#!/usr/bin/perl -w
#
# Clean a text file -- or directory of text files -- of stealth whitespace.
# WARNING: this can be a highly destructive operation. Use with caution.
#

use bytes;
use File::Basename;

# Default options
$max_width = 79;

# Clean up space-tab sequences, either by removing spaces or
# replacing them with tabs.
sub clean_space_tabs($)
{
 no bytes;			# Tab alignment depends on characters

 my($li) = @_;
 my($lo) = '';
 my $pos = 0;
 my $nsp = 0;
 my($i, $c);

 for ($i = 0; $i < length($li); $i++) {
	$c = substr($li, $i, 1);
	if ($c eq "\t") {
	 my $npos = ($pos+$nsp+8) & ~7;
	 my $ntab = ($npos >> 3) - ($pos >> 3);
	 $lo .= "\t" x $ntab;
	 $pos = $npos;
	 $nsp = 0;
	} elsif ($c eq "\n" || $c eq "\r") {
	 $lo .= "" x $nsp;
	 $pos += $nsp;
	 $nsp = 0;
	 $lo .= $c;
	 $pos = 0;
	} elsif ($c eq "") {
	 $nsp++;
	} else {
	 $lo .= "" x $nsp;
	 $pos += $nsp;
	 $nsp = 0;
	 $lo .= $c;
	 $pos++;
	}
 }
 $lo .= "" x $nsp;
 return $lo;
}

# Compute the visual width of a string
sub strwidth($) {
 no bytes;			# Tab alignment depends on characters

 my($li) = @_;
 my($c, $i);
 my $pos = 0;
 my $mlen = 0;

 for ($i = 0; $i < length($li); $i++) {
	$c = substr($li,$i,1);
	if ($c eq "\t") {
	 $pos = ($pos+8) & ~7;
	} elsif ($c eq "\n") {
	 $mlen = $pos if ($pos > $mlen);
	 $pos = 0;
	} else {
	 $pos++;
	}
 }

 $mlen = $pos if ($pos > $mlen);
 return $mlen;
}

$name = basename($0);

@files = ();

while (defined($a = shift(@ARGV))) {
 if ($a =~ /^-/) {
	if ($a eq '-width' || $a eq '-w') {
	 $max_width = shift(@ARGV)+0;
	} else {
	 print STDERR "Usage: $name [-width #] files...\n";
	 exit 1;
	}
 } else {
	push(@files, $a);
 }
}

foreach $f ( @files ) {
 print STDERR "$name: $f\n";

 if (! -f $f) {
	print STDERR "$f: not a file\n";
	next;
 }

 if (!open(FILE, '+<', $f)) {
	print STDERR "$name: Cannot open file: $f: $!\n";
	next;
 }

 binmode FILE;

 # First, verify that it is not a binary file; consider any file
 # with a zero byte to be a binary file. Is there any better, or
 # additional, heuristic that should be applied?
 $is_binary = 0;

 while (read(FILE, $data, 65536) > 0) {
	if ($data =~ /0円/) {
	 $is_binary = 1;
	 last;
	}
 }

 if ($is_binary) {
	print STDERR "$name: $f: binary file\n";
	next;
 }

 seek(FILE, 0, 0);

 $in_bytes = 0;
 $out_bytes = 0;
 $blank_bytes = 0;

 @blanks = ();
 @lines = ();
 $lineno = 0;

 while ( defined($line = <FILE>) ) {
	$lineno++;
	$in_bytes += length($line);
	$line =~ s/[ \t\r]*$//;		# Remove trailing spaces
	$line = clean_space_tabs($line);

	if ( $line eq "\n" ) {
	 push(@blanks, $line);
	 $blank_bytes += length($line);
	} else {
	 push(@lines, @blanks);
	 $out_bytes += $blank_bytes;
	 push(@lines, $line);
	 $out_bytes += length($line);
	 @blanks = ();
	 $blank_bytes = 0;
	}

	$l_width = strwidth($line);
	if ($max_width && $l_width > $max_width) {
	 print STDERR
		"$f:$lineno: line exceeds $max_width characters ($l_width)\n";
	}
 }

 # Any blanks at the end of the file are discarded

 if ($in_bytes != $out_bytes) {
	# Only write to the file if changed
	seek(FILE, 0, 0);
	print FILE @lines;

	if ( !defined($where = tell(FILE)) ||
	 !truncate(FILE, $where) ) {
	 die "$name: Failed to truncate modified file: $f: $!\n";
	}
 }

 close(FILE);
}