#!/usr/bin/perl

use RPM::Database;
use strict;

my $db = RPM::Database->new;
my %DB;

# load Requires: and Provides: from RPM database for the given packages
foreach my $pkg (@ARGV) {
	my $hdr = $$db{$pkg};
	unless ($hdr) {
		warn "package $pkg not found\n";
		next;
	}
	my $requires = $$hdr{REQUIRENAME};
	if ($requires) {
		$DB{$pkg}{req} = $requires;
	} else {
		warn "package $pkg requires nothing\n";
		$DB{$pkg}{req} = [];
	}
	my $provides = $$hdr{PROVIDES};
	if ($provides) {
		$DB{$pkg}{prov} = $provides;
	} else {
		warn "package $pkg provides nothing\n";
		$DB{$pkg}{prov} = [];
	}
}

use sort 'stable';
# try to optimize out packages with shortest names first
# alphabetical order is also in effect
my @packages = sort { length($a) <=> length($b) } sort keys %DB;

try: while (1) {
	foreach my $pkg (@packages) {
		my @rest = grep { $_ ne $pkg } @packages;
		if (my ($who, $what) = implies($pkg, @rest)) {
			warn "\t$who requires $pkg" . 
				($what eq $pkg ? "\n" : " through $what\n");
			warn "\t\t$pkg optimized out\n";
			@packages = @rest;
			next try;
		}
	}
	last;
}

@packages = sort @packages;
print "@packages\n";

sub implies {
	my ($pkg, @others) = @_;
	foreach my $prov (@{$DB{$pkg}{prov}}) {
		foreach my $who (@others) {
			foreach my $req (@{$DB{$who}{req}}) {
				return ($who, $req)
					if ($req eq $prov);
			}
		}
	}
	return;
}