state_machine.hpp

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#pragma once
 
#include "toast/log.hpp"
#include "toast/world/node.hpp"
 
#include <functional>
#include <lua.hpp>
#include <luabridge3/LuaBridge/detail/LuaRef.h>
#include <map>
#include <memory>
#include <optional>
#include <string>
#include <vector>
 
namespace toast {
 
struct Transition {
  std::string to;
  std::optional<std::function<bool()>> condition;
  std::optional<std::function<void()>> invoke;
};
 
struct State {
  std::optional<std::function<void()>> exit;
  std::optional<std::function<void()>> entry;
  std::optional<std::function<void()>> tick;
  std::vector<Transition> transitions;
};
 
class [[ToastNode]] TOAST_API StateMachine : public Node {
public:
  void addState(const std::string& name, const State& state);
 
  [[Reflect]]
  void addState(const std::string& name, const luabridge::LuaRef& table);
 
  [[Reflect]]
  void setState(const std::string& name);
 
  [[Reflect]]
  auto getState() -> std::string_view {
    return current_state;
  }
 
protected:
  [[nodiscard]]
  auto luaAffinity() const noexcept -> std::optional<size_t> override {
    return m_lua_vm;
  }
 
private:
  [[Reflect, ReadOnly]]
  std::string current_state;
 
  std::map<std::string, std::unique_ptr<State>> states;
  State* cached_state = nullptr;
  std::optional<size_t> m_lua_vm;    
 
  void begin();
  void end();
  void tick();
};
}