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use Carp;

use DateTime;
use DateTime::TimeZone;
# Cache UTC definition
our $UTC = DateTime::TimeZone->new( name => 'UTC' );

# Inherit from the Base translation class and not HdrTrans itself
# (which is just a class-less wrapper).

use base qw/ Astro::FITS::HdrTrans::FITS /;

our $VERSION = "1.66";

# in each class we have three sets of data.
#   - constant mappings
#   - unit mappings
#   - complex mappings

# For a constant mapping, there is no FITS header, just a generic
# header that is constant.
my %CONST_MAP = (
                );

# Unit mapping implies that the value propagates directly
# to the output with only a keyword name change.

my %UNIT_MAP = (
                MSBID              => 'MSBID',
                MSB_TRANSACTION_ID => 'MSBTID',
                SHIFT_TYPE         => "OPER_SFT",
               );

# Create the translation methods.
__PACKAGE__->_generate_lookup_methods( \%CONST_MAP, \%UNIT_MAP );

=head1 METHODS

=over 4

=item B<translate_from_FITS>

This routine overrides the base class implementation to enable the
caches to be cleared and for the location of the DATE-OBS/DATE-END field to
be found so that base class implementations will work correctly.

This means that some conversion methods (in particular those using time in
a base class) may not work properly outside the context of a full translation
unless they have been subclassed locally.

=cut

sub translate_from_FITS {
  my $class = shift;
  my $headers = shift;

  # sort out DATE-OBS and DATE-END
  $class->_fix_dates( $headers );

  # Go to the base class
  return $class->SUPER::translate_from_FITS( $headers, @_ );
}

=back

=head1 COMPLEX CONVERSIONS

These methods are more complicated than a simple mapping.  We have to
provide both from- and to-FITS conversions All these routines are
methods and the to_ routines all take a reference to a hash and return
the translated value (a many-to-one mapping).  The from_ methods take
a reference to a generic hash and return a translated hash (sometimes
these are many-to-many).

=over 4

=item B<to_OBSERVATION_ID>

Converts the C<OBSID> header directly into the C<OBSERVATION_ID>
generic header, or if that header does not exist, converts the
C<INSTRUME>, C<RUNNR>, and C<DATE-OBS> headers into C<OBSERVATION_ID>.

The form of the observation ID string is documented in
JSA/ANA/001 (http://docs.jach.hawaii.edu/JCMT/JSA/ANA/001/jsa_ana_001.pdf).

=cut

sub to_OBSERVATION_ID {
  my $self = shift;
  my $FITS_headers = shift;

  my $return;
  if ( exists( $FITS_headers->{'OBSID'} ) &&
       defined( $FITS_headers->{'OBSID'} ) ) {
    $return = $FITS_headers->{'OBSID'};
  } else {

    my $instrume = $self->to_INSTRUMENT( $FITS_headers );
    my $obsnum = $self->to_OBSERVATION_NUMBER( $FITS_headers );
    my $dateobs = $self->to_UTSTART( $FITS_headers );

    if ( defined $dateobs && defined $obsnum && defined $instrume ) {
      my $datetime = $dateobs->datetime;
      $datetime =~ s/-//g;
      $datetime =~ s/://g;

      $return = join '_', (lc $instrume), $obsnum, $datetime;
    }
  }

  return $return;

}

=item B<_fix_dates>

Sort out DATE-OBS and DATE-END in cases where they are not available directly.
This is mainly an issue with database retrievals where the date format is not
FITS compliant.

  Astro::FITS::HdrTrans::JAC->_fix_dates( \%headers );