package Error::TypeTiny::Assertion;

use 5.006001;
use strict;
use warnings;

BEGIN {
	if ($] < 5.008) { require Devel::TypeTiny::Perl56Compat };
}

BEGIN {
	$Error::TypeTiny::Assertion::AUTHORITY = 'cpan:TOBYINK';
	$Error::TypeTiny::Assertion::VERSION   = '1.000005';
}

require Error::TypeTiny;
our @ISA = 'Error::TypeTiny';

sub type               { $_[0]{type} };
sub value              { $_[0]{value} };
sub varname            { $_[0]{varname} ||= '$_' };
sub attribute_step     { $_[0]{attribute_step} };
sub attribute_name     { $_[0]{attribute_name} };

sub has_type           { defined $_[0]{type} }; # sic
sub has_attribute_step { exists $_[0]{attribute_step} };
sub has_attribute_name { exists $_[0]{attribute_name} };

sub new
{
	my $class = shift;
	my $self  = $class->SUPER::new(@_);
	
	if (ref $Method::Generate::Accessor::CurrentAttribute)
	{
		require B;
		my %d = %{$Method::Generate::Accessor::CurrentAttribute};
		$self->{attribute_name} = $d{name} if defined $d{name};
		$self->{attribute_step} = $d{step} if defined $d{step};
		
		if (defined $d{init_arg})
		{
			$self->{varname} = sprintf('$args->{%s}', B::perlstring($d{init_arg}));
		}
		elsif (defined $d{name})
		{
			$self->{varname} = sprintf('$self->{%s}', B::perlstring($d{name}));
		}
	}
	
	return $self;
}

sub message
{
	my $e = shift;
	$e->varname eq '$_'
		? $e->SUPER::message
		: sprintf('%s (in %s)', $e->SUPER::message, $e->varname);
}

sub _build_message
{
	my $e = shift;
	$e->has_type
		? sprintf('%s did not pass type constraint "%s"', Type::Tiny::_dd($e->value), $e->type)
		: sprintf('%s did not pass type constraint', Type::Tiny::_dd($e->value))
}

*to_string = sub
{
	my $e = shift;
	my $msg = $e->message;
	
	my $c = $e->context;
	$msg .= sprintf(" at %s line %s", $c->{file}||'file?', $c->{line}||'NaN') if $c;
	
	my $explain = $e->explain;
	return $msg unless @{ $explain || [] };
	
	$msg .= "\n";
	for my $line (@$explain) {
		$msg .= "    $line\n";
	}
	
	return $msg;
} if $] >= 5.008;

sub explain
{
	my $e = shift;
	return undef unless $e->has_type;
	$e->type->validate_explain($e->value, $e->varname);
}

1;

__END__

=pod

=encoding utf-8

=head1 NAME

Error::TypeTiny::Assertion - exception when a value fails a type constraint

=head1 STATUS

This module is covered by the
L<Type-Tiny stability policy|Type::Tiny::Manual::Policies/"STABILITY">.

=head1 DESCRIPTION

This exception is thrown when a value fails a type constraint assertion.

This package inherits from L<Error::TypeTiny>; see that for most
documentation. Major differences are listed below:

=head2 Attributes

=over

=item C<type>

The type constraint that was checked against. Weakened links are involved,
so this may end up being C<undef>.

=item C<value>

The value that was tested.

=item C<varname>

The name of the variable that was checked, if known. Defaults to C<< '$_' >>.

=item C<attribute_name>

If this exception was thrown as the result of an isa check or a failed
coercion for a Moo attribute, then this will tell you which attribute (if
your Moo is new enough).

(Hopefully one day this will support other OO frameworks.)

=item C<attribute_step>

If this exception was thrown as the result of an isa check or a failed
coercion for a Moo attribute, then this will contain either C<< "isa check" >>
or C<< "coercion" >> to indicate which went wrong (if your Moo is new enough).

(Hopefully one day this will support other OO frameworks.)

=back

=head2 Methods

=over

=item C<has_type>, C<has_attribute_name>, C<has_attribute_step>

Predicate methods.

=item C<message>

Overridden to add C<varname> to the message if defined.

=item C<explain>

Attempts to explain why the value did not pass the type constraint. Returns
an arrayref of strings providing step-by-step reasoning; or returns undef if
no explanation is possible.

=back

=head1 BUGS

Please report any bugs to
L<http://rt.cpan.org/Dist/Display.html?Queue=Type-Tiny>.

=head1 SEE ALSO

L<Error::TypeTiny>.

=head1 AUTHOR

Toby Inkster E<lt>tobyink@cpan.orgE<gt>.

=head1 COPYRIGHT AND LICENCE

This software is copyright (c) 2013-2014 by Toby Inkster.

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

=head1 DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

