source/game/system.h

   1 #ifndef MSP_GAME_SYSTEM_H_
   2 #define MSP_GAME_SYSTEM_H_
   3
   4 #include <functional>
   5 #include <msp/time/timedelta.h>
   6 #include "accessguard.h"
   7 #include "component.h"
   8 #include "reflection.h"
   9 #include "stage.h"
  10
  11 namespace Msp::Game {
  12
  13 class System
  14 {
  15 public:
  16         enum DependencyFlags
  17         {
  18                 NO_DEPENDENCY = 0,
  19                 READ_OLD = 1,
  20                 READ_FRESH = 3,
  21                 WRITE = 4,
  22                 UPDATE = READ_OLD | WRITE,
  23                 CHAINED_UPDATE = READ_FRESH | WRITE,
  24                 DATA_MASK = 7,
  25                 RUN_BEFORE = 8,
  26                 RUN_AFTER = 16,
  27                 ORDER_MASK = 24
  28         };
  29
  30         struct Dependency
  31         {
  32                 DependencyFlags flags = NO_DEPENDENCY;
  33                 const Reflection::ClassBase &type;
  34                 void (*prepare)(Stage &) = nullptr;
  35                 void (*commit)(Stage &) = nullptr;
  36                 void (*unblock)(DependencyFlags) = nullptr;
  37                 void (*block)(DependencyFlags) = nullptr;
  38
  39                 Dependency(const Reflection::ClassBase &t): type(t) { }
  40         };
  41
  42         class Activator: public NonCopyable
  43         {
  44         private:
  45                 System &system;
  46
  47         public:
  48                 Activator(System &s): system(s) { system.begin_tick(); }
  49                 ~Activator() { system.end_tick(); }
  50         };
  51
  52 protected:
  53         Stage &stage;
  54         std::vector<std::function<void()>> deferred_queue;
  55         std::vector<Dependency> dependencies;
  56
  57         static thread_local System *active;
  58
  59         System(Stage &s): stage(s) { }
  60 public:
  61         virtual ~System() = default;
  62
  63         Stage &get_stage() const { return stage; }
  64
  65 protected:
  66         template<typename T>
  67         void declare_dependency(DependencyFlags);
  68
  69 public:
  70         void begin_tick();
  71         virtual void tick(Time::TimeDelta) = 0;
  72         void end_tick();
  73         virtual void deferred_tick();
  74
  75 protected:
  76         template<typename F>
  77         void defer(F &&f) { deferred_queue.emplace_back(std::forward<F>(f)); }
  78 };
  79
  80
  81 template<typename T>
  82 inline void System::declare_dependency(DependencyFlags flags)
  83 {
  84         if((flags&DATA_MASK) && !std::is_base_of_v<Component, T>)
  85                 throw std::invalid_argument("System::declare_dependency");
  86         if((flags&ORDER_MASK) && !std::is_base_of_v<System, T>)
  87                 throw std::invalid_argument("System::declare_dependency");
  88
  89         const Reflection::ClassBase &type = stage.get_reflector().get_or_create_class<T>();
  90         auto i = find_if(dependencies, [&type](const Dependency &d){ return &d.type==&type; });
  91
  92         if(i!=dependencies.end())
  93                 flags = static_cast<DependencyFlags>(flags|i->flags);
  94         if((flags&RUN_BEFORE) && (flags&RUN_AFTER))
  95                 throw std::logic_error("conflicting order flags");
  96
  97         Dependency &dep = (i!=dependencies.end() ? *i : dependencies.emplace_back(type));
  98         dep.flags = flags;
  99         if constexpr(requires(T &c) { typename T::Data; c.prepare_tick(); c.commit_tick(); })
 100         {
 101 #ifdef DEBUG
 102                 dep.unblock = +[](DependencyFlags f){
 103                         if(f&READ_OLD) AccessGuard::get_instance().unblock<AccessGuard::Read<typename T::Data>>();
 104                         if(f&WRITE) AccessGuard::get_instance().unblock<AccessGuard::Write<typename T::Data>>();
 105                 };
 106                 dep.block = +[](DependencyFlags f){
 107                         if(f&READ_OLD) AccessGuard::get_instance().block<AccessGuard::Read<typename T::Data>>();
 108                         if(f&WRITE) AccessGuard::get_instance().block<AccessGuard::Write<typename T::Data>>();
 109                 };
 110 #endif
 111                 if(flags&WRITE)
 112                 {
 113                         dep.prepare = +[](Stage &s){ s.iterate_objects<T>([](T &c){ c.prepare_tick(); }); };
 114                         dep.commit = +[](Stage &s){ s.iterate_objects<T>([](T &c){ c.commit_tick(); }); };
 115                 }
 116         }
 117 }
 118
 119 } // namespace Msp::Game
 120
 121 #endif