package FU::Util 0.1;

use v5.36;
use FU::XS;
use Exporter 'import';

our @EXPORT_OK = qw/json_format json_parse/;

1;
__END__

=head1 NAME

FU::Util - Miscellaneous utility functions that really should have been part of
a core Perl installation but aren't for some reason because the Perl community
doesn't believe in the concept of a "batteries included" standard library.
</rant>

=head1 SYNOPSIS

    use FU::Util qw/json_format/;

    my $data = json_format [1, 2, 3];

=head1 DESCRIPTION

=head2 JSON parsing & formatting

This module comes with a custom C-based JSON parser and formatter. These
functions conform strictly to L<RFC-8259|https://tools.ietf.org/html/rfc8259>,
non-standard extensions are not supported and never will be. It also happens to
be pretty fast, refer to L<FU::Benchmarks> for some numbers.

JSON booleans are parsed into C<builtin::true> and C<builtin::false>. When
formatting, those builtin constants are the I<only> recognized boolean values -
alternative representations such as C<JSON::PP::true> and C<JSON::PP::false>
are not recognized and attempting to format such values will croak.

JSON numbers that are too large fit into a Perl integer are parsed into a
floating point value instead. This obviously loses precision, but is consistent
with C<JSON.parse()> in JavaScript land - except Perl does support the full
range of a 64bit integer. JSON numbers with a fraction or exponent are also
converted into floating point, which may lose precision as well.
L<Math::BigInt> and L<Math::BigFloat> are not currently supported. Attempting
to format a floating point C<NaN> or C<Inf> results in an error.

=over

=item json_parse($string, %options)

Parse a JSON string and return a Perl value. With the default options, this
function is roughly similar to:

    JSON::PP->new->allow_nonref->core_bools-decode($string);

Supported C<%options>:

=over

=item utf8

Boolean, interpret the input C<$string> as a UTF-8 encoded byte string instead
of a Perl Unicode string.

=back


=item json_format($scalar, %options)

Format a Perl value as JSON. With the default options, this function behaves
roughly similar to:

    JSON::PP->new->allow_nonref->core_bools->convert_blessed->encode($scalar);

Some modules escape the slash character in encoded strings to prevent a
potential XSS vulnerability when embedding JSON inside C<< <script> ..
</script> >> tags.  This function does I<not> do that because it might not even
be sufficient. The following is probably an improvement:

    json_format($data) =~ s{</}{<\\/}rg =~ s/<!--/<\\u0021--/rg;

The following C<%options> are supported:

=over

=item canonical

Boolean, write hash keys in deterministic (sorted) order. This option currently
has no effect on tied hashes.

=item pretty

Boolean, format JSON with newlines and indentation for easier reading.  Beauty
is in the eye of the beholder, this option currently follows the convention
used by L<JSON::XS> and others: 3 space indent and one space around the C<:>
separating object keys and values. The exact format might change in later
versions.

=item utf8

Boolean, returns a UTF-8 encoded byte string instead of a Perl Unicode string.

=item max_size

Maximum permitted size, in bytes, of the generated JSON string. Defaults to 1 GiB.

=item max_depth

Maximum permitted nesting depth of Perl values. Defaults to 512.

=back

=back

(Why the hell yet another JSON codec when CPAN is already full of them!? Well,
L<JSON::XS> is pretty cool but isn't going to be updated to support Perl's new
builtin booleans. L<JSON::PP> is slow and while L<Cpanel::JSON::XS> is
perfectly adequate, its codebase is too large and messy for my taste - too many
unnecessary features and C<#ifdef>s to support ancient perls and esoteric
configurations. Still, if you need anything not provided by these functions,
L<JSON::PP> and L<Cpanel::JSON::XS> are perfectly fine alternatives.
L<JSON::SIMD> and L<Mojo::JSON> also look like good and maintained candidates.)