package JSON::RPC2::Server;

use warnings;
use strict;
use Carp;

use version; our $VERSION = qv('1.0.0');    # update Changes & README

# update DEPENDENCIES in POD & Makefile.PL & README
use JSON::XS;

use constant ERR_PARSE  => -32700;
use constant ERR_REQ    => -32600;
use constant ERR_METHOD => -32601;
use constant ERR_PARAMS => -32602;


sub new {
    my ($class) = @_;
    my $self = {
        method  => {},
    };
    return bless $self, $class;
}

sub register {
    my ($self, $name, $cb) = @_;
    $self->{method}{ $name } = [ $cb, 1, 0 ];
    return;
}

sub register_named {
    my ($self, $name, $cb) = @_;
    $self->{method}{ $name } = [ $cb, 1, 1 ];
    return;
}

sub register_nb {
    my ($self, $name, $cb) = @_;
    $self->{method}{ $name } = [ $cb, 0, 0 ];
    return;
}

sub register_named_nb {
    my ($self, $name, $cb) = @_;
    $self->{method}{ $name } = [ $cb, 0, 1 ];
    return;
}

sub execute {
    my ($self, $json, $cb) = @_;
    croak 'require 2 params' if 1+2 != @_;
    croak 'second param must be callback' if ref $cb ne 'CODE';

    undef $@;
    my $request = ref $json ? $json : eval { decode_json($json) };
    if ($@) {
        return _error($cb, undef, ERR_PARSE, 'Parse error.');
    }
    if (ref $request eq 'HASH') {
        return $self->_execute($request, $cb);
    }
    if (ref $request ne 'ARRAY') {
        return _error($cb, undef, ERR_REQ, 'Invalid Request: expect Array or Object.');
    }
    if (!@{$request}) {
        return _error($cb, undef, ERR_REQ, 'Invalid Request: empty Array.');
    }

    my $pending = @{$request};
    my @responses;
    my $cb_acc = sub {
        my ($json_response) = @_;
        if ($json_response) {
            push @responses, $json_response;
        }
        if (!--$pending) {
            if (@responses) {
                $cb->( '[' . join(q{,}, @responses) . ']' );
            } else {
                $cb->( q{} );
            }
        }
        return;
    };
    for (@{$request}) {
        $self->_execute($_, $cb_acc);
    }

    return;
}

sub _execute {
    my ($self, $request, $cb) = @_;

    my $error = \&_error;
    my $done  = \&_done;

    # jsonrpc =>
    if (!defined $request->{jsonrpc} || ref $request->{jsonrpc} || $request->{jsonrpc} ne '2.0') {
        return $error->($cb, undef, ERR_REQ, 'Invalid Request: expect {jsonrpc}="2.0".');
    }

    # id =>
    my $id;
    if (exists $request->{id}) {
        # Request
        if (ref $request->{id}) {
            return $error->($cb, undef, ERR_REQ, 'Invalid Request: expect {id} is scalar.');
        }
        $id = $request->{id};
    }

    # method =>
    if (!defined $request->{method} || ref $request->{method}) {
        return $error->($cb, $id, ERR_REQ, 'Invalid Request: expect {method} is String.');
    }
    my $handler = $self->{method}{ $request->{method} };
    if (!$handler) {
        return $error->($cb, $id, ERR_METHOD, 'Method not found.');
    }
    my ($method, $is_blocking, $is_named) = @{$handler};

    # params =>
    if (!exists $request->{params}) {
        $request->{params} = $is_named ? {} : [];
    }
    if (ref $request->{params} ne 'ARRAY' && ref $request->{params} ne 'HASH') {
        return $error->($cb, $id, ERR_REQ, 'Invalid Request: expect {params} is Array or Object.');
    }
    if (ref $request->{params} ne ($is_named ? 'HASH' : 'ARRAY')) {
        return $error->($cb, $id, ERR_PARAMS, 'This method expect '.($is_named ? 'named' : 'positional').' params.');
    }
    my @params = $is_named ? %{ $request->{params} } : @{ $request->{params} };

    # id => (continue)
    if (!exists $request->{id}) {
        # Notification
        $error = \&_nothing;
        $done  = \&_nothing;
    }

    # execute
    if ($is_blocking) {
        my @returns = $method->( @params );
        $done->($cb, $id, \@returns);
    }
    else {
        my $cb_done = sub { $done->($cb, $id, \@_) };
        $method->( $cb_done, @params );
    }
    return;
}

sub _done {
    my ($cb, $id, $returns) = @_;
    my ($result, $code, $msg, $data) = @{$returns};
    if (defined $code) {
        return _error($cb, $id, $code, $msg, $data);
    }
    return _result($cb, $id, $result);
}

sub _error {
    my ($cb, $id, $code, $message, $data) = @_;
    $cb->( encode_json({
        jsonrpc     => '2.0',
        id          => $id,
        error       => {
            code        => $code,
            message     => $message,
            (defined $data ? ( data => $data ) : ()),
        },
    }) );
    return;
}

sub _result {
    my ($cb, $id, $result) = @_;
    $cb->( encode_json({
        jsonrpc     => '2.0',
        id          => $id,
        result      => $result,
    }) );
    return;
}

sub _nothing {
    my ($cb) = @_;
    $cb->( q{} );
    return;
}


1; # Magic true value required at end of module
__END__

=encoding utf8

=head1 NAME

JSON::RPC2::Server - Transport-independent json-rpc 2.0 server


=head1 SYNOPSIS

    use JSON::RPC2::Server;

    my $rpcsrv = JSON::RPC2::Server->new();

    $rpcsrv->register('func1', \&func1);
    $rpcsrv->register_nb('func2', \&func2);
    $rpcsrv->register_named('func3', \&func3);
    $rpcsrv->register_named_nb('func4', \&func4);

    # receive remote request in $json_request somehow, then:
    $rpcsrv->execute( $json_request, \&send_response );

    sub send_response {
        my ($json_response) = @_;
        # send $json_response somehow
    }

    sub func1 {
        my (@remote_params) = @_;
        if (success) {
            return ($result);
        } else {
            return (undef, $err_code, $err_message);
        }
    }

    sub func2 {
        my ($callback, @remote_params) = @_;
        # setup some event to call func2_finished($callback) later
    }
    sub func2_finished {
        my ($callback) = @_;
        if (success) {
            $callback->($result);
        } else {
            $callback->(undef, $err_code, $err_message);
        }
        return;
    }

    sub func3 {
        my (%remote_params) = @_;
        # rest the same as in func1
    }

    sub func4 {
        my ($callback, %remote_params) = @_;
        # rest the same as in func2
    }

    #
    # EXAMPLE of simple blocking STDIN-STDOUT server
    #

    my $rpcsrv = JSON::RPC2::Server->new();
    $rpcsrv->register('method1', \&method1);
    $rpcsrv->register('method2', \&method2);
    while (<STDIN>) {
        chomp;
        $rpcsrv->execute($_, sub { printf "%s\n", @_ });
    }
    sub method1 {
        return { my_params => \@_ };
    }
    sub method2 {
        return (undef, 0, "don't call me please");
    }

=head1 DESCRIPTION

Transport-independent implementation of json-rpc 2.0 server.
Server methods can be blocking (simpler) or non-blocking (useful if
method have to do some slow tasks like another RPC or I/O which can
be done in non-blocking way - this way several methods can be executing
in parallel on server).


=head1 INTERFACE 

=over

=item new()

Create and return new server object, which can be used to register and
execute user methods.

=item register( $rpc_method_name, \&method_handler )

=item register_named( $rpc_method_name, \&method_handler )

Register $rpc_method_name as allowed method name for remote procedure call
and set \&method_handler as BLOCKING handler for that method.

If there already was some handler set (using register() or
register_named() or register_nb() or register_named_nb()) for that
$rpc_method_name - it will be replaced by \&method_handler.

While processing request to $rpc_method_name user handler will be called
with parameters provided by remote side (as ARRAY for register() or HASH
for register_named()), and should return it result as list with 4
elements:

 ($result, $code, $message, $data) = method_handler(@remote_params);
 ($result, $code, $message, $data) = method_handler(%remote_params);

 $result        scalar or complex structure if method call success
 $code          error code (integer, > -32600) if method call failed
 $message       error message (string) if message call failed
 $data          optional scalar with additional error-related data

If $code is defined then $result shouldn't be defined; $message required
only if $code defined.

Return nothing.

=item register_nb( $rpc_method_name, \&nb_method_handler )

=item register_named_nb( $rpc_method_name, \&nb_method_handler )

Register $rpc_method_name as allowed method name for remote procedure call
and set \&method_handler as NON-BLOCKING handler for that method.

If there already was some handler set (using register() or
register_named() or register_nb() or register_named_nb()) for that
$rpc_method_name - it will be replaced by \&method_handler.

While processing request to $rpc_method_name user handler will be called
with callback needed to return result in first parameter and parameters
provided by remote side as next parameters (as ARRAY for register_nb() or
HASH for register_named_nb()), and should call provided callback with list
with 4 elements when done:

 nb_method_handler($callback, @remote_params);
 nb_method_handler($callback, %remote_params);

 # somewhere in that method handlers:
 $callback->($result, $code, $message, $data);
 return;

Meaning of ($result, $code, $message, $data) is same as documented in
register() above.

Return nothing.

=item execute( $json_request, $callback )

The $json_request can be either JSON string or ARRAYREF/HASHREF (useful
with C<< $handle->push_read(json => sub{...}) >> from L<AnyEvent::Handle>).

Parse $json_request and execute registered user handlers. Reply will be
sent into $callback, when ready:

 $callback->( $json_response );

The $callback will be always executed after finishing processing
$json_request - even if request type was "notification" (in this case
$json_response will be an empty string).

Return nothing.

=back


=head1 DIAGNOSTICS

None.


=head1 CONFIGURATION AND ENVIRONMENT

JSON::RPC2::Server requires no configuration files or environment variables.


=head1 DEPENDENCIES

 JSON::XS


=head1 INCOMPATIBILITIES

None reported.


=head1 BUGS AND LIMITATIONS

No bugs have been reported.

Please report any bugs or feature requests to
C<bug-json-rpc2-server@rt.cpan.org>, or through the web interface at
L<http://rt.cpan.org>.


=head1 AUTHOR

Alex Efros  C<< <powerman-asdf@ya.ru> >>


=head1 LICENSE AND COPYRIGHT

Copyright (c) 2009,2014, Alex Efros C<< <powerman-asdf@ya.ru> >>. All rights reserved.

This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself. See L<perlartistic>.


=head1 DISCLAIMER OF WARRANTY

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH
YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE
LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL,
OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF
SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES.