#!/usr/bin/env perl

use warnings;

#  This script is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License version 2 as
#  published by the Free Software Foundation.
#
#  See the COPYING and AUTHORS files for more details.

#
# Guards:
#
# +xxx   include if xxx is defined
# -xxx   exclude if xxx is defined
# +!xxx  include if xxx is not defined
# -!xxx  exclude if xxx is not defined
#

use FileHandle;
use Getopt::Long;
use strict;

# Prototypes
sub files_in($$);
sub parse($$);
sub help();

sub slashme($) {
    my ($dir) = @_;
    $dir =~ s#([^/])$#$&/#; # append a slash if necessary
    if ($dir eq './') {
	return '';
    } else {
	return $dir;
    }
}

# Generate a list of files in a directory
#
sub files_in($$) {
    my ($dir, $path) = @_;
    my $dh = new FileHandle;
    my (@files, $file);

    # @<file> syntax
    if ($path =~ s/^@//) {
	my $fh;
	open($fh, '<', $path) or die "$path: $!\n";
	@files = <$fh>;
	close($fh);
	chomp(@files);
	s:^$dir:: for @files;
	return @files;
    }

    $path = slashme($path);
    opendir $dh, length("$dir$path") ? "$dir$path" : '.'
	or die "$dir$path: $!\n";
    while ($file = readdir($dh)) {
	next if $file =~ /^(\.|\.\.|\.#.*|CVS|.*~)$/;
	if (-d "$dir$path$file") {
		@files = (@files, files_in($dir, "$path$file/"));
	} else {
		#print "[$path$file]\n";
		push @files, "$path$file";
	}
    }
    closedir $dh;
    return @files;
}

# Parse a configuration file
# Callback called with ($patch, @guards) arguments
#
sub parse($$) {
    my ($fh, $callback) = @_;

    my $line = "";

    while (<$fh>) {
	chomp;
	s/(^|\s+)#.*//;
	if (s/\\$/ /) {
		$line .= $_;
		next;
	}
	$line .= $_;
	my @guards = ();
	foreach my $token (split /[\s\t\n]+/, $line) {
	    next if $token eq "";
	    if ($token =~ /^[-+]/) {
		push @guards, $token;
	    } else {
		#print "[" . join(",", @guards) . "] $token\n";
		&$callback($token, @guards);
	    }
	}
	$line = "";
    }
}

# Command line options
#
my ($dir, $config, $default, $check, $list, $invert_match, $with_guards) =
   (  '',     '-',        1,      0,     0,             0,            0);
my @path;

# Help text
#
sub help() {
    print "$0 - select from a list of files guarded by conditions\n";
    print "SYNOPSIS: $0 [--prefix=dir] [--path=dir1:dir2:...]\n" .
	"	[--default=0|1] [--check|--list] [--invert-match]\n" .
	"	[--with-guards] [--config=file] symbol ...\n\n" .
	"	Defaults: --default=$default\n" .
	"	Use --path=\@<file> to read the list of entries from <file>\n";
    exit 0;
}

# Parse command line options
#
Getopt::Long::Configure ("bundling");
eval {
    unless (GetOptions (
	'd|prefix=s' => \$dir,
	'c|config=s' => \$config,
	'C|check' => \$check,
	'l|list' => \$list,
	'w|with-guards' => \$with_guards,
	'p|path=s' => \@path,
	'D|default=i' => \$default,
	'v|invert-match' => \$invert_match,
	'h|help' => sub { help(); exit 0; })) {
	help();
	exit 1;
    }
};
if ($@) {
    print "$@";
    help();
    exit 1;
}

@path = ('.')
    unless (@path);
@path = split(/:/, join(':', @path));

my $fh = ($config eq '-') ? \*STDIN : new FileHandle($config)
    or die "$config: $!\n";

$dir = slashme($dir);

if ($check) {
    # Check for duplicate files, or for files that are not referenced by
    # the specification.

    my $problems = 0;
    my @files;

    foreach (@path) {
	@files = (@files, files_in($dir, $_));
    }
    my %files = map { $_ => 0 } @files;

    parse($fh, sub {
	my ($patch, @guards) = @_;
	if (exists $files{$patch}) {
	    $files{$patch}++;
	} else {
	    if ($config eq '-') {
		print "Not found: $dir$patch\n";
	    } else {
		print "In $config but not found: $dir$patch\n";
	    }
	    $problems++;
	}});

    $fh->close();

    my ($file, $ref);
    while (($file, $ref) = each %files) {
	next if $ref == 1;

	if ($ref == 0) {
	    if ($config eq '-') {
		print "Unused: $file\n";
	    } else {
		print "Not in $config: $file\n";
	    }
	    $problems++;
	}
	if ($ref > 1) {
	    print "Warning: multiple uses";
	    print " in $config" if $config ne '-';
	    print ": $file\n";
	    # This is not an error if the entries are mutually exclusive...
	}
    }
    exit $problems ? 1 : 0;

} elsif ($list) {
    parse($fh, sub {
	my ($patch, @guards) = @_;
	print join(' ', @guards), ' '
		if (@guards && $with_guards);
	print "$dir$patch\n";
	});
} else {
    # Generate a list of patches to apply.

    my %symbols = map { $_ => 1 } @ARGV;

    parse($fh, sub {
	my ($patch, @guards) = @_;

	my $selected;
	if (@guards) {
	    # If the first guard is -xxx, the patch is included by default;
	    # if it is +xxx, the patch is excluded by default.
	    $selected = ($guards[0] =~ /^-/);

	    foreach (@guards) {
		/^([-+])(!?)(.*)?/
		    or die "Bad guard '$_'\n";

		# Check if the guard matches
		if (($2 eq '!' && !exists $symbols{$3}) ||
		    ($2 eq ''  && ( $3 eq '' || exists $symbols{$3}))) {
		    # Include or exclude
		    $selected = ($1 eq '+');
		}
	    }
	} else {
	    # If there are no guards, use the specified default result.
	    $selected = $default;
	}

	print "$dir$patch\n"
	    if $selected ^ $invert_match;
	});

    $fh->close();

    exit 0;
}

__END__

=head1 NAME

guards - select from a list of files guarded by conditions

=head1 SYNOPSIS

F<guards> [--prefix=F<dir>] [--path=F<dir1:dir2:...>] [--default=<0|1>]
[--check|--list] [--invert-match] [--with-guards] [--config=<file>]
I<symbol> ...

=head1 DESCRIPTION

The script reads a configuration file that may contain so-called guards, file
names, and comments, and writes those file names that satisfy all guards to
standard output. The script takes a list of symbols as its arguments. Each line
in the configuration file is processed separately. Lines may start with a
number of guards. The following guards are defined:

=over

+I<xxx> Include the file(s) on this line if the symbol I<xxx> is defined.

-I<xxx> Exclude the file(s) on this line if the symbol I<xxx> is defined.

+!I<xxx> Include the file(s) on this line if the symbol I<xxx> is not defined.

-!I<xxx> Exclude the file(s) on this line if the symbol I<xxx> is not defined.

- Exclude this file. Used to avoid spurious I<--check> messages.

=back

The guards are processed left to right. The last guard that matches determines
if the file is included. If no guard is specified, the I<--default>
setting determines if the file is included.

If no configuration file is specified, the script reads from standard input.

The I<--check> option is used to compare the specification file against the
file system. If files are referenced in the specification that do not exist, or
if files are not enlisted in the specification file warnings are printed. The
I<--path> option can be used to specify which directory or directories to scan.
Multiple directories are separated by a colon (C<:>) character. The
I<--prefix> option specifies the location of the files. Alternatively, the
I<--path=@E<lt>fileE<gt>> syntax can be used to specify a file from which the
file names will be read.

Use I<--list> to list all files independent of any rules. Use I<--invert-match>
to list only the excluded patches. Use I<--with-guards> to also include all
inclusion and exclusion rules.

=head1 AUTHOR

Andreas Gruenbacher <agruen@suse.de>, SUSE Labs