Solution: Dancer Calculator

package App;
use Dancer2;
use Scalar::Util qw(looks_like_number);

get '/' => sub {
    return <<'HTML';
<form action="/calc" method="POST">
<input type="text" name="x">
<select name="op">
<option value="add">+</option>
<option value="deduct">-</option>
<option value="div">/</option>
<option value="multiply">*</option>
</select>
<input type="text" name="y">
<input type="submit" value="Calculate">
</form>
HTML

};

post '/calc' => sub {
    my $x = body_parameters->get('x');
    my $y = body_parameters->get('y');
    my $op = body_parameters->get('op');

    my %valid_ops = map { $_ => 1 } qw(add deduct multiply div);

    if (not looks_like_number($x) or not looks_like_number($y) or not defined $op or not exists $valid_ops{$op}) {
        status 'bad_request';
        return 'Invalid input';
    }

    my $result;

    if ($op eq 'div' and $y == 0) {
        status 'bad_request';
        return 'Cannot divide by 0';
    }
    $result = $x + $y if $op eq 'add';
    $result = $x - $y if $op eq 'deduct';
    $result = $x * $y if $op eq 'multiply';
    $result = $x / $y if $op eq 'div';

    return "The result is $result";
};

App->to_app;

use strict;
use warnings;

use Test::More;
use Plack::Test;
use Plack::Util;
use HTTP::Request::Common;

my $app = Plack::Util::load_psgi './app.psgi';

my $test = Plack::Test->create($app);

subtest main => sub {
    my $res = $test->request(GET '/');

    is $res->status_line, '200 OK', 'Status';
    like $res->content, qr{<form action="/calc" method="POST">}, 'Content';
};

subtest calc => sub {
    my @cases = (
        [{ x => '10', y => '2', op => 'add'}, '12'],
        [{ x => '10', y => '2', op => 'multiply'}, '20'],
        [{ x => '10', y => '2', op => 'deduct'}, '8'],
        [{ x => '10', y => '2', op => 'div'}, '5'],
    );

    for my $case (@cases) {
        my $res = $test->request(POST '/calc', $case->[0]);
        is $res->status_line, '200 OK', "Status x=$case->[0]{x} y=$case->[0]{y} op=$case->[0]{op}";
        is $res->content, "The result is $case->[1]", 'Content';
    }

    my @bad_cases = (
        [{ x => 'hello', y => '2', op => 'add'}, 'Invalid input'],
        [{ x => '', y => '2', op => 'add'}, 'Invalid input'],
        [{ y => '2', op => 'add'}, 'Invalid input'],
        [{ x => '2', y => 'world', op => 'add'}, 'Invalid input'],
        [{ x => '2', y => 'world', op => 'add'}, 'Invalid input'],
        [{ x => '2', y => '', op => 'add'}, 'Invalid input'],
        [{ x => '2', op => 'add'}, 'Invalid input'],
        [{ x => '10', y => '2', op => 'else'}, 'Invalid input'],
        [{ x => '10', y => '2', op => ''}, 'Invalid input'],
        [{ x => '10', y => '2'}, 'Invalid input'],
    );

    for my $case (@bad_cases) {
        my $res = $test->request(POST '/calc', $case->[0]);
        no warnings 'uninitialized';
        is $res->status_line, '400 Bad Request', "Status x=$case->[0]{x} y=$case->[0]{y} op=$case->[0]{op}";
        is $res->content, $case->[1], "Content x=$case->[0]{x} y=$case->[0]{y} op=$case->[0]{op}";
    }

    my $res = $test->request(POST '/calc', { x => '3', y => '0', op => 'div'});
    is $res->status_line, '400 Bad Request', 'Status';
    is $res->content, 'Cannot divide by 0', 'Content';
};


done_testing();

• HTTP status
• HTTP status codes