/ 
WWW-RoboCop-0.000103
River stage zero No dependents
/ WWW::RoboCop

NAME

WWW::RoboCop - Police your URLs!

VERSION

version 0.000103

SYNOPSIS

use feature qw( state );

use WWW::RoboCop ();

my $robocop = WWW::RoboCop->new(
    is_url_allowed => sub {
        state $count = 0;
        return $count++ < 5; # just crawl 5 URLs
    },
);

$robocop->crawl( 'https://example.com' );

my %history = $robocop->get_report;

# %history = (
#    'http://myhost.com/one' => { status => 200, ... },
#    'http://myhost.com/two' => { status => 404, ... },
#    ...
# )

See examples/crawl-host.pl, which is included with this distribution, to get a quick start.

DESCRIPTION

WWW::RoboCop is a simple, somewhat opinionated robot. Given a starting page, this module will crawl only URLs which have been allowed by the is_url_allowed callback. It then creates a report of all visited pages, keyed on URL. You are encouraged to provide your own report creation callback so that you can collect all of the information which you require for each URL.

CONSTRUCTOR AND STARTUP

new()

Creates and returns a new WWW::RoboCop object.

Below are the arguments which you may pass to new when creating an object.

is_url_allowed

This argument is required. You must provide an anonymous subroutine which will return true or false based on some arbitrary criteria which you provide. The two arguments to this anonymous subroutine will be a WWW::Mechanize::Link object as well as the referring URL, in the form of a URI object.

Your sub might look something like this:

use feature qw( state );

use URI ();
use WWW::RoboCop ();

my $robocop = WWW::RoboCop->new(
    is_url_allowed => sub {
        my $link          = shift;
        my $referring_url = shift;

        my $upper_limit = 100;
        my $host = 'some.host.com';

        state $limit = 0;

        return 0 if $limit > $upper_limit;
        my $uri = URI->new( $link->url_abs );

        # if the referring_url matches the host then this is a 1st degree
        # outbound web link

        if ( $uri->host eq $host || $referring_url->host eq $host ) {
            ++$limit;
            return 1;
        }
        return 0;
    }
);

report_for_url

This argument is not required, but is highly recommended. The arguments to this anonymous subroutine will be an HTTP::Response object as well as the referring URL in the form of a URI object. Your sub might look something like this:

my $reporter = sub {
    my $response      = shift;    # HTTP::Response object
    my $referring_url = shift;    # URI object
    return {
        redirects => [
            map { +{ status => $_->code, uri => $_->base->as_string } }
                $res->redirects
        ],
        referrer => $referring_url,
        status   => $res->code,
    };
};

my $robocop = WWW::RoboCop->new(
    is_url_allowed => sub { ... },
    report_for_url     => $reporter,
);

That would give you a HashRef with the status code for each link visited (200, 404, 500, etc) as well as the referring URL (the page on which the link was found) and a list of any redirects which were followed in order to get to this URL.

The default report_for_url sub will already provide something like the above, but you should only treat this as a stub method while you get up and running. Since it's only meant to be an example, the format of the default report could change at some future date without notice. You should not rely on or expect it to remain consistent in future. If you are going to rely on this module, you should provide your own reporting logic.

ua( WWW::Mechanize )

You can provide your own UserAgent object to this class. It should be of the WWW::Mechanize family. If you're looking for a significant speed boost while under development, consider providing a WWW::Mechanize::Cached object. This can give you enough of a speedup to save you from getting distracted and going off to read Hacker News while you wait.

use CHI ();
use WWW::Mechanize::Cached ();
use WWW::RoboCop ();

my $cache = CHI->new(
    driver => 'File',
    root_dir => /tmp/cache-example',
);

my $robocop = WWW::RoboCop->new(
    is_url_allowed => sub { ... },
    ua => WWW::Mechanize::Cached->new( cache => $cache ),
);

If you're not using a Cached agent, be sure to disable autocheck.

my $robocop = WWW::RoboCop->new(
    is_url_allowed => sub { ... },
    ua => WWW::Mechanize->new( autocheck => 0 ),
);

crawl( $url )

This method sets the WWW::RoboCop in motion. The robot will only come to a halt once has exhausted all of the allowed URLs it can find.

get_report

This method returns a Hash of crawling results, keyed on the URLs visited. By default, it returns a very simple Hash, containing only the status code of the visited URL. You are encouraged to provide your own callback so that you can get a detailed report returned to you. You can do this by providing a report_for_url callback when instantiating the object.

The default report looks something like this:

# %history = (
#    'http://myhost.com/one' => { status => 200, ... },
#    'http://myhost.com/two' => { status => 404, ... },
# )

See examples/crawl-host.pl, which is included with this distribution, to get a dump of the default report.

AUTHOR

Olaf Alders <olaf@wundercounter.com>

COPYRIGHT AND LICENSE

This software is Copyright (c) 2015 by MaxMind, Inc.

This is free software, licensed under:

The Artistic License 2.0 (GPL Compatible)