Add StateMachine class

CopiumEngine/src/copium/util/StateMachine.h

@@ -0,0 +1,84 @@
+#pragma once
+
+#include <functional>
+#include <map>
+
+namespace copium
+{
+  template <typename State, typename Trigger>
+  class StateMachine
+  {
+  public:
+    StateMachine(State initialState)
+      : currentState{initialState},
+        failOnInvalidTrigger{false}
+    {
+    }
+
+    StateMachine(State initialState, bool failOnInvalidTrigger)
+      : currentState{initialState},
+        failOnInvalidTrigger{failOnInvalidTrigger}
+    {
+    }
+
+    void AddTransition(State from, State to, Trigger trigger)
+    {
+      auto& map = transitionMap[from];
+      CP_ASSERT(
+        map.find(trigger) == map.end(), "Transition already exists for state {} using trigger {}", from, trigger);
+
+      map[trigger] = to;
+    }
+
+    void HandleTrigger(Trigger trigger)
+    {
+      auto& map = transitionMap[currentState];
+      auto it = map.find(trigger);
+      if (it == map.end())
+      {
+        CP_ASSERT(!failOnInvalidTrigger, "Trigger {} doesn't exist for state {}", trigger, currentState);
+        return;
+      }
+
+      CP_DEBUG("Transitioning from state {} to state {} due to trigger {}", currentState, it->second, trigger);
+      RunTrigger(leaveTriggers);
+      currentState = it->second;
+      RunTrigger(enterTriggers);
+    }
+
+    void AddEnterTrigger(State from, std::function<void()> func)
+    {
+      CP_ASSERT(enterTriggers.find(from) == enterTriggers.end(), "State {} already has an enter trigger", from);
+      enterTriggers[from] = func;
+    }
+
+    void AddLeaveTrigger(State from, std::function<void()> func)
+    {
+      CP_ASSERT(leaveTriggers.find(from) == leaveTriggers.end(), "State {} already has a leave trigger", from);
+      leaveTriggers[from] = func;
+    }
+
+    State GetCurrentState() const
+    {
+      return currentState;
+    }
+
+  private:
+    State currentState;
+    bool failOnInvalidTrigger;
+
+    std::map<State, std::map<Trigger, State>> transitionMap;
+
+    std::map<State, std::function<void()>> enterTriggers;
+    std::map<State, std::function<void()>> leaveTriggers;
+
+    void RunTrigger(const std::map<State, std::function<void()>>& triggers)
+    {
+      auto it = triggers.find(currentState);
+      if (it != triggers.end())
+      {
+        it->second();
+      }
+    }
+  };
+}