/*
 *  Copyright 2005 The WebRTC Project Authors. All rights reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#ifndef RTC_BASE_TIMEUTILS_H_
#define RTC_BASE_TIMEUTILS_H_

#include <stdint.h>
#include <string>
#include <time.h>

#include "rtc_base/checks.h"
#include "rtc_base/strings/string_builder.h"

namespace rtc
{

static const int64_t kNumMillisecsPerSec = INT64_C(1000);
static const int64_t kNumMicrosecsPerSec = INT64_C(1000000);
static const int64_t kNumNanosecsPerSec = INT64_C(1000000000);

static const int64_t kNumMicrosecsPerMillisec = kNumMicrosecsPerSec / kNumMillisecsPerSec;
static const int64_t kNumNanosecsPerMillisec = kNumNanosecsPerSec / kNumMillisecsPerSec;
static const int64_t kNumNanosecsPerMicrosec = kNumNanosecsPerSec / kNumMicrosecsPerSec;

// TODO(honghaiz): Define a type for the time value specifically.

class ClockInterface
{
public:
    virtual ~ClockInterface() {}
    virtual int64_t TimeNanos() const = 0;
};

// Sets the global source of time. This is useful mainly for unit tests.
//
// Returns the previously set ClockInterface, or nullptr if none is set.
//
// Does not transfer ownership of the clock. SetClockForTesting(nullptr)
// should be called before the ClockInterface is deleted.
//
// This method is not thread-safe; it should only be used when no other thread
// is running (for example, at the start/end of a unit test, or start/end of
// main()).
//
// TODO(deadbeef): Instead of having functions that access this global
// ClockInterface, we may want to pass the ClockInterface into everything
// that uses it, eliminating the need for a global variable and this function.
ClockInterface* SetClockForTesting(ClockInterface* clock);

// Returns previously set clock, or nullptr if no custom clock is being used.
ClockInterface* GetClockForTesting();

// Returns the actual system time, even if a clock is set for testing.
// Useful for timeouts while using a test clock, or for logging.
int64_t SystemTimeNanos();
int64_t SystemTimeMillis();

// Returns the current time in milliseconds in 32 bits.
uint32_t Time32();

// Returns the current time in milliseconds in 64 bits.
int64_t TimeMillis();
// Deprecated. Do not use this in any new code.
inline int64_t Time()
{
    return TimeMillis();
}

// Returns the current time in microseconds.
int64_t TimeMicros();

// Returns the current time in nanoseconds.
int64_t TimeNanos();

// Returns a future timestamp, 'elapsed' milliseconds from now.
int64_t TimeAfter(int64_t elapsed);

// Number of milliseconds that would elapse between 'earlier' and 'later'
// timestamps.  The value is negative if 'later' occurs before 'earlier'.
int64_t TimeDiff(int64_t later, int64_t earlier);
int32_t TimeDiff32(uint32_t later, uint32_t earlier);

// The number of milliseconds that have elapsed since 'earlier'.
inline int64_t TimeSince(int64_t earlier)
{
    return TimeMillis() - earlier;
}

// The number of milliseconds that will elapse between now and 'later'.
inline int64_t TimeUntil(int64_t later)
{
    return later - TimeMillis();
}

class TimestampWrapAroundHandler
{
public:
    TimestampWrapAroundHandler();

    int64_t Unwrap(uint32_t ts);

private:
    uint32_t last_ts_;
    int64_t num_wrap_;
};

// Convert from tm, which is relative to 1900-01-01 00:00 to number of
// seconds from 1970-01-01 00:00 ("epoch"). Don't return time_t since that
// is still 32 bits on many systems.
int64_t TmToSeconds(const tm& tm);

// Return the number of microseconds since January 1, 1970, UTC.
// Useful mainly when producing logs to be correlated with other
// devices, and when the devices in question all have properly
// synchronized clocks.
//
// Note that this function obeys the system's idea about what the time
// is. It is not guaranteed to be monotonic; it will jump in case the
// system time is changed, e.g., by some other process calling
// settimeofday. Always use rtc::TimeMicros(), not this function, for
// measuring time intervals and timeouts.
int64_t TimeUTCMicros();

// Return the number of milliseconds since January 1, 1970, UTC.
// See above.
int64_t TimeUTCMillis();

// Interval of time from the range [min, max] inclusive.
class IntervalRange
{
public:
    IntervalRange()
        : min_(0)
        , max_(0)
    {
    }
    IntervalRange(int min, int max)
        : min_(min)
        , max_(max)
    {
        RTC_DCHECK_LE(min, max);
    }

    int min() const { return min_; }
    int max() const { return max_; }

    std::string ToString() const
    {
        rtc::StringBuilder ss;
        ss << "[" << min_ << "," << max_ << "]";
        return ss.Release();
    }

    bool operator==(const IntervalRange& o) const
    {
        return min_ == o.min_ && max_ == o.max_;
    }

    bool operator!=(const IntervalRange& o) const { return !operator==(o); }

private:
    int min_;
    int max_;
};

} // namespace rtc

#endif // RTC_BASE_TIMEUTILS_H_