#! perl

our $EXPR = 'resize (blur (load "/root/pix/das_fette_schwein.jpg", 1 + (counter 1) % 10, 10), w, h)';
#$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;

{
   package urxvt::bgdsl::vars;

   our ($self, $old, $new);
   our ($x, $y, $w, $h);

   package urxvt::bgdsl; # background language

   *repeat_black  = \&urxvt::RepeatNone; #TODO wtf
   *repeat_wrap   = \&urxvt::RepeatNormal;
   *repeat_pad    = \&urxvt::RepeatPad;
   *repeat_mirror = \&urxvt::RepeatReflect;

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

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

   sub root {
      die "root op not supported, exg, we need you";
   }

   sub resize {
      $_[0]->scale ($_[1], $_[2])
   }

   sub move {
      # TODO: must be simpler
      $_[0]->transform ($_[0]->w, $_[0]->h, $_[1],
         1, 0, -$_[2],
         0, 1, -$_[3],
         0, 0,      1,
      )
   }

   sub rotate {
      $_[0]->rotate ($_[0], $_[1], $_[2], $_[3] * (3.14159265 / 180))
   }

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

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

   sub contrast {
      my ($img, $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, $r, $g, $b, $a) = @_;
      ($g, $b) = ($r, $r) if @_ < 4;
      $a       = 1        if @_ < 5;
      $img = $img->clone;
      $img->brightness ($r, $g, $b, $a);
      $img
   }

   sub x { $new->{position_sensitive} = 1; $x }
   sub y { $new->{position_sensitive} = 1; $y }
   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];
      $self->{counter}++ + 0
   }
}

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) = @_;

   local $Data::Dumper::Deparse=1; use Data::Dumper; warn Dumper $expr;#d#
   $self->{expr} = $expr;
   $self->recalculate;
}

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

   local $urxvt::bgdsl::vars::self = $self;

   local $urxvt::bgdsl::vars::old = $self->{state};
   local $urxvt::bgdsl::vars::new = my $state = $self->{state} = {};

   ($urxvt::bgdsl::vars::x, $urxvt::bgdsl::vars::y, $urxvt::bgdsl::vars::w, $urxvt::bgdsl::vars::h) =
      $self->get_geometry;

   my $img = eval { $self->{expr}->() };
   warn $@ if $@;#d#

   if (my $again = $state->{again}) {
      warn $again;#d#
      $state->{again} = urxvt::timer->new->after ($again)->cb (sub { $self->recalculate });
   }

   # TODO: install handlers for geometry changes &c

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

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

   $self->set_expr (parse_expr $EXPR);

   ()
}