#!/usr/bin/perl
#!/home/jmc/bin/perl
#
# abcpar [+|-]interval [file]..
#
# Read an abc file (or passage from stdin), and write output that  has
# the  same  melody  plus  a  harmony  line  in  parallel at the given
# interval.  The default interval is +2, i.e., a third higher.
#
# Note that the interval is one less than the musical interval.  Maybe
# this should be changed ...

$| = 1;
$| = 1;
($me = $0) =~ s'.*/'';
$V = $ENV{"V_$me"} || $ENV{"T_$me"} || $ENV{"D_$me"} || 1;

@S = (
	"C,,","D,,","E,,","F,,","G,,","A,,","B,,",
	"C,", "D,", "E,", "F,", "G,", "A,", "B,", 
	"C",  "D",  "E",  "F",  "G",  "A",  "B",  
	"c",  "d",  "e",  "f",  "g",  "a",  "b",  
	"c'", "d'", "e'", "f'", "g'", "a'", "b'", 
	"c''","d''","e''","f''","g''","a''","b''",
);
for ($i=0; $i<@S; $i++) {
	$I{$S[$i]} = $i;
}

if  (($dir, $int) = ($ARGV[0] =~ /^([-+])(\d+)/)) {
	if ($dir eq '+') {
		$diff = $int - 1;	# Convert to upward difference.
	} else {
		$diff = 1 - $int;	# Downward difference.
	}
	shift;
} else {
	$diff = 2;	# Up  third.
}

$A = '[\^=_]*';	# Accidental.
$N = '[A-Ga-g][\',]*';	# Note.
$L = '[/\d.\<>]*';				# Length.

line:
for $line (<>) {
	while ($line) {
		if ($line =~ s/^(\s+)//) {print $1}
		if ($line =~ /^([A-Z]:)(\s*)/) {
			print $line;
			next line;
		} elsif ($line =~ s'^("[^"]*"\s*)'') {print $1; next;
		} elsif ($line =~ s'^(\(\d*\s*)'')   {print $1; next;
		} elsif ($line =~ s'^(\)\s*)'')      {print $1; next;
		} elsif ($line =~ s'^(\[\|\s*)'')    {print $1; next;
		} elsif ($line =~ s'^(\|\]*\s*)'')   {print $1; next;
		} elsif ($line =~ s'^(\[.*\]\s*)'')  {print $1; next;
		} elsif ($line =~ s/^($A)($N)($L)(\s*)//) {
			 $a = $1; $n = $2;  $l = $3; $s = $4;
			 $i = $I{$n};
			 $j = $i + $diff;
			 if ($h = $S[$j]) {
#				 if ($l) {
				 	print "[$a$n$l$a$h$l]$s";
#				 } else {
#				 	print "[$a$n$a$h]$l$s";
#				 }
				 next;
			 }
		}
		if ($line =~ s'^(.)'')          {print $1; next;
		}
		print "Left: \"$line\"\n" if $V>1;
	}
}