#!/usr/bin/env -S perl
##!/usr/bin/env -S perl -wd

use warnings;
use strict;
use feature ":all";
use Tkx;
use Tk;

sub factorial {
  my ($n) = @_;
  return 1 if $n == 0;
  return factorial($n-1) * $n;
}

sub recurWrapper {
    my $n = factorial(@_);
    say "after recursion: ", $n;
    return $n;
}

sub factorial_1 {
    (my $val) = @_;
    my $result = 1;
    while ( $val > 0 ) {
        $result *= $val;
        $val--;
    }
    say "\$result inside factorial_1: $result";
    return $result;
}

sub intOverflow {
    (my $val) = @_;
    return $val *= 1;
}

sub exponential {
    (my $val) = @_;
    my $n = 2**$val;
    say "\$result inside exponential $n";
    return $n;
}

say 'factorial(17):  ', factorial(17);

say 'factorial_1(17): ', factorial_1(17);

say '';
say 'exponential(31): ', exponential(31);
say 'exponential(32): ', exponential(32);
say 'exponential(33): ', exponential(33);

say '';
say 'intOverflow(2147483647): ', intOverflow(2147483647);
say 'intOverflow(2147483648): ', intOverflow(2147483648);
say 'intOverflow(2147483649): ', intOverflow(2147483649);

my $mw = Tkx::widget->new(".");
$mw->g_wm_title("Factorial Calculator");
$mw->g_wm_minsize(200, 150);

my $result;
my $value;
my $v = $mw->new_entry(
    -width        => 6,
    -relief       => "sunken",
    -textvariable => \$value,
);
#$v->Tkx::bind('<Return>', sub { say $value; $result = factorial($value); say $result; } );
$v->Tkx::bind('<Return>', sub { say $value; $result = recurWrapper($value); say $result; } );
#$v->Tkx::bind('<Return>', sub { say $value; $result = factorial_1($value); say $result; } );
#$v->Tkx::bind('<Return>', sub { say $value; $result = exponential($value); say $result; } );
#$v->Tkx::bind('<Return>', sub { say $value; $result = intOverFlow($value); say $result; } );

my $desc = $mw->new_label(
    -text => "Factorial is:",
);

my $r = $mw->new_label(
    -textvariable => \$result,
);

my $calc = $mw->new_button(
    -text => "Calculate",
#   -command => sub { say $value; $result = factorial($value);   say $result; },
    -command => sub { say $value; $result = recurWrapper($value);   say $result; },
#   -command => sub { say $value; $result = factorial_1($value); say $result; },
#   -command => sub { say $value; $result = exponential($value); say $result; },
#   -command => sub { say $value; $result = intOverflow($value); say $result; },
);

my $q = $mw->new_button(
    -text    => "QUIT",
    -command => sub { $mw->g_destroy; },
);

Tkx::grid($v, $desc, $r,   -padx => 10, -pady => 10);
Tkx::grid($calc, "-", "-", -padx => 10, -pady => 5);
Tkx::grid($q, "-", "-",    -padx => 10, -pady => 5);

Tkx::MainLoop()

__END__