#!/usr/bin/perl -w
# tempcon version 0.1      for Perl/Tk
# by Alan Ford <alan@whirlnet.demon.co.uk> 27/03/1999
#
# Description:
# Allows conversion of temperatures between different scales
#
# Features to come:
# - Info box
#
# Distributed with no warranty under the GNU Public License

# Since there are 5 different temperature scales, there are 25 
# conversions.  To simplify, always convert the input to kelvin,
# then convert to the output.
# This reduces the 25 to 10 (5 in, 5 out).
#
# Input conversions are:
# Kelvin:      k = 1.0 * (k   +   0.0)
# Celcius:     k = 1.0 * (c   + 273.16)
# Fahrenheit:  k = 5/9 * (f   + 459.688)
# Rankine:     k = 5/9 * (r   +   0.0)
# Reaumur:     k = (1.25 * R) + 273.16

my %mul = ('k'=>1.0,  'c'=>1.0,    'f'=>5.0/9.0, 'r'=>5.0/9.0, 'R'=>1.25);
my %add = ('k'=>0.0,  'c'=>273.16, 'f'=>459.688, 'r'=>0.0,     'R'=>273.16/1.25);
my %scales = ('c'=>"degrees Celsius", 
	      'f'=>"degrees Fahrenheit",
	      'k'=>"Kelvin",
	      'r'=>"degrees Rankine",
	      'R'=>"degrees Reaumur");

require 5.002;
# use English;
use Tk;
use Tk::DialogBox;
# use strict;
sub convert ;

my $MW = MainWindow->new;

# NOT IMPLEMENTED DUE TO AN ERROR ALWAYS CREATED BY ENTRY BOX!!!
# set up a warning handler that displays the warning in a Tk dialog box
#BEGIN {
#    $SIG{__WARN__} = sub {
#        if (defined $MW) {
#	    my $warnbox = $MW->DialogBox( -title   => "Warning",
#	    				  -buttons => [ "Acknowledge" ]);
#	    $warnbox->add("Label", -text => $_[0])->pack;
#	    $warnbox->Show;
#	} else {
#	    print STDOUT join("\n", @_), "n";
#	}
#   };
#}

$MW->title("Temperature Converter");
$MW->Label(-text => "Version 0.1 - Written by Alan Ford\n<alan\@whirlnet.demon.co.uk>")
    ->pack(-side => 'bottom');

my $ans;

my $exit = $MW->Button(-text => 'Exit',
			-command => sub 
			{
			 #print STDOUT "Goodbye.\n";
			 exit;
			});
$exit->pack(-side => 'bottom', -expand => '1', -fill => 'both');

my $convert = $MW->Button(-text => 'Convert',
			-command => sub 
			{
			 convert;
			});
$convert->pack(-side => 'bottom', -expand => '1', -fill => 'both');

my $answer_frame = $MW->Frame()->pack(-expand => '1', -fill => 'both', -side
=> 'bottom');

$answer_frame->Label(-text => "Converted value:")->pack(-side => 'left');
my $answer_value = $answer_frame->Entry(-width => '15', -relief => 'sunken')->pack(-side => 'right');

my $value_frame = $MW->Frame()->pack(-expand => '1', -fill => 'both', -side =>
'bottom');

$value_frame->Label(-text => "Enter value to convert:")->pack(-side => 'left');
my $convert_value = $value_frame->Entry(-width => '10', -relief => 'sunken')->pack(-side => 'right');
#$convert_value->bind('<Enter>' => convert);

my $from_frame = $MW->Frame(-relief => 'raised', -width => '100', -height => '200');
$from_frame->pack(-side => 'left', -expand => '1', -fill => 'both');

my $to_frame = $MW->Frame(-relief => 'raised', -width => '100', -height => '200');
$to_frame->pack(-side => 'right', -expand => '1', -fill => 'both');

$from_frame->Label(-text => "Convert From")->pack();
my $from_celsius = $from_frame->Radiobutton(-variable => \$from, -value   => 'c',
					    -text     => 'Celsius')
    ->pack(-side => 'top', -anchor => 'w');

my $from_fahrenheit = $from_frame->Radiobutton(-variable => \$from, -value=> 'f',
					       -text     => 'Fahrenheit')
    ->pack(-side => 'top', -anchor => 'w');

my $from_kelvin = $from_frame->Radiobutton(-variable => \$from, -value    => 'k',
					   -text     => 'Kelvin')
    ->pack(-side => 'top', -anchor => 'w');

my $from_rankine = $from_frame->Radiobutton(-variable => \$from, -value   => 'r',
					    -text     => 'Rankine')
    ->pack(-side => 'top', -anchor => 'w');

my $from_reaumur = $from_frame->Radiobutton(-variable => \$from, -value   => 'R',
					    -text     => 'Reaumur')
    ->pack(-side => 'top', -anchor => 'w');

$to_frame->Label(-text => "Convert To")->pack();
my $to_celsius = $to_frame->Radiobutton(-variable => \$to, -value    => 'c',
					-text     => 'Celsius')
    ->pack(-side => 'top', -anchor => 'w');

my $to_fahrenheit = $to_frame->Radiobutton(-variable => \$to, -value => 'f',
					   -text     => 'Fahrenheit')
    ->pack(-side => 'top', -anchor => 'w');

my $to_kelvin = $to_frame->Radiobutton(-variable => \$to, -value     => 'k',
				       -text     => 'Kelvin')
    ->pack(-side => 'top', -anchor => 'w');

my $to_rankine = $to_frame->Radiobutton(-variable => \$to, -value    => 'r',
				        -text     => 'Rankine')
    ->pack(-side => 'top', -anchor => 'w');

my $to_reaumur = $to_frame->Radiobutton(-variable => \$to, -value    => 'R',
				        -text     => 'Reaumur')
    ->pack(-side => 'top', -anchor => 'w');

#set defaults: Centigrade to Fahrenheit

$from_celsius->select;
$to_fahrenheit->select;

MainLoop;

#subs here
sub convert {
    my $question = $convert_value->get;
    # convert to kelvin
    my $kelvin_value = $mul{$from} * ( $question + $add{$from} );
    printf("From $question ($from) to $kelvin_value (k)\n");
    # convert to output - just do in reverse
    my $ans = $kelvin_value / $mul{$to} - $add{$to};
    printf("From $question ($from) to $ans ($to)\n");
    
    $answer_value->delete('0', 'end');
    $answer_value->insert('0', $ans);
    
    my $dialog = $MW->DialogBox( -title   => "Temperature Converter",
                                 -buttons => [ "OK" ],
				);
    $dialog->add("Label", -text => "$question $scales{$from} is $ans $scales{$to}")->pack;
    $dialog->Show;
}
 