#!/usr/bin/perl

# #################################################################
#
# Project:     CGI-Programming
#
# Filename:    calculator.cgi
#
# Version:     1.0
#
# Autor:       Akadia AG, Christoph Gaechter 26.12.1999
#
# Purpose:     Shows how to implement a simple form to
#              perform an operation with two numbers
#
# #################################################################
#
use strict;                                 # enforce variable declarations and quoting
use CGI qw(:standard);                      # load CGI module
use CGI::Carp qw(fatalsToBrowser carpout);  # Error Messages to Browser

my ($n1,$n2,$n3,$op,$exp,$msg);

print header(), start_html("Calculator");
print ("<link rel='stylesheet' href='https://www.akadia.com/docroot/css/website.css'>\n");
print h1("Calculator @ $ENV{SERVER_NAME}");

# Check for valid input

if (param()) {

  $n1 = param('number1');
  $n2 = param('number2');
  $op = param('operation');
  if (! $n1) {
    $msg = "Invalid first number, try again!";
  } elsif (! $n2) {
    $msg = "Invalid second number, try again!";
  }

  # Calculate the apropriate expression

  if (! $msg) {
    if ($op eq 'add') {
      $n3 = $n1 + $n2;
      $exp = "$n1 + $n2";
    } elsif ($op eq 'sub') {
      $n3 = $n1 - $n2;
      $exp = "$n1 - $n2";
    } elsif ($op eq 'mul') {
      $n3 = $n1 * $n2;
      $exp = "$n1 * $n2";
    } elsif ($op eq 'div') {
      $n3 = $n1 / $n2;
      $exp = "$n1 / $n2";
    } else {
      $msg = "Unknown operation, try again!";
    }
  }
}

# Create HTML Form with results

if ($msg) {
  print hr();
  print ("<p> Error occured: <b>$msg</b></p>\n");
}
else {
  print hr(), start_form();
  print ("<table border=0 width=500>\n");
  print ("<tr>\n");
  print ("<th align='LEFT' width='74'>First number</th>\n");
  print ("<td width='295'> <input type='text' size=15 maxlength=10 name='number1' value=''></td>\n");
  print ("</tr><tr>\n");
  print ("<th align=LEFT>Second number</th>\n");
  print ("<td> <input type='text' size=15 maxlength=10 name='number2' value=''></td>\n");
  print ("</tr><tr>\n");
  print ("<th align=LEFT valign=TOP>Operation</th>\n");
  print ("<td>\n");

  # Dynamicly create the radio buttons (checked / unchecked)

  $msg = "input type='radio' name='operation' value='add' ";
  if (! $op or $op eq 'add') {
    print ("<$msg checked>\n");
  } else {
    print ("<$msg>\n");
  }

  print ("Addition\n");
  print ("<br>\n");
  $msg = "input type=radio name='operation' value='sub' ";
  if ($op eq 'sub') {
    print ("<$msg checked>\n");
  } else {
    print ("<$msg>\n");
  }

  print ("Subtraction\n");
  print ("<br>\n");
  $msg = "input type=radio name='operation' value='mul' ";
  if ($op eq 'mul') {
    print ("<$msg checked>\n");
  } else {
    print ("<$msg>\n");
  }

  print ("Multiplication\n");
  print ("<br>\n");
  $msg = "input type=radio name='operation' value='div' ";
  if ($op eq 'div') {
    print ("<$msg checked>\n");
  } else {
    print ("<$msg>\n");
  }

  print ("Division\n");
  print ("</td></tr><tr>\n");
  print ("<td> &nbsp </td>\n");
  print ("</tr><tr>\n");
  print ("<th align=LEFT> Expression </th>\n");
  print ("<th align=LEFT> $exp </th>\n");
  print ("</tr><tr>\n");
  print ("<th align=LEFT> Result </th>\n");
  print ("<th align=LEFT> $n3 </th>\n");
  print ("</tr><tr>\n");
  print ("<td> &nbsp </td>\n");
  print ("</tr><tr>\n");
  print ("<td align=LEFT valign=TOP> <input type='submit' value='Execute'></td>\n");
  print ("<br>\n");
  print ("<td><a href='../src/calculator.txt' target='_top'>Show source</a>\n");
  print ("</p></td></tr></table>\n");
  print end_form();
}

# Build page footer

print hr();
print ("$ENV{SERVER_SIGNATURE}\n");
print end_html();