#!/bin/perl
use strict;
use warnings;

my %ERROR_MESSAGES;
$ERROR_MESSAGES{"invalid_stack_type"} = "invalid stack type. Only 7 and 17 are allowed, atm\n";

# cli parameters
my $gosub_offset;
my $stack_type;
my $target_offset; # offset you want to start the target mission at

my $useful_code_size; # for name_thread, etc
my $filler_code_size; # nops(0000) and alignment(FF05 FF)

my $filler_code;
my $thread_name_code;
my $gosub_code;
my $wait_code;


print STDERR "THREAD NAME STUFF IS FOR SA, ATM (rest is compatible with vc).\n";

($stack_type, $gosub_offset) = stack_stuff();
$target_offset = shift @ARGV;

$useful_code_size = 0;
$wait_code = "wait 0";
$useful_code_size += 4;

$gosub_code = "gosub \@loop\n:loop";
$useful_code_size += 7;

$thread_name_code = "03A4: 'perfect'";
$useful_code_size += 11;


$filler_code_size = $target_offset - $useful_code_size;
if( $filler_code_size % 2 == 1 ) {
    # needs alignment
    $filler_code = "9905 FF " . "00" x ($filler_code_size - 3);
}else{
    $filler_code = "00" x $filler_code_size;
}


#################
#Finally ;), print the code
#################
if( $stack_type eq "name_thread" ) {
    print "$thread_name_code\n";
    print "$gosub_code\n";
}elsif( $stack_type eq "immediate" ) {
    print "$gosub_code\n";
    print "$thread_name_code\n";
}else{
    die $ERROR_MESSAGES{"invalid_stack_type"};
}
print "
hex
$filler_code
end

$wait_code
jump \@loop
";





sub stack_stuff {
    if(@ARGV == 2) {
        $gosub_offset = shift @ARGV;
        if($gosub_offset == 7) {
            $stack_type = "immediate";
        }elsif($gosub_offset == 17) {
            $stack_type = "name_thread";
        }else{
            die $ERROR_MESSAGES{"invalid_stack_type"};
        }
    }else{
        $stack_type = "name_thread";
        $gosub_offset = 17;
    }
    return ($stack_type, $gosub_offset);
}