#!/usr/bin/perl

# Reads in a text file containing sprites (stx) and outputs p65 assembly for them.

# SPDX-FileCopyrightText: Chris Pressey, the original author of this work, has dedicated it to the public domain.
# For more information, please refer to <https://unlicense.org/>
# SPDX-License-Identifier: Unlicense

open FILE, "<$ARGV[0]";

my $ctr = 0;
my @lines = ();
while ($line = <FILE>)
{
    chomp $line;
    if ($line =~ /^\s*$/)
    {
        dump_sprite(@lines);
        @lines = ();
    }
    elsif ($line =~ /^\s*(\w+)\s*\:\s*$/)
    {
        print ".alias $1 sprite_0_page+$ctr\n";
        $ctr++;
    }
    elsif ($line =~/^\s*(........................)\s*$/)
    {
        push @lines, $1;
    }
}

sub dump_sprite
{
    my @lines = @_;
    my $ctr = 0;
    for my $line (@lines)
    {
        printf ".byte \$%02x,\$%02x,\$%02x\n",
                decode(substr($line, 0, 8)),
                decode(substr($line, 8, 8)),
                decode(substr($line, 16, 8));
        $ctr++;
    }
    die "Incorrect sprite size" if $ctr != 21;
    print "\n.byte 0\n\n";   # padding
}

sub decode
{
    my $text = shift;
    my $acc = 0;
    
    for my $bit (0 .. 7)
    {
        if (substr($text, $bit, 1) eq 'X') { $acc += (1 << (7 - $bit)); }
    }
    
    return $acc;
}

close FILE;