feat: fast forward

include/td/simulation/RealTimeSimulation.h

@@ -1,34 +1,61 @@
 #pragma once
 
 #include <td/game/World.h>
+#include <optional>
 
 namespace td {
 namespace sim {
 
 using GameHistory = std::vector<td::protocol::LockStep>;
+using GameBuffer = std::vector<std::optional<td::protocol::LockStep>>;
 
 class RealTimeSimulation {
   private:
 	std::uint64_t m_StepTime;
 	game::World& m_World;
-	GameHistory m_History;
+	GameBuffer m_History;
 	std::uint64_t m_CurrentTime;
 	std::uint64_t m_LastTime;
 	std::size_t m_CurrentStep;
 
+	std::shared_ptr<WorldSnapshot> m_LastSnapshot;
+	std::uint64_t m_LastValidStep;
+
+	static const protocol::LockStep EMPTY_LOCKSTEP;
+
   public:
 	/**
+	 * \brief Replay constructor
 	 * \param a_StepTime in ms
 	 */
-	RealTimeSimulation(game::World& a_World, GameHistory&& a_History, std::uint64_t a_StepTime);
+	RealTimeSimulation(game::World& a_World, const GameHistory& a_History, std::uint64_t a_StepTime);
+
+	/**
+	 * \brief Live update constructor (continuous game updates)
+	 * \param a_StepTime in ms
+	 */
+	RealTimeSimulation(game::World& a_World, std::uint64_t a_StepTime);
 
 	/**
 	 * \return the progress [0-1] between two steps
 	 */
 	float Update();
 
+	void HandlePacket(const protocol::packets::LockStepsPacket& a_LockSteps);
+	void HandlePacket(const protocol::packets::PredictCommandPacket& a_Predict);
+
   private:
 	void Step();
+
+	/**
+	 * \brief Ticks a_Count times
+	 */
+	void FastForward(std::size_t a_Count);
+
+	/**
+	 * \brief Tries to recompute simulation if needed (for example in late command receival)
+	 */
+	void FastReplay();
 };
 
 }  // namespace sim