////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2017 ArangoDB GmbH, Cologne, Germany
///
/// 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
///
///     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.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Manuel Baesler
////////////////////////////////////////////////////////////////////////////////

#include <date/date.h>
#include "Basics/datetime.h"
#include "Basics/NumberUtils.h"
#include "Logger/Logger.h"

#include <boost/algorithm/string.hpp>

#include <regex>
#include <vector>
  
namespace {
std::regex const iso8601Regex(
                          "(\\+|\\-)?\\d+(\\-\\d{1,2}(\\-\\d{1,2})?)?" // YY[YY]-MM-DD
                          "("
                          "("
                          // Time is optional
                            "(\\ |T)" // T or blank separates date and time
                            "\\d\\d\\:\\d\\d" // time: hh:mm
                            "(\\:\\d\\d(\\.\\d{1,3})?)?" // Optional: :ss.mmms
                            "("
                              "z|Z|" // trailing Z or start of timezone
                              "(\\+|\\-)" 
                              "\\d\\d\\:\\d\\d" // timezone hh:mm
                            ")?"
                          ")|"  
                          "(z|Z)" // Z
                          ")?"
                          );
    
/* REGEX GROUPS
12:34:56.789-12:34
submatch 0: '12:34:56.789-12:34'
submatch 1: '12'
submatch 2: '34'
submatch 3: ':56.789'
submatch 4: '56'
submatch 5: '.789'
submatch 6: '789'
submatch 7: '-12:34'
submatch 8: '-'
submatch 9: '12'
submatch 10: '34'
*/

std::regex const timeRegex(
    "(\\d\\d)\\:(\\d\\d)(\\:(\\d\\d)(\\.(\\d{1,3}))?)?((\\+|\\-)(\\d\\d)\\:"
    "(\\d\\d))?");
    
/* REGEX GROUPS
P1Y2M3W4DT5H6M7.891S
  submatch 0: P1Y2M3W4DT5H6M7.891S
  submatch 1: 1Y
  submatch 2: 1
  submatch 3: 2M
  submatch 4: 2
  submatch 5: 3W
  submatch 6: 3
  submatch 7: 4D
  submatch 8: 4
  submatch 9: T5H6M7.891S
  submatch 10: 5H
  submatch 11: 5
  submatch 12: 6M
  submatch 13: 6
  submatch 14: 7.891S
  submatch 15: 7
  submatch 16: .891
  submatch 17: 891
*/
std::regex const durationRegex("P((\\d+)Y)?((\\d+)M)?((\\d+)W)?((\\d+)D)?(T((\\d+)H)?((\\d+)M)?((\\d+)(\\.(\\d{1,3}))?S)?)?");

} // namespace


bool arangodb::basics::parse_dateTime(
    std::string const& dateTimeIn,
    tp_sys_clock_ms& date_tp) {
  using namespace date;
  using namespace std::chrono;

  std::string dateTime = dateTimeIn;
  std::string strDate, strTime;

  boost::algorithm::trim(dateTime);

  if (!std::regex_match(dateTime, ::iso8601Regex)) {
    LOG_TOPIC(DEBUG, arangodb::Logger::FIXME)
        << "regex failed for datetime '" << dateTime << "'";
    return false;
  }

  strDate = dateTime;

  if (strDate.back() == 'Z' || strDate.back() == 'z') {
    strDate.pop_back();
  }

  LOG_TOPIC(DEBUG, arangodb::Logger::FIXME)
      << "parse datetime '" << strDate << "'";

  if (strDate.find("T") != std::string::npos ||
      strDate.find(" ") != std::string::npos) {  // split into ymd / time
    std::vector<std::string> strs;
    boost::split(strs, strDate, boost::is_any_of("T "));

    strDate = strs[0];
    strTime = strs[1];
  }  // if

  // parse date component, moves pointer "p" forward
  // returns true if "p" pointed to a valid number, and false otherwise
  auto parseDateComponent = [](char const*& p, char const* e, int& result) -> bool {
    char const* s = p; // remember initial start
    if (p < e && *p == '-') {
      // skip over initial '-'
      ++p;
    }
    while (p < e && *p >= '0' && *p <= '9') {
      ++p;
    }
    if (p == s) {
      // did not find any valid character
      return false;
    }
    result = NumberUtils::atoi_unchecked<int>(s, p); 
    if (p < e && *p == '-') { 
      ++p; 
    }
    return true;
  };
  
  char const* p = strDate.data();
  char const* e = p + strDate.size();

  // month and day are optional, so they intentionally default to 1
  int parsedYear, parsedMonth = 1, parsedDay = 1; 
  
  // at least year must be valid
  if (!parseDateComponent(p, e, parsedYear)) {
    return false;
  }
  
  parseDateComponent(p, e, parsedMonth);
  parseDateComponent(p, e, parsedDay);

  if (parsedMonth < 1 || parsedMonth > 12 || parsedDay < 1 || parsedDay > 31) {
    // definitely invalid
    return false;
  }

  LOG_TOPIC(DEBUG, arangodb::Logger::FIXME)
      << "parsed YMD " << parsedYear << " " << parsedMonth << " " << parsedDay;

  date_tp = sys_days(year{parsedYear} / parsedMonth / parsedDay);

  // parse Time HH:MM:SS(.SSS)((+|-)HH:MM)
  if (1 < strTime.size()) {
    std::smatch time_parts;

    if (!std::regex_match(strTime, time_parts, ::timeRegex)) {
      LOG_TOPIC(DEBUG, arangodb::Logger::FIXME)
          << "regex failed for time " << strTime;
      return false;
    }

    // hour
    hours parsedHours{atoi(time_parts[1].str().c_str())};

    if (hours{23} < parsedHours) {
      return false;
    }
    date_tp += parsedHours;

    // minute
    minutes parsedMinutes{atoi(time_parts[2].str().c_str())};

    if (minutes{59} < parsedMinutes) {
      return false;
    }
    date_tp += parsedMinutes;

    // seconds
    seconds parsedSeconds{atoi(time_parts[4].str().c_str())};

    if (seconds{59} < parsedSeconds) {
      return false;
    }
    date_tp += parsedSeconds;

    // milliseconds .9 -> 900ms
    date_tp +=
        milliseconds{atoi((time_parts[6].str() + "00").substr(0, 3).c_str())};

    // time offset
    if (time_parts[8].str().size()) {
      hours parsedHours{atoi(time_parts[9].str().c_str())};  // hours

      if (hours{23} < parsedHours) {
        return false;
      }
      minutes offset = parsedHours;

      minutes parsedMinutes{atoi(time_parts[10].str().c_str())};  // minutes

      if (minutes{59} < parsedMinutes) {
        return false;
      }
      offset += parsedMinutes;

      if (time_parts[8].str() == "-") {
        offset *= -1;
      }
      date_tp -= offset;
    }
  }  // if

  return true;
}

bool arangodb::basics::regex_isoDuration(std::string const& isoDuration, std::smatch& durationParts) {
  if (isoDuration.length() <= 1) {
    return false;
  }

  if (!std::regex_match(isoDuration, durationParts, ::durationRegex)) {
    return false;
  }

  return true;
}