// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

#include <chrono>
#include <thread>
#include <iomanip>
#include <sstream>
#include <cstdlib>

#include "exprs/timezone_db.h"
#include "util/time.h"

using namespace impala;
using namespace std;

void impala::SleepForMs(const int64_t duration_ms) {
  this_thread::sleep_for(chrono::milliseconds(duration_ms));
}

static inline time_t GetSecond(const chrono::system_clock::time_point& t) {
  return chrono::system_clock::to_time_t(t);
}

static inline int64_t GetSubSecond(const chrono::system_clock::time_point& t,
    TimePrecision p) {
  auto frac = t.time_since_epoch();
  if (p == TimePrecision::Millisecond) {
    auto subsec = chrono::duration_cast<chrono::milliseconds>(frac) % MILLIS_PER_SEC;
    return subsec.count();
  } else if (p == TimePrecision::Microsecond) {
    auto subsec = chrono::duration_cast<chrono::microseconds>(frac) % MICROS_PER_SEC;
    return subsec.count();
  } else if (p == TimePrecision::Nanosecond) {
    auto subsec = chrono::duration_cast<chrono::nanoseconds>(frac) % NANOS_PER_SEC;
    return subsec.count();
  } else {
    return 0;
  }
}

// Convert the given 'second' unix timestamp, into a date-time string in the
// UTC time zone if 'utc' is true, or the local time zone if it is false.
// The returned string is of the form yyy-MM-dd HH::mm::SS.
// Note that for time points before the Unix epoch, 'subsecond' might have a negative
// value. In this case 'second' has to be adjusted.
static string FormatSecond(time_t second, int64_t subsecond, bool utc) {
  char buf[256];
  struct tm tmp;
  auto input_time = (subsecond < 0) ? second - 1 : second;

  // gcc 4.9 does not support C++14 get_time and put_time functions, so we're
  // stuck with strftime() for now.
  if (utc) {
    strftime(buf, sizeof(buf), "%F %T", gmtime_r(&input_time, &tmp));
  } else {
    strftime(buf, sizeof(buf), "%F %T", localtime_r(&input_time, &tmp));
  }
  return string(buf);
}

// Format the sub-second part of a time point, at the precision specified by 'p'. The
// returned string is meant to be appended to the string returned by FormatSecond()
// above. Note that for time points before the Unix epoch 'subsecond' might have a
// negative value. In this case 'subsecond' has to be adjusted based on the precision.
static string FormatSubSecond(int64_t subsecond, TimePrecision p) {
  stringstream ss;
  if (p == TimePrecision::Millisecond) {
    if (subsecond < 0) subsecond = 1000 + subsecond;
    ss << "." << std::setfill('0') << std::setw(3) << subsecond;
  } else if (p == TimePrecision::Microsecond) {
    if (subsecond < 0) subsecond = 1000000 + subsecond;
    ss << "." << std::setfill('0') << std::setw(6) << subsecond;
  } else if (p == TimePrecision::Nanosecond) {
    if (subsecond < 0) subsecond = 1000000000 + subsecond;
    ss << "." << std::setfill('0') << std::setw(9) << subsecond;
  } else {
    // 1-second precision or unknown unit. Return empty string.
    DCHECK_EQ(TimePrecision::Second, p);
    ss << "";
  }
  return ss.str();
}

// Convert time point 't' into date-time string at precision 'p'.
// Output string is in UTC time zone if 'utc' is true, else it is in the
// local time zone.
static string ToString(const chrono::system_clock::time_point& t, TimePrecision p,
    bool utc) {
  stringstream ss;
  time_t second = GetSecond(t);
  int64_t subsecond = GetSubSecond(t, p);
  ss << FormatSecond(second, subsecond, utc);
  ss << FormatSubSecond(subsecond, p);
  return ss.str();
}

// Convenience function to convert Unix time, specified as seconds since
// the Unix epoch, into a C++ time_point object.
static chrono::system_clock::time_point TimepointFromUnix(int64_t s) {
  return chrono::system_clock::time_point(chrono::seconds(s));
}

// Convenience function to convert Unix time, specified as milliseconds since
// the Unix epoch, into a C++ time_point object.
static chrono::system_clock::time_point TimepointFromUnixMillis(int64_t ms) {
  return chrono::system_clock::time_point(chrono::milliseconds(ms));
}

// Convenience function to convert Unix time, specified as microseconds since
// the Unix epoch, into a C++ time_point object.
static chrono::system_clock::time_point TimepointFromUnixMicros(int64_t us) {
  return chrono::system_clock::time_point(chrono::microseconds(us));
}

string impala::ToStringFromUnix(int64_t s, TimePrecision p) {
  chrono::system_clock::time_point t = TimepointFromUnix(s);
  return ToString(t, p, false);
}

string impala::ToUtcStringFromUnix(int64_t s, TimePrecision p) {
  chrono::system_clock::time_point t = TimepointFromUnix(s);
  return ToString(t, p, true);
}

string impala::ToStringFromUnixMillis(int64_t ms, TimePrecision p) {
  chrono::system_clock::time_point t = TimepointFromUnixMillis(ms);
  return ToString(t, p, false);
}

string impala::ToUtcStringFromUnixMillis(int64_t ms, TimePrecision p) {
  chrono::system_clock::time_point t = TimepointFromUnixMillis(ms);
  return ToString(t, p, true);
}

string impala::ToStringFromUnixMicros(int64_t us, TimePrecision p) {
  chrono::system_clock::time_point t = TimepointFromUnixMicros(us);
  return ToString(t, p, false);
}

string impala::ToUtcStringFromUnixMicros(int64_t us, TimePrecision p) {
  chrono::system_clock::time_point t = TimepointFromUnixMicros(us);
  return ToString(t, p, true);
}

string impala::ToStringFromUnixMicros(int64_t us, const Timezone& tz,
    TimePrecision p) {
  chrono::system_clock::time_point t = TimepointFromUnixMicros(us);
  const char* fmt;
  switch (p) {
    case TimePrecision::Millisecond:
      fmt = "%Y-%m-%d %H:%M:%E3S";
      break;
    case TimePrecision::Microsecond:
      fmt = "%Y-%m-%d %H:%M:%E6S";
      break;
    case TimePrecision::Nanosecond:
      fmt = "%Y-%m-%d %H:%M:%E9S";
      break;
    default:
      fmt = "%Y-%m-%d %H:%M:%S";
  }
  return cctz::format(fmt, t, tz);
}