#!/usr/bin/perl
# script: assert
# SSF 072110 tests a perl expression (like a file test) and emails you
+ if false
# Copyright (C) 2010 Xenoscience - released under GPLv3 - All rights r
+eserved

use strict;
use warnings;
use vars qw/$cmdMail $host/;
use LWP::MediaTypes qw(guess_media_type read_media_types);
use MIME::Entity;
use Safe;

BEGIN {
   $cmdMail='/usr/lib/sendmail';         # location of your sendmail
   $host=`whoami`.'@'.`hostname`;        # who am I
   read_media_types('/etc/mime.types');  # location of your mime.types
+ file
}

sub sendmail {   # returns undef or error
   my ($from,$to,$subject,$body,@attachments)=@_;
   my $ret;
   my $top=build MIME::Entity
         From         => $from,
         'Reply-to'   => $from,
         To           => $to,
         Subject      => $subject,
         Data         => $body;
   if (@attachments) {
      for my $path (@attachments) {
          my $type=guess_media_type($path);
          $top->attach(
              Path     => $path,
              Type     => $type,
              Encoding => '-SUGGEST'
          );
       }
    }
    $top->sync_headers(Length=>'COMPUTE') if @attachments;
    if (open(MAIL,"| $cmdMail -t -i")) {
       $top->print(\*MAIL);
       close MAIL;
    } else {
       $ret="Mail to $to failed: $!";
    }
    $ret;
}

my ($expr,$file,$email,$msg)=@ARGV;
die "usage:  assert 'expr' [file|1] [email] [message]\n" unless $expr;
$file||=1;
$expr=~s/:f:/q{$file}/g;
my $cpt=Safe->new('eval_safe');  # only one dungeon
$cpt->permit(':filesys_read');
my $value=$cpt->reval($expr);  
die "eval_safe { $expr }:\n$@\n" if $@;
if ($email=~/result/i) {
   my $result=defined $value ? $value : 'undef';
   print "$expr evaluated to $result\n";
} 
unless ($value) {
   $msg||="{ $expr } is false";
   if ($email=~/[@]/) {
      my $err=sendmail($host,$email,'Assertion failed',$msg);
      die $err if $err;
   } else {
      print $msg,"\n";
   }
}
exit;
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