#!perl -w

use strict;
use warnings;

use Qpsmtpd::Constants;

=head1 NAME

random_error

=head1 DESCRIPTION

This plugin randomly disconnects and issues DENYSOFTs.

=head1 CONFIG

one parameter is allowed, which is how often to error, as a percentage
of messages.  The default is 1. Use a negative number to disable.

2/5 of failures are DENYSOFT_DISCONNECT, 3/5 simply DENYSOFT.

For use with other plugins, scribble the revised failure rate to

   $self->connection->notes('random_fail_%');

=cut

sub register {
    my ($self, $qp, @args) = @_;

    die "Invalid args: '@args'" unless @args < 2;
    ($self->{__PACKAGE__ . '_how'}) = $args[0] || 1;

}

sub NEXT() { DECLINED }

sub random_fail {
    my $fpct = $_[0]->connection->notes('random_fail_%');

=head1 calculating the probability of failure

There are six tests a message must pass to reach the queueing stage, and we wish to
provide random failure for each one, with the combined probability being out
configuration argument. So we want to solve this equation:

       (1-x) ** 6 = ( 1 - input_number )

or 

       x = 1 - ( (1 - input_number ) ** (1/6) )

=cut

    my $successp = 1 - ($fpct / 100);
    $_[0]->log(LOGINFO,
               "to fail, rand(1) must be more than " . ($successp**(1 / 6)));
    rand(1) < ($successp**(1 / 6)) and return NEXT;
    rand(5) < 2 and return DENYSOFT_DISCONNECT, "random failure";
    return DENYSOFT, "random failure";
}

sub hook_connect {
    $_[0]->connection->notes('random_fail_%', $_[0]->{__PACKAGE__ . '_how'});
    goto &random_fail;
}

sub hook_helo {
    goto &random_fail;
}

sub hook_ehlo {
    goto &random_fail;
}

sub hook_mail {
    goto &random_fail;
}

sub hook_rcpt {
    goto &random_fail;
}

sub hook_data {
    goto &random_fail;
}

sub hook_data_post {
    goto &random_fail;
}