#!/usr/bin/perl -w

use strict;

sub print_usage {
	print "Usage: rbd package [...]\nPrint reverse build-depends list of given package(s)\n";
	exit;
}

print_usage unless(@ARGV);

foreach (0..$#ARGV) {
	print_usage if($ARGV[$_]=~/^-/);
}

my @results;
my $package;

foreach (</var/lib/apt/lists/*Sources>) {
	open FILE, "<$_" or die "Cannot open cache $_: $!\n";

	while (<FILE>) {
		if(/^Package:\s(.+)$/) {
			$package=$1;
		}
		if(/^Build-Depend(?:s|s-Indep):\s(.+)$/) {
			my $list=$1;
			foreach (0..$#ARGV) {
				push(@{$results[$_]}, $package) if($list=~/\b\Q$ARGV[$_]\E\b/);
			}
		}
	}
	close FILE or die $!;
}

foreach (0..$#ARGV) {
	print "$ARGV[$_]\nReverse Build-Depends:\n";
	if($results[$_]) {
		my @sorted=sort(@{$results[$_]});
		foreach my $package (@sorted) {
			print "  $package\n";
		}
	}
}