=head1 NAME

Class::ParmList - Methods for processing named parameter lists

=head1 SYNOPSIS

  use Class::ParmList qw(simple_parms parse_parms);

 $thingy->some_method({
      -bgcolor   => '#ff0000',
      -textcolor => '#000000'
      });

 sub some_method {
     my ($self) = shift;

     my ($parm_ref) = @_;

     my $parms = Class::ParmList->new ({
            -parms    => $parm_ref,
            -legal    => [qw (-textcolor -border -cellpadding)],
            -required => [qw (-bgcolor)],
            -defaults => {
                           -bgcolor   => "#ffffff",
                           -textcolor => "#000000"
                         }
         });

     if (not defined $parms) {
        my $error_message = Class::ParmList->error;
        die ($error_message);
     }

     # Stuff...

 }

  sub another_method {
    my $self = shift;
    my ($name,$rank,$serial_number) = simple_parms([qw(-name -rank -serial_number)], @_);

    #...
  }

  sub still_another {
     my $parms = parse_parms ({
            -parms    => \@_,
            -legal    => [qw (-textcolor -border -cellpadding)],
            -required => [qw (-bgcolor)],
            -defaults => {
                           -bgcolor   => "#ffffff",
                           -textcolor => "#000000"
                         }
         });
     if (not defined $parms) {
        my $error_message = Class::ParmList->error;
        die ($error_message);
     }

     # ...
  }

=head1 DESCRIPTION

This is a simple package for validating calling parameters to a subroutine or
method. It allows you to use "named parameters" while providing checking for
number and naming of parameters for verifying inputs are as expected and
meet any minimum requirements. It also allows the setting of default
values for the named parameters if omitted.

=cut

=head1 CHANGES

 1.00 1999.06.16 - Initial release

 1.01 1999.06.18 - Performance tweaks

 1.02 1999.06.21 - Fixing of failure to catch undeclared parm,
                   removal of 'use attrs qw(method)', and
                   extension of 'make test' support.

 1.03 2000.12.06 - Added exportable class functions 'simple_parms'
                   and 'parse_parms' and allowed 'stacking' references
                   for parms to the object to improve calling usage.

 1.04 2005.09.18 - Added META.yml, Build.PL, Artistic_License.txt
                   GPL_License.txt, LICENSE to distribution. Renamed
                   CHANGES to Changes. Extended build tests to 100%
                   coverage. Minor refactoring of module for speed.
                   Seperated documentation into .pod file.
                   Added POD/POD Coverage tests.

 1.05 2006.03.04 - Corrected mis-usage of Carp in error paths that
                   was causing less than useful error messages.

                   Added LICENSE and DISCLAIMER sections to
                   documentation.

=head1 METHODS

=over 4

=item new($parm_list_ref);

Returns a reference to an object that can be used to return
values. If an improper specification is passed, returns 'undef'.
Otherwise returns the reference.

Example:

     my $parms = Class::ParmList->new ({
            -parms    => $parm_ref,
            -legal    => [qw (-textcolor -border -cellpadding)],
            -required => [qw (-bgcolor)],
            -defaults => {
                           -bgcolor   => "#ffffff",
                           -textcolor => "#000000"
                         }
         });

All four parameters (-parms, -legal, -required, and -defaults) are
optional. It is liberal in that anything defined for a -default
or -required is automatically added to the '-legal' list.

If the '-legal' parameter is not _explicitly_ called out, no
checking against the legal list is done. If it _is_ explicitly
called out, then all -parms are checked against it and it will
fail with an error if a -parms parameter is present but not
defined in the -legal explict or implict definitions.

To simplify calling routines, the '-parms' parameters is allowed
to 'stack' anon list references: [['parm','value']]

This gives a calling routine the ability to parse @_ without
jumping through hoops to handle the cases of arrays vs hashes for
the passed parameters.

Example:

 sub example_sub {
   my $parms = Class::ParmList->new({ -parms => \@_,
                                      -legal => [],
                                   -required => ['-file','-data'],
                                   -defaults => {},
                                  });

   #...
 }

This routine would accept *either*

   example_sub({ '-file' => 'test', '-data' => 'stuff' });

or

   example_sub( '-file' => 'test', '-data' => 'stuff' );

with no code changes.

=back

=over 4

=item parse_parms({ -parms => \@parms,
                    -legal => ['list','legal','parms'],
                 -required => ['list','required','parms'],
                 -defaults => { 'default' => 'parameter values',
                              },
                         });

This is a functional equivalent to the 'new' method. Calling
parameters are identical, but it is called as a class function
that may be exported.

Example:

   my $parms = parse_parms({ -parms => \@_,
                             -legal => [],
                          -required => ['-file','-data'],
                          -defaults => {},
                         });

=back

=over 4

=item get($parm_name1, $parm_name2,...);

Returns the parameter value(s) specified in the call line. If
a parameter is not defined, it returns undef. If a set of
'-legal' parameters were declared, it croaks if a parameter
not in the '-legal' set is asked for.

Example:
  my ($help,$who) = $parms->get('-help','-who');

=back

=over 4

=item exists($parm_name);

Returns true if the parameter specifed by $parm_name (qv.
has been initialized), false if it does not exist.

  if ($parms->exists(-help) {
      # do stuff
  }

=back

=over 4

=item list_parms;

Returns the list of parameter names. (Names are always
presented in lowercase).

Example:

  my @parm_names = $parms->list_parms;

=back

=over 4

=item all_parms;

Returns an anonymous hash containing all the currently
set keys and values. This hash is suitable for usage
with Class::NamedParms or Class::ParmList for setting
keys/values. It works by making a shallow copy of
the data. This means that it copies the scalar values.

In the case of simple numbers and strings, this produces
a new copy, in the case of references to hashes and arrays or
objects, it returns the references to the original objects.

Example:

  my $parms = $parms->all_parms;

=back

=head1 FUNCTIONS

=over 4

=item error;

Returns the error message for the most recent invokation of
'new'.  (Static method - does not require an object to function)

Example:

     my $error_message = Class::ParmList->error;
     die ($error_message);

=back

=over 4

=item simple_parms(['-list','-of','-parameter_names'],@_);

Parses the passed named parameter list (croaking/confessing if extra or
missing parameters are found).

Examples:

 use Class::ParmList qw(simple_parms);

 sub some_method {
    my $self = shift;

    my ($name,$rank) = simple_parms([qw(-name -rank)],@_);
    # Now do stuff
 }

 sub some_function {
    my $serial_number = simple_parms([qw(-serial_number)],@_);
    # Now do stuff
 }

The passed parameter values for parsing this way may be either an anonymous hash of parameters

Example:
   a_function({ -parm1_name => $parm1_value, -parm2_name => $parm2_value }) )

or a straight list of parameters:

Example:
  a_function(-parm1_name => $parm1_value, -parm2_name => $parm2_value) )

Note that it *IS* legal for a parameter to be passed with an 'undef' value - it
will not trigger an error.

If you need optional parameters, this function is not well suited. You should
use the object methods above instead for that case - they are much more
flexible (but quite a bit slower and slightly more complex to use).

Its main virtues are that is is simple to use, has rugged error checking for
mis-usages and is reasonably fast.

'simple_parms' can be exported by specifying it on the 'use' line.

=back

=head1 VERSION

1.05 2006.03.04

=head1 COPYRIGHT

Copyright Benjamin Franz (<URL:http://www.nihongo.org/snowhare/>) and
FreeRun Technologies, Inc. (<URL:http://www.freeruntech.com/>). All Rights Reserved.

=head1 LICENSE

This program is free software; you can redistribute it
and/or modify it under the same terms and conditions as
Perl itself.

This means that you can, at your option, redistribute it and/or modify it under
either the terms the GNU Public License (GPL) version 1 or later, or under the
Perl Artistic License.

See http://dev.perl.org/licenses/

=head1 DISCLAIMER

THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS
OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE.

Use of this software in any way or in any form, source or binary,
is not allowed in any country which prohibits disclaimers of any
implied warranties of merchantability or fitness for a particular
purpose or any disclaimers of a similar nature.

IN NO EVENT SHALL I BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT,
SPECIAL, INCIDENTAL,  OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
USE OF THIS SOFTWARE AND ITS DOCUMENTATION (INCLUDING, BUT NOT
LIMITED TO, LOST PROFITS) EVEN IF I HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE

=head1 AUTHOR

Benjamin Franz, <snowhare@nihongo.org>

=head1 BUGS

None known

=head1 TODO

Memoization of parameter validation for performance.

=cut