#!/usr/bin/perl -w
 
use strict;
use warnings;
 
require_module('DateTime');
 
# Format classes to use for display
my @formats = qw( DateParse MySQL HTTP Mail RSS );
 
# Check for availability of format classes
my @available;
FORMAT_CLASS:
foreach my $format (@formats) {
  my $class = "DateTime::Format::$format";
 
  next FORMAT_CLASS unless optional_module($class);  
  
  push @available, {
    name       => $format,
    class      => $class,
    can_parse  => $class->can('parse_datetime'),
    can_format => $class->can('format_datetime'),
  };
}
 
# read dates
while (my $t = <>) {
  chomp($t);
  my $dt;
 
  if ($t =~ /^\d+$/) {
    $dt = DateTime->from_epoch( epoch => $t );
  }
  elsif ($t =~ /^(\d\d\d\d)[-\/](\d+)[-\/](\d+)$/) {
    $dt = DateTime->new(
        year  => $1,
        month => $2,
        day   => $3,
    );
  }
  elsif ($t =~ /^(\d+)[-\/](\d+)[-\/](\d\d\d\d)$/) {
    $dt = DateTime->new(
        year  => $3,
        month => $2,
        day   => $1,
    );
  }
  elsif ($t =~ /^(\d\d\d\d)[-\/](\d+)[-\/](\d+) (\d+):(\d+):(\d+)$/) {
    $dt = DateTime->new(
        year   => $1,
        month  => $2,
        day    => $3,
        hour   => $4,
        minute => $5,
        second => $6,
    );
  }
  elsif ($t =~ /^(\d+)[-\/](\d+)[-\/](\d\d\d\d) (\d+):(\d+):(\d+)$/) {
    $dt = DateTime->new(
        year   => $3,
        month  => $2,
        day    => $1,
        hour   => $4,
        minute => $5,
        second => $6,
    );
  }
  elsif ($t =~ /^(\d+):(\d+):(\d+)$/) {
    $dt = DateTime->new(
        hour   => $1,
        minute => $2,
        second => $3,
    );
  }
  else {
    foreach my $helper (@available) {
      next unless $helper->{can_parse};
      eval { $dt = $helper->{class}->parse_datetime($t) };
      last if $dt;
    }
  }
 
  if ($dt) {
    print "    $t -- $dt ", $dt->epoch, " (hex ", sprintf('%0.4x', $dt->epoch) ,")\n";
    foreach my $helper (@available) {
      next unless $helper->{can_format};
      print "    $t -- format $helper->{name} is: ", $helper->{class}->format_datetime($dt), "\n";
    }
  }
  else {
    print "   $t -- could not parse this\n"
  }
}
 
 
#####################################
# Deal with required/optional modules
 
sub require_module {
  my $module = shift;
  
  eval "require $module";
  if (my $e = $@) {
    print STDERR "FATAL: $0 requires the Perl module '$module'.\n\n";
    print STDERR "You can install it with:\n\n";
    print STDERR "    cpan $module\n\n";
    exit(1);
  }
  $module->import(@_);
}
 
sub optional_module {
  my $module = shift;
  
  eval "require $module";
  return 0 if $@;
  
  $module->import(@_);
  return 1;
}