/*
 * Copyright (C) 2014 Cloudius Systems, Ltd.
 */

#ifndef DB_CLOCK_HH_
#define DB_CLOCK_HH_

#include <chrono>
#include <cstdint>
#include "gc_clock.hh"

// the database clock follows Java - 1ms granularity, 64-bit counter, 1970 epoch

class db_clock {
public:
    using base = std::chrono::system_clock;
    using rep = int64_t;
    using period = std::ratio<1, 1000>; // milliseconds
    using duration = std::chrono::duration<rep, period>;
    using time_point = std::chrono::time_point<db_clock, duration>;

    static constexpr bool is_steady = base::is_steady;
    static std::time_t to_time_t(time_point t) {
        return std::chrono::duration_cast<std::chrono::seconds>(t.time_since_epoch()).count();
    }
    static time_point from_time_t(std::time_t t) {
        return time_point(std::chrono::duration_cast<duration>(std::chrono::seconds(t)));
    }
    static time_point now() {
        auto now_since_epoch = base::now() - base::from_time_t(0);
        return time_point(std::chrono::duration_cast<duration>(now_since_epoch)) + get_clocks_offset();
    }
    static uint64_t now_in_usecs() {
        return now().time_since_epoch().count() * 1000;
    }
};

static inline
gc_clock::time_point to_gc_clock(db_clock::time_point tp) {
    static_assert(std::is_same<db_clock::base, gc_clock::base>::value, "Below we assume that base is the same");
    return gc_clock::time_point(std::chrono::duration_cast<gc_clock::duration>(tp.time_since_epoch()));
}

#endif /* DB_CLOCK_HH_ */