#!/usr/bin/perl

# Remember to change the above line if it's different on
# your system.

###############################################################
# THIS SECTION OF THE SCRIPT CONTAINS VARIABLES THAT YOU      #
# *MUST* CUSTOMIZE FOR YOUR OWN SITE!                         #
#                                                             #
# This variable is the *full* URL of the guest book file:     #
$guest_book_url = "http://YOURSITE.COM/CGI-BIN/guests.html";

# This one tells the script which file to modify; since all   #
# the files are in the same directory, a simple file name     #
# will suffice.  If you want to put the Guest Book elsewhere, #
# you'll need a relative or absolute path:                    #
$guest_book_file = "guests.html";

# This is the name of the current script.  You need to define #
# it here so that the script can generate a new form that     #
# refers to $guest_book_script.                               #
$guest_book_script = "guestbk.cgi";

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

# Convert the form input to a usable form, using the
# 'ReadParse' subroutine from "cgi-lib.pl":
require "cgi-lib.pl";
&ReadParse;

# Run the 'CurrentTime' subroutine, which formats the current
# date and time and puts them into the $datetime variable:
&CurrentTime;

# Let them know if they forgot to enter their name or comments.
# In English, the first line says, "run the 'Missing' sub-
# routine unless the $in{'comments'} variable exists."  The
# second line says the same thing for the $in{'name'} variable.
# If both variables are there, 'Missing' is not called at all.
&Missing  unless  $in{'comments'};
&Missing  unless  $in{'name'};


# This is the trickiest part of this script; we'll take it one
# piece at a time.  First, open a new *filehandle* named FILE,
# and fill it with the contents of the file named by the
# $guest_book_file variable.  A filehandle is like a nickname
# for a pile of data.  It's similar to an ordinary file name,
# but it only exists within the program.
open (FILE,"$guest_book_file");

# Create an array called @LINES (arrays start with a @ symbol),
# and set it equal to FILE.  When you dump a filehandle into
# an array like this, each element in the array is one complete
# *line* of the filehandle.  At this point, @LINES now holds
# the complete contents of the Guest Book file.
@LINES = <FILE>;

# Close the FILE filehandle.  Since you've read all of its
# data into the @LINES array, you don't need it anymore.
close(FILE);

# Open a new filehandle called GUESTBOOK.  Rather than read
# another file *into* this filehandle, you're going to
# redirect everything that comes into GUESTBOOK into the file
# named $guest_book_file, replacing the old contents of the
# $guest_book_file.  This is done by placing a 'greater than'
# sign (>) in front of the file name.
open (GUESTBOOK,">$guest_book_file");

# Start a 'foreach' loop.  A foreach loop says, in English,
# "repeat everything within my curly brackets as long as there
# continues to be input." In this case, it will go through the
# entire @LINES array and stop after it has evaluated the last
# line in the array.
foreach ( @LINES ) {

  # Now you're within the 'foreach' loop.  If the current
  # input (one line of the GUESTBOOK file, read as an element
  # of the @LINES array) contains <!--begin-->, execute the
  # statements between the curly brackets. (The first few lines
  # of the file will *not* contain <!--begin-->, so nothing in
  # the 'if' statement will take place; the program will skip
  # to the 'else' down below.)
  if (/<!--begin-->/)  { 

     # If the program has made it here, inside the 'if'
     # statement's curly brackets, it must have found the
     # "begin" marker.  It will spit out a new <!--begin-->
     # line, and then the new guest book entry.  Because you
     # are outputting to a filehandle rather than to the
     # "standard" output, the 'print' statements all begin
     # with 'print GUESTBOOK' rather than just 'print'.
     print GUESTBOOK "<!--begin-->\n";
     print GUESTBOOK "$datetime:<BR>\n";
     print GUESTBOOK "$in{'comments'}<BR>\n";
     print GUESTBOOK "- <I>$in{'name'}";

     # Everything up to this point was straightforward: the
     # "begin" marker, the $datetime variable, the comments,
     # and the person's name, with some line breaks and HTML
     # tags thrown in.
     # But we didn't *require* them to write down their e-mail
     # address, city, state, or country, so we have to create
     # 'if' statements to decide whether to print them.  This
     # is easy.  Look at the first one: "if the $in{'email'}
     # variable exists, then output it to GUESTBOOK, with some
     # parentheses around it."  The rest are all very similar.
     #
     # The last line in this section simply finishes up the
     # new entry with a line break and a horizontal rule line,
     # and the curly bracket closes off the 'if' statement that
     # looked for the "begin" marker.
     if ( $in{'email'} )
       { print GUESTBOOK " ($in{'email'})";    }
     if ( $in{'city'} )
       { print GUESTBOOK ", $in{'city'}";      }
     if ( $in{'state'} )
       { print GUESTBOOK ", $in{'state'}";     }
     if ( $in{'country'} )
       { print GUESTBOOK ", $in{'country'}";   }
     print GUESTBOOK "</I><BR>\n<HR>\n";
  }

  # If the current line does NOT contain <!--begin-->, print
  # out the current input ($_) again, unchanged.  ($_ is a
  # special, predefined variable.)  This ensures that whatever
  # was in the Guest Book before will still be there:
  else { print GUESTBOOK "$_"; }

# This bracket simply finishes off the 'foreach' loop:
}

# Close the Guest Book filehandle, thus ending any output
# to the file named by $guest_book_file:
close (GUESTBOOK);

# Send the user to the Guest Book HTML file so they can see
# what they wrote.  This is just a simple HTTP header, which
# you should know all about by now:
print "Location: $guest_book_url\n\n";

# [END OF MAIN PROGRAM]

# Earlier, we promised that we'd tell you how to make the
# new entries show up at the bottom of the list rather than
# the top.  Here's how: in the 'print GUESTBOOK' statements
# where the new entry is placed into the Guest Book, move the
# 'print GUESTBOOK "<!--begin-->\n"' statement to the *end*
# of the output -- right before the curly bracket that finishes
# the 'if (/<!--begin-->/)' statement) -- rather than at the
# beginning.  It's as simple as that!


##############################################################
# The "Missing" subroutine takes care of situations where the
# user leaves either the Name or Comments field blank.
sub Missing {

# Print the HTTP header and the start of a new form that
# tells people to supply whichever information was missing.
# These will be ordinary print statements, as opposed to the
# ones in the main program that sent output to a filehandle:
print "Content-type: text/html\n\n";
print "<HTML>\n";
print "<HEAD><TITLE>Need more information</TITLE></HEAD>\n";
print "<BODY>\n";

# You need to figure whether it was the Name or Comments field
# that was left blank.  By default, you will say that the
# missing information was BOTH fields; if information is found
# in either one of those, the $missing_info variable will be
# changed later.
$missing_info = "both the Name AND the Comments fields!";

# But if the Name field exists, then it was only the Comments
# which were left blank.  Nothing is output at this stage; you
# are just filling in variables.
if ( $in{'name'} )
  { $missing_info = "the Comments field."; }

# If there are Comments, then the Name must be missing.
if ( $in{'comments'} )
  { $missing_info = "the Name field."; }

# Now you simply tell them which information they forgot to
# to write, using the $missing_info variable:
print "You forgot to fill in $missing_info";

# Now you just have to give them a new form to fill in.  It
# will look much like the original Guest Book entry form, but
# the original information will be placed into the form boxes
# by using the 'value' attribute of the <INPUT> tags.  You can
# use the good old 'ENDOFTEXT' trick.
print<<ENDOFTEXT;

Please add the missing information and resubmit the form.  Thanks.
<HR>

<FORM method="POST" action="$guest_book_script">
Your Name:
   <INPUT type="text" name="name"
   value="$in{'name'}" size=30> <BR>
E-Mail:
   <INPUT type="text" name="email" size=40
   value="$in{'email'}"> <BR>
City:
   <INPUT type="text" name="city" size=15
   value="$in{'city'}">
State:
   <INPUT type="text" name="state" size=2
   value="$in{'state'}">
Country:
   <INPUT type="text" name="country" size=15
   value="$in{'country'}">
<P>
Comments: <BR>
   <TEXTAREA name="comments"
   cols=60 rows=6>$in{'comments'}
   </TEXTAREA> <BR>
(Comments will be formatted as HTML, so you'll need to
include your own <TT>&lt;BR&gt;</TT> tags if you want
line breaks.)
<P>
<INPUT type=submit> <INPUT type=reset>
</FORM>

<HR>
<A href="$guest_book_url">Return to the guest book</A>.
</BODY>
</HTML>

ENDOFTEXT

# The 'exit' statement makes the script stop right here in the
# subroutine, rather than returning to the main program.  The
# curly bracket officially finishes off the subroutine.
exit;
}


##############################################################
# The "CurrentTime" subroutine converts Perl's localtime(time)
# variable to a more readable format.
sub CurrentTime {

# Perl's 'time' function counts the number of seconds since
# a certain date in the past.  The 'localtime' function
# converts this number to a list of nine elements. You can
# dump this list into nine meaningful scalar variables with
# the following statement ($isdst tells whether it's Daylight
# Saving Time or not):
($sec,$min,$hour,$mday,$month,$year,$wday,$yday,$isdst) =
    localtime(time);

# 'Localtime(time)' thinks January is 0 and December is 11, so
# you need to add 1 to the $month variable.  Also, set a new
# variable called $ampm to "AM" by default.
$month = $month + 1;
$ampm = "AM";

# The hour will be in 24-hour time, so 0 is really 12.  Also,
# hours greater than 12 will be reduced by 12, and the $ampm
# variable will become "PM".  Finally, minutes less than 10
# need to have a leading zero added.
if ($hour == 0) { $hour = 12; }
if ($hour > 12) { $hour = $hour - 12; $ampm = "PM" }
if ($min < 10) { $min = "0$min"; }

# This statement just strings all the date & time pieces
# together and puts them in a variable called $datetime.  This
# subroutine does *not* have an 'exit' statement, because it
# *should* return to the main program when it's done.
$datetime = "$month/$mday/$year, $hour:$min $ampm";

}