// Copyright 2017 The Abseil Authors.

//

// Licensed 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

//

//      https://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 <string.h>

#include <cctype>

#include <cstdint>

#include "absl/strings/match.h"

#include "absl/strings/string_view.h"

#include "absl/time/internal/cctz/include/cctz/time_zone.h"

#include "absl/time/time.h"

namespace cctz = absl::time_internal::cctz;

namespace absl {

ABSL_NAMESPACE_BEGIN

ABSL_DLL extern const char RFC3339_full[] = "%Y-%m-%d%ET%H:%M:%E*S%Ez";

ABSL_DLL extern const char RFC3339_sec[] = "%Y-%m-%d%ET%H:%M:%S%Ez";

ABSL_DLL extern const char RFC1123_full[] = "%a, %d %b %E4Y %H:%M:%S %z";

ABSL_DLL extern const char RFC1123_no_wday[] = "%d %b %E4Y %H:%M:%S %z";

namespace {

const char kInfiniteFutureStr[] = "infinite-future";

const char kInfinitePastStr[] = "infinite-past";

struct cctz_parts {

  cctz::time_point<cctz::seconds> sec;

  cctz::detail::femtoseconds fem;

};

inline cctz::time_point<cctz::seconds> unix_epoch() {

  return std::chrono::time_point_cast<cctz::seconds>(

      std::chrono::system_clock::from_time_t(0));

}

// Splits a Time into seconds and femtoseconds, which can be used with CCTZ.

// Requires that 't' is finite. See duration.cc for details about rep_hi and

// rep_lo.

cctz_parts Split(absl::Time t) {

  const auto d = time_internal::ToUnixDuration(t);

  const int64_t rep_hi = time_internal::GetRepHi(d);

  const int64_t rep_lo = time_internal::GetRepLo(d);

  const auto sec = unix_epoch() + cctz::seconds(rep_hi);

  const auto fem = cctz::detail::femtoseconds(rep_lo * (1000 * 1000 / 4));

  return {sec, fem};

}

// Joins the given seconds and femtoseconds into a Time. See duration.cc for

// details about rep_hi and rep_lo.

absl::Time Join(const cctz_parts& parts) {

  const int64_t rep_hi = (parts.sec - unix_epoch()).count();

  const uint32_t rep_lo =

      static_cast<uint32_t>(parts.fem.count() / (1000 * 1000 / 4));

  const auto d = time_internal::MakeDuration(rep_hi, rep_lo);

  return time_internal::FromUnixDuration(d);

}

}  // namespace

std::string FormatTime(absl::string_view format, absl::Time t,

                       absl::TimeZone tz) {

  if (t == absl::InfiniteFuture()) return std::string(kInfiniteFutureStr);

  if (t == absl::InfinitePast()) return std::string(kInfinitePastStr);

  const auto parts = Split(t);

  return cctz::detail::format(std::string(format), parts.sec, parts.fem,

                              cctz::time_zone(tz));

}

std::string FormatTime(absl::Time t, absl::TimeZone tz) {

  return FormatTime(RFC3339_full, t, tz);

}

std::string FormatTime(absl::Time t) {

  return absl::FormatTime(RFC3339_full, t, absl::LocalTimeZone());

}

bool ParseTime(absl::string_view format, absl::string_view input,

               absl::Time* time, std::string* err) {

  return absl::ParseTime(format, input, absl::UTCTimeZone(), time, err);

}

// If the input string does not contain an explicit UTC offset, interpret

// the fields with respect to the given TimeZone.

bool ParseTime(absl::string_view format, absl::string_view input,

               absl::TimeZone tz, absl::Time* time, std::string* err) {

  auto strip_leading_space = [](absl::string_view* sv) {

    while (!sv->empty()) {

      if (!std::isspace(sv->front())) return;

      sv->remove_prefix(1);

    }

  };

  // Portable toolchains means we don't get nice constexpr here.

  struct Literal {

    const char* name;

    size_t size;

    absl::Time value;

  };

  static Literal literals[] = {

      {kInfiniteFutureStr, strlen(kInfiniteFutureStr), InfiniteFuture()},

      {kInfinitePastStr, strlen(kInfinitePastStr), InfinitePast()},

  };

  strip_leading_space(&input);

  for (const auto& lit : literals) {

    if (absl::StartsWith(input, absl::string_view(lit.name, lit.size))) {

      absl::string_view tail = input;

      tail.remove_prefix(lit.size);

      strip_leading_space(&tail);

      if (tail.empty()) {

        *time = lit.value;

        return true;

      }

    }

  }

  std::string error;

  cctz_parts parts;

  const bool b =

      cctz::detail::parse(std::string(format), std::string(input),

                          cctz::time_zone(tz), &parts.sec, &parts.fem, &error);

  if (b) {

    *time = Join(parts);

  } else if (err != nullptr) {

    *err = error;

  }

  return b;

}

// Functions required to support absl::Time flags.

bool AbslParseFlag(absl::string_view text, absl::Time* t, std::string* error) {

  return absl::ParseTime(RFC3339_full, text, absl::UTCTimeZone(), t, error);

}

std::string AbslUnparseFlag(absl::Time t) {

  return absl::FormatTime(RFC3339_full, t, absl::UTCTimeZone());

}

bool ParseFlag(const std::string& text, absl::Time* t, std::string* error) {

  return absl::ParseTime(RFC3339_full, text, absl::UTCTimeZone(), t, error);

}

std::string UnparseFlag(absl::Time t) {

  return absl::FormatTime(RFC3339_full, t, absl::UTCTimeZone());

}

ABSL_NAMESPACE_END

}  // namespace absl