/* Copyright (c) 2014-2015, Stanislaw Halik <sthalik@misaki.pl>

 * Permission to use, copy, modify, and/or distribute this
 * software for any purpose with or without fee is hereby granted,
 * provided that the above copyright notice and this permission
 * notice appear in all copies.
 */

#pragma once
#include <ctime>

#if defined (_WIN32)
#   include <windows.h>
#elif defined(__MACH__)
#   include <inttypes.h>
#   include <mach/mach_time.h>
#endif

class Timer
{
private:
    struct timespec state;
    long long conv_nsecs(const struct timespec& cur) const
    {
        return (cur.tv_sec - state.tv_sec) * 1000000000LL + (cur.tv_nsec - state.tv_nsec);
    }
    long conv_usecs(const struct timespec& cur) const
    {
        return (cur.tv_sec - state.tv_sec) * 1000000LL + (cur.tv_nsec - state.tv_nsec) / 1000;
    }
#ifdef _WIN32
    static LARGE_INTEGER otr_get_clock_frequency()
    {
        LARGE_INTEGER freq = {};
        (void) QueryPerformanceFrequency(&freq);
        return freq;
    }
    static void otr_clock_gettime(struct timespec* ts)
    {
        static LARGE_INTEGER freq = otr_get_clock_frequency();

        LARGE_INTEGER d;

        (void) QueryPerformanceCounter(&d);

        using ll = long long;
        using ld = long double;
        const long long part = ll(d.QuadPart / ld(freq.QuadPart) * 1000000000.L);
        using t_s = decltype(ts->tv_sec);
        using t_ns = decltype(ts->tv_nsec);

        ts->tv_sec = t_s(part / 1000000000LL);
        ts->tv_nsec = t_ns(part % 1000000000LL);
    }
#elif defined(__MACH__)
    static mach_timebase_info_data_t otr_get_mach_frequency()
    {
        mach_timebase_info_data_t timebase_info;
        (void) mach_timebase_info(&timebase_info);
        return timebase_info;
    }
    static void otr_clock_gettime(struct timespec* ts)
    {
        static mach_timebase_info_data_t timebase_info = otr_get_mach_frequency();
        uint64_t state, nsec;
        state = mach_absolute_time();
        nsec = state * timebase_info.numer / timebase_info.denom;
        ts->tv_sec = nsec / 1000000000L;
        ts->tv_nsec = nsec % 1000000000L;
    }
#endif

public:
    Timer()
    {
        start();
    }
    static inline void wrap_gettime(struct timespec* state)
    {
#if defined(_WIN32) || defined(__MACH__)
        otr_clock_gettime(state);
#else
        (void) clock_gettime(CLOCK_MONOTONIC, state);
#endif
    }

    void start()
    {
        wrap_gettime(&state);
    }
    long long elapsed_nsecs() const
    {
        struct timespec cur = {};
        wrap_gettime(&cur);
        return conv_nsecs(cur);
    }
    long elapsed_usecs() const
    {
        struct timespec cur = {};
        wrap_gettime(&cur);
        return long(conv_usecs(cur));
    }
    long elapsed_ms() const
    {
        return elapsed_usecs() / 1000L;
    }
    double elapsed_seconds() const
    {
        return double(elapsed_nsecs() * 1e-9L);
    }
};