#pragma once

#include <array>
#include <chrono>
#include <cstdint>
#include <functional>
#include <optional>
#include <string>
#include <vector>

#include "secsgem/gem/carrier_state.hpp"  // shared CarrierTransition template

// E116 §6 Equipment Performance Tracking — top-level equipment state
// model that classifies operating time into productive / non-productive
// categories.  Each transition is timestamped so the application can
// compute MTBF / availability / utilization from the same source.
//
// The states correspond directly to the SEMI-defined buckets in E116-
// 0712 §6.2; the wire byte values match the order the spec presents.
namespace secsgem::gem {

enum class EptState : uint8_t {
  NonScheduledTime    = 0,   // equipment not scheduled to operate
  ScheduledDowntime   = 1,   // scheduled maintenance
  UnscheduledDowntime = 2,   // unscheduled downtime (faults)
  Engineering         = 3,   // engineering / qualification time
  Standby             = 4,   // idle, available but not producing
  Productive          = 5,   // actively producing
  NoState             = 255,
};

const char* ept_state_name(EptState s);
std::optional<EptState> parse_ept_state(const std::string& s);

// Events correspond to transitions the equipment can declare; events
// are intentionally state-neutral (any -> X) since EPT is a "what kind
// of time is this" classifier rather than a strict lifecycle.
enum class EptEvent {
  EnterNonScheduled,
  EnterScheduledDown,
  EnterUnscheduledDown,
  EnterEngineering,
  EnterStandby,
  EnterProductive,
};

const char* ept_event_name(EptEvent e);

using EptTable = CarrierTransitionTable<EptState, EptEvent>;
EptTable default_ept_table();

class EptStateMachine {
 public:
  using StateChangeHandler =
      std::function<void(EptState from, EptState to, EptEvent,
                         std::chrono::milliseconds dwell_before_change)>;

  EptStateMachine();

  EptState state() const { return state_; }
  void set_state_change_handler(StateChangeHandler h) { on_change_ = std::move(h); }

  // Fire a transition.  Returns true if a row matched.  The dwell time
  // (how long we sat in the previous state) is computed off the
  // monotonic clock and surfaced to the handler so accounting code
  // doesn't need a parallel timestamp tracker.
  bool on_event(EptEvent e);

  // --- E116 time-bucket accounting --------------------------------------
  // Total accumulated time spent in `s` since the FSM was constructed
  // or since reset_history() was last called.  Time spent in the
  // *current* state up to now is included.
  std::chrono::milliseconds accumulated(EptState s) const;

  // Total time across all states (= time since reset_history()).  Useful
  // as the denominator for utilization / availability ratios.
  std::chrono::milliseconds total_elapsed() const;

  // S2F43-style history clear.  Sets every bucket to zero and re-anchors
  // the current-state timer at "now".
  void reset_history();

 private:
  EptTable table_;
  EptState state_ = EptState::NonScheduledTime;
  std::chrono::steady_clock::time_point entered_;
  std::chrono::steady_clock::time_point reset_anchor_;
  std::array<std::chrono::milliseconds, 6> buckets_{};  // indexed by EptState 0..5
  StateChangeHandler on_change_;
};

}  // namespace secsgem::gem