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# ABSTRACT: Exception objects for formula functions
our $VERSION = '0.08'; # VERSION


has message => ( is => 'rw', required => 1 );

sub mine {
	return Language::FormulaEngine::ErrorMine->new($_[0]);
}

sub BUILDARGS {
	my $pkg= shift;
	return $_[0] if @_ == 1 && ref $_[0] eq 'HASH';
	# If odd number of arguments, and first is a scalar, then treat it as the message
	unshift @_, 'message' if @_ & 1 and !ref $_[0];
	return { @_ };
}

our %err_patterns= (
	ErrNA    => qr/uninitialized|undefined/,
	ErrNUM   => qr/numeric/,
);
sub auto_wrap_error {
	# allow to be called as package method, or not
	shift if @_ && !ref $_[0] && $_[0]->isa(__PACKAGE__);
	my $msg= shift;
	# return things which are already Error objects (or mines)
	if (ref $msg) {
		return $msg->disarm if ref($msg)->can('disarm');
		return $msg if ref($msg)->can('message');
	}
	# Match message against patterns that Perl might have generated
	if (defined $msg) {
		$msg =~ s/ at \(eval.*//; # isn't useful
		for (keys %err_patterns) {
			return (__PACKAGE__.'::'.$_)->new(message => $msg)
				if $msg =~ $err_patterns{$_};
		}
	} else {
		$msg= '<undef>';
	}
	return __PACKAGE__->new(message => $msg);
}

sub _fake_inc {
	(my $pkg= caller) =~ s,::,/,g;
	$INC{$pkg.'.pm'}= $INC{'Language/FormulaEngine/Error.pm'};
}

sub _stringify {
	my $self= shift;
	my $cls= ref $self;
	$cls =~ s/^Language::FormulaEngine::Error:://;
	$cls . ': ' . $self->message;
}

use overload '""' => \&_stringify;

package Language::FormulaEngine::ErrorMine;
Language::FormulaEngine::Error::_fake_inc();
use overload # SOMEONE SET US UP THE BOMB!
	'0+' => sub { die ${$_[0]} },
	'""' => sub { die ${$_[0]} },
	bool => sub { die ${$_[0]} };

sub new { bless $_[0], shift }
sub disarm { ${$_[0]} }

package Language::FormulaEngine::Error::ErrInval;
Language::FormulaEngine::Error::_fake_inc();
use Moo;
extends 'Language::FormulaEngine::Error';

package Language::FormulaEngine::Error::ErrNA;
Language::FormulaEngine::Error::_fake_inc();
use Moo;
extends 'Language::FormulaEngine::Error';

package Language::FormulaEngine::Error::ErrREF;
Language::FormulaEngine::Error::_fake_inc();
use Moo;
extends 'Language::FormulaEngine::Error';

package Language::FormulaEngine::Error::ErrNUM;
Language::FormulaEngine::Error::_fake_inc();
use Moo;
extends 'Language::FormulaEngine::Error::ErrInval';

package Language::FormulaEngine::Error::ErrNAME;
Language::FormulaEngine::Error::_fake_inc();
use Moo;
extends 'Language::FormulaEngine::Error';

1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Language::FormulaEngine::Error - Exception objects for formula functions

=head1 VERSION

version 0.08

=head1 DESCRIPTION

In keeping with the theme of spreadsheet formulas, this module collection provides exception
objects that can be used for similar exception handling.  These objects are intended to be
thrown using "die", but they can also be wrapped with a "trap" object so that they don't die
until used.  For example, in a spreadsheet the error is I<returned> from a function, but
anything that uses that value needs to generate a similar error.  That would require a lot of
argument checking and prevent using native Perl operations, but by returning an error wrapped
in a trap, any perl operation that attempts to use the trap will instead throw the exception
object.

=head1 ATTRIBUTES