#! /usr/bin/env perl
use warnings;
use strict;

# for each filename on the command line
# get the modtime
# make a backup of the file
# - error if there is already a backup?
# flush the  live version(?)
# start a line-by-line copy of the backup to the new file,
# doing the BeginDate/EndDate substitution

# <!-- #BeginDate format:En1m -->3-oct-11  18:20<!-- #EndDate -->
# <!-- #BeginDate format:En2m -->01-Aug-2011  17:56<!-- #EndDate -->
# without the 'm' no minutes are included.

my $i;
my $mod_time;
my $stamp;
my @m_abbr = qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec);

foreach ( @ARGV ) {
    $i = $_;
    $mod_time = (stat ($i))[9];
    $stamp = localtime($mod_time);
    my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
                                                localtime($mod_time);
    $year += 1900;

    # print "<$i> at <$stamp>\n";

    open(my $IFILE, "<", $i) or die "Cannot open < $i: $!";
    open(my $OFILE, ">", $i.".new") or die "Cannot open > $i.new: $!";
    while(<$IFILE>) {
	if (/(.*<!--\s*#BeginDate\s*format:)(\S*)(\s*-->).*(<!--\s*#EndDate\s*-->.*)/) {
	    # print "Got: $_";
	    # print "as: <$1><$2><$3>...<$4>\n";
	    print { $OFILE } $1,$2,$3;
	    printf { $OFILE } "%s-%s-%s  %02d:%02d", $mday,$m_abbr[$mon],$year,$hour,$min;
	    print { $OFILE } $4,"\n";
	}
	else {
	    print { $OFILE } $_;
	}
    }
    close($IFILE);
    close($OFILE);
    #
    utime(time, $mod_time, "$i.new") || die "touch $i.new failed: $!";
    #
    rename $i,"$i.old" || die "rename $i,$i.old failed: $!";
    rename "$i.new",$i || die "rename $i.new,$i failed: $!";
}