#!/usr/bin/perl

#########################################
# "Damage"
# --------
#
# Damage the number by typing
# expressions. The result of the
# expressions will be subtracted from
# the current number. When the current
# number gets to 0 you win. If it goes
# below 0 you lose.
#
# Expression rules:
#
# 1. The two numbers in an expression
#    cannot be the same numbers.
# 2. The only valid operators are
#    + - * /.
# 3. There must be 3 parts in the
#    expression all seperated by a
#    single space. These are a
#    number, an operator, then the
#    other number.
# 4. You can't use the current
#    number in the expression.
# 5. The numbers in the expression
#    can only use digits that are
#    in the start number.
# 6. You can't divide by 0.
# 7. When dividing, the result must
#    be an integer.
# 8. You can't multiply by 1.
#
# By Jeremy Ruten ("Jeremysr")
# E-mail: jeremy.ruten@gmail.com
# Website: http://bio-gaming.com/jeremy
########################################

do {
	print "\nHow many digits? [1-5] ";
	$digits = <STDIN>;
} until ($digits >= 1 && $digits <= 5);

if ($digits == 1) {
	$range = 8; $minimum = 1;
} elsif ($digits == 2) {
	$range = 89; $minimum = 10;
} elsif ($digits == 3) {
	$range = 899; $minimum = 100;
} elsif ($digits == 4) {
	$range = 8999; $minimum = 1000;
} elsif ($digits == 5) {
	$range = 89999; $minimum = 10000;
} else {
	die("That's not an integer!");
}

$the_number = int(rand($range)) + $minimum;
$current_number = $the_number;

$turns = 0;

while ($current_number > 0) {
	print "\nThe current number is: $current_number\n[Start number is $the_number]\n\nYour expression:";
	$expression = <STDIN>;

	@expression = split(/ /, $expression);

	# Validate it
	$valid = "";
	if ($expression[0] == $expression[2]) { $valid = "Can't use same number on both sides of expression"; }
	if ($expression[1] ne "+" && $expression[1] ne "-" && $expression[1] ne "*" && $expression[1] ne "/") { $valid = "Invalid operator"; }
	if ($#expression != 2) { $valid = "Wrong number of parts to expression (must be 3 parts)"; }
	if ($expression[0] == $current_number || $expression[2] == $current_number) { $valid = "Expression can't use current number"; }
	if ($expression[2] == 0 && $expression[1] eq "/") { $valid = "Division by 0"; }
	if ($expression[0] !~ /[0-9]/ || $expression[2] !~ /[0-9]/) { $valid = "Numbers must be integers"; }
	if ($expression[1] eq "/" && $valid eq "") { if ($expression[0] / $expression[2] !~ /[0-9]/) { $valid = "Expression results in a non-integer"; } }

	# Make sure it has the right digits
	if ($valid eq "") {
		@valid_digits = split("", $the_number);
		@test_digits = split("", $expression[0]);
		@test_digits2 = split("", $expression[2]);
		push(@test_digits, @test_digits2);
		pop(@test_digits);

		foreach $current_digit (@test_digits) {
			$digit_valid = 0;
			foreach $current_valid_digit (@valid_digits) {
				if ($current_digit eq $current_valid_digit) {
					$digit_valid = 1;
				}
			}
			if ($digit_valid == 0) {
				$valid = "Numbers use digits not in start number";
			}
		}
	}

	if ($valid eq "") {
		if ($expression[1] eq "+") { $current_number -= $expression[0] + $expression[2]; }
		elsif ($expression[1] eq "-") { $current_number -= $expression[0] - $expression[2]; }
		elsif ($expression[1] eq "*") { $current_number -= $expression[0] * $expression[2]; }
		elsif ($epxression[1] eq "/") { $current_number -= $expression[0] / $expression[2]; }

		$turns++;
	} else {
		print "\nINVALID EXPRESSION [$valid]\n\n";
	}
}

if ($current_number == 0) {
	print "CONGRATULATIONS!\n\nYou have won in $turns turns!\n\n";
} else {
	print "You have lost after $turns turns! (Ended up with the number $current_number)\n\n";
}