#pragma once

#include <algorithm>
#include <map>
#include <memory>
#include <optional>
#include <string>
#include <utility>
#include <vector>

#include "secsgem/gem/process_job_state.hpp"

namespace secsgem::gem {

// One Process Job record. The FSM is heap-allocated through unique_ptr so
// the per-PJ state-change handler can capture a stable pointer to
// `this`-style state without invalidation on map rehash.
struct ProcessJob {
  std::string prjobid;
  std::string ppid;                          // recipe identifier
  std::vector<std::string> mtrloutspec;      // material identifiers
  bool alert_enabled = true;                  // S16F9 alerts on/off
  std::unique_ptr<ProcessJobStateMachine> fsm;
};

class ProcessJobStore {
 public:
  using TransitionTableFactory =
      std::function<ProcessJobTransitionTable()>;
  using StateChangeHandler =
      std::function<void(const std::string& prjobid,
                         ProcessJobState from, ProcessJobState to,
                         ProcessJobEvent trigger)>;

  ProcessJobStore()
      : factory_([] { return ProcessJobTransitionTable::default_table(); }) {}

  // The per-PJ FSM closes over `this`, so the store must keep a stable
  // address. unique_ptr makes copying impossible anyway; moves would
  // silently dangle the per-PJ lambdas — disallow them explicitly.
  ProcessJobStore(const ProcessJobStore&) = delete;
  ProcessJobStore& operator=(const ProcessJobStore&) = delete;
  ProcessJobStore(ProcessJobStore&&) = delete;
  ProcessJobStore& operator=(ProcessJobStore&&) = delete;

  void set_table_factory(TransitionTableFactory f) { factory_ = std::move(f); }
  void set_state_change_handler(StateChangeHandler h) { on_change_ = std::move(h); }

  enum class CreateResult {
    Created,
    Denied_AlreadyExists,
    Denied_InvalidPpid,
  };

  // Validate `ppid` against the optional callback; if accepted, create
  // the PJ in Queued and fire the Created -> Queued change handler.
  CreateResult create(std::string prjobid, std::string ppid,
                      std::vector<std::string> materials,
                      const std::function<bool(const std::string&)>& ppid_exists =
                          [](const std::string&) { return true; }) {
    if (jobs_.count(prjobid)) return CreateResult::Denied_AlreadyExists;
    if (!ppid_exists(ppid))   return CreateResult::Denied_InvalidPpid;
    auto fsm = std::make_unique<ProcessJobStateMachine>(factory_(),
                                                        ProcessJobState::Queued);
    // Dispatch through *this so a later set_state_change_handler() takes
    // effect for existing PJs (the captured-at-create snapshot pattern
    // would otherwise pin the old handler on jobs already in the map).
    fsm->set_state_change_handler(
        [this, id = prjobid](ProcessJobState from, ProcessJobState to,
                             ProcessJobEvent trig) {
          if (on_change_) on_change_(id, from, to, trig);
        });
    order_.push_back(prjobid);
    jobs_.emplace(prjobid, ProcessJob{prjobid, std::move(ppid),
                                      std::move(materials), true,
                                      std::move(fsm)});
    // Synthetic NoState -> Queued so subscribers observe creation. The
    // server filters this so it doesn't emit a bogus S16F9 for a PJ
    // that's still being acked.
    if (on_change_) {
      on_change_(jobs_.find(prjobid)->first, ProcessJobState::NoState,
                 ProcessJobState::Queued, ProcessJobEvent::Created);
    }
    return CreateResult::Created;
  }

  bool has(const std::string& prjobid) const {
    return jobs_.count(prjobid) > 0;
  }

  const ProcessJob* get(const std::string& prjobid) const {
    auto it = jobs_.find(prjobid);
    return it == jobs_.end() ? nullptr : &it->second;
  }
  ProcessJob* get(const std::string& prjobid) {
    auto it = jobs_.find(prjobid);
    return it == jobs_.end() ? nullptr : &it->second;
  }

  ProcessJobState state(const std::string& prjobid) const {
    auto it = jobs_.find(prjobid);
    return it == jobs_.end() ? ProcessJobState::NoState
                              : it->second.fsm->state();
  }

  // Host-initiated S16F5 PRJobCommand. Returns InvalidObject for unknown
  // PJs; CannotDoNow when the current PJ state has no row for the event.
  // For HOQ the FSM gates legality (Queued only) and the store performs
  // the actual reorder so the next CJ Select picks this PJ first.
  HostCmdAck on_host_command(const std::string& prjobid, ProcessJobEvent event) {
    auto* pj = get(prjobid);
    if (!pj) return HostCmdAck::InvalidObject;
    HostCmdAck ack = pj->fsm->on_host_command(event);
    if (ack == HostCmdAck::Accept && event == ProcessJobEvent::HeadOfQueue) {
      move_to_head(prjobid);
    }
    return ack;
  }

  // Position of `prjobid` in the queue order (insertion order; HOQ rewrites
  // it). Returns -1 if unknown. Exposed for tests and CJ promotion logic.
  int position(const std::string& prjobid) const {
    auto it = std::find(order_.begin(), order_.end(), prjobid);
    return it == order_.end() ? -1 : static_cast<int>(it - order_.begin());
  }

  // Internal events from the application (recipe runner etc.).
  bool fire_internal(const std::string& prjobid, ProcessJobEvent event) {
    auto* pj = get(prjobid);
    if (!pj) return false;
    return pj->fsm->on_internal(event);
  }

  // Dequeue S16F13: only legal while QUEUED.
  HostCmdAck dequeue(const std::string& prjobid) {
    auto it = jobs_.find(prjobid);
    if (it == jobs_.end()) return HostCmdAck::InvalidObject;
    if (it->second.fsm->state() != ProcessJobState::Queued)
      return HostCmdAck::CannotDoNow;
    erase_from_order(prjobid);
    jobs_.erase(it);
    return HostCmdAck::Accept;
  }

  // Remove a terminal job from the store (caller responsibility to ensure
  // ProcessComplete before deleting). Used after CJ Completed cleanup.
  bool remove(const std::string& prjobid) {
    erase_from_order(prjobid);
    return jobs_.erase(prjobid) > 0;
  }

  // Per-PJ S16F9 alert gate. E40 §10.3 leaves PRALERT control to the host
  // (S16F1/F2 in the full multi-create form, which we don't model yet);
  // exposed here so application code can toggle alerts directly.
  bool set_alert(const std::string& prjobid, bool enabled) {
    auto* pj = get(prjobid);
    if (!pj) return false;
    pj->alert_enabled = enabled;
    return true;
  }

  std::size_t size() const { return jobs_.size(); }

  // Insertion-order list of PRJOBIDs, mutated by HOQ. Used by CJ promotion
  // logic and by tests that need to assert ordering.
  const std::vector<std::string>& ids() const { return order_; }

 private:
  void erase_from_order(const std::string& prjobid) {
    auto it = std::find(order_.begin(), order_.end(), prjobid);
    if (it != order_.end()) order_.erase(it);
  }
  void move_to_head(const std::string& prjobid) {
    auto it = std::find(order_.begin(), order_.end(), prjobid);
    if (it == order_.end() || it == order_.begin()) return;
    std::rotate(order_.begin(), it, it + 1);
  }

  std::map<std::string, ProcessJob> jobs_;
  std::vector<std::string> order_;        // queue position (E40 HOQ-aware)
  TransitionTableFactory factory_;
  StateChangeHandler on_change_;
};

}  // namespace secsgem::gem