#pragma once

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

#include "secsgem/secs2/item.hpp"

namespace secsgem::gem {

namespace s2 = secsgem::secs2;

enum class HostCmdAck : uint8_t {
  Accept = 0,
  InvalidCommand = 1,
  CannotDoNow = 2,
  ParameterInvalid = 3,
  AcceptedWillFinishLater = 4,
  Rejected = 5,
  InvalidObject = 6,
};

// One <CPNAME, CPVAL> entry on S2F41. The messages catalog declares this
// struct external_struct: true so the codegen references it rather than
// redefining it.
struct CommandParameter {
  std::string name;
  s2::Item value;
};

class HostCommandRegistry {
 public:
  // Declarative effect, loaded from YAML.
  struct Spec {
    HostCmdAck ack = HostCmdAck::Accept;
    std::optional<uint32_t> emit_ceid;
    std::optional<uint32_t> set_alarm;
    std::optional<bool>     force_spool;  // toggles the SpoolStore's flag
  };

  struct Result {
    HostCmdAck ack = HostCmdAck::InvalidCommand;
    std::optional<uint32_t> emit_ceid;
    std::optional<uint32_t> set_alarm;
    std::optional<bool>     force_spool;
  };

  // Behaviour hook: vendor code that actually *does* something when the host
  // sends a command (run a recipe, move hardware, validate the parameters).
  // The handler receives the live <CPNAME, CPVAL> parameter list and returns
  // the HCACK to send back; returning anything other than Accept suppresses
  // the Spec's declarative side effects, since the router only applies
  // emit_ceid / set_alarm / force_spool on Accept.  Without a handler a
  // command stays purely declarative (the YAML Spec's static ack), which is
  // the pre-existing behaviour.
  using Handler = std::function<HostCmdAck(
      const std::string& rcmd, const std::vector<CommandParameter>& params)>;

  void register_command(std::string rcmd, Spec spec) {
    by_rcmd_.insert_or_assign(std::move(rcmd), std::move(spec));
  }
  // Attach behaviour to an already-registered command.  Independent of
  // register_command so the data dictionary (YAML) and the behaviour
  // (application code) can be wired separately.
  void set_handler(std::string rcmd, Handler h) {
    handlers_.insert_or_assign(std::move(rcmd), std::move(h));
  }
  bool has(const std::string& rcmd) const { return by_rcmd_.count(rcmd) > 0; }
  bool has_handler(const std::string& rcmd) const { return handlers_.count(rcmd) > 0; }
  Result dispatch(const std::string& rcmd,
                  const std::vector<CommandParameter>& params) const {
    auto it = by_rcmd_.find(rcmd);
    if (it == by_rcmd_.end()) return {HostCmdAck::InvalidCommand, std::nullopt, std::nullopt, std::nullopt};
    HostCmdAck ack = it->second.ack;
    if (auto hit = handlers_.find(rcmd); hit != handlers_.end() && hit->second)
      ack = hit->second(rcmd, params);  // vendor behaviour decides the outcome
    return {ack, it->second.emit_ceid, it->second.set_alarm, it->second.force_spool};
  }

 private:
  std::map<std::string, Spec> by_rcmd_;
  std::map<std::string, Handler> handlers_;
};

}  // namespace secsgem::gem