#!/usr/bin/env perl
use strict;
use warnings;
no warnings "uninitialized";
use CGI ":standard";

my $csv_file = "/tmp/test.csv";

# Initial variables
my @languages = ("English", "Francais");
my @colours = ("Red", "Orange", "Yellow", "Green", "Blue", "Indigo",
               "Violet", "Black");

my %dispatch = ( default => \&select_language,
                 select_color => \&select_color,
                 select_download => \&select_download,
                 download => \&download );

my $action = param("action");
my $execute = $dispatch{$action} || $dispatch{default};
$execute->();

# print CGI::Dump(); # Uncomment for debugging help.

exit;

sub select_language {
    print header(),
        start_html(),
        h2("Welcome to this basic form"),
        startform(),
        hidden({ -name => "action",
                 -value => "select_color",
                 -override => 1 }),
        popup_menu({ -name => "language",
                     -values => \@languages,
                     -default => $languages[0] }),
        submit({-value => "Continue"}),
        endform;
}

sub select_color {
    print header(),
        start_html(),
        h2("Part Two"),
        startform,
        hidden({ -name => "action",
                 -value => "select_download",
                 -override => 1 }),
        hidden({ -name => "language" }),
        "<p>Please choose your favourite colour: </p>",
        radio_group({ -name => "colour",
                      -values => \@colours,
                      -default => $colours[0],
                      -linebreak => "true" }),
        submit({-value => "Continue"}),
    endform;
}

sub select_download {
    print header(),
        start_html(),
        h2("Almost Done!"),
        startform(),
        hidden({-name => "action",
                -value => "download",
                -override => 1 }),
        hidden({-name => "language"}),
        hidden({-name => "colour"}),
        "<p>Download the CSV file if you dare.</p>",
        submit({-value => "Download"}),
        endform;
}

sub download {
    my $ok = open my $fh, "<", $csv_file;
    unless ( $ok ) # Ad hoc error handling, don't do this for real.
    {
        print header("text/plain"), "SORRY! $csv_file: $!";
        exit 1;
    }

    print header(-type => "application/x-download",
                 -attachment => "arbitrary-name.csv" );

    for my $param ( param() )
    {
        print join(",", $param, param($param)), $/;
    }

    print while <$fh>;
}