use strict;
use warnings;
use Data::Dump qw/pp dd/;
use Scalar::Util qw/reftype/;
use autovivification;
use Test::More;

use constant DBG => 0;



my  @rules;



sub parse_arr (\@$) {
    my ( $arr, $path ) = @_;
    for ( my $i=0; $i <= @$arr; $i++ ) {
        my $item = $arr->[$i];
        parse( $item, "${path}[$i]");
    }
}

sub parse_hsh (\%$) {
    my ( $hsh, $path ) = @_;
    while ( my ($key,$val) = each %$hsh ) {
        parse( $val, "${path}{$key}");
    }
}


sub parse {
    my ( $item, $path ) = @_;
    $path //= '';

    my $type = ref $item;

    return
      unless $type;

    if ( $type eq "GRAB") {
        push @rules, [ $item->{ref} , $path ];
    } elsif ( $type eq "ARRAY" ) {
        parse_arr( @$item, $path )
    } elsif ( $type eq "HASH" ) {
        parse_hsh( %$item, $path )
    } else {
        warn "Unknown $type";
    }
}



sub assign (++){
    my ($pattern,$in) =@_;

    @rules = ();

    parse($pattern);
    warn pp @rules if DBG;
    no autovivification;
    for my $rule (@rules) {
        my ($ref,$path) = @$rule;

        my $code = "\$in->$path";
        $$ref = eval($code);
    }
}


sub set (\[@$%]) {
    bless {ref => $_[0]}, "GRAB";
}


my @pattern = ( 1,2,3, set my $y , [ 5,6, set my $z ] );

my $src = [ 1,2,3, 42 , [5,6, 666] ];

assign
  @pattern
  =>
  $src;



is_deeply
  (
   [$z,$y],
   [666, 42],
   "AoA grabbing different levels"
  );




assign
  { u => [undef, set( my $u )], v => set my $v }
  =>
  { u => [1,123] , v => "VVV"}
  ;


is_deeply
  (
   [$u,$v],
   [123,"VVV"],
   "HoA grabbing different levels"
  );

done_testing;