#! /usr/bin/env perl

use strict;
use warnings;

use Data::Dumper;

my $source = shift;
my $target = shift;

die "Usage: replicate source target\n" unless $source && $target;

my $dryRun = 1; # if set, will only display the command to be executed

my $config = {
   # compile the regex
   'pattern' => qr/(\d{4}.\d{2}.\d{2}.\d{2}.\d{2})/
   };

sub parseDataSet {
   my $data = shift;
   my %return;
   my ( $server, $dataset ) = split( ':', $data );
   if ( $dataset ) { # they passed a server:dataset
      $return{'server'} = $server;
      $return{'dataset'} = $dataset;
   } else { # only passing in dataset, so assume localhost
      $return{'server'} = '';
      $return{'dataset'} = $server;
   }
   return \%return;
}

# runs a command, redirecting stderr to stdout (which it ignores)
# then returns 0 and $output on success.
# if error, returns error code and string describing error
sub run {
   my $command = shift;
   my $output = qx/$command 2>&1/;
   if ($? == -1) {
      return (-1,"failed to execute: $!");
   } elsif ($? & 127) {
      return ($?, sprintf "child died with signal %d, %s coredump",
        ($? & 127),  ($? & 128) ? 'with' : 'without' );
   } else {
      return ($? >> 8, sprintf "child exited with value %d", $? >> 8 ) if $? >> 8;
   }
   return (0,$output);
}


sub getSnaps {
   my ($config,$pattern) = @_;
   my %return;
   # actual command to run to get all snapshots, recursively, of the dataset
   my $command = 'zfs list -r -t snap ' . $config->{'dataset'};
   $command = "ssh $config->{server} '$command'" if $config->{'server'};
   #die "$command\n";
   my ($error, $output ) = &run( $command );
   #die "Error running $command with output\n$output" if $error;
   my @snaps = split( "\n", $output );
   chomp @snaps;
   for (my $i = 0; $i < @snaps; $i++ ) {
      # parse out the space delmited fields
      my ($fullname, $used, $avail, $refer, $mount) = split( /\s+/, $snaps[$i] );
      # break the name into dataset and snapname
      my ($dataset, $snap) = split( '@', $fullname );
      # remove the root dataset name
      $dataset =~ s/^$config->{'dataset'}//;
      # skip anything not matching our regex
      next unless $pattern && $snap && $snap =~ m/$pattern/;
      # grab the matched key
      $return{$dataset}{'snaps'}{$snap}{'key'} = $1;
      # and remove all non-numerics
      $return{$dataset}{'snaps'}{$snap}{'key'} =~ s/[^0-9]//g;
      # get the transfer size
      $return{$dataset}{'snaps'}{$snap}{'refer'} = $refer;
      # get the actual disk space used
      $return{$dataset}{'snaps'}{$snap}{'used'} = $used;
   }
   return \%return;
}

sub diffSnaps {
   my ( $source, $target ) = @_;
   my @source = sort keys %$source;
   my @target = sort keys %$target;
#   print "===Source\n" . join( "\n", @source ) . "\n===Target\n" . join( "\n", @target ) . "\n";

   my $s = 0;
   my $t = 0;
   my %return;
   $return{'deleteTarget'} = [];
   $return{'addTarget'} = [];
   $return{'lastMatch'} = 0;
   $return{'finalSync'} = 0;
   while ( $s < @source && $t < @target ) {
      if ( $source[$s] eq $target[$t] ) { # matchies, just keep going
#         print "Source $s [$source[$s]] matches target $t [$target[$t]]\n";
         $return{'lastMatch'} = $source[$s]; # keep track of the largest match
         $s++; $t++;
      } elsif ( $target[$t] ne $source[$s] ) { # we are processing stuff that needs to be deleted on target
         push @{$return{'deleteTarget'}}, $target[$t];
#         print "Adding delete target $t [$target[$t]]\n";
         $t++;
      }
   }
   die "Could not reconcile snapshots, ran out of source too soon\n" if $s > @source;
   # put a value into finalSync to make sure there is one. If we do not have any sync
   # to do, final and lastMatch will be the same
   $return{'finalSync'} = $return{'lastMatch'};
   while ( $s < @source ) {
      push @{$return{'addTarget'}}, $source[$s];
      $return{'finalSync'} = $source[$s];
      $s++;
   }
#   die Dumper( \%return );
   return \%return;
}
   
sub arrayEquals {
   my ($a, $b ) = @_;
   return 0 unless @{$a} == @{$b}; # they are different sizes
   for ( my $i = 0; $i < @$a; $i++ ) {
      if ( $$a[$i] ne $$b[$i] ) {
         print STDERR "No Match!\n" . join( "\t", @$a ) . "\n" . join( "\t", @$b ) . "\n";
         return 0;
      }
   }
   return 1;
}
   
sub createCommands {
   my ( $source, $target, $config ) = @_;
   my @return;
   # check for new snapshots to sync
   if ( $source ne $target ) {
      # first create the replicate command. The send command request recursion (-R)
      # and the range of snapshots including all intermediate ones (-I)
      my $sourceCommand = 'zfs send -RI ';
      $sourceCommand .= $config->{'source'}->{'dataset'} . '@' . $target . ' ';
      $sourceCommand .= $config->{'source'}->{'dataset'} . '@' . $source;
      $sourceCommand = "ssh $config->{source}->{server} '$sourceCommand'" if $config->{'source'}->{'server'};

      my $targetCommand = 'zfs receive -v ';
      $targetCommand .= $config->{'target'}->{'dataset'};
      $targetCommand = "ssh $config->{target}->{server} '$sourceCommand'" if $config->{'target'}->{'server'};
      push @return, $sourceCommand . ' | ' . $targetCommand;
   } else {
      push @return, '# Nothing new to sync';
   }
   # now, check for snapshots to remove
   #if ( $config->{'actions'}->{'deleteTarget'} ) {
   #   my $delete = $config->{'actions'}->{'deleteTarget'};
   #   foreach my $ds ( @$delete ) {
   #      push @return, "zfs destroy -r $config->{target}->{'dataset'}\@$ds";
   #   }
   #} else {
   #   push @return, "# No old snapshots to be removed";
   #}
   return \@return;
}
   
# find the last snapshot in a hash. The hash is assumed to have a subkey
# 'key'. look for the largest subkey, and return the key for it
sub getLastSnapshot {
   my $snapList = shift;
   my $lastKey = 0;
   my $lastSnap = '';
   foreach my $snap ( keys %$snapList ) {
      if ( $snapList->{$snap}->{'key'} > $lastKey ) {
         $lastKey = $snapList->{$snap}->{'key'};
         $lastSnap = $snap;
      }
   }
   return $lastSnap;
}


sub calculate {
   my $config = shift;

   my @warnings;
   
   # find the last snapshot date in each dataset, on each target
   foreach my $machine ( 'source', 'target' ) {
      $config->{$machine}->{'last'} = 0; # track the last entry in all children in dataset
      $config->{$machine}->{'allOk'} = 1; # assumed to be true, becomes false if some children do not have snapshots
      foreach my $child ( keys %{ $config->{$machine}->{'snapshots'} } ) {
         $config->{$machine}->{'snapshots'}->{$child}->{'last'} = 
            &getLastSnapshot( $config->{$machine}->{'snapshots'}->{$child}->{'snaps'} );
         # set the machine last if we haven't done so yet
         $config->{$machine}->{'last'} = $config->{$machine}->{'snapshots'}->{$child}->{'last'} unless $config->{$machine}->{'last'};
         # keep track of the last snapshot for each set
         if ( $config->{$machine}->{'last'} ne $config->{$machine}->{'snapshots'}->{$child}->{'last'} ) {
            $config->{$machine}->{'allOk'} = 0;
            push @warnings, "Warning: $machine does not have consistent snapshots at $child";;
         }
      }
   }
   # make sure the source has a corresponding snap for target->last
   foreach my $child ( keys %{ $config->{'target'}->{'snapshots'} } ) {
      if (! exists ($config->{'source'}->{'snapshots'}->{$child}->{'snaps'}->{$config->{'target'}->{'snapshots'}->{$child}->{'last'}} ) ) {
         $config->{'source'}->{'allOk'} = 0;
         push @warnings, "Warning: We  do not have consistent snapshots";
      }
   }
   my $return;
   if ( $config->{'source'}->{'allOk'} and $config->{'target'}->{'allOk'} ) { # whew, they match
      return( $config->{'source'}->{'last'}, $config->{'target'}->{'last'}, \@warnings );
   } else {
      return( '','',\@warnings);
   }
}

$config->{'source'} = &parseDataSet( $source );
$config->{'target'} = &parseDataSet( $target );

# both source and target can not have a server portion; one must be local
die "Source and Target can not both be remote\n" if $config->{'source'}->{'server'} && $config->{'target'}->{'server'};

$config->{'source'}->{'snapshots'} = &getSnaps( $config->{'source'}, $config->{'pattern'} );
$config->{'target'}->{'snapshots'} = &getSnaps( $config->{'target'}, $config->{'pattern'} );

# $config->{'actions'} = &calculate( $config );
my ( $lastSource, $lastTarget ) = &calculate( $config );

#print Dumper( $config ) . "\nSource = $lastSource\nTarget = $lastTarget\n"; die;

my $commands = &createCommands( $lastSource, $lastTarget, $config );
for ( my $i = 0; $i < @{$commands}; $i++ ) {
   print "$$commands[$i]\n";
   if ( $dryRun ) {
      print "Dry Run\n";
   } else {
      print qx/$$commands[$i]/ if $$commands[$i] =~ m/^[a-zA-Z]/;
   }
}

#print Dumper( $config );

1;