#pragma once

#include <cstdint>
#include <optional>
#include <string>
#include <utility>
#include <variant>
#include <vector>

#include "secsgem/gem/control_state.hpp"
#include "secsgem/gem/data_model.hpp"
#include "secsgem/secs2/item.hpp"
#include "secsgem/secs2/message.hpp"

// GEM (E30 / E5) message builders for the SxFy primaries and replies the demo
// and tests exercise. Builders construct a `secs2::Message`; parsers do the
// inverse and return `std::optional<...>` on shape mismatch.
namespace secsgem::gem {

namespace s2 = secsgem::secs2;

// -------------------------------------------------------------------------
//                            small Item helpers
// -------------------------------------------------------------------------

inline std::optional<uint32_t> as_u4_scalar(const s2::Item& item) {
  if (item.format() != s2::Format::U4) return std::nullopt;
  const auto& v = std::get<std::vector<uint32_t>>(item.storage());
  if (v.empty()) return std::nullopt;
  return v.front();
}

inline std::optional<uint8_t> as_binary_first(const s2::Item& item) {
  if (item.format() != s2::Format::Binary) return std::nullopt;
  const auto& v = item.as_bytes();
  if (v.empty()) return std::nullopt;
  return v.front();
}

inline std::optional<std::string> as_ascii(const s2::Item& item) {
  if (item.format() != s2::Format::ASCII) return std::nullopt;
  return item.as_ascii();
}

inline s2::Item u4_list(const std::vector<uint32_t>& ids) {
  return s2::Item::u4(ids);  // a single U4 array — SECS-II elements, not a list of items
}

// -------------------------------------------------------------------------
//                  S1F1 / S1F2  Are You There / On Line Data
// -------------------------------------------------------------------------

inline s2::Message s1f1_are_you_there() { return s2::Message(1, 1, true); }

inline s2::Message s1f2_on_line_data(const std::string& mdln, const std::string& softrev) {
  return s2::Message(1, 2, false,
                     s2::Item::list({s2::Item::ascii(mdln), s2::Item::ascii(softrev)}));
}

// -------------------------------------------------------------------------
//        S1F3 / S1F4  Selected Equipment Status Request / Data
//
//   S1F3 W:  <L,n  <U4 SVID> ... >   (n=0 means "all SVIDs")
//   S1F4  :  <L,n  <Item> ... >      (empty list for unknown SVIDs per E5)
// -------------------------------------------------------------------------

inline s2::Message s1f3_selected_status_request(const std::vector<uint32_t>& svids) {
  s2::Item::List children;
  children.reserve(svids.size());
  for (auto id : svids) children.push_back(s2::Item::u4(id));
  return s2::Message(1, 3, true, s2::Item::list(std::move(children)));
}

inline std::optional<std::vector<uint32_t>> parse_s1f3(const s2::Message& m) {
  if (!m.body || !m.body->is_list()) return std::nullopt;
  std::vector<uint32_t> out;
  for (const auto& child : m.body->as_list()) {
    auto v = as_u4_scalar(child);
    if (!v) return std::nullopt;
    out.push_back(*v);
  }
  return out;
}

inline s2::Message s1f4_selected_status_data(const std::vector<std::optional<s2::Item>>& values) {
  s2::Item::List children;
  children.reserve(values.size());
  for (const auto& v : values) {
    children.push_back(v ? *v : s2::Item::list({}));  // empty L for unknown
  }
  return s2::Message(1, 4, false, s2::Item::list(std::move(children)));
}

// -------------------------------------------------------------------------
//        S1F11 / S1F12  Status Variable Namelist Request / Data
//
//   S1F11 W: <L,n <U4 SVID> ... >   (n=0 = all)
//   S1F12  : <L,n <L,3 <U4 SVID> <A SVNAME> <A SVUNITS>> ... >
// -------------------------------------------------------------------------

inline s2::Message s1f11_status_namelist_request(const std::vector<uint32_t>& svids) {
  s2::Item::List children;
  children.reserve(svids.size());
  for (auto id : svids) children.push_back(s2::Item::u4(id));
  return s2::Message(1, 11, true, s2::Item::list(std::move(children)));
}

inline s2::Message s1f12_status_namelist_data(const std::vector<StatusVariable>& items) {
  s2::Item::List children;
  children.reserve(items.size());
  for (const auto& sv : items) {
    children.push_back(s2::Item::list(
        {s2::Item::u4(sv.id), s2::Item::ascii(sv.name), s2::Item::ascii(sv.units)}));
  }
  return s2::Message(1, 12, false, s2::Item::list(std::move(children)));
}

struct StatusName {
  uint32_t id;
  std::string name;
  std::string units;
};

inline std::optional<std::vector<StatusName>> parse_s1f12(const s2::Message& m) {
  if (!m.body || !m.body->is_list()) return std::nullopt;
  std::vector<StatusName> out;
  for (const auto& row : m.body->as_list()) {
    if (!row.is_list() || row.as_list().size() != 3) return std::nullopt;
    auto id = as_u4_scalar(row.as_list()[0]);
    auto name = as_ascii(row.as_list()[1]);
    auto units = as_ascii(row.as_list()[2]);
    if (!id || !name || !units) return std::nullopt;
    out.push_back({*id, *name, *units});
  }
  return out;
}

// -------------------------------------------------------------------------
//   S1F13 / S1F14  Establish Communications
// -------------------------------------------------------------------------

inline s2::Message s1f13_establish_comms(const std::string& mdln, const std::string& softrev) {
  return s2::Message(1, 13, true,
                     s2::Item::list({s2::Item::ascii(mdln), s2::Item::ascii(softrev)}));
}

inline s2::Message s1f14_establish_comms_ack(CommAck ack, const std::string& mdln,
                                             const std::string& softrev) {
  return s2::Message(
      1, 14, false,
      s2::Item::list({s2::Item::binary({static_cast<uint8_t>(ack)}),
                      s2::Item::list({s2::Item::ascii(mdln), s2::Item::ascii(softrev)})}));
}

// -------------------------------------------------------------------------
//   S1F15 / S1F16  Request OFFLINE / OFFLINE Acknowledge
//   S1F17 / S1F18  Request ONLINE / ONLINE Acknowledge
// -------------------------------------------------------------------------

inline s2::Message s1f15_request_offline() { return s2::Message(1, 15, true); }
inline s2::Message s1f16_offline_ack(OfflineAck ack) {
  return s2::Message(1, 16, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}
inline s2::Message s1f17_request_online() { return s2::Message(1, 17, true); }
inline s2::Message s1f18_online_ack(OnlineAck ack) {
  return s2::Message(1, 18, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}

// Generic helper for messages whose body is a single <B ack>.
inline std::optional<uint8_t> ack_byte(const s2::Message& msg) {
  if (!msg.body) return std::nullopt;
  return as_binary_first(*msg.body);
}

// -------------------------------------------------------------------------
//   S2F13 / S2F14  Equipment Constant Request / Data
//   S2F15 / S2F16  New Equipment Constant Send / Acknowledge
// -------------------------------------------------------------------------

inline s2::Message s2f13_ec_request(const std::vector<uint32_t>& ecids) {
  s2::Item::List children;
  children.reserve(ecids.size());
  for (auto id : ecids) children.push_back(s2::Item::u4(id));
  return s2::Message(2, 13, true, s2::Item::list(std::move(children)));
}

inline s2::Message s2f14_ec_data(const std::vector<s2::Item>& values) {
  return s2::Message(2, 14, false, s2::Item::list(values));
}

inline s2::Message s2f15_ec_send(
    const std::vector<std::pair<uint32_t, s2::Item>>& sets) {
  s2::Item::List rows;
  rows.reserve(sets.size());
  for (const auto& [id, val] : sets) {
    rows.push_back(s2::Item::list({s2::Item::u4(id), val}));
  }
  return s2::Message(2, 15, true, s2::Item::list(std::move(rows)));
}

inline std::optional<std::vector<std::pair<uint32_t, s2::Item>>> parse_s2f15(
    const s2::Message& m) {
  if (!m.body || !m.body->is_list()) return std::nullopt;
  std::vector<std::pair<uint32_t, s2::Item>> out;
  for (const auto& row : m.body->as_list()) {
    if (!row.is_list() || row.as_list().size() != 2) return std::nullopt;
    auto id = as_u4_scalar(row.as_list()[0]);
    if (!id) return std::nullopt;
    out.emplace_back(*id, row.as_list()[1]);
  }
  return out;
}

inline s2::Message s2f16_ec_ack(EquipmentAck eac) {
  return s2::Message(2, 16, false, s2::Item::binary({static_cast<uint8_t>(eac)}));
}

// -------------------------------------------------------------------------
//   S2F17 / S2F18  Date and Time Request / Data
//   S2F31 / S2F32  Date and Time Set Request / Acknowledge
// -------------------------------------------------------------------------

inline s2::Message s2f17_date_time_request() { return s2::Message(2, 17, true); }
inline s2::Message s2f18_date_time_data(const std::string& time_str) {
  return s2::Message(2, 18, false, s2::Item::ascii(time_str));
}
inline std::optional<std::string> parse_s2f18(const s2::Message& m) {
  if (!m.body) return std::nullopt;
  return as_ascii(*m.body);
}

inline s2::Message s2f31_date_time_set(const std::string& time_str) {
  return s2::Message(2, 31, true, s2::Item::ascii(time_str));
}
inline std::optional<std::string> parse_s2f31(const s2::Message& m) {
  if (!m.body) return std::nullopt;
  return as_ascii(*m.body);
}
inline s2::Message s2f32_date_time_ack(TimeAck ack) {
  return s2::Message(2, 32, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}

// -------------------------------------------------------------------------
//   S2F41 / S2F42  Host Command / Host Command Acknowledge
//
//   S2F41 W: <L,2 <A RCMD> <L,n <L,2 <A CPNAME> <Item CPVAL>>>>
//   S2F42  : <L,2 <B HCACK> <L,n <L,2 <A CPNAME> <B CPACK>>>>
// -------------------------------------------------------------------------

inline s2::Message s2f41_host_command(
    const std::string& rcmd,
    const std::vector<EquipmentDataModel::CommandParam>& params = {}) {
  s2::Item::List param_rows;
  param_rows.reserve(params.size());
  for (const auto& p : params) {
    param_rows.push_back(s2::Item::list({s2::Item::ascii(p.name), p.value}));
  }
  return s2::Message(
      2, 41, true,
      s2::Item::list({s2::Item::ascii(rcmd), s2::Item::list(std::move(param_rows))}));
}

struct HostCommand {
  std::string rcmd;
  std::vector<EquipmentDataModel::CommandParam> params;
};

inline std::optional<HostCommand> parse_s2f41(const s2::Message& m) {
  if (!m.body || !m.body->is_list() || m.body->as_list().size() != 2) return std::nullopt;
  const auto& outer = m.body->as_list();
  auto rcmd = as_ascii(outer[0]);
  if (!rcmd) return std::nullopt;
  HostCommand cmd{*rcmd, {}};
  if (!outer[1].is_list()) return std::nullopt;
  for (const auto& row : outer[1].as_list()) {
    if (!row.is_list() || row.as_list().size() != 2) return std::nullopt;
    auto name = as_ascii(row.as_list()[0]);
    if (!name) return std::nullopt;
    cmd.params.push_back({*name, row.as_list()[1]});
  }
  return cmd;
}

inline s2::Message s2f42_host_command_ack(
    HostCmdAck hcack,
    const std::vector<std::pair<std::string, uint8_t>>& cpacks = {}) {
  s2::Item::List cp_rows;
  cp_rows.reserve(cpacks.size());
  for (const auto& [name, code] : cpacks) {
    cp_rows.push_back(s2::Item::list({s2::Item::ascii(name), s2::Item::binary({code})}));
  }
  return s2::Message(
      2, 42, false,
      s2::Item::list({s2::Item::binary({static_cast<uint8_t>(hcack)}),
                      s2::Item::list(std::move(cp_rows))}));
}

struct HostCommandReply {
  HostCmdAck hcack;
  std::vector<std::pair<std::string, uint8_t>> cpacks;
};

inline std::optional<HostCommandReply> parse_s2f42(const s2::Message& m) {
  if (!m.body || !m.body->is_list() || m.body->as_list().size() != 2) return std::nullopt;
  const auto& outer = m.body->as_list();
  auto hcack = as_binary_first(outer[0]);
  if (!hcack) return std::nullopt;
  HostCommandReply rep{static_cast<HostCmdAck>(*hcack), {}};
  if (!outer[1].is_list()) return std::nullopt;
  for (const auto& row : outer[1].as_list()) {
    if (!row.is_list() || row.as_list().size() != 2) return std::nullopt;
    auto name = as_ascii(row.as_list()[0]);
    auto code = as_binary_first(row.as_list()[1]);
    if (!name || !code) return std::nullopt;
    rep.cpacks.emplace_back(*name, *code);
  }
  return rep;
}

// -------------------------------------------------------------------------
//   S10F1 / S10F2  Terminal Display, Single (host -> equipment)
//   S10F3 / S10F4  Terminal Display, Single (equipment -> host)
// -------------------------------------------------------------------------

inline s2::Message s10f1_terminal_display_single(uint8_t tid, const std::string& text) {
  return s2::Message(10, 1, true,
                     s2::Item::list({s2::Item::binary({tid}), s2::Item::ascii(text)}));
}

struct TerminalDisplay {
  uint8_t tid;
  std::string text;
};

inline std::optional<TerminalDisplay> parse_terminal_display(const s2::Message& m) {
  if (!m.body || !m.body->is_list() || m.body->as_list().size() != 2) return std::nullopt;
  const auto& l = m.body->as_list();
  auto tid = as_binary_first(l[0]);
  auto text = as_ascii(l[1]);
  if (!tid || !text) return std::nullopt;
  return TerminalDisplay{*tid, *text};
}

inline s2::Message s10f2_terminal_display_ack(TerminalAck ack) {
  return s2::Message(10, 2, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}

inline s2::Message s10f3_terminal_display_single(uint8_t tid, const std::string& text) {
  return s2::Message(10, 3, true,
                     s2::Item::list({s2::Item::binary({tid}), s2::Item::ascii(text)}));
}

inline s2::Message s10f4_terminal_display_ack(TerminalAck ack) {
  return s2::Message(10, 4, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}

// =========================================================================
//                  Extended GEM SxFy (events, alarms, recipes)
// =========================================================================

// Generic <L,n <U4 id>> body reader, used by several messages.
inline std::optional<std::vector<uint32_t>> parse_u4_list_body(const s2::Message& m) {
  if (!m.body || !m.body->is_list()) return std::nullopt;
  std::vector<uint32_t> out;
  for (const auto& c : m.body->as_list()) {
    auto v = as_u4_scalar(c);
    if (!v) return std::nullopt;
    out.push_back(*v);
  }
  return out;
}

inline s2::Item u4_list_item(const std::vector<uint32_t>& ids) {
  s2::Item::List children;
  children.reserve(ids.size());
  for (auto id : ids) children.push_back(s2::Item::u4(id));
  return s2::Item::list(std::move(children));
}

// -------------------------------------------------------------------------
//   S2F29 / S2F30  Equipment Constant Namelist Request / Data
//   S2F30: <L,n <L,6 <U4 ECID> <A ECNAME> <A ECMIN> <A ECMAX> <A ECDEF> <A ECUNITS>>>
// -------------------------------------------------------------------------

inline s2::Message s2f29_ec_namelist_request(const std::vector<uint32_t>& ecids) {
  return s2::Message(2, 29, true, u4_list_item(ecids));
}

inline s2::Message s2f30_ec_namelist_data(const std::vector<EquipmentConstant>& ecs) {
  s2::Item::List rows;
  rows.reserve(ecs.size());
  for (const auto& ec : ecs) {
    rows.push_back(s2::Item::list({
        s2::Item::u4(ec.id),
        s2::Item::ascii(ec.name),
        s2::Item::ascii(ec.min_str),
        s2::Item::ascii(ec.max_str),
        s2::Item::ascii(""),  // ECDEF rendering left simple
        s2::Item::ascii(ec.units),
    }));
  }
  return s2::Message(2, 30, false, s2::Item::list(std::move(rows)));
}

// -------------------------------------------------------------------------
//   S2F33 / S2F34  Define Report
//
//   S2F33 W: <L,2 <U4 DATAID> <L,a <L,2 <U4 RPTID> <L,n <U4 VID>>>>>
//   S2F34  : <B DRACK>
// -------------------------------------------------------------------------

inline s2::Message s2f33_define_report(
    uint32_t dataid,
    const std::vector<std::pair<uint32_t, std::vector<uint32_t>>>& reports) {
  s2::Item::List rows;
  rows.reserve(reports.size());
  for (const auto& [rptid, vids] : reports) {
    rows.push_back(s2::Item::list({s2::Item::u4(rptid), u4_list_item(vids)}));
  }
  return s2::Message(2, 33, true,
                     s2::Item::list({s2::Item::u4(dataid), s2::Item::list(std::move(rows))}));
}

struct DefineReportRequest {
  uint32_t dataid;
  std::vector<std::pair<uint32_t, std::vector<uint32_t>>> reports;
};

inline std::optional<DefineReportRequest> parse_s2f33(const s2::Message& m) {
  if (!m.body || !m.body->is_list() || m.body->as_list().size() != 2) return std::nullopt;
  const auto& outer = m.body->as_list();
  auto dataid = as_u4_scalar(outer[0]);
  if (!dataid) return std::nullopt;
  DefineReportRequest req{*dataid, {}};
  if (!outer[1].is_list()) return std::nullopt;
  for (const auto& row : outer[1].as_list()) {
    if (!row.is_list() || row.as_list().size() != 2) return std::nullopt;
    auto rptid = as_u4_scalar(row.as_list()[0]);
    if (!rptid) return std::nullopt;
    auto vids = std::vector<uint32_t>{};
    if (!row.as_list()[1].is_list()) return std::nullopt;
    for (const auto& v : row.as_list()[1].as_list()) {
      auto u = as_u4_scalar(v);
      if (!u) return std::nullopt;
      vids.push_back(*u);
    }
    req.reports.emplace_back(*rptid, std::move(vids));
  }
  return req;
}

inline s2::Message s2f34_define_report_ack(DefineReportAck ack) {
  return s2::Message(2, 34, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}

// -------------------------------------------------------------------------
//   S2F35 / S2F36  Link Event Report
//
//   S2F35 W: <L,2 <U4 DATAID> <L,a <L,2 <U4 CEID> <L,n <U4 RPTID>>>>>
//   S2F36  : <B LRACK>
// -------------------------------------------------------------------------

inline s2::Message s2f35_link_event_report(
    uint32_t dataid,
    const std::vector<std::pair<uint32_t, std::vector<uint32_t>>>& links) {
  s2::Item::List rows;
  rows.reserve(links.size());
  for (const auto& [ceid, rpts] : links) {
    rows.push_back(s2::Item::list({s2::Item::u4(ceid), u4_list_item(rpts)}));
  }
  return s2::Message(2, 35, true,
                     s2::Item::list({s2::Item::u4(dataid), s2::Item::list(std::move(rows))}));
}

struct LinkEventReportRequest {
  uint32_t dataid;
  std::vector<std::pair<uint32_t, std::vector<uint32_t>>> links;
};

inline std::optional<LinkEventReportRequest> parse_s2f35(const s2::Message& m) {
  if (!m.body || !m.body->is_list() || m.body->as_list().size() != 2) return std::nullopt;
  const auto& outer = m.body->as_list();
  auto dataid = as_u4_scalar(outer[0]);
  if (!dataid) return std::nullopt;
  LinkEventReportRequest req{*dataid, {}};
  if (!outer[1].is_list()) return std::nullopt;
  for (const auto& row : outer[1].as_list()) {
    if (!row.is_list() || row.as_list().size() != 2) return std::nullopt;
    auto ceid = as_u4_scalar(row.as_list()[0]);
    if (!ceid) return std::nullopt;
    std::vector<uint32_t> rpts;
    if (!row.as_list()[1].is_list()) return std::nullopt;
    for (const auto& v : row.as_list()[1].as_list()) {
      auto u = as_u4_scalar(v);
      if (!u) return std::nullopt;
      rpts.push_back(*u);
    }
    req.links.emplace_back(*ceid, std::move(rpts));
  }
  return req;
}

inline s2::Message s2f36_link_event_report_ack(LinkEventAck ack) {
  return s2::Message(2, 36, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}

// -------------------------------------------------------------------------
//   S2F37 / S2F38  Enable / Disable Event Report
//
//   S2F37 W: <L,2 <BOOLEAN CEED> <L,n <U4 CEID>>>
//   S2F38  : <B ERACK>
// -------------------------------------------------------------------------

inline s2::Message s2f37_enable_event(bool enable, const std::vector<uint32_t>& ceids) {
  return s2::Message(2, 37, true,
                     s2::Item::list({s2::Item::boolean(enable), u4_list_item(ceids)}));
}

struct EnableEventRequest {
  bool enable;
  std::vector<uint32_t> ceids;
};

inline std::optional<EnableEventRequest> parse_s2f37(const s2::Message& m) {
  if (!m.body || !m.body->is_list() || m.body->as_list().size() != 2) return std::nullopt;
  const auto& outer = m.body->as_list();
  if (outer[0].format() != s2::Format::Boolean) return std::nullopt;
  const auto& bytes = outer[0].as_bytes();
  if (bytes.empty()) return std::nullopt;
  EnableEventRequest req{bytes.front() != 0, {}};
  if (!outer[1].is_list()) return std::nullopt;
  for (const auto& v : outer[1].as_list()) {
    auto u = as_u4_scalar(v);
    if (!u) return std::nullopt;
    req.ceids.push_back(*u);
  }
  return req;
}

inline s2::Message s2f38_enable_event_ack(EnableEventAck ack) {
  return s2::Message(2, 38, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}

// -------------------------------------------------------------------------
//   S5F1 / S5F2  Alarm Report Send / Ack
//
//   S5F1 W: <L,3 <B ALCD> <U4 ALID> <A ALTX>>
//   S5F2  : <B ACKC5>
// -------------------------------------------------------------------------

inline s2::Message s5f1_alarm_report(uint8_t alcd, uint32_t alid, const std::string& altx) {
  return s2::Message(5, 1, true,
                     s2::Item::list({s2::Item::binary({alcd}), s2::Item::u4(alid),
                                     s2::Item::ascii(altx)}));
}

struct AlarmReport {
  uint8_t alcd;
  uint32_t alid;
  std::string altx;
  bool is_set() const { return (alcd & 0x80) != 0; }
  uint8_t category() const { return alcd & 0x7F; }
};

inline std::optional<AlarmReport> parse_s5f1(const s2::Message& m) {
  if (!m.body || !m.body->is_list() || m.body->as_list().size() != 3) return std::nullopt;
  const auto& l = m.body->as_list();
  auto alcd = as_binary_first(l[0]);
  auto alid = as_u4_scalar(l[1]);
  auto altx = as_ascii(l[2]);
  if (!alcd || !alid || !altx) return std::nullopt;
  return AlarmReport{*alcd, *alid, *altx};
}

inline s2::Message s5f2_alarm_ack(AlarmAck ack) {
  return s2::Message(5, 2, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}

// -------------------------------------------------------------------------
//   S5F3 / S5F4  Enable / Disable Alarm Send
//
//   S5F3 W: <L,2 <B ALED> <U4 ALID>>     (ALED 0x80 = enable, 0x00 = disable)
//   S5F4  : <B ACKC5>
// -------------------------------------------------------------------------

inline constexpr uint8_t kAlarmEnableByte = 0x80;
inline constexpr uint8_t kAlarmDisableByte = 0x00;

inline s2::Message s5f3_enable_alarm(bool enable, uint32_t alid) {
  return s2::Message(
      5, 3, true,
      s2::Item::list({s2::Item::binary({enable ? kAlarmEnableByte : kAlarmDisableByte}),
                      s2::Item::u4(alid)}));
}

struct EnableAlarmRequest {
  bool enable;
  uint32_t alid;
};

inline std::optional<EnableAlarmRequest> parse_s5f3(const s2::Message& m) {
  if (!m.body || !m.body->is_list() || m.body->as_list().size() != 2) return std::nullopt;
  const auto& l = m.body->as_list();
  auto aled = as_binary_first(l[0]);
  auto alid = as_u4_scalar(l[1]);
  if (!aled || !alid) return std::nullopt;
  return EnableAlarmRequest{(*aled & 0x80) != 0, *alid};
}

inline s2::Message s5f4_enable_alarm_ack(AlarmAck ack) {
  return s2::Message(5, 4, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}

// -------------------------------------------------------------------------
//   S5F5 / S5F6  List Alarms Request / Data
//
//   S5F5 W: <L,n <U4 ALID>>   (empty = all)
//   S5F6  : <L,n <L,3 <B ALCD> <U4 ALID> <A ALTX>>>
// -------------------------------------------------------------------------

inline s2::Message s5f5_list_alarms_request(const std::vector<uint32_t>& alids) {
  return s2::Message(5, 5, true, u4_list_item(alids));
}

inline s2::Message s5f6_list_alarms_data(const std::vector<Alarm>& alarms,
                                         const std::function<bool(uint32_t)>& active) {
  s2::Item::List rows;
  rows.reserve(alarms.size());
  for (const auto& a : alarms) {
    const uint8_t alcd = (a.severity_category & 0x7F) |
                         static_cast<uint8_t>(active(a.id) ? 0x80 : 0x00);
    rows.push_back(s2::Item::list(
        {s2::Item::binary({alcd}), s2::Item::u4(a.id), s2::Item::ascii(a.text)}));
  }
  return s2::Message(5, 6, false, s2::Item::list(std::move(rows)));
}

// -------------------------------------------------------------------------
//   S6F11 / S6F12  Event Report Send
//
//   S6F11 W: <L,3 <U4 DATAID> <U4 CEID> <L,a <L,2 <U4 RPTID> <L,n <Item>>>>>
//   S6F12  : <B ACKC6>
// -------------------------------------------------------------------------

inline s2::Message s6f11_event_report(uint32_t dataid, uint32_t ceid,
                                      const std::vector<ReportData>& reports) {
  s2::Item::List rows;
  rows.reserve(reports.size());
  for (const auto& r : reports) {
    s2::Item::List values(r.values.begin(), r.values.end());
    rows.push_back(s2::Item::list({s2::Item::u4(r.rptid), s2::Item::list(std::move(values))}));
  }
  return s2::Message(6, 11, true,
                     s2::Item::list({s2::Item::u4(dataid), s2::Item::u4(ceid),
                                     s2::Item::list(std::move(rows))}));
}

struct EventReportMessage {
  uint32_t dataid;
  uint32_t ceid;
  std::vector<ReportData> reports;
};

inline std::optional<EventReportMessage> parse_s6f11(const s2::Message& m) {
  if (!m.body || !m.body->is_list() || m.body->as_list().size() != 3) return std::nullopt;
  const auto& outer = m.body->as_list();
  auto dataid = as_u4_scalar(outer[0]);
  auto ceid = as_u4_scalar(outer[1]);
  if (!dataid || !ceid) return std::nullopt;
  EventReportMessage out{*dataid, *ceid, {}};
  if (!outer[2].is_list()) return std::nullopt;
  for (const auto& row : outer[2].as_list()) {
    if (!row.is_list() || row.as_list().size() != 2) return std::nullopt;
    auto rptid = as_u4_scalar(row.as_list()[0]);
    if (!rptid) return std::nullopt;
    if (!row.as_list()[1].is_list()) return std::nullopt;
    ReportData rd{*rptid, {}};
    for (const auto& v : row.as_list()[1].as_list()) rd.values.push_back(v);
    out.reports.push_back(std::move(rd));
  }
  return out;
}

inline s2::Message s6f12_event_report_ack(EventReportAck ack) {
  return s2::Message(6, 12, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}

// -------------------------------------------------------------------------
//   S7F3 / S7F4  Process Program Send / Ack
//   S7F5 / S7F6  Process Program Request / Data
//   S7F19/ S7F20 Current EPPD List Request / Data
// -------------------------------------------------------------------------

inline s2::Message s7f3_process_program_send(const std::string& ppid, const std::string& ppbody) {
  return s2::Message(
      7, 3, true,
      s2::Item::list({s2::Item::ascii(ppid),
                      s2::Item::binary(std::vector<uint8_t>(ppbody.begin(), ppbody.end()))}));
}

struct ProcessProgram {
  std::string ppid;
  std::string ppbody;
};

inline std::optional<ProcessProgram> parse_s7f3(const s2::Message& m) {
  if (!m.body || !m.body->is_list() || m.body->as_list().size() != 2) return std::nullopt;
  const auto& l = m.body->as_list();
  auto ppid = as_ascii(l[0]);
  if (!ppid) return std::nullopt;
  if (l[1].format() != s2::Format::Binary) return std::nullopt;
  const auto& bytes = l[1].as_bytes();
  return ProcessProgram{*ppid, std::string(bytes.begin(), bytes.end())};
}

inline s2::Message s7f4_process_program_ack(ProcessProgramAck ack) {
  return s2::Message(7, 4, false, s2::Item::binary({static_cast<uint8_t>(ack)}));
}

inline s2::Message s7f5_process_program_request(const std::string& ppid) {
  return s2::Message(7, 5, true, s2::Item::ascii(ppid));
}

inline std::optional<std::string> parse_s7f5(const s2::Message& m) {
  if (!m.body) return std::nullopt;
  return as_ascii(*m.body);
}

inline s2::Message s7f6_process_program_data(const std::string& ppid, const std::string& ppbody) {
  return s2::Message(
      7, 6, false,
      s2::Item::list({s2::Item::ascii(ppid),
                      s2::Item::binary(std::vector<uint8_t>(ppbody.begin(), ppbody.end()))}));
}

inline std::optional<ProcessProgram> parse_s7f6(const s2::Message& m) {
  return parse_s7f3(m);  // identical body shape
}

inline s2::Message s7f19_current_eppd_request() { return s2::Message(7, 19, true); }

inline s2::Message s7f20_current_eppd_data(const std::vector<std::string>& ppids) {
  s2::Item::List rows;
  rows.reserve(ppids.size());
  for (const auto& p : ppids) rows.push_back(s2::Item::ascii(p));
  return s2::Message(7, 20, false, s2::Item::list(std::move(rows)));
}

inline std::optional<std::vector<std::string>> parse_s7f20(const s2::Message& m) {
  if (!m.body || !m.body->is_list()) return std::nullopt;
  std::vector<std::string> out;
  for (const auto& c : m.body->as_list()) {
    auto s = as_ascii(c);
    if (!s) return std::nullopt;
    out.push_back(*s);
  }
  return out;
}

}  // namespace secsgem::gem