#!/bin/perl -w

# Written by David Stewart (last updated 4/21/2005)
# Assembler for Simulated Toy Machine 

# Please save this file as "assem.pl"


%translate = (
	LOA =>	[0,2],
	STO => 	[1,2],
	CPR =>	[2,2],
	LOI =>	[3,2],
	STI =>	[4,2],
	ADD =>	[5,3],
	SUB =>	[6,3],
	MUL =>	[7,3],
	DIV =>	[8,4],
	INC =>	[9,1],
	DCR =>	[10,1],
	GTR =>	[11,3],
	JMP =>	[12,1],
	IFZ =>	[13,2],
	JMI =>	[14,1],
	TRP =>	[15,0],
);

$const_count = 0;
$lineNum = 0;
$buffer = "";

$file = shift;

open(IN, "<$file");

while($line = <IN>) {
	chomp $line;
	if($line =~ m/^(\w{3}) *(.*)$/) {
    $op = $1;
    $args = $2;
		$continue = 0;

		if(exists($translate{$op})) {
			if($op eq "JMP") { $string = sprintf "0%x", $translate{$op}[0]; }	# JMP has an unused arguement. . .
			else { $string = sprintf "%x", $translate{$op}[0]; }
			@tokens = split(/ /, $args);
			for($i=0;$i<$translate{$op}[1];$i++) {
				if($tokens[$i] =~ /^R(\d+)/i) {
					$string = sprintf("%x%s", $1, $string);
				}
				else {
					$string = "<$tokens[$i]>$string";
					$constants{$tokens[$i]}[0] = $const_count++;
				}
			}
			@arguments = splice @tokens, 0, $translate{$op}[1];
			$comment = join " ", @tokens;
			$comment =~ s/^\s*//;
			$args = join " ", @arguments;
			$lineString = sprintf "%4x", $lineNum;
			$string = pack "a2 a15 a6 a4 a20", "0x", $string, $lineString, $op, $args;
			$string =~ tr/[a-f]/[A-F]/;
			print "$op => $string\n";
			$buffer .= join "", $string, $comment, "\n";
			$lineNum++;
		}
		else{
			$continue = 1;
		}
	}
	else { $continue = 1; }
	if($continue && $line =~ /^\s*([A-Z]+)\s*$/) {	# line is a place label (ie a jump destination)
	$hexLine = sprintf("%x", $lineNum);
	  if($constants{$1}) {
			$constants{$1}[1] = $hexLine;
		}
		else {
			$constants{$1}[0] = $const_count++;
			$constants{$1}[1] = $hexLine;
		}
		$buffer = join "", $buffer, "         $1\n";
	}
	else { $buffer = join "", $buffer, $line, "\n" if $continue; }
}

close IN;

foreach $const (keys %constants) {
	if(!defined($constants{$const}[1])) {
		print "Constant found.\n";
		while(1) {
			print "What integer would you like to assign \"$const\"? ";
			$input = <STDIN>;
			if($input =~ /(\d+)/) {
				$hexLine = sprintf("%x", $lineNum++);
				$constants{$const}[1] = $hexLine;
				$line = pack "a19 a4 a*", $1, $hexLine, $const;
				$line =~ tr/[a-f]/[A-F]/;
				$buffer .= "$line\n";
				last;
			}
			else {
				print "Input not an integer!\n";
			}
		}
	}
	$pad = " " x (length($const) - length($constants{$const}[1]) + 2);
	$buffer =~ s/<$const>(\w*)/$constants{$const}[1]\1$pad/g;
}

print "$file\n";
$file =~ s/\..*$//;
print "$file\n";
open(OUT, ">$file.stm");
print OUT $buffer;
close OUT;