#! perl

# this plug-in prefetches maps. everytime a player enters a map,
# it will asynchronously prefetch files from disk (it will not load them
# into the server, but into the OS cache only).

use Errno ();
use Time::HiRes;
use Fcntl;
use IO::AIO;

# find all potential exit paths, this is slow, so this info is cached
sub find_exits {
   my ($map) = @_;

   my %exit;

   # normal exits
   for my $x (0 .. $map->width - 1) {
      for my $y (0 .. $map->height - 1) {
         for (grep $_->type == 66, $map->at ($x, $y)) {
            my $path = $_->slaying;

            next if 3 > length $path;

            # TODO: improve unique exit detection etc.
            $exit{cf::maps_directory cf::path_combine_and_normalize $map->path, $path}++;
         }
      }
   }

   # tiled maps
   for (0..3) {
      my $path = $map->tile_path ($_)
         or next;

      $exit{cf::maps_directory cf::path_combine_and_normalize $map->path, $path}++;
   }

   [keys %exit]
}

my $PREFETCHING;
my @PREFETCH;
my %FILE_TIMEOUT;

sub _prefetch;

my $empty_cb = sub { };

sub load_file {
   my ($path, $cb) = @_;

   my $NOW = Time::HiRes::time;

   aio_open $path, O_RDONLY, 0, sub {
      my $fh = shift
        or return $cb->(), _prefetch;

      aio_readahead $fh, 0, -s $fh, sub {
         my $time = Time::HiRes::time - $NOW;
         warn "LONG PREFETCH $path $time\n" if $time > 0.3;

         $cb->(), _prefetch;
      };
   };
}

sub prefetch($$;$) {
   my ($type, $path, $cb) = @_;

   push @PREFETCH, [$type, $path, $cb || $empty_cb];
   _prefetch unless $PREFETCHING;
}

sub _prefetch {
   $PREFETCHING = 1;

   while (@PREFETCH) {
      my ($type, $path, $cb) = @{ shift @PREFETCH };

      my $NOW = Time::HiRes::time;
      $cb->(), next if $FILE_TIMEOUT{$path} > $NOW;
      $FILE_TIMEOUT{$path} = $NOW + 60 + rand 60;

      if ($type eq "map") {
         if (my $map = cf::map::has_been_loaded $path) {
            $cb->(), next if $map->in_memory == cf::MAP_IN_MEMORY;

            prefetch file => $map->tmpname
               if $map->in_memory == cf::MAP_SWAPPED;
         }
      }

      load_file $path, $cb;
      return;
   }

   $PREFETCHING = 0;
}

my %MAP_EXITS;

sub prefetch_map($) {
   my ($map) = @_;

   my $exit = $MAP_EXITS{$map->path} ||= find_exits $map;
   prefetch map => $_ for @$exit;
}

cf::attach_to_players prio => -900,
   on_map_change => sub {
      my ($pl, $new, $x, $x) = @_;

      prefetch_map $new;
   },
;

if (0) { #test#
# prefetch a few players/second
{
   my @players;

   Event->timer (interval => 0.2, cb => sub {
      @players = map $_->ob->name, cf::player::list unless @players;
      my $player = cf::player::find pop @players
         or return;

      if (my $map = $player->ob->map) {
         prefetch_map $map;
      }

      prefetch map => +($player->get_savebed)[0];
   });
}

# prefetch all .pl files every few minutes (thats only a "few" megabytes)
Event->timer (after => 1, interval => 600, cb => sub {
   my $playerdir = cf::localdir . "/" . cf::playerdir;

   aio_readdir $playerdir, sub {
      my ($players) = @_;
      my $prefetch; $prefetch = sub {
         my $player = pop @$players
            or return;

         load_file "$playerdir/$player/$player.pl", $prefetch;
      };

      $prefetch->(); $prefetch->();
   };
});
}