The form generator, formgen.pl, runs as a CGI script. It requires at least one argument, which tells the generator which instance of Docbase to use. For example, the CGI call:

/cgi-bin/Docbase/formgen.pl?app=ProductAnalysis

produces the form shown in Figure 6.1.

Figure 6-1. Default ProductAnalysis input form

The assignment date, overridden by the |assigndate| marker, appears as static text. All other fields are open for input. However, this CGI call:

/cgi-bin/Docbase/formgen.pl?app=ProductAnalysis&duedate=1999-05-01&
  analyst=Jon%20Udell&company=Netscape&product=Collabra%20Server%204.0

produces the form shown in Figure 6.2.

Figure 6-2. Customized ProductAnalysis input form

Here, the generator, using the services of the Docbase::Input module, has overridden every replaceable marker with a computed or preassigned value. The analyst who completes this form needs to fill in only four of the fields: Title, Summary, Full Report, and Contact Info.

The form generator, formgen.pl, appears in Example 6.2. It’s brief, because most of the work is done by two modules: TinyCGI and Docbase::Input.

#!/usr/bin/perl -w

use strict;

use TinyCGI;                 # load basic CGI services
my $tc = TinyCGI->new();
print $tc->printHeader();
my $vars = $tc->readParse(); # get form variables into hashref

use Docbase::Input;         
my $di =                     # set up for this docbase
  Docbase::Input->new($vars->{app});  

$di->formGen($vars);         # pass form-variable hashref to form generator

TinyCGI, which I’ll use often, is a minimalistic CGI library. In it I’ve collected the four simple routines that are at the heart of all CGI programming—printHeader( ) to emit the all-important Content-type: header, readParse( ) to gather variables from GET and POST transactions and put them into a Perl hashtable, escape( ) to encode data for HTTP transmission, and unescape( ) to reverse the effects of escape( ). There’s nothing new here; TinyCGI simply repackages, for efficiency and convenience, the 1 percent of Perl’s standard CGI module that I use 99 percent of the time.

sub formGen                       # merge form template with form variables
  {
  my ($self,$vars) = @_;
  my $app = $self->{app};
  my $form =                      # create the template's name
    "$cgi_absolute/$app/form-template.htm"; 

  open(F,$form) or print "cannot open form template $form"; 

  while (<F>)                     # for each line of form template
    {
    if ( m/(!ACTION!)/ )          # rewrite form action
      {
      s#$1#$cgi_relative/$app/submit.pl#;
      }
    if ( m#</form># )             # tack on $app for next script's use
      {
      print "<input type="hidden" name="app" value="$app">
";
      }
    if ( m/|(w+)|/ )           # perform builtin function
      {
      my $fn = $1;                # grab function's name
      s/|$1|/&{$builtins{$fn}}/e;  # call function, replace marker with value
      }
    if ( m/~(w+)~/ )             # handle form variables that can be overridden
      {
      my $var = $1;               # grab variable's name
      my $val = $vars->{$var};    # access corresponding hashtable slot
      if (defined $val)           # if slot nonempty, print value on form
        {                         # and pass along in hidden variable
        s/~$var~/$val <input type="hidden" name="$var" value="$val">/;
        }
      else                        # turn other form variables into input boxes
        {
        s/~$var~/<input name=$var size=40>/;
        }
      }
    print $_;                     # emit the line
    }
  }