#pragma once

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

#include "secsgem/gem/store/host_commands.hpp"  // HostCmdAck

namespace secsgem::gem {

// E40 §6 Process Job state model.
//
// Per E40-0705 §6.3 the PJ lifecycle is a directed graph over the eight
// states below. The values match the PRJOBSTATE byte that S16F9 carries
// on the wire (E40-0705 §10.3.2): 0 QUEUED, 1 SETTING-UP,
// 2 WAITING-FOR-START, 3 PROCESSING, 4 PROCESS-COMPLETE, 5 PAUSED,
// 6 STOPPING, 7 ABORTING.  NoState (255) is our sentinel for "doesn't
// exist yet / freshly deleted" so the same enum can be used in the API.
enum class ProcessJobState : uint8_t {
  Queued           = 0,
  SettingUp        = 1,
  WaitingForStart  = 2,
  Processing       = 3,
  ProcessComplete  = 4,
  Paused           = 5,
  Stopping         = 6,
  Aborting         = 7,
  NoState          = 255,
};

const char* process_job_state_name(ProcessJobState s);
std::optional<ProcessJobState> parse_process_job_state(const std::string& s);

// Inputs that drive the PJ FSM. Names mirror the E40 spec verbs: the
// host-initiated PJSTART / PJPAUSE / ... arrive as S16F5 PRCMD strings;
// the internal SetupComplete / ProcessComplete fire from the equipment's
// application logic (recipe runner, abort controller, etc.).
//
// `Created` is a synthetic observer signal — the store fires it through
// the change handler when a PJ first lands in Queued, so subscribers can
// distinguish "created in Queued" from "transitioned into Queued" (the
// latter never happens, but the signal is still useful for bookkeeping).
// It deliberately does NOT appear in the transition table and the YAML
// loader rejects `on: created` rows.
enum class ProcessJobEvent {
  Created,            // synthetic NoState -> Queued (observer only)
  Select,             // QUEUED -> SETTING-UP (CJ promoted this PJ)
  SetupComplete,      // SETTING-UP -> WAITING-FOR-START
  Start,              // WAITING-FOR-START -> PROCESSING (host: PJSTART)
  Pause,              // PROCESSING -> PAUSED (host: PJPAUSE)
  Resume,             // PAUSED -> PROCESSING (host: PJRESUME)
  Stop,               // ... -> STOPPING (host: PJSTOP)
  Abort,              // ... -> ABORTING (host: PJABORT)
  HeadOfQueue,        // QUEUED -> QUEUED (host: PJHOQ; reorder only)
  ProcessComplete,    // PROCESSING/STOPPING -> PROCESS-COMPLETE
  AbortComplete,      // ABORTING -> PROCESS-COMPLETE
};

const char* process_job_event_name(ProcessJobEvent e);
std::optional<ProcessJobEvent> parse_process_job_event(const std::string& s);

// Wire-name -> event mapping for the PRCMD string on S16F5. Returns
// nullopt for unknown verbs (server should reply HCACK=InvalidCommand).
std::optional<ProcessJobEvent> pr_cmd_to_event(const std::string& prcmd);

// One row of the PJ transition table. Same shape conventions as
// ControlTransition (see control_state.hpp): `to` absent means the row
// only validates the event (e.g. HOQ is a reorder, not a state change),
// and `ack_code` is the HCACK the equipment should return to the host
// when the event came from S16F5.
struct ProcessJobTransition {
  ProcessJobState from;
  ProcessJobEvent on;
  std::optional<ProcessJobState> to;
  std::optional<uint8_t> ack_code;  // HostCmdAck when applicable
};

class ProcessJobTransitionTable {
 public:
  void add(ProcessJobTransition row);
  const ProcessJobTransition* find(ProcessJobState from,
                                   ProcessJobEvent on) const;
  std::size_t size() const { return rows_.size(); }
  const std::vector<ProcessJobTransition>& rows() const { return rows_; }

  // Built-in default table matching data/process_job_state.yaml exactly.
  // Tests use this so they don't depend on the YAML being present.
  static ProcessJobTransitionTable default_table();

 private:
  std::vector<ProcessJobTransition> rows_;
};

// PJ FSM engine. One instance per Process Job — the ProcessJobStore
// keeps them keyed by PRJOBID.  Behaviour rules live in the table.
class ProcessJobStateMachine {
 public:
  using StateChangeHandler =
      std::function<void(ProcessJobState from, ProcessJobState to,
                         ProcessJobEvent trigger)>;

  ProcessJobStateMachine();
  explicit ProcessJobStateMachine(ProcessJobTransitionTable table,
                                  ProcessJobState initial = ProcessJobState::Queued);

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

  // Apply the host-initiated event from S16F5.  Returns the HCACK the
  // equipment should reply with: Accept if a row exists with no
  // ack_code override, otherwise the row's ack.  CannotDoNow if the
  // (state, event) pair has no matching row.
  HostCmdAck on_host_command(ProcessJobEvent event);

  // Apply an internal event (SetupComplete, ProcessComplete,
  // AbortComplete). Returns true if a transition fired.
  bool on_internal(ProcessJobEvent event);

 private:
  const ProcessJobTransition* fire(ProcessJobEvent on);
  void transition(ProcessJobState next, ProcessJobEvent trigger);

  ProcessJobTransitionTable table_;
  ProcessJobState state_;
  StateChangeHandler on_change_;
};

}  // namespace secsgem::gem