# Copyright 2020 Florida State University, Center for Ocean-Atmospheric Prediction Studies

# Permission is hereby granted, free of charge, to any person obtaining a copy 
# of this software and associated documentation files (the "Software"), to deal 
# in the Software without restriction, including without limitation the rights 
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
# copies of the Software, and to permit persons to whom the Software is 
# furnished to do so, subject to the following conditions:

# The above copyright notice and this permission notice shall be included in 
# all copies or substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
# SOFTWARE.
package CoapsTime;
use strict;
use integer;
use DateTime;

use Exporter qw(import);

our @EXPORT = qw(invtime convtime);

sub invtime {
   # This subroutine takes a timestamp representing the minutes from 
   # 1-1-1980 00:00 and converts it to strings with the human readable time.
   #
   # The return value has two parts: (YYYYMMDD, HHMM)
   #
   # Example:
   #     my ($yyyymmdd, $hhmm) = invtime(9411643);
   #
   #     print "$yyyymmdd $hhmm\n";
   # 
   # The above example prints "19971122 2043" 

   my $samos_epoch = $_[0];
   my $logfilepath = $_[1];

   # redirect standard error to a log file if given
   if ($logfilepath ne "") {
      *OLD_STDERR = *STDERR;
      open my $logfile, '>', $logfilepath;
      *STDERR = $logfile;
   }

   my $start = DateTime->new(
      year => 1980,
      month => 1,
      day => 1,
   )->epoch();

   my $unix_epoch = $samos_epoch*60 + $start;

   my $datetime = DateTime->from_epoch( epoch => $unix_epoch );

   my $date = $datetime->ymd('');
   my $time = $datetime->hms('');

   # restore standard error
   if ($logfilepath ne "") {
      *STDERR = *OLD_STDERR;
   }

   return ($date, $time);
}

sub convtime {
   # this subroutine takes five parameters and
   # returns an integer which is the number of minutes from 1-1-1980 00:00
   #
   # In particular, this subroutine will convert a given year, month, day, hour,
   # and minute to a minutes from 1-1-1980 00:00 time stamp.

   # for example:
   #  print "dfdfdf ",convtime(1980, 1, 1, 0, 0)," dfdfdfd\n";
   #
   #  within a Perl script should cause the line:
   #
   #  dfdfdf 0 dfdfdfd
   #
   #  to be written out to default output.
   #
   # print "dfdfdfdf ", convtime(2019, 12, 13, 0,  0), "\n";
   #
   # yields
   #
   # dfdfdfdf 21011040
   #
   #  print "dfdfdfdf ", convtime(2019, 2, 29, 0,  0), "\n";
   #
   #  yields
   #
   #  ERROR ---- Feb. day out of range (1-28) at ConvTime.pl line 111.

   # Originally written by Shawn Smith (smith@coaps.fsu.edu) in FORTRAN
   # Updated Spring 1999 for Y2K compliance by Anthony Arguez
   # (anthony@coaps.fsu.edu).
   #
   # Perl version created by James Lamm (lamm@coaps.fsu.edu)
   #
   # work with integer math rather than (the default) floating point

   my $year = @_[0];
   my $month = @_[1];
   my $day = @_[2];
   my $hour = @_[3];
   my $minute = @_[4];
   my $logfilepath = @_[5];

   # redirect standard error to a log file if given
   if ($logfilepath ne "") {
      *OLD_STDERR = *STDERR;
      open my $logfile, '>', $logfilepath;
      *STDERR = $logfile;
   }

   # get the unix epoch times for our start date and input dates
   my $start = DateTime->new(
      year => 1980,
      month => 1,
      day => 1,
      hour => 0,
      minute => 0
   )->epoch();

   my $input = DateTime->new(
      year => $year,
      month => $month,
      day => $day,
      hour => $hour,
      minute => $minute
   )->epoch();

   # convert the times to minutes
   # note that since the resolution of our input time is only to the minute,
   # the difference will always be a multiple of 60, so we don't need to
   # worry about rounding
   my $diff = ($input - $start)/60;

   if ($diff lt 0) {
      print STDERR "convtime: Date given is before 1980: $year-$month-$day $hour:$minute:00";
      # restore standard error
      if ($logfilepath ne "") {
         *STDERR = *OLD_STDERR;
      }
      exit(1);
   }

   # restore standard error
   if ($logfilepath ne "") {
      *STDERR = *OLD_STDERR;
   }

   return $diff;
}