1 files changed, 180 insertions, 0 deletions
diff --git a/entityx/System.h b/entityx/System.h
new file mode 100644
index 0000000..3d2e4b2
--- /dev/null
+++ b/entityx/System.h
@@ -0,0 +1,180 @@
+/*
+ * Copyright (C) 2012 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#pragma once
+
+
+#include <cstdint>
+#include <unordered_map>
+#include <utility>
+#include <cassert>
+#include "entityx/config.h"
+#include "entityx/Entity.h"
+#include "entityx/Event.h"
+#include "entityx/help/NonCopyable.h"
+
+
+namespace entityx {
+
+
+class SystemManager;
+
+
+/**
+ * Base System class. Generally should not be directly used, instead see System<Derived>.
+ */
+class BaseSystem : entityx::help::NonCopyable {
+ public:
+  typedef size_t Family;
+
+  virtual ~BaseSystem();
+
+  /**
+   * Called once all Systems have been added to the SystemManager.
+   *
+   * Typically used to set up event handlers.
+   */
+  virtual void configure(EntityManager &entities, EventManager &events) {
+	(void)entities;
+    configure(events);
+  }
+
+  /**
+   * Legacy configure(). Called by default implementation of configure(EntityManager&, EventManager&).
+   */
+  virtual void configure(EventManager &events) { (void)events; }
+
+  /**
+   * Apply System behavior.
+   *
+   * Called every game step.
+   */
+  virtual void update(EntityManager &entities, EventManager &events, TimeDelta dt) = 0;
+
+  static Family family_counter_;
+
+ protected:
+};
+
+
+/**
+ * Use this class when implementing Systems.
+ *
+ * struct MovementSystem : public System<MovementSystem> {
+ *   void update(EntityManager &entities, EventManager &events, TimeDelta dt) {
+ *     // Do stuff to/with entities...
+ *   }
+ * }
+ */
+template <typename Derived>
+class System : public BaseSystem {
+ public:
+  virtual ~System() {}
+
+private:
+  friend class SystemManager;
+
+  static Family family() {
+    static Family family = family_counter_++;
+    return family;
+  }
+};
+
+
+class SystemManager : entityx::help::NonCopyable {
+ public:
+  SystemManager(EntityManager &entity_manager,
+                EventManager &event_manager) :
+                entity_manager_(entity_manager),
+                event_manager_(event_manager) {}
+
+  /**
+   * Add a System to the SystemManager.
+   *
+   * Must be called before Systems can be used.
+   *
+   * eg.
+   * std::shared_ptr<MovementSystem> movement = entityx::make_shared<MovementSystem>();
+   * system.add(movement);
+   */
+  template <typename S>
+  void add(std::shared_ptr<S> system) {
+    systems_.insert(std::make_pair(S::family(), system));
+  }
+
+  /**
+   * Add a System to the SystemManager.
+   *
+   * Must be called before Systems can be used.
+   *
+   * eg.
+   * auto movement = system.add<MovementSystem>();
+   */
+  template <typename S, typename ... Args>
+  std::shared_ptr<S> add(Args && ... args) {
+    std::shared_ptr<S> s(new S(std::forward<Args>(args) ...));
+    add(s);
+    return s;
+  }
+
+  /**
+   * Retrieve the registered System instance, if any.
+   *
+   *   std::shared_ptr<CollisionSystem> collisions = systems.system<CollisionSystem>();
+   *
+   * @return System instance or empty shared_std::shared_ptr<S>.
+   */
+  template <typename S>
+  std::shared_ptr<S> system() {
+    auto it = systems_.find(S::family());
+    assert(it != systems_.end());
+    return it == systems_.end()
+        ? std::shared_ptr<S>()
+        : std::shared_ptr<S>(std::static_pointer_cast<S>(it->second));
+  }
+
+  /**
+   * Call the System::update() method for a registered system.
+   */
+  template <typename S>
+  void update(TimeDelta dt) {
+    assert(initialized_ && "SystemManager::configure() not called");
+    std::shared_ptr<S> s = system<S>();
+    s->update(entity_manager_, event_manager_, dt);
+  }
+
+  /**
+   * Call System::update() on all registered systems.
+   *
+   * The order which the registered systems are updated is arbitrary but consistent,
+   * meaning the order which they will be updated cannot be specified, but that order
+   * will stay the same as long no systems are added or removed.
+   *
+   * If the order in which systems update is important, use SystemManager::update()
+   * to manually specify the update order. EntityX does not yet support a way of
+   * specifying priority for update_all().
+   */
+  void update_all(TimeDelta dt);
+
+  /**
+   * Configure the system. Call after adding all Systems.
+   *
+   * This is typically used to set up event handlers.
+   */
+  void configure();
+
+ private:
+  bool initialized_ = false;
+  EntityManager &entity_manager_;
+  EventManager &event_manager_;
+  std::unordered_map<BaseSystem::Family, std::shared_ptr<BaseSystem>> systems_;
+};
+
+}  // namespace entityx