#!/usr/bin/perl

use warnings;
use strict;
use CGI;
use CGI::Cookie ();
use MD5 ();

use constant TRIES       => 6;
use constant COOKIE_NAME => 'guess_number_3';
use constant SECRET      => 'mySuperSecretSecret';
my $game                 =  CGI->new;

# state maintenance subroutines
sub get_state {
    my %state = $game->cookie( COOKIE_NAME );
    return undef unless %state;
    authentication_error() unless cookie_check( \%state, 'check');
    return \%state;
}

sub initialize {
    my $state = shift;
    $state = {} unless $state;
    $state->{NUMBER}            = int( rand( 99 ) ) + 1;
    $state->{GAMENO}            += 1;
    $state->{GUESSES_LEFT}      = TRIES;
    $state->{WON}               += 0;
    $state->{GUESSED}           = '';
    return $state;
}

sub save_state {
    my $state = shift;
    cookie_check( $state, 'generate' );
    return CGI::Cookie->new (
        -name           => COOKIE_NAME,
        -value          => $state,
        -expires        => '+1M',
    );
}

# game play logic
sub process_guess {
    my ( $guess, $state ) = @_;

    # process list of previous guesses
    my %guessed = map { $_ => 1 } split /,/, $state->{GUESSED};

    # do nothing if user did not enter a guess
    return ('', 'continue') unless $guess;

    # ensure guess is a valid number between 1 and 100
    return ("Not a valid guess.", 'error')
        unless $guess =~ m/^[1-9][0-9]?$|^100$/;

    # check if user already entered this guess previously
    return ("You already guessed that number.", 'error')
        if $guessed{ $guess };

    # we have a valid guess.  update list of guesses
    $guessed{ $guess } = 1;
    $state->{GUESSED} = join ',', sort keys %guessed;

    $state->{GUESSES_LEFT}--;

    # the order of the checks is important here.  At this point, it's
    # possible that the player has used their last guess.  Therefore,
    # we first check whether the guess is correct

    # guess is correct!
    if ( $guess == $state->{NUMBER} ) {
        $state->{WON}++;
        return ("Congratulations! You guessed that the correct number
            was $state->{NUMBER}!", 'won');
    }

    # if the guess is not correct AND we are out of guesses...
    return ("Sorry, you ran out of turns. The number was $state->{NUMBER}.",
        'lost') unless ($state->{GUESSES_LEFT} && $guess != $state->{NUMBER});

    # otherwise...
    # guess too low
    return ("Your guess is too low.", 'continue')
        if ( $guess < $state->{NUMBER} );

    # ...or
    # guess is too high
    return ("Your guess is too high.", 'continue')
        if ( $guess > $state->{NUMBER} );

}

# html generation subroutines
sub print_header {
    my $state = shift;
    print $game->header(
        -type       => "text/html",
        -charset    => 'utf-8',
        -cookie     => save_state( $state ),
    );
    print $game->start_html(
        -title      => "Guess a Secret Number!",
        -onLoad     => 'if (document.gf) document.gf.guess.focus()'
    );
    print $game->h1( 'Guess a Secret Number Interactive Game' );
}

sub print_status {
    my ( $message, $state ) = @_;

    # draw table
    print
        $game->table( { -border=>"0", -width=>"50%" },
            $game->Tr(
                $game->td( $game->b("Game #: "), $state->{GAMENO} ),
                $game->td( $game->b("Wins: "),   $state->{WON} )
            ),
            $game->Tr(
                $game->td( $game->b("Guesses Left: "),    $state->{GUESSES_LEFT} ),
                $game->td( $game->b("Numbers Guessed: "), $state->{GUESSED} )
            )
        );
    print $game->h2( $game->font( {-color => 'red'}, $message ))
        if $message;
}

sub show_restart_form {
    my $state = shift;
    print $game->start_form();
    print $game->p(
        #-style => 'padding-right: 25px',
        'Do you want to play again?',
    );
    print $game->submit (
        -name  => 'restart',
        -value => 'Play again',
        #-style => 'padding-left: 25px; padding-right: 25px',
    );
    print $game->checkbox (
        -name  => 'clear',
        -label => 'Clear history',
    );
    print $game->end_form();
}

sub show_guess_form {
    my $state = shift;
    print $game->start_form( -name => 'gf' );
    print "Your guess: ";
    print $game->textfield (
        -inputmode     => 'numeric', # force number pad on mobile
        -pattern  => '[0-9]*',       # force number pad on mobile
        -name     => 'guess',
        -value    => '',
        -override => 1
    );
    print $game->submit (
        -name     => '_guess',
        -value    => 'Guess'
    );
    print $game->end_form();
}

sub print_footer {
    print $game->hr;
    print $game->p(
        'inspired by Hangman game from ',
        $game->a(
            { -href => "https://www.oreilly.com/library/view/writing-apache-modules/156592567X/"},
            $game->i( 'Writing Apache Modules with Perl and C')
        ),
        ' by Lincoln Stein and Doug MacEachern.'
    );
    print $game->end_html();
}

# message authentication checks
sub cookie_check {
    my ($state, $action) = @_;
    return unless ref( $state );
    my @fields = @{$state}{qw(NUMBER GUESSES_LEFT GUESSED GAMENO WON)};
    my $newmac = MD5->hexhash(
        SECRET . MD5->hexhash( join '', SECRET, @fields )
    );
    return $state->{MAC} = $newmac if $action eq 'generate';
    return $newmac eq $state->{MAC} if $action eq 'check';
    return undef;
}

sub authentication_error {
    my $cookie = CGI::Cookie->new(-name => COOKIE_NAME, -value=>'',-expires => '-1d');
    print $game->header(-cookie => $cookie),
          $game->start_html(-title => 'Authentication Error'),
          $game->h1($game->font({-color => 'red'}, 'Authentication Error')),
          $game->p('This application was unable to confirm the integrity of the',
          'cookie that holds your current score.',
          'Please reload the page to start a fresh session.'),
          $game->p('If the problem persists, contact the webmaster.');
    exit 0;
}

# begin main program
# retrieve current state
my $state = get_state() unless $game->param( 'clear' );

# initialize state if we are starting from the beginning (!$state)
# or if we are playing another game ($game->param( 'restart' )).
if ( !$state || $game->param( 'restart' ) ) {
    $state = initialize( $state );
}

# process current guess, if any
my ( $message, $status ) =
    process_guess( $game->param( 'guess' ) || '', $state );

# generate the HTML page
print_header( $state );
print_status( $message, $state );

# prompt user
if ( $status =~ /^(won|lost)$/ ) {
    show_restart_form( $state );
} else {
    show_guess_form( $state );
}

print_footer();