package LogMessages;

use strict;
use warnings;
use Attribute::Handlers;

our @ISA=qw/Exporter/;

use constant DEBUG => 1;

our @EXPORT=qw/
_log
/;

sub new{
        my $invocant=shift;
        my $class=ref($invocant) || $invocant;
        my $randomFileName=rand;
        print "Logging execution to $randomFileName\n";
        my $self={
                logfile=>$randomFileName,
                @_      # Override the default value.
        };

        bless($self, $class);
        print "Logging execution to $self->{logfile}\n";
        return $self;
}

sub getLogTime{
        my @months = qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec);
        my @weekDays = qw(Sun Mon Tue Wed Thu Fri Sat Sun);
        my ($second, $minute, $hour, $dayOfMonth, $month, $yearOffset, $dayOfWeek, $dayOfYear, $daylightSavings) = localtime();
        my $year = 1900 + $yearOffset;
        my $time = "$hour:$minute:$second, $weekDays[$dayOfWeek] $months[$month] $dayOfMonth, $year";
        return $time;
}

sub log_message{
        my $self=shift;

        open(LOGFILE, ">>$self->{logfile}") or die "Cannot open logfile";
        my $time=getLogTime();
        print LOGFILE $time, " ";
        for (@_){
                print LOGFILE @_;
        }
}

sub _log : ATTR(CODE) {                 # CODE means the attrib applies only to subroutines.
        my ($pkg, $sym, $code) = @_;    # pkg in which the subroutine was compiled.
                                        # reference to the typeglob where its symbol lives.
                                        # reference to subroutine itself.

        if( DEBUG ) {
                my $name = *{ $sym }{NAME};

                no warnings 'redefine'; # Turn off symbol redefinitions within the block.

                *{ $sym } = sub {
                        log_message("Entering sub $pkg\:\:$name\n");
                        my @ret = $code->( @_ );
                        log_message("Leaving sub $pkg\:\:$name\n");
                        return @ret;
                };
        }
}

##</code><code>##

use strict;
use warnings;
use lib "/home/sho/perl/dev/";
use LogMessages;

sub do_something : _log {
        print "I'm doing something.\n";
}

do_something();

##</code><code>##

Invalid CODE attribute: _log at ./demoLogMessages.pl line 6
BEGIN failed--compilation aborted at ./demoLogMessages.pl line 8.

##</code><code>##

Invalid CODE attribute: _log at demoLogMessages.pl line 27
 at /usr/lib/perl5/5.8.8/attributes.pm line 65
        attributes::import('attributes', 'main', 'CODE(0x926b08c)', '_log') called at demoLogMessages.pl line 27
        main::BEGIN() called at demoLogMessages.pl line 29
        eval {...} called at demoLogMessages.pl line 29
BEGIN failed--compilation aborted at demoLogMessages.pl line 29.
 at demoLogMessages.pl line 29
Debugged program terminated.  Use q to quit or R to restart,