#!/usr/bin/env perl
# 
# Copyright (C) 2006 Felix Fietkau <nbd@nbd.name>
#
# This is free software, licensed under the GNU General Public License v2.
# See /LICENSE for more information.
#

use warnings;
use strict;

my @arg;
my $PREFIX = "CONFIG_";

sub set_config($$$$) {
	my $config = shift;
	my $idx = shift;
	my $newval = shift;
	my $mod_plus = shift;

	if (!defined($config->{$idx}) or !$mod_plus or
	    $config->{$idx} eq '#undef' or $newval eq 'y') {
		$config->{$idx} = $newval;
	}
}

sub load_config($$) {
	my $file = shift;
	my $mod_plus = shift;
	my %config;

	open FILE, "$file" or die "can't open file '$file'";
	while (<FILE>) {
		chomp;
		/^$PREFIX(.+?)=(.+)/ and do {
			set_config(\%config, $1, $2, $mod_plus);
			next;
		};
		/^# $PREFIX(.+?) is not set/ and do {
			set_config(\%config, $1, "#undef", $mod_plus);
			next;
		};
		/^#/ and next;
		/^(.+)$/ and warn "WARNING: can't parse line: $1\n";
	}
	return \%config;
}


sub config_and($$) {
	my $cfg1 = shift;
	my $cfg2 = shift;
	my %config;

	foreach my $config (keys %$cfg1) {
		my $val1 = $cfg1->{$config};
		my $val2 = $cfg2->{$config};
		$val2 and ($val1 eq $val2) and do {
			$config{$config} = $val1;
		};
	}
	return \%config;
}


sub config_add($$$) {
	my $cfg1 = shift;
	my $cfg2 = shift;
	my $mod_plus = shift;
	my %config;
	
	for ($cfg1, $cfg2) {
		my %cfg = %$_;
		
		foreach my $config (keys %cfg) {
			if ($mod_plus and $config{$config}) {
				next if $config{$config} eq "y";
				next if $cfg{$config} eq '#undef';
			}
			$config{$config} = $cfg{$config};
		}
	}
	return \%config;
}

sub config_diff($$$) {
	my $cfg1 = shift;
	my $cfg2 = shift;
	my $new_only = shift;
	my %config;
	
	foreach my $config (keys %$cfg2) {
		if (!defined($cfg1->{$config}) or $cfg1->{$config} ne $cfg2->{$config}) {
			next if $new_only and !defined($cfg1->{$config}) and $cfg2->{$config} eq '#undef';
			$config{$config} = $cfg2->{$config};
		}
	}
	return \%config
}

sub config_sub($$) {
	my $cfg1 = shift;
	my $cfg2 = shift;
	my %config = %{$cfg1};
	
	foreach my $config (keys %$cfg2) {
		delete $config{$config};
	}
	return \%config;
}

sub print_cfgline($$) {
	my $name = shift;
	my $val = shift;
	if ($val eq '#undef' or $val eq 'n') {
		print "# $PREFIX$name is not set\n";
	} else {
		print "$PREFIX$name=$val\n";
	}
}


sub dump_config($) {
	my $cfg = shift;
	die "argument error in dump_config" unless ($cfg);
	my %config = %$cfg;
	foreach my $config (sort keys %config) {
		print_cfgline($config, $config{$config});
	}
}

sub parse_expr {
	my $pos = shift;
	my $mod_plus = shift;
	my $arg = $arg[$$pos++];

	die "Parse error" if (!$arg);

	if ($arg eq '&') {
		my $arg1 = parse_expr($pos);
		my $arg2 = parse_expr($pos);
		return config_and($arg1, $arg2);
	} elsif ($arg =~ /^\+/) {
		my $arg1 = parse_expr($pos);
		my $arg2 = parse_expr($pos);
		return config_add($arg1, $arg2, 0);
	} elsif ($arg =~ /^m\+/) {
		my $arg1 = parse_expr($pos);
		my $arg2 = parse_expr($pos, 1);
		return config_add($arg1, $arg2, 1);
	} elsif ($arg eq '>') {
		my $arg1 = parse_expr($pos);
		my $arg2 = parse_expr($pos);
		return config_diff($arg1, $arg2, 0);
	} elsif ($arg eq '>+') {
		my $arg1 = parse_expr($pos);
		my $arg2 = parse_expr($pos);
		return config_diff($arg1, $arg2, 1);
	} elsif ($arg eq '-') {
		my $arg1 = parse_expr($pos);
		my $arg2 = parse_expr($pos);
		return config_sub($arg1, $arg2);
	} else {
		return load_config($arg, $mod_plus);
	}
}

while (@ARGV > 0 and $ARGV[0] =~ /^-\w+$/) {
	my $cmd = shift @ARGV;
	if ($cmd =~ /^-n$/) {
		$PREFIX = "";
	} elsif ($cmd =~ /^-p$/) {
		$PREFIX = shift @ARGV;
	} else {
		die "Invalid option: $cmd\n";
	}
}
@arg = @ARGV;

my $pos = 0;
dump_config(parse_expr(\$pos));
die "Parse error" if ($arg[$pos]);