package Specio::Constraint::Simple;

use strict;
use warnings;

our $VERSION = '0.22';

use Role::Tiny::With;
use Specio::OO;

with 'Specio::Constraint::Role::Interface';

__PACKAGE__->_ooify;

1;

# ABSTRACT: Class for simple (non-parameterized or specialized) types

__END__

=pod

=encoding UTF-8

=head1 NAME

Specio::Constraint::Simple - Class for simple (non-parameterized or specialized) types

=head1 VERSION

version 0.22

=head1 SYNOPSIS

    my $str = t('Str');

    print $str->name; # Str

    my $parent = $str->parent;

    if ( $str->value_is_valid($value) ) { ... }

    $str->validate_or_die($value);

    my $code = $str->inline_coercion_and_check('$_[0]');

=head1 DESCRIPTION

This class implements simple type constraints, constraints without special
properties or parameterization.

It does not actually contain any real code of its own. The entire
implementation is provided by the L<Specio::Constraint::Role::Interface> role,
but the primary API for type constraints is documented here.

All other type constraint classes in this distribution implement this API,
except where otherwise noted.

=head1 API

This class provides the following methods.

=head2 Specio::Constraint::Simple->new(...)

This creates a new constraint. It accepts the following named parameters:

=over 4

=item * name => $name

This is the type's name. The name is optional, but if provided it must be a
string.

=item * parent => $type

The type's parent type. This must be an object which does the
L<Specio::Constraint::Role::Interface> role.

This parameter is optional.

=item * constraint => sub { ... }

A subroutine reference implementing the constraint. It will be called as a
method on the object and passed a single argument, the value to check.

It should return true or false to indicate whether the value matches the
constraint.

This parameter is mutually exclusive with C<inline_generator>.

You can also pass this option with the key C<where> in the parameter list.

=item * inline_generator => sub { ... }

This should be a subroutine reference which returns a string containing a
single term. This code should I<not> end in a semicolon. This code should
implement the constraint.

The generator will be called as a method on the constraint with a single
argument. That argument is the name of the variable being coerced, something
like C<'$_[0]'> or C<'$var'>.

The inline generator is expected to include code to implement both the current
type and all its parents. Typically, the easiest way to do this is to write a
subroutine something like this:

  sub {
      my $self = shift;
      my $var  = shift;

      return $_[0]->parent->inline_check( $_[1] )
          . ' and more checking code goes here';
  }

This parameter is mutually exclusive with C<constraint>.

You can also pass this option with the key C<inline> in the parameter list.

=item * inline_environment => {}

This should be a hash reference of variable names (with sigils) and values for
that variable. The values should be I<references> to the values of the
variables.

This environment will be used when compiling the constraint as part of a
subroutine. The named variables will be captured as closures in the generated
subroutine, using L<Eval::Closure>.

It should be very rare to need to set this in the constructor. It's more
likely that a special type subclass would need to provide values that it
generates internally.

If you do set this, you are responsible for generating variable names that
won't clash with anything else in the inlined code.

This parameter defaults to an empty hash reference.

=item * message_generator => sub { ... }

A subroutine to generate an error message when the type check fails. The
default message says something like "Validation failed for type named Int
declared in package Specio::Library::Builtins
(.../Specio/blib/lib/Specio/Library/Builtins.pm) at line 147 in sub named (eval)
with value 1.1".

You can override this to provide something more specific about the way the
type failed.

The subroutine you provide will be called as a subroutine, I<not as a method>,
with two arguments. The first is the description of the type (the bit in the
message above that starts with "type named Int ..." and ends with "... in sub
named (eval)". This description says what the thing is and where it was
defined.

The second argument is the value that failed the type check, after any
coercions that might have been applied.

You can also pass this option with the key C<message> in the parameter list.

=item * declared_at => $declared_at

This parameter must be a L<Specio::DeclaredAt> object.

This parameter is required.

=back

It is possible to create a type without a constraint of its own.

=head2 $type->name, $type->parent

Returns the value of these parameters as they were passed to the constructor.

=head2 $type->is_anon

Returns false for named types, true otherwise.

=head2 $type->is_a_type_of($other_type)

Given a type object, this returns true if the type this method is called on is
a descendant of that type or is that type.

=head2 $type->is_same_type_as($other_type)

Given a type object, this returns true if the type this method is called on is
the same as that type.

=head2 $type->coercions

Returns a list of L<Specio::Coercion> objects which belong to this constraint.

=head2 $type->coercion_from_type($name)

Given a type name, this method returns a L<Specio::Coercion> object which
coerces from that type, if such a coercion exists.

=head2 $type->validate_or_die($value)

This method does nothing if the value is valid. If it is not, it throws a
L<Specio::Exception>.

=head2 $type->value_is_valid($value)

Returns true or false depending on whether the C<$value> passes the type
constraint.

=head2 $type->has_real_constraint

This returns true if the type was created with a C<constraint> or
C<inline_generator> parameter. This is used internally to skip type checks for
types that don't actually implement a constraint.

=head2 $type->id

This is a unique id for the type as a string. This is useful if you need to
make a hash key based on a type, for example.

=head2 $type->add_coercion($coercion)

This adds a new L<Specio::Coercion> to the type. If the type already has a
coercion from the same type as the new coercion, it will throw an error.

=head2 $type->has_coercion_from_type($other_type)

This method returns true if the type can coerce from the other type.

=head2 $type->coerce_value($value)

This attempts to coerce a value into a new value that matches the type. It
checks all of the type's coercions. If it finds one which has a "from" type
that accepts the value, it runs the coercion and returns the new value.

If it cannot find a matching coercion it returns the original value.

=head2 $type->inline_coercion_and_check($var)

Given a variable name, this returns a string of code and an environment hash
that implements all of the type's coercions as well as the type check itself.

This will throw an exception unless both the type and all of its coercions are
inlinable.

The generated code will throw a L<Specio::Exception> if the type constraint
fails. If the constraint passes, then the generated code returns the (possibly
coerced) value.

The return value is a two-element list. The first element is the code. The
second is a hash reference containing variables which need to be in scope for
the code to work. This is intended to be passed to L<Eval::Closure>'s
C<eval_closure> subroutine.

The returned code is a single C<do { }> block without a terminating
semicolon.

=head2 $type->inline_assert($var)

Given a variable name, this generates code that implements the constraint and
throws an exception if the variable does not pass the constraint.

The return value is a two-element list. The first element is the code. The
second is a hash reference containing variables which need to be in scope for
the code to work. This is intended to be passed to L<Eval::Closure>'s
C<eval_closure> subroutine.

=head2 $type->inline_check($var)

Given a variable name, this returns a string of code that implements the
constraint. If the type is not inlinable, this method throws an error.

=head2 $type->coercion_sub

This method returns a sub ref that takes a single argument and applied all
relevant coercions to it. This sub ref will use L<Sub::Quote> if all the
type's coercions are inlinable.

This method exists primarily for the benefit of L<Moo>.

=head1 OVERLOADING

All constraints overloading subroutine de-referencing for the benefit of
L<Moo>. The returned subroutine uses L<Sub::Quote> if the type constraint is
inlinable.

=head1 ROLES

This role does the L<Specio::Constraint::Role::Interface> and
L<Specio::Role::Inlinable> roles.

=head1 SUPPORT

Bugs may be submitted through L<the RT bug tracker|http://rt.cpan.org/Public/Dist/Display.html?Name=Specio>
(or L<bug-specio@rt.cpan.org|mailto:bug-specio@rt.cpan.org>).

I am also usually active on IRC as 'drolsky' on C<irc://irc.perl.org>.

=head1 AUTHOR

Dave Rolsky <autarch@urth.org>

=head1 COPYRIGHT AND LICENCE

This software is Copyright (c) 2016 by Dave Rolsky.

This is free software, licensed under:

  The Artistic License 2.0 (GPL Compatible)

=cut
