#!/usr/bin/perl -w
# (c) 2010 Thomas Schoebel-Theuer / 1&1 Internet AG

use strict;
use English;
use warnings;

my $mars = "/mars";
my $host = `uname -n` or die "cannot determine my network node name\n";
chomp $host;
my $ip = `ip a` or die "cannot determine my IP address\n";
$ip =~ s/\A.*inet +(?!127\.0\.)([0-9]+\.[0-9]+\.[0-9]+\.[0-9]+).*?\Z/$1/ms or die "cannot parse my IP address\n";
chomp $ip;
print "my IP is $ip\n";

umask 0077;
die "only root may use this tool\n" unless `whoami` eq "root\n"; # getpid() seems to be missing in perlfunc

##################################################################

# syntactic checks

sub check_id {
  my $str = shift;
  die "identifier '$str' has disallowed characters" unless $str =~ m/^[A-Za-z_][-A-Za-z0-9_]*$/;
  die "identifier '$str' is too long (only 16 chars allowed)" if length($str) > 16;
}

##################################################################

# semantic checks

sub check_res {
  my $res = shift;
  if(not -d "$mars/resource-$res") {
    # DO WHAT I MEAN: try to substitute a device name for a badly given resource name if it is unique
    my $count = 0;
    my $found;
    my @tests = glob("$mars/resource-*/device-$host");
    foreach my $test (@tests) {
      my $target = readlink($test);
      if($target eq $res) {
	$found = $test;
	$count++;
      }
    }
    if(!$count) {
      @tests = glob("$mars/resource-*/_direct-*-$host");
      foreach my $test (@tests) {
	my $target = readlink($test);
	$target =~ s/^.*,//;
	if($target eq $res) {
	  $found = $test;
	  $count++;
	}
    }
    }
    die "resource '$res' does not exist ($count replacements found)\n" unless $count == 1 and $found;
    $found =~ s:^.*/resource-(.*)/.*$:$1:;
    warn "substituting bad resource name '$res' by uniquely matching resource name '$found'\n";
    $res = $found;
  }
  return $res;
}

sub check_res_member {
  my $res = shift;
  die "sorry, I have not yet joined to resource '$res'\n" unless -e "$mars/resource-$res/data-$host";
}

sub check_sync_finished {
  my ($res, $host) = @_;
  my $lnk = "$mars/resource-$res/syncstatus-$host";
  if(lstat($lnk)) {
    my $syncstatus = readlink($lnk);
    my $size = readlink("$mars/resource-$res/size") or die "cannot read size\n";
    die "sync has not yet finished, only $syncstatus / $size bytes transferred\n" unless $syncstatus >= $size;
  }
  print "OK, it seems that sync has finished on $host.\n";
}

sub check_primary_gone {
  my ($res) = @_;
  for(;;) {
    my @links = glob("$mars/resource-$res/actual-*/is-primary");
    my $found = 0;
    foreach my $link (@links) {
      my $val = readlink($link);
      $found++ if $val;
    }
    last if !$found;
    print "waiting for $found other primary host(s) to disappear....\n";
    sleep(5);
  }
}

sub check_status {
  my ($res, $key, $val) = @_;
  for(;;) {
    my $path = "$mars/resource-$res/actual-$host/$key";
    my $link = readlink($path) or die "cannot read symlink '$path'\n";
    last if $link == $val;
    print "waiting until $key reaches the value $val....\n";
    sleep(5);
  }
}

sub check_splitbrain {
  my ($res, $host) = @_;
  my @links = glob("$mars/resource-$res/version-[0-9]*-$host");
  die "no version information available for host $host\n" unless @links;
  my $link = pop @links;
  die "cannot pop last link element\n" unless $link;
  my $version = readlink($link);
  die "cannot get version information for $link\n" unless $version;
  my $serial = $link;
  $serial =~ s:$mars/resource-$res/version-([0-9]+).*$:$1:;
  print "my    version: $link -> $version\n";
  foreach my $other (glob("$mars/resource-$res/version-[0-9]*-*")) {
    $other =~ m:$mars/resource-$res/version-([0-9]+)-(.*)$:;
    my $other_serial = $1;
    my $other_host = $2;
    next if $serial ne $other_serial;
    next if $host eq $other_host;
    my $other_version = readlink($other);
    print "other version: $other -> $other_version\n";
    die "split brain detected: $other_version != $version\n" unless $version eq $other_version;
  }
}

sub get_size {
  my $arg = shift;
  return -1 unless $arg =~ m/^[0-9.]+[kmgtp]?$/i;
  my $mod = $arg;
  $arg =~ s/[^0-9]+$//;
  $mod =~ s/^[0-9]+//;
  $_ = $mod;
 SWITCH: {
    /k/i and $arg *= 1024, last SWITCH;
    /m/i and $arg *= 1024 * 1024, last SWITCH;
    /g/i and $arg *= 1024 * 1024 * 1024, last SWITCH;
    /t/i and $arg *= 1024 * 1024 * 1024 * 1024, last SWITCH;
    /p/i and $arg *= 1024 * 1024 * 1024 * 1024 * 1024, last SWITCH;
  }
  return $arg;
}

##################################################################

# helpers

sub _trigger {
  system("(echo 1 > /proc/sys/mars) >/dev/null 2>&1");
}

sub _switch {
  my ($cmd, $res, $path, $on) = @_;
  my $src = $on ? "1" : "0";

  my $old = readlink($path);
  if($old && $old eq $src) {
    print "${cmd} on resource $res is already activated\n" if $cmd;
    return;
  }

  my $tmp = $path;
  $tmp =~ s/\/([^\/]+)$/.tmp.$1/;
  symlink($src, $tmp) or die "cannot create switch symlink\n";
  rename($tmp, $path) or die "cannot rename switch symlink\n";
  print "successfully started ${cmd} on resource $res\n" if $cmd;
}

sub _writable {
  my ($path, $on) = @_;
  my $oldmode = (lstat $path)[2] & 0700;
  my $newmode = $on ? $oldmode | 0200 : $oldmode & ~0200;
  print "chmod '$path' $oldmode $newmode";
  chmod($newmode, $path) == 1 or die "cannot chmod '$path'\n";
}

##################################################################

# commands

sub ignore_cmd {
  my ($cmd, $res) = @_;
  print "ignoring command '$cmd' on resource '$res'\n";
  exit(0);
}

sub senseless_cmd {
  my ($cmd, $res) = @_;
  print "command '$cmd' makes no sense with MARS (ignoring)\n";
  exit(0);
}

sub forbidden_cmd {
  my ($cmd, $res) = @_;
  die "command '$cmd' cannot be used with MARS (it is impossible to carry out uniquely and could therefore lead to a disaster)\n";
}

sub nyi_cmd {
  my ($cmd, $res) = @_;
  die "command '$cmd' is not yet implemented\n";
}

sub _create_cluster {
  my ($cmd) = @_;
  system("mkdir $mars") unless -d $mars;
  system("mkdir $mars/ips") unless -d "$mars/ips";
  system("mkdir $mars/defaults") unless -d "$mars/defaults";
  system("mkdir $mars/defaults-$host") unless -d "$mars/defaults-$host";
  symlink($ip, "$mars/ips/ip-$host");
}

sub create_cluster {
  my ($cmd, $peer, $force) = @_;
  die "cluster is already created\n" if !$force && -d "$mars/ips";
  _create_cluster(@_);
}

sub join_cluster {
  my ($cmd, $peer, $force) = @_;
  if(glob("$mars/resource-*")) {
    die "Sorry, some resources already exist!\nThis is dangerous!\nIf you are sure that no resource clash is possible, re-invoke this command with '--force' option\n" unless ($force and $force =~ m/--force/);
  }
  print "joining cluster via rsync (peer='$peer')\n";
  _create_cluster(@_);
  system("rsync --recursive --links -v $peer:$mars/ips/ $mars/ips/") == 0 or die "oops\n";
  symlink($ip, "$mars/ips/ip-$host");
  system("rsync --recursive --links -v $mars/ips/ $peer:$mars/ips/") == 0 or die "oops\n";
}

sub create_res {
  my ($cmd, $res, $dev, $appear) = @_;
  my $create = ($cmd eq "create-resource");

  die "undefined device or size argument\n" unless $dev;
  $appear = $res if !$appear;
  check_id($appear) if $appear;

  if($create) {
    die "resource '$res' already exists\n" if -d "$mars/resource-$res";
    print "creating new resource '$res'\n";
  } else {
    print "joining to existing resource '$res'\n";
  }

  my $size = get_size($dev);
  if($size > 0) {
    $dev = "";
  } else {
    die "block device '$dev' does not exist\n" unless -b $dev;
    die "block device '$dev' must be an absolute path starting with '/'\n" unless $dev =~ m/^\//;
    use Fcntl 'SEEK_END';
    open(TEST, "<$dev") or die "cannot open device for reading\n";
    $size = sysseek(TEST, 0, SEEK_END);
    close(TEST);
    print "device size = $size bytes\n";
    die "implausible size" unless $size > 0;
  }

  my $tmp = "$mars/.tmp.$res";
  my $primary;
  my $replay;
  if($create) {
    _create_cluster(@_);
    system("rm -rf $tmp");
    system("mkdir $tmp") == 0 or die "could not create resource '$res'\n";
    symlink($size, "$tmp/size") or die "cannot create size indicator symlink\n";
  } else {
    $tmp = "$mars/resource-$res";
    die "resource '$res' does not exist\n" unless -d $tmp;
    $primary = readlink("$tmp/primary") or die "cannot determine primary\n";
    if($primary eq "(none)") {
      my @list = glob("$tmp/replay-*") or die "cannot find any candidate for primary\n";
      my $first = pop @list or die "bad glob list\n";
      $primary = readlink($first) or die "cannot determine peer\n";
      $primary =~ s/^log-[0-9]+-(.*),.*,.*$/$1/;
      print "using '$primary' as primary\n";
    }
    die "resource '$res' is already joined\n" if -e "$tmp/data-$host";
    die "my ip '$ip' is not registered -- please run 'join-cluster' first\n" unless -l "$mars/ips/ip-$host";
    my $oldsize = readlink("$tmp/size") or die "cannot determine old size\n";
    if($size < $oldsize) {
      print "adjusting size to $oldsize\n";
      $size = $oldsize;
    }
    die "sizes differ: real size = $oldsize, but requested size = $size\n" unless $oldsize == $size;
    $replay = readlink("$tmp/replay-$primary") or die "cannot read replay status of primary '$primary'\n";
    $replay =~ s/-$primary,[0-9]+,[0-9]+/-$host,0,0/ or die "something is wrong here\n";
    my $nr = $replay;
    $nr =~ s/^.*log-([0-9]+)-.+$/$1/;
    if($nr > 1) { # fake version symlink for predecessor logfile
      my $prev = sprintf("$tmp/version-%09d-$primary", $nr - 1);
      my $version = readlink($prev) or die "cannot read symlink '$prev'\n";
      my $old = sprintf("$tmp/version-%09d-$host", $nr - 1);
      symlink($version, $old) or die "cann create symlink '$old'\n";
    }
  }

  my $file = "$tmp/data-$host";
  if(!$dev) {
    print "creating sparse file '$file' with size $size\n";
    open(OUT, ">$file") or die "could not open '$file'\n";
    use Fcntl 'SEEK_SET';
    sysseek(OUT, $size-1, SEEK_SET) == $size-1 or die "could not seek\n";
    syswrite(OUT, '\0', 1) == 1 or die "cannot init sparse file\n";
    close OUT;
  } else {
    print "using existing device '$dev'\n";
    symlink($dev, $file) or die "cannot create device symlink\n";
  }
  if($appear) {
    # TODO: check for uniqeness of $appear
    print "resource '$res' will appear as local device '/dev/mars/$appear'\n";
    system("rm -f $tmp/device-$host");
    symlink($appear, "$tmp/device-$host") or die "cannot create symlink for local device appearance\n";
  }

  mkdir("$tmp/defaults") unless -d "$tmp/defaults";
  mkdir("$tmp/defaults-$host");
  mkdir("$tmp/actual-$host");
  my $todo = "$tmp/todo-$host";
  mkdir($todo);
  symlink("1", "$todo/attach");
  symlink("0", "$todo/connect");
  symlink("1", "$todo/sync");
  system("rm -f $tmp/syncstatus-$host");

  if($create) {
    symlink($host, "$tmp/primary") or die "cannot create primary symlink\n";
    symlink($size, "$tmp/syncstatus-$host") or die "cannot create primary syncstatus\n";
    symlink("log-000000001-$host,0,0", "$tmp/replay-$host") or die "cannot create replay status\n";
    system("touch $tmp/log-000000001-$host");
    rename($tmp, "$mars/resource-$res") or die "cannot finalize resource '$res'\n";
    print "successfully created resource '$res'\n";
  } else {
    system("rm -f $tmp/replay-$host");
    symlink($replay, "$tmp/replay-$host") or die "cannot create replay status\n";
    symlink("0", "$tmp/syncstatus-$host") or die "cannot start initial sync\n";
    system("rm -f $tmp/connect-$host");
    symlink($primary, "$tmp/connect-$host") or die "cannot create peer connect symlink\n";
    symlink($host, "$tmp/connect-$primary") unless -l "$tmp/connect-$primary";
    print "successfully joined resource '$res'\n";
  }
}

sub logrotate_res {
  my ($cmd, $res) = @_;
  my @paths = glob("$mars/resource-$res/log-*-$host") or die "cannot find any logfiles\n";
  @paths = sort(@paths);
  my $last = pop(@paths);
  if(-z $last) {
    print "an empty logfile '$last' already exists, nothing to do.\n";
    return;
  }
  my $nr = $last;
  $nr =~ s/^.*log-([0-9]+)-.+$/$1/;
  my $next = sprintf("$mars/resource-$res/log-%09d-$host", $nr + 1);
  die "logfile '$next' already exists\n" if -e $next;
  system("touch $next");
}

sub attach_res {
  my ($cmd, $res) = @_;
  my $detach = ($cmd eq "detach");
  my $path = "$mars/resource-$res/todo-$host/attach";
  _switch($cmd, $res, $path, !$detach);
}

sub connect_res {
  my ($cmd, $res) = @_;
  my $disconnect = ($cmd eq "disconnect");
  my @paths = glob("$mars/resource-$res/todo-*/connect");
  for my $path (@paths) {
    _switch($cmd, $res, $path, !$disconnect);
  }
}

sub connect_local_res {
  my ($cmd, $res) = @_;
  my $disconnect = ($cmd eq "disconnect-local");
  my $path = "$mars/resource-$res/todo-$host/connect";
  _switch($cmd, $res, $path, !$disconnect);
}

sub pause_res {
  my ($cmd, $res) = @_;
  my $pause = ($cmd eq "pause-sync");
  my @paths = glob("$mars/resource-$res/todo-*/sync");
  for my $path (@paths) {
    _switch($cmd, $res, $path, !$pause);
  }
}

sub pause_local_res {
  my ($cmd, $res) = @_;
  my $pause = ($cmd eq "pause-sync-local");
  my $path = "$mars/resource-$res/todo-$host/sync";
  _switch($cmd, $res, $path, !$pause);
}

sub up_res {
  my ($cmd, $res) = @_;
  my $down = ($cmd eq "down");
  if($down) {
    pause_res("pause-sync", $res);
    connect_res("disconnect", $res);
    attach_res("detach", $res);
  } else {
    attach_res("attach", $res);
    connect_res("connect", $res);
    pause_res("resume-sync", $res);
  }
}

sub fake_local_res {
  my ($cmd, $res) = @_;
  my $path = "$mars/resource-$res/todo-$host/sync";
  _switch($cmd, $res, $path, 0);
  #check_status($res, "copy-syncstatus-$host", 0);
  my $size = readlink("$mars/resource-$res/size") or die "cannot read size\n";
  my $target = "$mars/resource-$res/syncstatus-$host";
  symlink($size, "$target.tmp") or die "cannot create faked syncstatus\n";
  rename("$target.tmp", $target) or die "cannot reaname symlink\n";
}

sub _primary_res {
  my ($res, $host, $pri, $old) = @_;
  my $tmp = "$mars/resource-$res/.tmp.primary";
  system("rm -f $tmp");
  symlink($host, $tmp) or die "cannot create new primary symlink\n";
  rename($tmp, $pri) or die "cannot install new primary symlink\n";
  print "primary changed from '$old' to '$host'\n";
}

sub primary_res {
  my ($cmd, $res) = @_;
  my $sec = ($cmd eq "secondary");
  my $pri = "$mars/resource-$res/primary";
  my $old = readlink($pri) or die "cannot determine current primary\n";
  if($sec) {
    die "for safety reasons, switching to secondary is only allowed when I ($host) am primary\n" if($old ne $host);
    $host = "(none)";
  } elsif($old eq $host) {
    print "I am already primary.\n";
    exit(0);
  } elsif($cmd eq "force-primary") {
    print "forcing myself ($host) to primary...\n";
  } else { # try to switch myself to primary
    print "trying to switch $host to primary...\n";
    check_sync_finished($res, $host);
    _primary_res($res, "(none)", $pri, $old) unless $old eq "(none)";
    check_primary_gone($res);
    check_splitbrain($res, $host);
  }
  _primary_res($res, $host, $pri, $old);
}

sub invalidate_res {
  my ($cmd, $res) = @_;
  my $pri = "$mars/resource-$res/primary";
  my $old = readlink($pri) or die "cannot determine current primary\n";
  my $dst = "$mars/resource-$res/syncstatus-$host";

  die "primary side cannot be invalidated\n" if $old eq $host;

  system("rm -f $dst");
  symlink("0", $dst) or die "cannot create invalidation symlink '$dst'\n";
}

sub role_cmd {
  my ($cmd, $res) = @_;
  my $pri = "$mars/resource-$res/primary";
  my $old = readlink($pri) or die "cannot determine current primary\n";
  if($old eq $host) {
    print "primary\n";
  } else {
    print "secondary\n";
  }
}

##################################################################

my %cmd_table =
  (
   # new keywords
   "create-cluster"     => \&create_cluster,
   "join-cluster"       => \&join_cluster,
   "create-resource"   => \&create_res,
   "join-resource"     => \&create_res,
   "logrotate"         => \&logrotate_res,
   "fake-sync"         => \&fake_local_res,

   # compatible keywords
   "attach"            => \&attach_res,
   "detach"            => \&attach_res,
   "connect"           => \&connect_res,
   "disconnect"        => \&connect_res,
   "connect-local"     => \&connect_local_res,
   "disconnect-local"  => \&connect_local_res,
   "syncer"            => \&ignore_cmd,
   "up"                => \&up_res,
   "down"              => \&up_res,
   "primary"           => \&primary_res,
   "secondary"         => \&primary_res,
   "force-primary"     => \&primary_res,
   "invalidate"        => \&invalidate_res,
   "invalidate-remote" => \&forbidden_cmd,
   "resize"            => \&nyi_cmd,
   "create-md"         => \&senseless_cmd,
   "get-gi"            => \&ignore_cmd,
   "show-gi"           => \&ignore_cmd,
   "dump-md"           => \&senseless_cmd,
   "outdate"           => \&ignore_cmd,
   "adjust"            => \&ignore_cmd,
   "wait-connect"      => \&nyi_cmd,
   "role"              => \&role_cmd,
   "state"             => \&role_cmd,
   "cstate"            => \&nyi_cmd,
   "status"            => \&nyi_cmd,
   "dump"              => \&senseless_cmd,
   "verify"            => \&nyi_cmd,
   "pause-sync"        => \&pause_res,
   "resume-sync"       => \&pause_res,
   "pause-sync-local"  => \&pause_local_res,
   "resume-sync-local" => \&pause_local_res,
   "new-current-uuid"  => \&senseless_cmd,
   "dstate"            => \&nyi_cmd,
   "hidden-commands"   => \&ignore_cmd,
  );

my $cmd = shift || die "command argument is missing\n";
die "unknown command '$cmd'\n" if !exists $cmd_table{$cmd};

my $res = "";
unless($cmd =~ m/^create-cluster$/) {
  $res = shift || die "resource argument is missing\n";
  check_id($res);
}

sub do_res {
  my $cmd = shift;
  my $res = shift;

  $res = check_res($res) unless $cmd =~ m/^(join|create)-cluster|create-resource$/;
  check_res_member($res) unless $cmd =~ m/^(join|create)-(cluster|resource)$/;

  my $func = $cmd_table{$cmd};
  &{$func}($cmd, $res, @_);
}

if($res eq "all") {
  foreach $res (glob("$mars/resource-*")) {
    next unless -e "$res/data-$host";
    $res =~ s/^.*\/resource-(.*)$/$1/;
    print "--------- resource $res\n";
    do_res($cmd, $res, @ARGV);
  }
} else {
  do_res($cmd, $res, @ARGV);
}

_trigger();