#! perl

#:META:X_RESOURCE:%.expr:string:background expression
#:META:X_RESOURCE:%.enable:boolean:some boolean
#:META:X_RESOURCE:%.extra.:value:extra config

our $EXPR = 'move X, Y, load "MagnoliaAlpha.png"';
#$EXPR = '
#   rotate W, H, 50, 50, counter 1/59.95, repeat_mirror,
#   clip X, Y, W, H, repeat_mirror,
#   load "/root/pix/das_fette_schwein.jpg"
#';
#$EXPR = 'solid "red"';
#$EXPR = 'blur root, 10, 10'
#$EXPR = 'blur move (root, -x, -y), 5, 5'
#resize load "/root/pix/das_fette_schwein.jpg", w, h

use Safe;

our ($bgdsl_self, $old, $new);
our ($l, $t, $w, $h);

# enforce at least this interval between updates
our $MIN_INTERVAL = 1/100;

{
   package urxvt::bgdsl; # background language

#   *repeat_empty  = \&urxvt::RepeatNone;
#   *repeat_tile   = \&urxvt::RepeatNormal;
#   *repeat_pad    = \&urxvt::RepeatPad;
#   *repeat_mirror = \&urxvt::RepeatReflect;

=head2 PROVIDERS/GENERATORS

=over 4

=item load $path

=cut

   sub load($) {
      my ($path) = @_;

      $new->{load}{$path} = $old->{load}{$path} || $bgdsl_self->new_img_from_file ($path);
   }

   sub root() {
      $new->{rootpmap_sensitive} = 1;
      die "root op not supported, exg, we need you";
   }

   sub solid($;$$) {
      my $img = $bgdsl_self->new_img (urxvt::PictStandardARGB32, $_[1] || 1, $_[2] || 1);
      $img->fill ($_[0]);
      $img
   }

=back

=head2 VARIABLES

=over 4

=cut

   sub X() { $new->{position_sensitive} = 1; $l }
   sub Y() { $new->{position_sensitive} = 1; $t }
   sub W() { $new->{size_sensitive}     = 1; $w }
   sub H() { $new->{size_sensitive}     = 1; $h }

   sub now() { urxvt::NOW }

   sub again($) {
      $new->{again} = $_[0];
   }

   sub counter($) {
      $new->{again} = $_[0];
      $bgdsl_self->{counter} + 0
   }

=back

=head2 OPERATORS

=over 4

=cut

#   sub clone($) {
#      $_[0]->clone
#   }

   sub clip($;$$;$$) {
      my $img = pop;
      $img->sub_rect ($_[0], $_[1], $_[2] || W, $_[3] || H)
   }

   sub resize($$$) {
      my $img = pop;
      $img->scale ($_[0], $_[1])
   }

   # TODO: ugly
   sub move($$;$) {
      my $img = pop->clone;
      $img->move ($_[0], $_[1]);
      $img
#      my $img = pop;
#      $img->sub_rect (
#         $_[0], $_[1],
#         $img->w, $img->h,
#         $_[2],
#      )
   }

   sub rotate($$$$$$) {
      my $img = pop;
      $img->rotate (
         $_[0],
         $_[1],
         $_[2] * $img->w * .01,
         $_[3] * $img->h * .01,
         $_[4] * (3.14159265 / 180),
      )
   }

   sub blur($$$) {
      my ($rh, $rv, $img) = @_;

      $img->blur ($rh, $rv);
   }

   sub contrast($$;$$;$) {
      my $img = pop;
      my ($r, $g, $b, $a) = @_;

      ($g, $b) = ($r, $r) if @_ < 4;
      $a       = 1        if @_ < 5;

      $img = $img->clone;
      $img->contrast ($r, $g, $b, $a);
      $img
   }

   sub brightness($$;$$;$) {
      my $img = pop;
      my ($r, $g, $b, $a) = @_;

      ($g, $b) = ($r, $r) if @_ < 4;
      $a       = 1        if @_ < 5;

      $img = $img->clone;
      $img->brightness ($r, $g, $b, $a);
      $img
   }

=back

=cut

}

sub parse_expr {
   my $expr = eval "sub {\npackage urxvt::bgdsl;\n#line 0 'background expression'\n$_[0]\n}";
   die if $@;
   $expr
}

# compiles a parsed expression
sub set_expr {
   my ($self, $expr) = @_;

   $self->{expr} = $expr;
   $self->recalculate;
}

# evaluate the current bg expression
sub recalculate {
   my ($self) = @_;

   # rate limit evaluation

   if ($self->{next_refresh} > urxvt::NOW) {
      $self->{next_refresh_timer} = urxvt::timer->new->after ($self->{next_refresh} - urxvt::NOW)->cb (sub {
         $self->recalculate;
      });
      return;
   }

   $self->{next_refresh} = urxvt::NOW + $MIN_INTERVAL;

   # set environment to evaluate user expression

   local $bgdsl_self = $self;

   local $old = $self->{state};
   local $new = my $state = $self->{state} = {};

   ($l, $t, $w, $h) =
      $self->get_geometry;

   # evaluate user expression

   my $img = eval { $self->{expr}->() };
   warn $@ if $@;#d#
   die if !UNIVERSAL::isa $img, "urxvt::img";

   # if the expression is sensitive to external events, prepare reevaluation then

   my $repeat;

   if (my $again = $state->{again}) {
      $repeat = 1;
      $state->{timer} = $again == $old->{again}
                        ? $old->{timer}
                        : urxvt::timer->new->after ($again)->interval ($again)->cb (sub {
                             ++$self->{counter};
                             $self->recalculate
                          });
   }

   if (delete $state->{position_sensitive}) {
      $repeat = 1;
      $self->enable (position_change => sub { $_[0]->recalculate });
   } else {
      $self->disable ("position_change");
   }

   if (delete $state->{size_sensitive}) {
      $repeat = 1;
      $self->enable (size_change => sub { $_[0]->recalculate });
   } else {
      $self->disable ("size_change");
   }

   if (delete $state->{rootpmap_sensitive}) {
      $repeat = 1;
      $self->enable (rootpmap_change => sub { $_[0]->recalculate });
   } else {
      $self->disable ("rootpmap_change");
   }

   # clear stuff we no longer need

   %$old = ();

   unless ($repeat) {
      delete $self->{state};
      delete $self->{expr};
   }

   # prepare and set background pixmap

   $img = $img->sub_rect (0, 0, $w, $h)
      if $img->w != $w || $img->h != $h;

   $self->set_background ($img);
   $self->scr_recolour (0);
   $self->want_refresh;
}

sub on_start {
   my ($self) = @_;

   $self->set_expr (parse_expr $EXPR);

   ()
}