#!/usr/bin/perl -w
use strict;
use warnings;

print "I will calculate whatever\n";

print "you specify according to\n";

print "Ohm's law. What shall I\n";

print "calculate? Type either\n";

print "voltage, current, or\n";

print "resistance.\n";

my $i = 0;

while($i == 0)
{
    my $calculation = <STDIN>;
    
    chomp $calculation;
    
    if($calculation =~ m/voltage/)
    {
        print "Type the current of the circuit.\n";
        
        print "Add mA at the end of your answer\n";
        
        print "if your answer is in milliAmps.\n";
        
        my $current = <STDIN>;
        
        chomp $current;
        
        print "Now type the resistance of the circuit.\n";
        
        my $resistance = <STDIN>;
        
        chomp $resistance;
        
        if($current =~ m/mA/)
        {
            $current =~ s/mA//;
            
            $current =~ s/^\s+//;
            
            $current =~ s/ //;
            
            $current /= 1000;
        }
        else
        {
            
        }
        
        my $voltage = $current * $resistance;
        
        print "Ohm's law is V = IR, so the voltage of\n";
        
        print "the circuit is $voltage volts.\n";
        
        $i++;
    }
    elsif($calculation =~ m/current/)
    {
        print "Type the resistance of the circuit.\n";
        
        my $resistance = <STDIN>;
        
        chomp $resistance;
        
        print "Now type the voltage of the circuit.\n";
        
        my $voltage = <STDIN>;
        
        chomp $voltage;
        
        my $current = $voltage / $resistance;
        
        chomp $current;
        
        my $otherCurrent = $current / 1000;
        
        chomp $otherCurrent;
        
        print "Ohm's law is V = IR, so the current of\n";
        
        print "the circuit is $current amps,\n";
        
        print "or $otherCurrent milliAmps.\n";
        
        $i++;
    }
    elsif($calculation =~ m/resistance/)
    {
        print "Type the current of the circuit.\n";
        
        print "Add mA at the end of your answer\n";
        
        print "if your answer is in milliAmps.\n";
        
        my $current = <STDIN>;
        
        chomp $current;
        
        print "Now type the voltage of the circuit.\n";
        
        my $voltage = <STDIN>;
        
        chomp $voltage;
        
        if($current =~ m/mA/)
        {
            $current =~ s/mA//;
            
            $current =~ s/^\s+//;
            
            $current =~ s/ //;
            
            $current /= 1000;
        }
        else
        {
            
        }
        
        my $resistance = $voltage / $current;
            
        chomp $resistance;
        
        print "Ohm's law is V = IR, so the resistance of\n";
       
        print "the circuit is $resistance ohms.\n";
        
        $i++;
    }
    else
    {
        print "That is not a valid answer.\n";
            
        print "Retype your answer.\n";
    }
}