#!/usr/bin/env perl

# This example online to try at
# http://www.wellho.net/cgi-bin/demo/sweetest.pl

=head1 Perl web application framework - sessions and hidden fields

=head2 Introduction to general code

This is a demonstration program showing which provides the shell
framework for a web based CGI application written in Perl.

This example if the third of three - known as "sweetest". The other
two examples, also downloadable from http://www.wellho.net, are
known as sweet and sweeter. You can learn / study sweet and
sweeter to help you understand the principles involved. We suggest
you work with sweetest if you're going to write an application
yourself that's based on the principles illustrated here.

=item 1. read any incoming form

=item 2. Use the value read to pick up the session

=item 3. Do any work to analyse inputs and validate them

=item 4. Do work to prepare for next page

=item 5. Save the session

=item 6. Send out the response page

=cut

# Date stamp for page
@now = (gmtime())[3,4,5];
$fill{"now"} = sprintf("%d/%d/%d",$now[0],$now[1]+1,$now[2]+1900);

$fill{"title"} = "Sample Perl/CGI session (shopping cart) demo";

$sessdir = "../../sessions";

print "Content-type: text/html\n\n";

# item 1. read any incoming form
#-------------------------------

collect_form();

# item 2. Use the value read to pick up the session
#--------------------------------------------------

if ($form{plsess}) {
        $sessname = $form{plsess};
        open (FHS,"$sessdir/$sessname.ses");
        while (<FHS>) {
                chop;
                ($name,$val) = split;
                $val =~ tr/+/ /;
                $val =~ s/%(..)/pack("C",hex($1))/eg;
                $session{$name} = $val;
        }
} else {
        $sessname = $$.time();
        # Take the opportunity of a new session to clean up stale ones
        opendir (DH,$sessdir);
        while ($fname = readdir DH) {
                next if ($fname =~ /^\./);
                if (-M "$sessdir/$fname" > 0.5) { # half a day
                        unlink "$sessdir/$fname";
                }
        }
}
$fill{plsess} = $sessname;
$stepnumber = $session{step};

# Inputs in %session and %form translate to %session and %fill

# item 3. Do any work to analyse inputs and validate them
#--------------------------------------------------------

$aok = 1;
$errstr = "";
if ($stepnumber == 0) { # Initialisation
        # Move on to next step - prepare for page 1
        $stepnumber = 1;
} elsif ($stepnumber == 1) {
        $aok *= checkinput("yourname","name",'\w',
                "Name must include a word character");
        $aok *= checkinput("youremail","email",'^\s*\S+@\S+\s*$',
                "email address of form xxx\@xxx.xxx required");
        $stepnumber++ if ($aok);
} elsif ($stepnumber == 2) {
        $aok *= checkinput("yourtown","town",'^\s*\w',
                "Town name must start with a letter");
        $aok *= checkinput("yourpostcode","postcode",
                "^\s*[A-Z]{1,2}[1-9]",
                "Must start with 1 or 2 capital letters followed by a digit");
        $stepnumber++ if ($aok);
} else {
}

# item 4. Do work to prepare for next page
#-----------------------------------------

$fill{status} = "You are at page $stepnumber of 3";
$fill{stuff} = "Results will appear here";
$fill{errstr} = $errstr;
$fill{form} = "<form method=POST><table border=1><input name=plsess type=hidden ".
                "value=".$fill{plsess}.">";

if ($stepnumber == 1) {
        $fill{"form"} .= formbox("Please enter your name","yourname");
        $fill{"form"} .= formbox("Please enter your email address","youremail");
} elsif ($stepnumber == 2) {
        $fill{"form"} .= formbox("Please tell us your town name","yourtown");
        $fill{"form"} .= formbox("Please enter your postcode","yourpostcode");
} elsif ($stepnumber == 3) {
        # This is where all the data entry has been completed and has been checked
        # to be valid and in a complete application we would add the code to conclude
        # the transaction. For the demonstration, we just echo the user's inputs and
        # then clear up the session behind ourself.
        $fill{stuff} = "<b>Hello ".webify($session{name})." from ".
                webify($session{town})."<br>";
        $fill{stuff} .= "email ".webify($session{email})." pc ".
                webify($session{postcode})."</b><br>";
        $stepnumber = 0;
        unlink "$sessdir/$sessname.ses";
        $completed = 1;
} else {
}

$fill{form} .= "<tr><td>&nbsp;</td><td><input type=submit></td></tr></table></form>";
$fill{form} = "<a href=\"\">Restart Demonstration</a>" if ($completed); # No next form if application completed

# item 5. Save the session
#-------------------------

# If the user's session has been completed, don't save the "in progress" file"

if (! $completed) {
        $session{step} = $stepnumber;
        open (FHS,">$sessdir/$sessname.ses");
        foreach $name (keys %session) {
                $val = $session{$name};
                $val =~ s/%/%25/g;
                $val =~ s/\+/%2b/g;
                $val =~ s/\n/%0a/g;
                print FHS "$name $val\n";
                }
        close FHS;
        }

# item 6. Send out the response page
#-----------------------------------
# Complete the output template and send it to the user

$fill{step} = $stepnumber;

while (<DATA>) {
        s/%(\w+)%/$fill{$1}/g;
        print;
        }

################## Standard functions

=head2 Standard functions

Note that the following standard functions would be placed into a
separate file (a module) for a live application. For the purpose of
this demo, we've put everyting into the one file

=cut

########################

# Code to "clean" up text strings for safe web display

sub webify {
        $_ = $_[0];
        s/&/&amp;/g;
        s/</&lt;/g;
        s/>/&gt;/g;
        s/"/&quot;/g;
        return $_;
        }

########################

# Code to translate form inputs (GET or POST) into a hash

sub collect_form {

if ($ENV{"REQUEST_METHOD"} eq "POST") {
        read(STDIN,$buffer,$ENV{"CONTENT_LENGTH"});
        $form{"method"} = "POST";
} else {
        $buffer = $ENV{QUERY_STRING};
        $form{"method"} = "GET";
}

@fof = split(/&/,$buffer);
foreach $field(@fof) {
        ($name,$value) = split(/=/,$field);
        $value =~ tr/+/ /;
        $value =~ s/%([a-fA-F0-9]{2})/pack("C",hex($1))/eg;
        if ($form{$name}) {
                $form{$name} .= "\n$value";
        } else {
                $form{$name} = $value;
                }
        }
}

########################

# Code to generate a table row that includes a prompt and an input box
# Adds error messages and old ("sticky") values in

sub formbox {
        my ($text,$fieldname) = @_;
        $add = "";
        if ($errtab{$fieldname}) {
                $add="<br><font color=red>$errtab{$fieldname}</font>";
                }
        $text = "<tr><td>".webify($text)."$add</td><td><input name=$fieldname ".
                "value=\"".webify($form{$fieldname})."\"></td></tr>";
        return $text;
        }

########################

# Validate a form input against a regular expression

sub checkinput {
        my ($fieldname,$sessname,$rematch,$errmsg) = @_;
        $good = 1;
        if ($form{$fieldname} !~ /$rematch/) {
                $good = 0;
                $errtab{$fieldname} = $errmsg;
                $errstr = "Please correct the errors noted and resubmit";
        } else {
                $session{$sessname} = $form{$fieldname};
        }
        return $good;
}
##################################################################

# After the __END__ we'll place the template for all response pages

__END__
<html><head>
<title>%title% - Well House Consultants demo</title>
</head>
<body bgcolor=#CCFFFF>
<h1>Demonstration - %title%</h1>
This is the introductory piece of text about this application.<hr>
This is the current status:<br><br>%status%<hr>
<font color=red>%errstr%</font>
%form%<hr>
Here are your results:<br><br>%stuff%<hr>
<i>This is a sample page generated by a training course example from
<a href=http://www.wellho.net/>Well House Consultants</a>. You can learn
how to write web based applications such as this on our
<a href=http://www.wellho.net/course/pw.html>Perl on the Web</a> course.</i><br><br>
Copyright Well House Consultants, %now% <br><br>
<h4>debug info: page no. %step%, session %plsess%</h4>
</body></html>