#!/usr/bin/perl
use warnings;
use strict;

use Test::More;
use Benchmark qw(cmpthese);


my %dispatch = (
                simple => sub { my ($n, $d) = @_; 0 == $n % $d },
                1 => sub { 1 },
                2 => sub { shift =~ /[02468]$/ },
                3 => sub {
                    my $n = shift;
                    while (1 < length $n) {
                        my $sum = 0;
                        $sum += $_ for split //, $n;
                        $n = $sum;
                    }
                    return grep $_ == $n, 0, 3, 6, 9;
                },
                4 => sub {
                    my ($n) = shift =~ /(..)$/;
                    0 == $n % 4;
                },
                5 => sub { shift =~ /[05]$/ },
                7 => sub {
                    my $n = shift;
                    while (1 < length $n) {
                        my $last = substr $n, -1, 1, q();
                        $n = abs($n - 2 * $last);
                    }
                    return (0 == $n or 7 == $n);
                },
                10 => sub { shift =~ /0$/ },
                11 => sub {
                    my $n = shift;
                    while (2 < length $n) {
                        my $check = 0;
                        my $i = 1;
                        for (split //, $n) {
                            $check += $i * $_;
                            $i *= -1;
                        }
                        $n = abs $check;
                    }
                    return ($n == 0 or $n =~ /^(.)\1$/);
                },
               );

my @divisors = sort { $a <=> $b } grep 'simple' ne $_, keys %dispatch;

my @test_data  = map int rand 1e12, 1 .. 1e7;
for my $divisor (@divisors) {
    cmp_ok($dispatch{simple}->($_, $divisor),
           '==',
           $dispatch{$divisor}->($_)) for @test_data[0 .. 99];
}

for my $divisor (@divisors) {
    print "\n$divisor\n";
    my ($mogi, $magi) = (0, 0);
    cmpthese(1e7, {
        mod     => sub { $dispatch{simple}->($test_data[$mogi++],$divisor) },
        machine => sub { $dispatch{$divisor}->($test_data[$magi++])},
    });
}

done_testing();