add a couple bits and pieces

[dbsrgits/DBIx-Data-Store-old.git] / lib / DBIx / Data / Collection / Set.pm

package DBIx::Data::Collection::Set;

use Moose;
use Method::Signatures::Simple;
use Data::Perl::Stream::Array;
use Data::Perl::Collection::Set;
use Scalar::Util qw(weaken refaddr);

has _store => (is => 'ro', required => 1, init_arg => 'store');

has _class => (is => 'ro', predicate => '_has_class', init_arg => 'class');

has _set_over => (is => 'ro', required => 1, init_arg => 'set_over');

## member cache (all members)

has _member_cache => (
  is => 'ro', lazy_build => 1,
  predicate => '_member_cache_built',
  writer => '_set_member_cache',
);

method _build__member_cache {
  my $stream = $self->_new_raw_stream;
  my @cache;
  while (my ($raw) = $stream->next) {
    my $obj = do {
      if (my ($obj) = $self->_key_cache_get_raw($raw)) {
        # can't just $self->_merge($obj, $raw) since $obj might have changed
        $self->_refresh($obj, $raw)
      } else {
        $self->_add_to_key_cache($self->_inflate($raw))
      }
    };
    push @cache, $obj;
  }
  $self->_notify_observers(all_members => \@cache);
  \@cache
}

method _add_to_member_cache ($to_add) {
  return $to_add unless $self->_member_cache_built;
  push @{$self->_member_cache}, $to_add;
  $to_add
}

method _remove_from_member_cache ($to_remove) {
  return $to_remove unless $self->_member_cache_built;
  @{$self->_member_cache} = grep $_ ne $to_remove, @{$self->_member_cache};
  $to_remove
}

## key cache - by primary/unique key

has _key_cache => (is => 'ro', default => sub { {} });

method _add_to_key_cache ($to_add) {
  $self->_key_cache->{$self->_object_to_id($to_add)} = $to_add;
  $to_add
}

method _remove_from_key_cache ($to_remove) {
  # should return $to_remove
  delete $self->_key_cache->{$self->_object_to_id($to_remove)}
}

method _key_cache_has_raw ($raw) {
  exists $self->_key_cache->{$self->_raw_to_id($raw)}
}

method _key_cache_has_object ($obj) {
  exists $self->_key_cache->{$self->_object_to_id($obj)}
}

method _key_cache_get_raw ($raw) {
  $self->_key_cache_get_id($self->_raw_to_id($raw))
}

method _key_cache_get_object ($obj) {
  $self->_key_cache_get_id($self->_object_to_id($obj))
}

method _key_cache_get_object_spec ($spec) {
  # see _object_spec_to_id for doc of what the difference is
  $self->_key_cache_get_id($self->_object_spec_to_id($spec))
}

method _key_cache_get_id ($id) {
  exists $self->_key_cache->{$id}
    ? ($self->_key_cache->{$id})
    : ()
}

method _all_key_cache_members {
  values %{$self->_key_cache}
}

method _set_key_cache_members ($members) {
  %{$self->_key_cache} = (map +($self->_object_to_id($_) => $_), @$members);
  return
}

## observers

has _observer_callbacks => (
  is => 'ro', default => sub { {} },
);

method _notify_observers ($event, $payload) {
  my $oc = $self->_observer_callbacks;
  foreach my $refaddr (keys %$oc) {
    my ($obj, $cb) = @{$oc->{$refaddr}};
    unless (defined $obj) { # weak ref was garbage collected
      delete $oc->{$refaddr};
      next;
    }
    $obj->$cb($self, $event, $payload);
  }
  $payload
}

method _register_observer ($obj, $cb) {
  my $entry = [ $obj, $cb ];
  weaken($entry->[0]);
  $self->_observer_callbacks->{refaddr($obj)} = $entry;
  return
}

method _setup_observation_of ($other) {
  $other->_register_observer($self, method ($from, $event, $payload) {
    if ($event eq 'add' or $event eq 'get') {
      $self->_add_to_caches($payload);
    } elsif ($event eq 'remove') {
      $self->_remove_from_caches($payload);
    } elsif ($event eq 'all_members') {
      # separate arrayref since future add will trigger push()
      $self->_set_caches([ @$payload ]);
    }
  });
  return
}

## thunking between the store representation and the set representation
#
# _inflate is raw data -> final repr
# _deflate is final repr -> raw data
# _merge takes final repr + raw data and updates the repr
#    (this is used for pk-generated values and later lazy loading)
#
# _deflate_spec is attributes of final repr -> raw data
# _merge_spec is final repr + extra attributes and update repr

method _inflate ($raw) {
  bless($raw, $self->_class) if $self->_has_class;
  $raw
}

method _deflate ($obj) {
  +{ %$obj }
}

method _merge ($obj, $raw) {
  @{$obj}{keys %$raw} = values %$raw;
  $obj
}

method _refresh ($obj, $raw) {
  # if $obj has been changed but not flushed we'd destroy data doing
  # a blind merge - but if $obj has change tracking of some sort then
  # we -could- do something safely, so this method exists to be mangled
  # by subclasses
  $obj
}

method _deflate_spec ($spec) {
  $spec
}

method _merge_spec ($obj, $spec) {
  @{$obj}{keys %$spec} = values %$spec;
  $obj
}

## methods to get ids

method _raw_to_id ($raw) {
  # XXX must escape this. or do something else.
  join ';', map $raw->{$_}, @{$self->_set_over}
}

method _object_to_id ($obj) {
  $self->_raw_to_id($self->_deflate($obj))
}

method _object_spec_to_id ($spec) {
  # intentionally C&P from _raw_to - this is not the same thing. If a column
  # were mapped to an attribute of a different name, the raw would have the
  # column name as a key but an object spec would have the attribute name
  join ';', map $spec->{$_}, @{$self->_set_over}
}

## array-ish operations - i.e. get all members

method _new_raw_stream {
  $self->_store->new_select_command({})->execute
}

method flatten {
  @{$self->_member_cache};
}

method as_stream {
  Data::Perl::Stream::Array->new(array => $self->_member_cache);
}

# theoretically inefficient except that if we're being asked this then
# either the data should have been pre-loaded or we're going to get all
# elements anyway

method count {
  scalar $self->flatten
}

method map ($sub) {
  Data::Perl::Collection::Set->new(
    members => [ map $sub->($_), $self->flatten ]
  )
}

method _set_caches ($members) {
  $self->_set_member_cache($members);
  $self->_set_key_cache_members($members);
  return
}

## load single row

method get ($spec) {
  if (my ($got) = $self->_key_cache_get_object_spec($spec)) {
    return $got
  }
  if (my ($raw) = $self->_get_from_store($self->_deflate_spec($spec))) {
    return $self->_notify_observers(
      get => $self->_add_to_key_cache($self->_inflate($raw))
    );
  }
  return undef # we aren't handling cache misses here yet
}

method _get_from_store ($raw) {
  $self->_store->new_select_single_command($raw)->execute
}

## add member

method add ($new) {
  $self->_add_to_store($new);
  $self->_add_to_caches($new);
  $self->_notify_observers(add => $new);
  $new
}

method _add_to_store ($new) {
  my $new_raw = $self->_deflate($new);
  $self->_merge($new, $self->_store->new_insert_command($new_raw)->execute);
  $new
}

method _add_to_caches ($new) {
  $self->_add_to_member_cache($new);
  $self->_add_to_key_cache($new);
  $new
}

## remove member

method remove ($old) {
  $self->_remove_from_store($old);
  $self->_remove_from_caches($old);
  $self->_notify_observers(remove => $old);
  $old
}

method _remove_from_store ($old) {
  $self->_store->new_delete_single_command($self->_deflate($old))->execute
}

method _remove_from_caches ($old) {
  $self->_remove_from_member_cache($old);
  $self->_remove_from_key_cache($old);
  $old
}

## update member

method _update_in_store ($obj) {
  # this is currently a call command but we should think about it
  # being a row command so that we can have RETURNING or other
  # mechanisms handle things like set-on-update datetime values
  $self->_store->new_update_single_command($self->_deflate($obj))->execute
}

# I do wonder if we needed _merge_spec or if we'd be better off with
# just using the raw merge routine ...

method _update_set_in_store ($spec) {
  $self->_store->new_update_command($self->_deflate_spec($spec))->execute;
  if ($self->_member_cache_built) {
    my $cache = $self->_member_cache;
    foreach my $obj (@{$cache}) {
      $self->_merge_spec($obj, $spec);
    }
    $self->_notify_observers(all_members => $cache);
  }
  return
}

method _remove_set_from_store {
  $self->_store->new_delete_command->execute;
  $self->_set_caches([]);
  $self->_notify_observers(all_members => []);
  return
}

1;