path: root/IkiWiki/Plugin/external.pm

#!/usr/bin/perl
# Support for external plugins written in other languages.
# Communication via XML RPC to a pipe.
# See externaldemo for an example of a plugin that uses this.
package IkiWiki::Plugin::external;

use warnings;
use strict;
use IkiWiki 2.00;
use RPC::XML;
use RPC::XML::Parser;
use IPC::Open2;
use IO::Handle;

my %plugins;

sub import {
    my $self=shift;
    my $plugin=shift;
    return unless defined $plugin;

    my ($plugin_read, $plugin_write);
    my $pid = open2($plugin_read, $plugin_write,
        IkiWiki::possibly_foolish_untaint($plugin));

    # open2 doesn't respect "use open ':utf8'"
    binmode($plugin_read, ':utf8');
    binmode($plugin_write, ':utf8');

    $plugins{$plugin}={in => $plugin_read, out => $plugin_write, pid => $pid,
        accum => ""};
    $RPC::XML::ENCODING="utf-8";

    rpc_call($plugins{$plugin}, "import");
}

sub rpc_write ($$) {
    my $fh=shift;
    my $string=shift;

    $fh->print($string."\n");
    $fh->flush;
}

sub rpc_call ($$;@) {
    my $plugin=shift;
    my $command=shift;

    # send the command
    my $req=RPC::XML::request->new($command, @_);
    rpc_write($plugin->{out}, $req->as_string);

    # process incoming rpc until a result is available
    while ($_ = $plugin->{in}->getline) {
        $plugin->{accum}.=$_;
        while ($plugin->{accum} =~ /^\s*(<\?xml\s.*?<\/(?:methodCall|methodResponse)>)\n(.*)/s) {
            $plugin->{accum}=$2;
            my $r = RPC::XML::Parser->new->parse($1);
            error("XML RPC parser failure: $r") unless ref $r;
            if ($r->isa('RPC::XML::response')) {
                my $value=$r->value;
                if ($r->is_fault($value)) {
                    # throw the error as best we can
                    print STDERR $value->string."\n";
                    return "";
                }
                elsif ($value->isa('RPC::XML::array')) {
                    return @{$value->value};
                }
                elsif ($value->isa('RPC::XML::struct')) {
                    my %hash=%{$value->value};

                    # XML-RPC v1 does not allow for
                    # nil/null/None/undef values to be
                    # transmitted, so until
                    # XML::RPC::Parser honours v2
                    # (<nil/>), external plugins send
                    # a hash with one key "null" pointing
                    # to an empty string.
                    if (exists $hash{null} &&
                        $hash{null} eq "" &&
                        int(keys(%hash)) == 1) {
                        return undef;
                    }

                    return %hash;
                }
                else {
                    return $value->value;
                }
            }

            my $name=$r->name;
            my @args=map { $_->value } @{$r->args};

            # When dispatching a function, first look in 
            # IkiWiki::RPC::XML. This allows overriding
            # IkiWiki functions with RPC friendly versions.
            my $ret;
            if (exists $IkiWiki::RPC::XML::{$name}) {
                $ret=$IkiWiki::RPC::XML::{$name}($plugin, @args);
            }
            elsif (exists $IkiWiki::{$name}) {
                $ret=$IkiWiki::{$name}(@args);
            }
            else {
                error("XML RPC call error, unknown function: $name");
            }

            # XML-RPC v1 does not allow for nil/null/None/undef
            # values to be transmitted, so until XML::RPC::Parser
            # honours v2 (<nil/>), send a hash with one key "null"
            # pointing to an empty string.
            if (! defined $ret) {
                $ret={"null" => ""};
            }

            my $string=eval { RPC::XML::response->new($ret)->as_string };
            if ($@ && ref $ret) {
                # One common reason for serialisation to
                # fail is a complex return type that cannot
                # be represented as an XML RPC response.
                # Handle this case by just returning 1.
                $string=eval { RPC::XML::response->new(1)->as_string };
            }
            if ($@) {
                error("XML response serialisation failed: $@");
            }
            rpc_write($plugin->{out}, $string);
        }
    }

    return undef;
}

package IkiWiki::RPC::XML;
use Memoize;

sub getvar ($$$) {
    my $plugin=shift;
    my $varname="IkiWiki::".shift;
    my $key=shift;

    no strict 'refs';
    my $ret=$varname->{$key};
    use strict 'refs';
    return $ret;
}

sub setvar ($$$;@) {
    my $plugin=shift;
    my $varname="IkiWiki::".shift;
    my $key=shift;
    my $value=shift;

    no strict 'refs';
    my $ret=$varname->{$key}=$value;
    use strict 'refs';
    return $ret;
}

sub getstate ($$$$) {
    my $plugin=shift;
    my $page=shift;
    my $id=shift;
    my $key=shift;

    return $IkiWiki::pagestate{$page}{$id}{$key};
}

sub setstate ($$$$;@) {
    my $plugin=shift;
    my $page=shift;
    my $id=shift;
    my $key=shift;
    my $value=shift;

    return $IkiWiki::pagestate{$page}{$id}{$key}=$value;
}

sub getargv ($) {
    my $plugin=shift;

    return \@ARGV;
}

sub setargv ($@) {
    my $plugin=shift;
    my $array=shift;

    @ARGV=@$array;
}

sub inject ($@) {
    # Bind a given perl function name to a particular RPC request.
    my $plugin=shift;
    my %params=@_;

    if (! exists $params{name} || ! exists $params{call}) {
        die "inject needs name and call parameters";
    }
    my $sub = sub {
        IkiWiki::Plugin::external::rpc_call($plugin, $params{call}, @_)
    };
    $sub=memoize($sub) if $params{memoize};

    # This will add it to the symbol table even if not present.
    no warnings;
    eval qq{*$params{name}=\$sub};
    use warnings;

    # This will ensure that everywhere it was exported to sees
    # the injected version.
    IkiWiki::inject(name => $params{name}, call => $sub);
    return 1;
}

sub hook ($@) {
    # the call parameter is a function name to call, since XML RPC
    # cannot pass a function reference
    my $plugin=shift;
    my %params=@_;

    my $callback=$params{call};
    delete $params{call};

    IkiWiki::hook(%params, call => sub {
        IkiWiki::Plugin::external::rpc_call($plugin, $callback, @_);
    });
}

sub pagespec_match ($@) {
    # convert pagespec_match's return object into a XML RPC boolean
    my $plugin=shift;

    return RPC::XML::boolean->new(0 + IkiWiki::pagespec_march(@_));
}

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