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         class Dependency
  31         {
  32                 friend class System;
  33
  34         private:
  35                 DependencyFlags flags = NO_DEPENDENCY;
  36                 const Reflection::ClassBase &type;
  37                 void (*prepare)(Stage &) = nullptr;
  38                 void (*commit)(Stage &) = nullptr;
  39                 void (*unblock)(DependencyFlags) = nullptr;
  40                 void (*block)(DependencyFlags) = nullptr;
  41
  42         public:
  43                 Dependency(const Reflection::ClassBase &t): type(t) { }
  44
  45                 DependencyFlags get_flags() const { return flags; }
  46                 const Reflection::ClassBase &get_type() const { return type; }
  47         };
  48
  49         class Activator: public NonCopyable
  50         {
  51         private:
  52                 System &system;
  53
  54         public:
  55                 Activator(System &s): system(s) { system.begin_tick(); }
  56                 ~Activator() { system.end_tick(); }
  57         };
  58
  59 protected:
  60         Stage &stage;
  61         std::vector<std::function<void()>> deferred_queue;
  62         std::vector<Dependency> dependencies;
  63
  64         static thread_local System *active;
  65
  66         System(Stage &s): stage(s) { }
  67 public:
  68         virtual ~System() = default;
  69
  70         Stage &get_stage() const { return stage; }
  71
  72 protected:
  73         template<typename T>
  74         void declare_dependency(DependencyFlags);
  75
  76 public:
  77         const std::vector<Dependency> &get_dependencies() const { return dependencies; }
  78
  79         void begin_tick();
  80         virtual void tick(Time::TimeDelta) = 0;
  81         void end_tick();
  82         virtual void deferred_tick();
  83
  84 protected:
  85         template<typename F>
  86         void defer(F &&f) { deferred_queue.emplace_back(std::forward<F>(f)); }
  87 };
  88
  89
  90 template<typename T>
  91 inline void System::declare_dependency(DependencyFlags flags)
  92 {
  93         if((flags&DATA_MASK) && !std::is_base_of_v<Component, T>)
  94                 throw std::invalid_argument("System::declare_dependency");
  95         if((flags&ORDER_MASK) && !std::is_base_of_v<System, T>)
  96                 throw std::invalid_argument("System::declare_dependency");
  97
  98         const Reflection::ClassBase &type = stage.get_reflector().get_or_create_class<T>();
  99         auto i = find_if(dependencies, [&type](const Dependency &d){ return &d.type==&type; });
 100
 101         if(i!=dependencies.end())
 102                 flags = static_cast<DependencyFlags>(flags|i->flags);
 103         if((flags&RUN_BEFORE) && (flags&RUN_AFTER))
 104                 throw std::logic_error("conflicting order flags");
 105
 106         Dependency &dep = (i!=dependencies.end() ? *i : dependencies.emplace_back(type));
 107         dep.flags = flags;
 108         if constexpr(requires(T &c) { typename T::Data; c.prepare_tick(); c.commit_tick(); })
 109         {
 110 #ifdef DEBUG
 111                 dep.unblock = +[](DependencyFlags f){
 112                         if(f&READ_OLD) AccessGuard::get_instance().unblock<AccessGuard::Read<typename T::Data>>();
 113                         if(f&WRITE) AccessGuard::get_instance().unblock<AccessGuard::Write<typename T::Data>>();
 114                 };
 115                 dep.block = +[](DependencyFlags f){
 116                         if(f&READ_OLD) AccessGuard::get_instance().block<AccessGuard::Read<typename T::Data>>();
 117                         if(f&WRITE) AccessGuard::get_instance().block<AccessGuard::Write<typename T::Data>>();
 118                 };
 119 #endif
 120                 if(flags&WRITE)
 121                 {
 122                         dep.prepare = +[](Stage &s){ s.iterate_objects<T>([](T &c){ c.prepare_tick(); }); };
 123                         dep.commit = +[](Stage &s){ s.iterate_objects<T>([](T &c){ c.commit_tick(); }); };
 124                 }
 125         }
 126 }
 127
 128 } // namespace Msp::Game
 129
 130 #endif