//========= Copyright Valve Corporation, All rights reserved. ============//
//
// Purpose:
//
//=============================================================================//

#ifndef APPARENT_VELOCITY_HELPER_H
#define APPARENT_VELOCITY_HELPER_H
#ifdef _WIN32
#pragma once
#endif

inline float CalcDistance(float x, float y) { return x - y; }

inline float CalcDistance(const Vector &a, const Vector &b) {
    return a.DistTo(b);
}

template <class T>
class CDefaultCalcDistance {
   public:
    static inline float CalcDistance(const T &a, const T &b) {
        return ::CalcDistance(a, b);
    }
};

class CCalcDistance2D {
   public:
    static inline float CalcDistance(const Vector &a, const Vector &b) {
        return (a - b).Length2D();
    }
};

template <class T, class Functor = CDefaultCalcDistance<T> >
class CApparentVelocity {
   public:
    CApparentVelocity(const T &t0) {
        m_LastTime = -1;
        m_LastValue = t0;
    }

    float AddSample(float time, T value) {
        float flRet = 0;
        if (m_LastTime != -1) {
            flRet =
                Functor::CalcDistance(value, m_LastValue) / (time - m_LastTime);
        }

        m_LastTime = time;
        m_LastValue = value;

        return flRet;
    }

   private:
    T m_LastValue;
    float m_LastTime;
};

#endif  // APPARENT_VELOCITY_HELPER_H