline, ControlEvent::HostRequestOnline, std::nullopt,
         std::nullopt, static_cast<uint8_t>(OnlineAck::NotAccept)});
  ControlStateMachine sm(t, ControlState::HostOffline);
  CHECK(sm.on_host_request_online() == OnlineAck::NotAccept);
  CHECK(sm.state() == ControlState::HostOffline);
}

// ---- multi-observer (HandlerSlot) ------------------------------------------

TEST_CASE("add_state_change_handler observers fire alongside the primary, in order") {
  ControlStateMachine sm;
  std::vector<int> order;
  Recorder primary, obs1, obs2;

  sm.set_state_change_handler([&](ControlState f, ControlState t, ControlEvent e) {
    order.push_back(0);
    primary.handler()(f, t, e);
  });
  sm.add_state_change_handler([&](ControlState f, ControlState t, ControlEvent e) {
    order.push_back(1);
    obs1.handler()(f, t, e);
  });
  sm.add_state_change_handler([&](ControlState f, ControlState t, ControlEvent e) {
    order.push_back(2);
    obs2.handler()(f, t, e);
  });

  CHECK(sm.on_host_request_online() == OnlineAck::Accept);  // 2 transitions

  // All three saw both transitions, primary before observers each time.
  CHECK(primary.changes.size() == 2);
  CHECK(obs1.changes.size() == 2);
  CHECK(obs2.changes.size() == 2);
  REQUIRE(order.size() == 6);
  CHECK(order == std::vector<int>{0, 1, 2, 0, 1, 2});
}

TEST_CASE("set_state_change_handler replaces the primary but observers survive") {
  ControlStateMachine sm;
  Recorder old_primary, new_primary, observer;

  sm.set_state_change_handler(old_primary.handler());
  sm.add_state_change_handler(observer.handler());
  sm.set_state_change_handler(new_primary.handler());  // replaces old_primary ONLY

  sm.on_host_request_online();

  CHECK(old_primary.changes.empty());     // replaced
  CHECK(new_primary.changes.size() == 2); // active primary
  CHECK(observer.changes.size() == 2);    // survived the re-set
}

TEST_CASE("observers work with no primary handler installed") {
  ControlStateMachine sm;
  Recorder observer;
  sm.add_state_change_handler(observer.handler());
  sm.on_host_request_online();
  CHECK(observer.changes.size() == 2);
}