#pragma once

#include <algorithm>
#include <cstdint>
#include <cstdio>
#include <filesystem>
#include <fstream>
#include <functional>
#include <map>
#include <memory>
#include <optional>
#include <string>
#include <system_error>
#include <utility>
#include <vector>

#include "secsgem/gem/carrier_state.hpp"
#include "secsgem/gem/load_port_state.hpp"

namespace secsgem::gem {

// One slot in a carrier slot map.  E87-0716 slot states: Empty (0),
// NotEmpty (1), Undefined (3) — we keep the wire byte directly rather
// than wrapping it in an enum, since the application may carry tool-
// specific extensions.
struct CarrierSlot {
  uint8_t state = 3;  // undefined by default
};

struct Carrier {
  std::string carrierid;
  uint8_t port_id = 0;             // 0 = unbound; ports are 1-based
  std::vector<CarrierSlot> slots;  // length == capacity (typ. 25)
  std::unique_ptr<CarrierStateMachine> fsm;
  std::filesystem::path journal_path;  // empty when persistence disabled
};

struct LoadPort {
  uint8_t port_id;
  std::string carrierid;  // empty when nothing associated
  std::unique_ptr<LoadPortStateMachine> fsm;
  std::filesystem::path journal_path;  // empty when persistence disabled
};

// Both stores are non-movable for the same reason ProcessJobStore is —
// per-row FSMs close over `this` via their change-handler lambdas.
class CarrierStore {
 public:
  using IDChangeHandler =
      std::function<void(const std::string& carrierid, CarrierIDStatus from,
                         CarrierIDStatus to, CarrierIDEvent)>;
  using SlotMapChangeHandler =
      std::function<void(const std::string& carrierid, SlotMapStatus from,
                         SlotMapStatus to, SlotMapEvent)>;
  using AccessChangeHandler =
      std::function<void(const std::string& carrierid, CarrierAccessStatus from,
                         CarrierAccessStatus to, CarrierAccessEvent)>;

  CarrierStore() = default;
  CarrierStore(const CarrierStore&) = delete;
  CarrierStore& operator=(const CarrierStore&) = delete;
  CarrierStore(CarrierStore&&) = delete;
  CarrierStore& operator=(CarrierStore&&) = delete;

  void set_id_handler(IDChangeHandler h)             { on_id_ = std::move(h); }
  void set_slot_map_handler(SlotMapChangeHandler h)  { on_sm_ = std::move(h); }
  void set_access_handler(AccessChangeHandler h)     { on_acc_ = std::move(h); }

  enum class CreateResult { Created, Denied_AlreadyExists };

  CreateResult create(std::string carrierid, uint8_t port_id = 0,
                      std::size_t capacity = 25) {
    if (carriers_.count(carrierid)) return CreateResult::Denied_AlreadyExists;
    install_(carrierid, port_id, std::vector<CarrierSlot>(capacity),
             /*restore_id=*/std::nullopt, std::nullopt, std::nullopt);
    if (persistent_) write_record_(carrierid);
    return CreateResult::Created;
  }

  bool has(const std::string& cid) const { return carriers_.count(cid) > 0; }
  const Carrier* get(const std::string& cid) const {
    auto it = carriers_.find(cid);
    return it == carriers_.end() ? nullptr : &it->second;
  }
  Carrier* get(const std::string& cid) {
    auto it = carriers_.find(cid);
    return it == carriers_.end() ? nullptr : &it->second;
  }

  bool fire_id_event(const std::string& cid, CarrierIDEvent e) {
    auto* c = get(cid);
    if (!(c && c->fsm->on_id_event(e))) return false;
    if (persistent_) write_record_(cid);
    return true;
  }
  bool fire_slot_map_event(const std::string& cid, SlotMapEvent e) {
    auto* c = get(cid);
    if (!(c && c->fsm->on_slot_map_event(e))) return false;
    if (persistent_) write_record_(cid);
    return true;
  }
  bool fire_access_event(const std::string& cid, CarrierAccessEvent e) {
    auto* c = get(cid);
    if (!(c && c->fsm->on_access_event(e))) return false;
    if (persistent_) write_record_(cid);
    return true;
  }

  // Application sets slots[i].state directly; persistence sync is opt-in
  // through this helper so the journal records the new slot map.
  void set_slot_state(const std::string& cid, std::size_t slot_idx,
                      uint8_t state) {
    auto* c = get(cid);
    if (!c || slot_idx >= c->slots.size()) return;
    c->slots[slot_idx].state = state;
    if (persistent_) write_record_(cid);
  }

  bool remove(const std::string& cid) {
    auto it = carriers_.find(cid);
    if (it == carriers_.end()) return false;
    if (persistent_ && !it->second.journal_path.empty()) {
      std::error_code ec;
      std::filesystem::remove(it->second.journal_path, ec);
    }
    carriers_.erase(it);
    return true;
  }
  std::size_t size() const { return carriers_.size(); }
  std::vector<std::string> ids() const {
    std::vector<std::string> out;
    out.reserve(carriers_.size());
    for (const auto& kv : carriers_) out.push_back(kv.first);
    return out;
  }

  // ---- Persistence ----------------------------------------------------
  // Mirrors SpoolStore::enable_persistence: scan `dir` for *.car records,
  // replay them into the in-memory map, then keep the directory in sync
  // on subsequent create / fire_* / remove calls.  Atomic writes via
  // .tmp + rename.  Records that fail magic/version are silently dropped
  // so a single bad file can't poison the whole store.
  void enable_persistence(std::filesystem::path dir) {
    namespace fs = std::filesystem;
    journal_dir_ = std::move(dir);
    persistent_ = true;
    std::error_code ec;
    fs::create_directories(journal_dir_, ec);

    std::vector<std::pair<uint64_t, fs::path>> existing;
    for (auto& entry : fs::directory_iterator(journal_dir_, ec)) {
      if (!entry.is_regular_file()) continue;
      const auto& p = entry.path();
      if (p.extension() != ".car") continue;
      uint64_t seq = 0;
      try { seq = std::stoull(p.stem().string()); }
      catch (...) { continue; }
      existing.emplace_back(seq, p);
    }
    std::sort(existing.begin(), existing.end(),
              [](const auto& a, const auto& b) { return a.first < b.first; });

    for (auto& [seq, path] : existing) {
      auto rec = load_record_(path);
      if (!rec) { fs::remove(path, ec); continue; }
      install_(rec->carrierid, rec->port_id, std::move(rec->slots),
               rec->id_state, rec->sm_state, rec->acc_state);
      auto* c = get(rec->carrierid);
      if (c) c->journal_path = path;
      if (seq >= next_seq_) next_seq_ = seq + 1;
    }
  }

  bool persistence_enabled() const { return persistent_; }
  std::filesystem::path journal_dir() const { return journal_dir_; }

 private:
  struct Record {
    std::string carrierid;
    uint8_t port_id;
    std::vector<CarrierSlot> slots;
    CarrierIDStatus     id_state;
    SlotMapStatus       sm_state;
    CarrierAccessStatus acc_state;
  };

  // Carrier record layout, big-endian throughout:
  //   [u8 magic = 0xC4][u8 version = 1]
  //   [u8 id_state][u8 sm_state][u8 acc_state][u8 port_id]
  //   [u16 slot_count][slot_count × u8 slot.state]
  //   [u16 cid_len][cid_len × u8 carrierid]
  static constexpr uint8_t kMagic   = 0xC4;
  static constexpr uint8_t kVersion = 0x01;

  void install_(const std::string& carrierid, uint8_t port_id,
                std::vector<CarrierSlot> slots,
                std::optional<CarrierIDStatus> id_state,
                std::optional<SlotMapStatus> sm_state,
                std::optional<CarrierAccessStatus> acc_state) {
    auto fsm = std::make_unique<CarrierStateMachine>();
    if (id_state || sm_state || acc_state) {
      fsm->restore_state(id_state.value_or(CarrierIDStatus::NotConfirmed),
                         sm_state.value_or(SlotMapStatus::NotRead),
                         acc_state.value_or(CarrierAccessStatus::NotAccessed));
    }
    const std::string id = carrierid;
    fsm->set_id_handler([this, id](CarrierIDStatus f, CarrierIDStatus t,
                                   CarrierIDEvent e) {
      if (on_id_) on_id_(id, f, t, e);
    });
    fsm->set_slot_map_handler([this, id](SlotMapStatus f, SlotMapStatus t,
                                         SlotMapEvent e) {
      if (on_sm_) on_sm_(id, f, t, e);
    });
    fsm->set_access_handler([this, id](CarrierAccessStatus f, CarrierAccessStatus t,
                                       CarrierAccessEvent e) {
      if (on_acc_) on_acc_(id, f, t, e);
    });
    carriers_.emplace(carrierid, Carrier{carrierid, port_id, std::move(slots),
                                         std::move(fsm), {}});
  }

  void write_record_(const std::string& carrierid) {
    namespace fs = std::filesystem;
    auto* c = get(carrierid);
    if (!c) return;
    fs::path target = c->journal_path;
    if (target.empty()) {
      char namebuf[32];
      std::snprintf(namebuf, sizeof(namebuf), "%010llu.car",
                    static_cast<unsigned long long>(next_seq_++));
      target = journal_dir_ / namebuf;
      c->journal_path = target;
    }
    fs::path tmp = target;
    tmp += ".tmp";
    std::ofstream out(tmp, std::ios::binary | std::ios::trunc);
    if (!out) return;
    uint8_t header[6] = {
        kMagic, kVersion,
        static_cast<uint8_t>(c->fsm->id_status()),
        static_cast<uint8_t>(c->fsm->slot_map_status()),
        static_cast<uint8_t>(c->fsm->access_status()),
        c->port_id};
    out.write(reinterpret_cast<const char*>(header), sizeof(header));
    auto write_be16 = [&](uint16_t v) {
      uint8_t b[2] = {static_cast<uint8_t>(v >> 8), static_cast<uint8_t>(v)};
      out.write(reinterpret_cast<const char*>(b), 2);
    };
    write_be16(static_cast<uint16_t>(c->slots.size()));
    for (const auto& s : c->slots) {
      out.put(static_cast<char>(s.state));
    }
    write_be16(static_cast<uint16_t>(c->carrierid.size()));
    out.write(c->carrierid.data(),
              static_cast<std::streamsize>(c->carrierid.size()));
    out.flush();
    out.close();
    std::error_code ec;
    fs::rename(tmp, target, ec);
    if (ec) fs::remove(tmp, ec);
  }

  static std::optional<Record> load_record_(const std::filesystem::path& p) {
    std::ifstream in(p, std::ios::binary);
    if (!in) return std::nullopt;
    uint8_t header[6];
    in.read(reinterpret_cast<char*>(header), sizeof(header));
    if (!in || header[0] != kMagic || header[1] != kVersion) return std::nullopt;
    Record r;
    r.id_state  = static_cast<CarrierIDStatus>(header[2]);
    r.sm_state  = static_cast<SlotMapStatus>(header[3]);
    r.acc_state = static_cast<CarrierAccessStatus>(header[4]);
    r.port_id   = header[5];
    auto read_be16 = [&](uint16_t& v) {
      uint8_t b[2];
      in.read(reinterpret_cast<char*>(b), 2);
      if (!in) return false;
      v = static_cast<uint16_t>((uint16_t(b[0]) << 8) | b[1]);
      return true;
    };
    uint16_t slot_count = 0;
    if (!read_be16(slot_count)) return std::nullopt;
    r.slots.resize(slot_count);
    for (auto& s : r.slots) {
      int c = in.get();
      if (c == std::char_traits<char>::eof()) return std::nullopt;
      s.state = static_cast<uint8_t>(c);
    }
    uint16_t cid_len = 0;
    if (!read_be16(cid_len)) return std::nullopt;
    r.carrierid.resize(cid_len);
    in.read(r.carrierid.data(), cid_len);
    if (!in) return std::nullopt;
    return r;
  }

  std::map<std::string, Carrier> carriers_;
  IDChangeHandler      on_id_;
  SlotMapChangeHandler on_sm_;
  AccessChangeHandler  on_acc_;
  bool persistent_ = false;
  std::filesystem::path journal_dir_;
  uint64_t next_seq_ = 0;
};

class LoadPortStore {
 public:
  using TransferChangeHandler =
      std::function<void(uint8_t portid, LoadPortTransferState from,
                         LoadPortTransferState to, LoadPortTransferEvent)>;
  using ReservationChangeHandler =
      std::function<void(uint8_t portid, LoadPortReservationStatus from,
                         LoadPortReservationStatus to, LoadPortReservationEvent)>;
  using AssociationChangeHandler =
      std::function<void(uint8_t portid, LoadPortAssociationStatus from,
                         LoadPortAssociationStatus to, LoadPortAssociationEvent)>;

  LoadPortStore() = default;
  LoadPortStore(const LoadPortStore&) = delete;
  LoadPortStore& operator=(const LoadPortStore&) = delete;
  LoadPortStore(LoadPortStore&&) = delete;
  LoadPortStore& operator=(LoadPortStore&&) = delete;

  void set_transfer_handler(TransferChangeHandler h)       { on_tx_ = std::move(h); }
  void set_reservation_handler(ReservationChangeHandler h) { on_rs_ = std::move(h); }
  void set_association_handler(AssociationChangeHandler h) { on_as_ = std::move(h); }

  // Idempotent: re-create a port_id is a no-op.
  bool create(uint8_t port_id) {
    if (ports_.count(port_id)) return false;
    install_(port_id, "", std::nullopt, std::nullopt, std::nullopt);
    if (persistent_) write_record_(port_id);
    return true;
  }

  bool has(uint8_t pid) const { return ports_.count(pid) > 0; }
  const LoadPort* get(uint8_t pid) const {
    auto it = ports_.find(pid);
    return it == ports_.end() ? nullptr : &it->second;
  }
  LoadPort* get(uint8_t pid) {
    auto it = ports_.find(pid);
    return it == ports_.end() ? nullptr : &it->second;
  }

  bool associate(uint8_t pid, std::string carrierid) {
    auto* p = get(pid);
    if (!p) return false;
    p->carrierid = std::move(carrierid);
    bool ok = p->fsm->on_association_event(LoadPortAssociationEvent::Associate);
    if (persistent_) write_record_(pid);
    return ok;
  }

  bool disassociate(uint8_t pid) {
    auto* p = get(pid);
    if (!p) return false;
    p->carrierid.clear();
    bool ok = p->fsm->on_association_event(LoadPortAssociationEvent::Disassociate);
    if (persistent_) write_record_(pid);
    return ok;
  }

  bool fire_transfer_event(uint8_t pid, LoadPortTransferEvent e) {
    auto* p = get(pid);
    if (!(p && p->fsm->on_transfer_event(e))) return false;
    if (persistent_) write_record_(pid);
    return true;
  }
  bool fire_reservation_event(uint8_t pid, LoadPortReservationEvent e) {
    auto* p = get(pid);
    if (!(p && p->fsm->on_reservation_event(e))) return false;
    if (persistent_) write_record_(pid);
    return true;
  }

  std::size_t size() const { return ports_.size(); }
  std::vector<uint8_t> ids() const {
    std::vector<uint8_t> out;
    out.reserve(ports_.size());
    for (const auto& kv : ports_) out.push_back(kv.first);
    return out;
  }

  // ---- Persistence ----------------------------------------------------
  // One file per port: `<port_id 0-padded>.lp`.  Port IDs are 1–255 so
  // we can use the port id directly as the filename stem.
  void enable_persistence(std::filesystem::path dir) {
    namespace fs = std::filesystem;
    journal_dir_ = std::move(dir);
    persistent_ = true;
    std::error_code ec;
    fs::create_directories(journal_dir_, ec);

    for (auto& entry : fs::directory_iterator(journal_dir_, ec)) {
      if (!entry.is_regular_file()) continue;
      const auto& p = entry.path();
      if (p.extension() != ".lp") continue;
      auto rec = load_record_(p);
      if (!rec) { fs::remove(p, ec); continue; }
      install_(rec->port_id, rec->carrierid, rec->tx_state, rec->rs_state,
               rec->as_state);
      auto* lp = get(rec->port_id);
      if (lp) lp->journal_path = p;
    }
  }

  bool persistence_enabled() const { return persistent_; }
  std::filesystem::path journal_dir() const { return journal_dir_; }

 private:
  struct Record {
    uint8_t port_id;
    std::string carrierid;
    LoadPortTransferState     tx_state;
    LoadPortReservationStatus rs_state;
    LoadPortAssociationStatus as_state;
  };

  // Load-port record:
  //   [u8 magic = 0xC5][u8 version = 1]
  //   [u8 port_id][u8 tx_state][u8 rs_state][u8 as_state]
  //   [u16 cid_len][cid_len × u8 carrierid]
  static constexpr uint8_t kMagic   = 0xC5;
  static constexpr uint8_t kVersion = 0x01;

  void install_(uint8_t port_id, std::string carrierid,
                std::optional<LoadPortTransferState> tx,
                std::optional<LoadPortReservationStatus> rs,
                std::optional<LoadPortAssociationStatus> as) {
    auto fsm = std::make_unique<LoadPortStateMachine>();
    if (tx || rs || as) {
      fsm->restore_state(tx.value_or(LoadPortTransferState::InService),
                         rs.value_or(LoadPortReservationStatus::NotReserved),
                         as.value_or(LoadPortAssociationStatus::NotAssociated));
    }
    const uint8_t pid = port_id;
    fsm->set_transfer_handler([this, pid](LoadPortTransferState f,
                                          LoadPortTransferState t,
                                          LoadPortTransferEvent e) {
      if (on_tx_) on_tx_(pid, f, t, e);
    });
    fsm->set_reservation_handler([this, pid](LoadPortReservationStatus f,
                                             LoadPortReservationStatus t,
                                             LoadPortReservationEvent e) {
      if (on_rs_) on_rs_(pid, f, t, e);
    });
    fsm->set_association_handler([this, pid](LoadPortAssociationStatus f,
                                             LoadPortAssociationStatus t,
                                             LoadPortAssociationEvent e) {
      if (on_as_) on_as_(pid, f, t, e);
    });
    ports_.emplace(port_id, LoadPort{port_id, std::move(carrierid),
                                     std::move(fsm), {}});
  }

  void write_record_(uint8_t pid) {
    namespace fs = std::filesystem;
    auto* lp = get(pid);
    if (!lp) return;
    if (lp->journal_path.empty()) {
      char namebuf[16];
      std::snprintf(namebuf, sizeof(namebuf), "%03u.lp", unsigned(pid));
      lp->journal_path = journal_dir_ / namebuf;
    }
    fs::path tmp = lp->journal_path;
    tmp += ".tmp";
    std::ofstream out(tmp, std::ios::binary | std::ios::trunc);
    if (!out) return;
    uint8_t header[6] = {
        kMagic, kVersion, pid,
        static_cast<uint8_t>(lp->fsm->transfer_state()),
        static_cast<uint8_t>(lp->fsm->reservation_state()),
        static_cast<uint8_t>(lp->fsm->association_state())};
    out.write(reinterpret_cast<const char*>(header), sizeof(header));
    uint16_t cid_len = static_cast<uint16_t>(lp->carrierid.size());
    uint8_t lb[2] = {static_cast<uint8_t>(cid_len >> 8),
                     static_cast<uint8_t>(cid_len)};
    out.write(reinterpret_cast<const char*>(lb), 2);
    out.write(lp->carrierid.data(),
              static_cast<std::streamsize>(lp->carrierid.size()));
    out.flush();
    out.close();
    std::error_code ec;
    fs::rename(tmp, lp->journal_path, ec);
    if (ec) fs::remove(tmp, ec);
  }

  static std::optional<Record> load_record_(const std::filesystem::path& p) {
    std::ifstream in(p, std::ios::binary);
    if (!in) return std::nullopt;
    uint8_t header[6];
    in.read(reinterpret_cast<char*>(header), sizeof(header));
    if (!in || header[0] != kMagic || header[1] != kVersion) return std::nullopt;
    Record r;
    r.port_id  = header[2];
    r.tx_state = static_cast<LoadPortTransferState>(header[3]);
    r.rs_state = static_cast<LoadPortReservationStatus>(header[4]);
    r.as_state = static_cast<LoadPortAssociationStatus>(header[5]);
    uint8_t lb[2];
    in.read(reinterpret_cast<char*>(lb), 2);
    if (!in) return std::nullopt;
    uint16_t cid_len = static_cast<uint16_t>((uint16_t(lb[0]) << 8) | lb[1]);
    r.carrierid.resize(cid_len);
    in.read(r.carrierid.data(), cid_len);
    if (cid_len && !in) return std::nullopt;
    return r;
  }

  std::map<uint8_t, LoadPort> ports_;
  TransferChangeHandler    on_tx_;
  ReservationChangeHandler on_rs_;
  AssociationChangeHandler on_as_;
  bool persistent_ = false;
  std::filesystem::path journal_dir_;
};

}  // namespace secsgem::gem