#pragma once

#include <td/game/World.h>
#include <optional>
#include <td/misc/Signal.h>

namespace td {
namespace sim {

using GameHistory = std::vector<td::protocol::LockStep>;
using GameBuffer = std::vector<std::optional<td::protocol::LockStep>>;

// TODO: OnEnd signal
class ClientSimulation : public protocol::PacketHandler {
  private:
	std::uint64_t m_StepTime;
	game::World& m_World;
	GameBuffer m_History;
	float m_CurrentTime;
	StepTime m_CurrentStep;

	std::shared_ptr<WorldSnapshot> m_LastSnapshot;
	StepTime m_LastValidStep;

	static const protocol::LockStep EMPTY_LOCKSTEP;

	using protocol::PacketHandler::Handle;

  public:
	utils::Signal<const std::vector<StepTime>&> OnMissingLockSteps;

	/**
	 * \brief Replay constructor
	 * \param a_StepTime in ms
	 */
	ClientSimulation(game::World& a_World, GameHistory&& a_History, std::uint64_t a_StepTime);

	/**
	 * \brief Live update constructor (continuous game updates)
	 * \param a_StepTime in ms
	 */
	ClientSimulation(game::World& a_World, std::uint64_t a_StepTime);

	/**
	 * \return the progress [0-1] between two steps
	 */
	float Update(float a_Delta);

	virtual void Handle(const protocol::packets::LockStepsPacket& a_LockSteps) override;
	virtual void Handle(const protocol::packets::LockStepResponsePacket& a_LockSteps) override;

  private:
	/**
	 * \returns false if the empty lockstep was used
	 */
	bool Step();

	/**
	 * \brief Ticks a_Count times
	 */
	std::size_t FastForward(std::size_t a_Count);

	/**
	 * \brief Tries to recompute simulation if needed (for example in late command receival)
	 */
	void FastReplay();
};

}  // namespace sim
}  // namespace td