=item $ua->request($request, $arg [, $size])

Process a request, including redirects and security.  This method may
actually send several different simple requests.

The arguments are the same as for C<simple_request()>.

=cut

sub request
{
    my($self, $request, $arg, $size, $previous) = @_;

    LWP::Debug::trace('()');

    my $response = $self->simple_request($request, $arg, $size);

    my $code = $response->code;
    $response->previous($previous) if defined $previous;

    LWP::Debug::debug('Simple response: ' .
		      (HTTP::Status::status_message($code) ||
		       "Unknown code $code"));

    if ($code == &HTTP::Status::RC_MOVED_PERMANENTLY or
	$code == &HTTP::Status::RC_MOVED_TEMPORARILY) {

	# Make a copy of the request and initialize it with the new URI
	my $referral = $request->clone;

	# And then we update the URL based on the Location:-header.
	my $referral_uri = $response->header('Location');
	{
	    # Some servers erroneously return a relative URL for redirects,
	    # so make it absolute if it not already is.
	    local $URI::ABS_ALLOW_RELATIVE_SCHEME = 1;
	    my $base = $response->base;
	    $referral_uri = $HTTP::URI_CLASS->new($referral_uri, $base)
		            ->abs($base);
	}

	$referral->url($referral_uri);

	return $response unless $self->redirect_ok($referral);

	# Check for loop in the redirects
	my $count = 0;
	my $r = $response;
	while ($r) {
	    if (++$count > 13 ||
                $r->request->url->as_string eq $referral_uri->as_string) {
		$response->header("Client-Warning" =>
				  "Redirect loop detected");
		return $response;
	    }
	    $r = $r->previous;
	}

	return $self->request($referral, $arg, $size, $response);

    } elsif ($code == &HTTP::Status::RC_UNAUTHORIZED ||
	     $code == &HTTP::Status::RC_PROXY_AUTHENTICATION_REQUIRED
	    )
    {
	my $proxy = ($code == &HTTP::Status::RC_PROXY_AUTHENTICATION_REQUIRED);
	my $ch_header = $proxy ?  "Proxy-Authenticate" : "WWW-Authenticate";
	my @challenge = $response->header($ch_header);
	unless (@challenge) {
	    $response->header("Client-Warning" => 
			      "Missing Authenticate header");
	    return $response;
	}

	require HTTP::Headers::Util;
	CHALLENGE: for my $challenge (@challenge) {
	    $challenge =~ tr/,/;/;  # "," is used to separate auth-params!!
	    ($challenge) = HTTP::Headers::Util::split_header_words($challenge);
	    my $scheme = lc(shift(@$challenge));
	    shift(@$challenge); # no value
	    $challenge = { @$challenge };  # make rest into a hash
	    for (keys %$challenge) {       # make sure all keys are lower case
		$challenge->{lc $_} = delete $challenge->{$_};
	    }

	    unless ($scheme =~ /^([a-z]+(?:-[a-z]+)*)$/) {
		$response->header("Client-Warning" => 
				  "Bad authentication scheme '$scheme'");
		return $response;
	    }
	    $scheme = $1;  # untainted now
	    my $class = "LWP::Authen::\u$scheme";
	    $class =~ s/-/_/g;
	
	    no strict 'refs';
	    unless (%{"$class\::"}) {
		# try to load it
		eval "require $class";
		if ($@) {
		    if ($@ =~ /^Can\'t locate/) {
			$response->header("Client-Warning" =>
					  "Unsupported authentication scheme '$scheme'");
		    } else {
			$response->header("Client-Warning" => $@);
		    }
		    next CHALLENGE;
		}
	    }
	    return $class->authenticate($self, $proxy, $challenge, $response,
					$request, $arg, $size);
	}
	return $response;
    }
    return $response;
}