#!/usr/bin/perl -w

# gentablature.pl
#
# «A script for those who like writing guitar tablatures»
#
# Copyright © 2003, crashnburn
# Under the terms of BSD License#
#
# The infile format is:
# 
# <E-fret>, <A-fret>, <D-fret>, <G-fret>, <B-fret>, <e-fret>
# 
# The fret can be an x or X if the it is not pressed.
# Each new line is a space (useful for chords or timing)
# 
# TODO:    Add "tab break" support with an optional repeater (like 2x
#       or 4x) and "automatic new line" support.
#
# PS:    This is one of my first scripts, and I haven't learned a lot
#        of PERL yet, so if there are any errors, bad implementations,
#        comments on the    code, whatever... please mail me to
#        crashnburn@ip.pt

use strict;
#use warnings;
#use diagnostics;

use constant SPACE        => "space";
use constant NOTPLAYED    => "xX";

my @music;
my @tablature = split(/\s/, "|- " x 6);

sub sintaxe {
    print STDERR "usage: ", $0, " <infile> [<outfile>]\n";
    exit 1;
}

# Returns the length (1 or 2) of the biggest number of the played
# notes of the fret, for alignment purposes
sub biggest {
    foreach (@_) {
        if (length > 1) {
            return 2;
        }
    }

    return 1;
}

# Converts each line of the @music array (the values from the file) to
# Converts each line of the @music array (the values from the file) to
# a visible tablature
sub convertToTablature {
    while ($_ = shift @music) {
        if ($_ eq SPACE) {
            foreach (@tablature) {
                $_ .= "-";
            }
        } else {
            my @frets = split / /;
            my $B = &biggest(@frets);
            
            foreach (@frets) {
                if (eval "/[" . NOTPLAYED . "]/") {
                    $_ = "-";
                }
                if (length > 2) {
                    die "Syntax error: Each value can only have one ",
                        "or two characters\n";
                } elsif ($B > length) {
                    $_ = "-" . $_;
                }
            }
                
            for (my $i = 0; $i < 6; $i++) {
                $tablature[$i] .= $frets[$i] . "-";
            }
        }
    }
    
    foreach (@tablature) {
        $_ .= "|";
    }
}

if (@ARGV < 1 || $ARGV[0] =~ /-h|--help/) {
    &sintaxe;
}

# Reads values and interprets some meanings (only new line yet)
open INFILE, $ARGV[0] or die "Error reading from $ARGV[0]: $!\n";

while (<INFILE>) {
    chomp;
    if ($_) {
        my @frets = split /[,+\s+]+/;
        die "Syntax error: Each line of the infile must have exactly",
            "  6 elements\n" unless @frets == 6;
        push @music, "@frets";
    } else {
        push @music, "space";
    }
}

close INFILE;

&convertToTablature(@music);

# Opens outfile if any
if (@ARGV >= 2) {
    open OUTFILE, ">$ARGV[1]" or die "Error writing to $ARGV[1]:",
        " $!\n";
    select(OUTFILE);
}

foreach (reverse(@tablature)) {
    print $_ . "\n";
}

close;