package Config::MVP::Section;
# ABSTRACT: one section of an MVP configuration sequence
$Config::MVP::Section::VERSION = '2.200012';
use Moose 0.91;

use Class::Load 0.17 ();
use Config::MVP::Error;

#pod =head1 DESCRIPTION
#pod
#pod For the most part, you can just consult L<Config::MVP> to understand what this
#pod class is and how it's used.
#pod
#pod =attr name
#pod
#pod This is the section's name.  It's a string, and it must be provided.
#pod
#pod =cut

has name => (
  is  => 'ro',
  isa => 'Str',
  required => 1
);

#pod =attr package
#pod
#pod This is the (Perl) package with which the section is associated.  It is
#pod optional.  When the section is instantiated, it will ensure that this package
#pod is loaded.
#pod
#pod =cut

has package => (
  is  => 'ro',
  isa => 'Str', # should be class-like string, but can't be ClassName
  required  => 0,
  predicate => 'has_package',
);

#pod =attr multivalue_args
#pod
#pod This attribute is an arrayref of value names that should be considered
#pod multivalue properties in the section.  When added to the section, they will
#pod always be wrapped in an arrayref, and they may be added to the section more
#pod than once.
#pod
#pod If this attribute is not given during construction, it will default to the
#pod result of calling section's package's C<mvp_multivalue_args> method.  If the
#pod section has no associated package or if the package doesn't provide that
#pod method, it default to an empty arrayref.
#pod
#pod =cut

has multivalue_args => (
  is   => 'ro',
  isa  => 'ArrayRef',
  lazy => 1,
  default => sub {
    my ($self) = @_;

    return []
      unless $self->has_package and $self->package->can('mvp_multivalue_args');

    return [ $self->package->mvp_multivalue_args ];
  },
);

#pod =attr aliases
#pod
#pod This attribute is a hashref of name remappings.  For example, if it contains
#pod this hashref:
#pod
#pod   {
#pod     file => 'files',
#pod     path => 'files',
#pod   }
#pod
#pod Then attempting to set either the "file" or "path" setting for the section
#pod would actually set the "files" setting.
#pod
#pod If this attribute is not given during construction, it will default to the
#pod result of calling section's package's C<mvp_aliases> method.  If the
#pod section has no associated package or if the package doesn't provide that
#pod method, it default to an empty hashref.
#pod
#pod =cut

has aliases => (
  is   => 'ro',
  isa  => 'HashRef',
  lazy => 1,
  default => sub {
    my ($self) = @_;

    return {} unless $self->has_package and $self->package->can('mvp_aliases');

    return $self->package->mvp_aliases;
  },
);

#pod =attr payload
#pod
#pod This is the storage into which properties are set.  It is a hashref of names
#pod and values.  You should probably not alter the contents of the payload, and
#pod should read its contents only.
#pod
#pod =cut

has payload => (
  is  => 'ro',
  isa => 'HashRef',
  init_arg => undef,
  default  => sub { {} },
);

#pod =attr is_finalized
#pod
#pod This attribute is true if the section has been marked finalized, which will
#pod prevent any new values from being added to it.  It can be set with the
#pod C<finalize> method.
#pod
#pod =cut

has is_finalized => (
  is  => 'ro',
  isa => 'Bool',
  traits   => [ 'Bool' ],
  init_arg => undef,
  default  => 0,
  handles  => { finalize => 'set' },
);

before finalize => sub {
  my ($self) = @_;

  Config::MVP::Error->throw("can't finalize unsequenced Config::MVP::Section")
    unless $self->sequence;
};

#pod =attr sequence
#pod
#pod This attributes points to the sequence into which the section has been
#pod assembled.  It may be unset if the section has been created but not yet placed
#pod in a sequence.
#pod
#pod =cut

has sequence => (
  is  => 'ro',
  isa => 'Config::MVP::Sequence',
  weak_ref  => 1,
  predicate => '_sequence_has_been_set',
  reader    => '_sequence',
  writer    => '__set_sequence',
  clearer   => '_clear_sequence',
);

sub _set_sequence {
  my ($self, $seq) = @_;

  Config::MVP::Error->throw("Config::MVP::Section cannot be resequenced")
    if $self->sequence;

  $self->__set_sequence($seq);
}

sub sequence {
  my ($self) = @_;
  return undef unless $self->_sequence_has_been_set;
  my $seq = $self->_sequence;

  Config::MVP::Error->throw("can't access section's destroyed sequence")
    unless defined $seq;

  return $seq;
}

#pod =method add_value
#pod
#pod   $section->add_value( $name => $value );
#pod
#pod This method sets the value for the named property to the given value.  If the
#pod property is a multivalue property, the new value will be pushed onto the end of
#pod an arrayref that will store all values for that property.
#pod
#pod Attempting to add a value for a non-multivalue property whose value was already
#pod added will result in an exception.
#pod
#pod =cut

sub add_value {
  my ($self, $name, $value) = @_;

  confess "can't add values to finalized section " . $self->name
    if $self->is_finalized;

  my $alias = $self->aliases->{ $name };
  $name = $alias if defined $alias;

  my $mva = $self->multivalue_args;

  if (grep { $_ eq $name } @$mva) {
    my $array = $self->payload->{$name} ||= [];
    push @$array, $value;
    return;
  }

  if (exists $self->payload->{$name}) {
    Carp::croak "multiple values given for property $name in section "
              . $self->name;
  }

  $self->payload->{$name} = $value;
}

#pod =method load_package
#pod
#pod   $section->load_package($package, $section_name);
#pod
#pod This method is used to ensure that the given C<$package> is loaded, and is
#pod called whenever a section with a package is created.  By default, it delegates
#pod to L<Class::Load>.  If the package can't be found, it calls the
#pod L<missing_package> method.  Errors in compilation are not suppressed.
#pod
#pod =cut

sub load_package {
  my ($self, $package, $section_name) = @_;

  Class::Load::load_optional_class($package)
    or $self->missing_package($package, $section_name);
}

#pod =method missing_package
#pod
#pod   $section->missing_package($package, $section_name);
#pod
#pod This method is called when C<load_package> encounters a package that is not
#pod installed.  By default, it throws an exception.
#pod
#pod =cut

sub missing_package {
  my ($self, $package, $section_name) = @_ ;

  my $class = Moose::Meta::Class->create_anon_class(
    superclasses => [ 'Config::MVP::Error' ],
    cached       => 1,
    attributes   => [
      Moose::Meta::Attribute->new(package => (
        is       => 'ro',
        required => 1,
      )),
      Moose::Meta::Attribute->new(section_name => (
        is       => 'ro',
        required => 1,
      )),
    ],
  );

  $class->name->throw({
    ident   => 'package not installed',
    message => "$package (for section $section_name) does not appear to be installed",
    package => $package,
    section_name => $section_name,
  });
}

sub _BUILD_package_settings {
  my ($self) = @_;

  return unless defined (my $pkg = $self->package);

  confess "illegal package name $pkg" unless Params::Util::_CLASS($pkg);

  $self->load_package($pkg, $self->name);

  # We call these accessors for lazy attrs to ensure they're initialized from
  # defaults if needed.  Crash early! -- rjbs, 2009-08-09
  $self->multivalue_args;
  $self->aliases;
}

sub BUILD {
  my ($self) = @_;
  $self->_BUILD_package_settings;
}

no Moose;
1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Config::MVP::Section - one section of an MVP configuration sequence

=head1 VERSION

version 2.200012

=head1 DESCRIPTION

For the most part, you can just consult L<Config::MVP> to understand what this
class is and how it's used.

=head1 ATTRIBUTES

=head2 name

This is the section's name.  It's a string, and it must be provided.

=head2 package

This is the (Perl) package with which the section is associated.  It is
optional.  When the section is instantiated, it will ensure that this package
is loaded.

=head2 multivalue_args

This attribute is an arrayref of value names that should be considered
multivalue properties in the section.  When added to the section, they will
always be wrapped in an arrayref, and they may be added to the section more
than once.

If this attribute is not given during construction, it will default to the
result of calling section's package's C<mvp_multivalue_args> method.  If the
section has no associated package or if the package doesn't provide that
method, it default to an empty arrayref.

=head2 aliases

This attribute is a hashref of name remappings.  For example, if it contains
this hashref:

  {
    file => 'files',
    path => 'files',
  }

Then attempting to set either the "file" or "path" setting for the section
would actually set the "files" setting.

If this attribute is not given during construction, it will default to the
result of calling section's package's C<mvp_aliases> method.  If the
section has no associated package or if the package doesn't provide that
method, it default to an empty hashref.

=head2 payload

This is the storage into which properties are set.  It is a hashref of names
and values.  You should probably not alter the contents of the payload, and
should read its contents only.

=head2 is_finalized

This attribute is true if the section has been marked finalized, which will
prevent any new values from being added to it.  It can be set with the
C<finalize> method.

=head2 sequence

This attributes points to the sequence into which the section has been
assembled.  It may be unset if the section has been created but not yet placed
in a sequence.

=head1 METHODS

=head2 add_value

  $section->add_value( $name => $value );

This method sets the value for the named property to the given value.  If the
property is a multivalue property, the new value will be pushed onto the end of
an arrayref that will store all values for that property.

Attempting to add a value for a non-multivalue property whose value was already
added will result in an exception.

=head2 load_package

  $section->load_package($package, $section_name);

This method is used to ensure that the given C<$package> is loaded, and is
called whenever a section with a package is created.  By default, it delegates
to L<Class::Load>.  If the package can't be found, it calls the
L<missing_package> method.  Errors in compilation are not suppressed.

=head2 missing_package

  $section->missing_package($package, $section_name);

This method is called when C<load_package> encounters a package that is not
installed.  By default, it throws an exception.

=head1 AUTHOR

Ricardo Signes <rjbs@cpan.org>

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2021 by Ricardo Signes.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut