#! /usr/bin/env perl

use strict;
use warnings;

use YAML::Tiny; # pkg install p5-YAML-Tiny-1.74

BEGIN {
   use FindBin;
   use File::Spec;
   # use libraries from the directory this script is in
   use Cwd 'abs_path';
   use File::Basename;
   use lib dirname( abs_path( __FILE__ ) );
}

my $cwd = $FindBin::RealBin;
my $configFileName = $cwd . '/sync.yaml';
my $replicateScript = $cwd . '/replicate';

my $TESTING=0;

my $configuration;
   
use Data::Dumper;
use Email::Simple; # cpan install Email::Simple

# load Configuration File
# read the config file and return it
sub readConfig {
   my $filename = shift;
   die "Config file $filename not found: $!" unless -f $filename;
   my $yaml = YAML::Tiny->new( {} );
   if ( -f $filename ) {
      $yaml = YAML::Tiny->read( $filename );
   }
   return $yaml->[0];
}



# this calls gshred which will overwrite the file 3 times, then
# remove it.
# NOTE: this will not work on ZFS, since ZFS is CopyOnWrite (COW)
# so assuming /tmp is a ramdisk
sub shredFile {
   my $filename = shift;
   `/usr/local/bin/gshred -u -f -s 32 $filename`;
}


# runs a command, redirecting stderr to stdout (which it ignores)
# then returns 0 on success.
# if error, returns string describing error
sub runCommand {
   my $command = shift;
   my $output = qx/$command 2>&1/;
   if ($? == -1) {
      return (-1, "failed to execute: $!" );
   } elsif ($? & 127) {
      return (-1,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);
}
   
# grabs the encryption key from the remote server, and uses it to unlock the 
# datasets, then mount the drives.
# a return of '' is success, anything else is an error
sub mountDrives {
   my $config = shift;
   # try to grab the file from the remote machine
   &runCommand( "scp $config->{remoteMachine}->{ip}:$config->{remoteMachine}->{encryptionKeyPath} $config->{localMachine}->{encryptionKeyPath}" );
   # If we do not have the encryption key, we need to abort
   return "Could not copy file $config->{remoteMachine}->{ip}:$config->{remoteMachine}->{encryptionKeyPath}, aborting" 
      unless -f $config->{'localMachine'}->{'encryptionKeyPath'};
   my $error = '';
   my $output = '';
   # load the key into zfs and unlock all volumes
   ($error,$output) = &runCommand( "zfs load-key -a" );
   # finally, remount all of the zfs shares which need the key
   ($error,$output) = &runCommand( "zfs mount -a" ) unless $error;
   # if we succeeded, we want to shred the keyfile
   &shredFile( $config->{localMachine}->{encryptionKeyPath} ) if -f $config->{localMachine}->{encryptionKeyPath};
   return $error;
}

# a very simple mailer, using Email::Simple to just get status messages out
sub sendMail {
   my ($message, $config, $subject ) = @_;
   $config->{'email'}->{'notify'} = 'root' unless $config->{'email'}->{'notify'};
   die "No message in outgoing message\n" unless $message;
   my $email = Email::Simple->create(
      header => [
         To     => $config->{'email'}->{'notify'},
         Subject=> $config->{'email'}->{'subject'} . ( $subject ? " - $subject" : '' ),
         From   => $config->{'email'}->{'from'}
      ],
      body => $message
   );
   $message = $email->as_string;
   `echo '$message' | sendmail $config->{'email'}->{'notify'}`;
}

# checks to see if we should be in maintenance mode
# if $remoteMachine->{'maintenanceMode'} exists, set mode
# otherwise, wait localMachine->{'waittime'} minutes, then check
# $localMachine->{'maintenanceMode'}.
# if neither exists, begin sync
sub checkMaintenance {
   my $config = shift;
   # see if maintenance is set on remote. If so, simply return the message
   if ( $config->{'remoteMachine'}->{'up'} ) {
      my ($error, $output) = &runCommand( "ssh $configuration->{remoteMachine}->{ip} 'ls $configuration->{remoteMachine}->{maintenanceFlag}'" );
      if ( ! $error ) {
         # remove the file from the remote server
         &runCommand( "ssh $configuration->{remoteMachine}->{ip} 'rm $configuration->{remoteMachine}->{maintenanceFlag}'" );
         # create a valid return, which will exit the program
         return "Maintenance Flag found on remote machine";
      }
   }
   # not on remote machine, so give them waitTime seconds to put it here
   # we'll loop, checking every $sleepTime seconds until our wait time
   # ($config->{'localMachine'}->{'waitTime'}) has expired
   my $sleepTime = 60;
   for ( my $i = $config->{'localMachine'}->{'waitTime'}; $i > 0; $i -= $sleepTime ) {
      sleep $sleepTime;
      # then look for the maintenance flag file on the local machine
      return "Maintenance Flag found on local machine" if -f $config->{'localMachine'}->{'maintenanceFlag'};
   }
   # no maintenance flags found, so return false
   return 0;
}

sub shutdownMachine {
   my $config = shift;
   my $subject = shift;
   push @_, "Shutting down";
   &sendMail( join( "\n", @_), $configuration, $subject );   
   &runCommand( "poweroff" ) unless $TESTING;
   die "Shutting down machine now\n";
}

# returns the current time as a string
sub currentTime {
   my $format = shift;
   # default to YY-MM-DD HH-MM-SS
   $format = '%Y-%m-%d %H-%M-%S' unless $format;
   use POSIX;
   return POSIX::strftime( $format, localtime() );
}

my @status;   

$configuration = &readConfig($configFileName);

&sendMail( "mc-009 has been started, " . &currentTime() . " checking for maintenance mode", $configuration );
# see if remote machine is up by sending one ping. Expect response in 5 seconds
my ( $error,$output) = &runCommand( "ping -c 1 -t 5 " . $configuration->{'remoteMachine'}->{'ip'} );
$configuration->{'remoteMachine'}->{'up'} = ! $error;

push @status, "remote machine ($configuration->{'remoteMachine'}->{'ip'}) is " . ( $configuration->{'remoteMachine'}->{'up'} ? 'Up' : 'Down' ) . "\n";
# check for maintenance flags, exit if we should go into mainteannce mode
if ( my $result = &checkMaintenance( $configuration ) ) {
   push @status,$result;
   &sendMail( join( "\n", @status), $configuration, "Maintenance Mode" );
   die;
}

# we can not connect to the remote server, so just shut down
&shutdownMachine( $configuration, "No connection to remote machine", @status ) unless $configuration->{'remoteMachine'}->{'up'};

# try to mount the datasets
($error,$output) = &mountDrives( $configuration );
if ( $error ) { # could not mount datasets
   push @status, $error;
   &shutdownMachine( $configuration, "Mount Drive Error: [$output]", @status );
}

&sendMail( "Backup has been started at " . &currentTime(), $configuration, "Backup Starting" );
push @status, "Backup started at: " . &currentTime();


# For each dataset, let's find the snapshots we need
foreach my $sourceDir ( keys %{$configuration->{'remoteMachine'}->{'dataset'}} ) {
   my $command = $replicateScript . ' ' .
                 $configuration->{'remoteMachine'}->{'ip'} . ':' . 
                 $configuration->{'remoteMachine'}->{'dataset'}->{$sourceDir} . '/' . $sourceDir . ' ' .
                 $configuration->{'localMachine'}->{'targetDataset'} . '/' . $sourceDir;
   push @status, "=== Running $command at " . &currentTime();
   my ($error, $output) = &runCommand( $command );
   push @status, $output;
   push @status, "=== Completed $command with status $error at " . &currentTime();
}

push @status, "==== Backup finished at: " . &currentTime();

&shutdownMachine( $configuration, "Backup Complete", @status );

1;