#!/usr/bin/perl

use warnings;
use strict;
use File::Temp qw/ tempfile tempdir /;

my $SSLPATH = '/usr/bin/openssl';

#Usage
sub print_usage {
  print "ZFS Snapshot diff\n";
  print "\t$0 [-dhirv] <zfs shapshot name> [filename]\n\n";
  print " -d  Display the lines that are different (diff output)\n";
  print " -h  Display this usage\n";
  print " -m  Use md5sum when checking for file differences";
  print " -i  Ignore files that don't exist in the snapshot (only necessary for recursing)\n";
  print " -r  Recursively diff every file in the snapshot (filename not required)\n";
  print " -v  Verbose mode\n\n";

  print " [filename] is the filename RELATIVE to the ZFS snapshot root. For example, if\n";
  print " I had a filesystem snapshot called pool/data/zone\@initial. The filename '/etc/passwd'\n";
  print " would refer to the filename /pool/data/zone/etc/passwd in the filesystem and filename\n";
  print " /pool/data/zone/.zfs/snapshot/initial/etc/passwd in the snapshot.\n\n";

  print " A couple of examples:\n";
  print "\t$0 -v -r -i pool/zones/lava2019\@Fri\n";
  print "\t\tChecks the current pool/zones/lava2019 filesystem against the snapshot\n";
  print "\t\treturning the md5sum difference of any files (ignore files that don't\n";
  print "\t\texist in the snapshot). With verbose mode\n\n";

  print "\t$0 -d pool/zones/lava2019\@Mon /root/etc/passwd\n";
  print "\t\tCheck the md5sum for /pool/zones/lava2019/root/etc/passwd and compare\n";
  print "\t\tit to /pool/zones/lava2019/.zfs/snapshot/Mon/root/etc/passwd. Display\n";
  print "\t\tthe lines that are different also.\n\n";

  exit(0);
}

use Getopt::Long;
my %options = ();
my $verbose;

GetOptions("h" => \$options{help},
           "r!" => \$options{recurse},
           "d!" => \$options{diff},
           "i!" => \$options{ignore},
	   "m!" => \$options{md5sum},
           "v!" => \$verbose
           );

if ($options{help}) {
  print_usage();
}

if ($options{recurse}) {
  recurse_diff(shift || die "Need a ZFS snapshot name\n");
} else {
  my $zfsname = shift || die "Need a ZFS snapshot name\n";
  my $file = shift || die "Need a filename\n";
  diff_single_file($zfsname,$file);
}

exit(0);

sub recurse_diff {
  my $zfssnap = shift;
  print "Recursive diff on $zfssnap\n" if $verbose;

  $zfssnap =~ /(.+)\@(.+)/i;
  if(($1 eq "") || ($2 eq "")) { die "-E- Invalid snapshot name\n"; }
  my $fsname = "/" . $1;
  my $snapname = $2;
  if(! -d $fsname && $fsname =~ /\/\S+?(\/.*)/) { $fsname = $1; }
  elsif(! -d $fsname && $fsname =~ /\/\S+?/) { $fsname = "/"; }
  print "Filesystem: $fsname, Snapshot: $snapname\n" if $verbose;

  my $snappath = $fsname . "/.zfs/snapshot/" . $snapname . "/";
  my $fspath = $fsname . "/";
  $fspath =~ s/\/\//\//gi;
  $snappath =~ s/\/\//\//gi;
  print "Comparing: $fspath\nto: $snappath\n" if $verbose;

  my $dir = tempdir( CLEANUP => 0 );
  my ($fh, $filename) = tempfile( DIR => $dir );

  print "-> Finding files in $fspath to compare against files in $snappath\n";
  `find $fspath -name "*" -type f > $filename`;
  print "-> Performing a diff operation on each file found\n";

  my $num_files = `cat $filename | wc | awk '{print \$1}'`;
  
  foreach my $file (<$fh>) {
    chomp($file);
    $file =~ /(.*)\/(.*)/;
    my $shortname = $2;
    $file =~ /$fspath(.*)/;
    my $diff = $snappath . $1;
    if (!-e $diff) {
      print "$file does not exist in snapshot\n" if !$options{ignore};
      next;
    }

    if($options{md5sum}) { 
	# do the md5 sums
	my $orig = `$SSLPATH md5 $file`;
	my $snap = `$SSLPATH md5 $diff`;
	$orig =~ /[\s\S]+= (.+)/;
	my $sum1 = $1;
	$snap =~ /[\s\S]+= (.+)/;
	my $sum2 = $1;
	if ($sum1 ne $sum2) {
	    print "** $file is different\n";
	    print "** $orig** $snap" if $verbose;
	}
    } else {
	my $differ = system("diff \"$file\" \"$diff\" > /dev/null 2>&1");
	if($differ) { print "** $file is different\n"; }
    }
    if ($options{diff}) {
      system("diff \"$file\" \"$diff\"");
    }
  }
}

sub diff_single_file {
  my $zfssnap = shift;
  my $filename = shift;
  print "Single-file diff on $zfssnap, file: $filename\n" if $verbose;

  $zfssnap =~ /(.+)\@(.+)/i;
  my $fsname = "/" . $1 . "/";
  my $snapname = $2;
  if(! -d $fsname && $fsname =~ /\/\S+?(\/.*)/) { $fsname = $1; }
  print "Filesystem: $fsname, Snapshot: $snapname\n" if $verbose;

  my $fspath;
  if($filename !~ /^\//) { $fspath = $ENV{'PWD'} . "/" . $filename; }
  else { $fspath = $filename; }

  my $snapfspath = $fspath;
  $snapfspath =~ s/$fsname//g;
  my $snappath = $fsname . "/.zfs/snapshot/" . $snapname . "/" . $snapfspath;
  $fspath =~ s/\/\//\//gi;
  $snappath =~ s/\/\//\//gi;
  print "Comparing: $fspath\nto: $snappath\n" if $verbose;
  if(! -f $fspath) { print "-E- Cannot find source file: $fspath\n"; exit 1; }
  if(! -f $snappath) { print "-E- Cannot find source file: $snappath\n"; exit 1; }

  if($options{md5sum}) { 
      my $orig = `$SSLPATH md5 $fspath`;
      my $snap = `$SSLPATH md5 $snappath`;
      $orig =~ /[\s\S]+= (.+)/;
      my $sum1 = $1;
      $snap =~ /[\s\S]+= (.+)/;
      my $sum2 = $1;
      if ($sum1 ne $sum2) {
	  print "** Files are different\n";
	  print "** $orig** $snap" if $verbose;
      }
  } else {
      my $differ = system("diff \"$fspath\" \"$snappath\" > /dev/null 2>&1");
      if($differ) { print "** Files are different\n"; }
  }
  if ($options{diff}) {
    system("diff \"$fspath\" \"$snappath\"");
  }
}