use strict;
use warnings;

package Paranoic;
print "Paranoic.pm here..\n";

sub calculate_module_md5{
	my $path = shift;
	open my $file, '<', $path or die "Impossible to open [$path]";
	my $ctx = Digest::MD5->new;
	$ctx->addfile ($file);
	my $md5 = $ctx->hexdigest;
	close $file;
	return $md5;
}
sub load_md5_from_file{
	my %paranoic_INC;
	open my $file, '<', 'md5-check.txt' or die "Unable to load [md5-check.txt]";
	while (<$file>){
		chomp $_;
		next if /^#/;
		next unless $_;
		my ($name,$path,$md5) = split /\s+/,$_;
		$paranoic_INC{ $name } = {
			path 			=> $path,
			expected_md5 	=> $md5,
		};
	}
	return \%paranoic_INC;	
}
sub traverse_INC{
	my $filename = shift;
	my @original_INC = @_;
}
BEGIN {
	my @original_INC = @INC;
	use Digest::MD5 ;
	use File::Spec;
	#print "BEFORE: ",map {"$_ $INC{$_}\n"} keys %INC;
	print "BEFORE any hook I will check md5 of already loaded module:\n";
	my $paranoic_inc = load_md5_from_file();
	foreach my $module ( keys %INC ){
		# SKIP itself while developping it
		# next if $module eq 'Paranoic.pm';
		#test
		#if ($module eq 'Exporter.pm'){$$paranoic_inc{$module}{expected_md5}.='XXXXX'}
		
		my $md5 = calculate_module_md5( $INC{$module} );
		
		# NOT FOUND
		if (! exists $$paranoic_inc{$module} ){
			# this is a die
			print "Cannot find a stored md5 for [$module]";
			print "\n-->DEBUG: $module\t$INC{$module}\t$md5\n";			
		}
		# WHITELIST
		elsif ( 'ALLOW' eq $$paranoic_inc{$module}{expected_md5}  ){
			print "  WHITELIST for $module at $$paranoic_inc{$module}{path} [$md5]\n";
		}
		# BLACKLIST
		elsif ( 'DENY' eq $$paranoic_inc{$module}{expected_md5} ){
			# this is a die
			print "  DENY for $module at $$paranoic_inc{$module}{path} [$md5]\n";
		}
		# EXPECTED MD5
		elsif ( $md5 eq $$paranoic_inc{$module}{expected_md5} ){
			print "  OK $module at $$paranoic_inc{$module}{path} has the expected md5: ".
					"$$paranoic_inc{$module}{expected_md5}\n";
		}
		# WRONG MD5
		elsif ( $md5 ne $$paranoic_inc{$module}{expected_md5} ){
			# this is a die..
			print "ERROR: $module at $$paranoic_inc{$module}{path} has [$md5] ".
					"insetead of [$$paranoic_inc{$module}{expected_md5}]";
		}
		# UNKNOWN RESULT
		else{
			die "UNKNOWN error for $module at $$paranoic_inc{$module}{path} with md5 [$md5]"
		}
	}

	print "\nAFTER I will use some hook to check md5 of modules loaded by the calling program\n";
	if ( $^V ge '5.38.0'){
		print "====> Perl $^V using \$^HOOK\n";
		${^HOOK}{require__before} = sub {
			my $filename = shift;
				if ( exists $INC{$filename} ){
					print "    SKIP [$filename] already processed\n";
					return;
				}
				print "Paranoically considering [$filename]\n";
		};
	}
	else{
		print "====> Perl $^V using \@INC\n";
		unshift @INC, sub {
			my ($self,$filename) = @_;
			print "Paranoically considering [$filename]\n";
		};
	}
}


1;

##</code><code>##

warnings.pm	/usr/local/lib/perl5/5.36.1/warnings.pm	7167a8489aafb9faddbbe48c6480f47c
strict.pm	/usr/local/lib/perl5/5.36.1/strict.pm	31b6105d6dc1cde54154291b86c8b285
Digest/MD5.pm	/usr/local/lib/perl5/5.36.1/x86_64-linux/Digest/MD5.pm	d75a3d708ce93ad8d99fcbdefa2c8429
Digest/base.pm	/usr/local/lib/perl5/5.36.1/Digest/base.pm	b5de2696c583dfec247af39b45288735
XSLoader.pm	/usr/local/lib/perl5/5.36.1/XSLoader.pm	74a2550b5b0731996c0c825930003013
Exporter.pm	/usr/local/lib/perl5/5.36.1/Exporter.pm	9ac6b836ee45f6e08e5c8a84cee5e619

#
Paranoic.pm	Paranoic.pm ALLOW
#
Cwd.pm	/usr/local/lib/perl5/5.36.1/x86_64-linux/Cwd.pm  8f620379a0649ad32f14f1ce50b88bc0
File/Spec.pm	/usr/local/lib/perl5/5.36.1/x86_64-linux/File/Spec.pm	7be482dda6bd364dd65e286b24cd8691
warnings/register.pm	/usr/local/lib/perl5/5.36.1/warnings/register.pm	2d8f6ce093a2176b982c0e12c0194b3b
File/Spec/Unix.pm	/usr/local/lib/perl5/5.36.1/x86_64-linux/File/Spec/Unix.pm	bf252d457a243d20eabbd91292fcf3f4
constant.pm	/usr/local/lib/perl5/5.36.1/constant.pm	56cde6eba0f667ab56196613df3933c1

##</code><code>##

use strict;
use warnings;
use List::Util;

##</code><code>##

BEFORE any hook I will check md5 of already loaded module:
  OK Exporter.pm at /usr/local/lib/perl5/5.36.1/Exporter.pm has the expected md5: 9ac6b836ee45f6e08e5c8a84cee5e619
  OK warnings.pm at /usr/local/lib/perl5/5.36.1/warnings.pm has the expected md5: 7167a8489aafb9faddbbe48c6480f47c
  WHITELIST for Paranoic.pm at Paranoic.pm [f929845aba01aa4bf162a15cc254c123]
  OK strict.pm at /usr/local/lib/perl5/5.36.1/strict.pm has the expected md5: 31b6105d6dc1cde54154291b86c8b285
  OK Cwd.pm at /usr/local/lib/perl5/5.36.1/x86_64-linux/Cwd.pm has the expected md5: 8f620379a0649ad32f14f1ce50b88bc0
  OK Digest/base.pm at /usr/local/lib/perl5/5.36.1/Digest/base.pm has the expected md5: b5de2696c583dfec247af39b45288735
  OK constant.pm at /usr/local/lib/perl5/5.36.1/constant.pm has the expected md5: 56cde6eba0f667ab56196613df3933c1
  OK File/Spec/Unix.pm at /usr/local/lib/perl5/5.36.1/x86_64-linux/File/Spec/Unix.pm has the expected md5: bf252d457a243d20eabbd91292fcf3f4
  OK Digest/MD5.pm at /usr/local/lib/perl5/5.36.1/x86_64-linux/Digest/MD5.pm has the expected md5: d75a3d708ce93ad8d99fcbdefa2c8429
  OK File/Spec.pm at /usr/local/lib/perl5/5.36.1/x86_64-linux/File/Spec.pm has the expected md5: 7be482dda6bd364dd65e286b24cd8691
  OK warnings/register.pm at /usr/local/lib/perl5/5.36.1/warnings/register.pm has the expected md5: 2d8f6ce093a2176b982c0e12c0194b3b
  OK XSLoader.pm at /usr/local/lib/perl5/5.36.1/XSLoader.pm has the expected md5: 74a2550b5b0731996c0c825930003013

AFTER I will use some hook to check md5 of modules loaded by the calling program
====> Perl v5.36.1 using @INC
Paranoic.pm here..
Paranoically considering [List/Util.pm]


##</code><code>##

AFTER I will use some hook to check md5 of modules loaded by the calling program
====> Perl v5.38.0 using $^HOOK
Paranoic.pm here..
    SKIP [strict.pm] already processed
    SKIP [warnings.pm] already processed
Paranoically considering [List/Util.pm]
    SKIP [strict.pm] already processed
    SKIP [warnings.pm] already processed
    SKIP [strict.pm] already processed
    SKIP [Exporter.pm] already processed
    SKIP [XSLoader.pm] already processed