#!/usr/bin/perl

## This script converts a date string to the corresponding time for a
## given netcdf file by using the NCL function ut_inv_calendar.

$usage = "Usage: date2time netcdf-file yyyy-mm-dd [hh:mm]\n";    


if (@ARGV < 2 or @ARGV > 3) {
    die $usage;
}

$file = $ARGV[0];

($year, $month, $day) = split /[-\/]/, $ARGV[1];

($hour, $minute, $second) = split /\:/, $ARGV[2];

$hour += 0;
$minute += 0;
$second += 0;

# Check for numeric validity

if ($year !~ /\d{4}/            or
    $month  < 0 or $month  > 12 or 
    $day    < 0 or $day    > 31 or
    $hour   < 0 or $hour   > 24 or
    $minute < 0 or $minute > 60 or
    $second < 0 or $second > 60){
    die "Invalid date specification: $year/$month/$day $hour:$minute:$second (should be YYYY/MM/DD [hh:mm:ss])\n";
}


$units = `ncdump -h $file | grep time:units | cut -f 2 -d \\\"`;
unless ($units) {die "No units found in netcdf file $file.\n";}

$calendar = `ncdump -h $file | grep time:calendar | cut -f 2 -d \\\"`;
unless ($calendar) {die "No calendar found in netcdf file $file.\n";}

chomp $units;
chomp $calendar;

$tempfile = ".date2time.$$";

open(NCL, ">$tempfile");


$nclscript = <<END;
c = 0
c\@calendar = \"$calendar\"
date = cd_inv_calendar($year,$month,$day,$hour,$minute,$second,\"$units\",c)
print(sprintf("%.4f",date))
END

    print NCL "$nclscript";

close(NCL);

$result = `ncl -n -Q $tempfile`;
print "$result";

`rm $tempfile`;

# Copyright 2010-2012 Univ. Corp. for Atmos. Research
# Author: Seth McGinnis, mcginnis@ucar.edu