package urpm;

use strict;
use vars qw($VERSION @ISA);

$VERSION = '1.5';

=head1 NAME

urpm - Mandrake perl tools to handle urpmi database

=head1 SYNOPSYS

    require urpm;

    my $urpm = new urpm;

    $urpm->read_depslist();
    $urpm->read_provides();
    $urpm->read_compss();
    $urpm->read_config();

=head1 DESCRIPTION

C<urpm> is used by urpmi executable to manipulate packages and mediums
on a Linux-Mandrake distribution.

=head1 SEE ALSO

rpmtools package is used to manipulate at a lower level hdlist and rpm
files.

=head1 COPYRIGHT

Copyright (C) 2000 MandrakeSoft <fpons@mandrakesoft.com>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

=cut

use rpmtools;

#- create a new urpm object.
sub new {
    my ($class) = @_;
    bless {
	   config     => "/etc/urpmi/urpmi.cfg",
	   skiplist   => "/etc/urpmi/skip.list",
	   depslist   => "/var/lib/urpmi/depslist.ordered",
	   provides   => "/var/lib/urpmi/provides",
	   compss     => "/var/lib/urpmi/compss",
	   statedir   => "/var/lib/urpmi",
	   cachedir   => "/var/cache/urpmi",
	   media      => undef,
	   params     => new rpmtools,

	   error      => sub { printf STDERR "%s\n", $_[0] },
	   log        => sub { printf STDERR "%s\n", $_[0] },
	  }, $class;
}

#- quoting/unquoting a string that may be containing space chars.
sub quotespace { local $_ = $_[0]; s/(\s)/\\$1/g; $_ }
sub unquotespace { local $_ = $_[0]; s/\\(\s)/$1/g; $_ }

#- read /etc/urpmi/urpmi.cfg as config file, keep compability with older
#- configuration file by examining if one entry is of the form
#-   <name> <url> {
#-      ...
#-   }
#- else only this form is used
#-   <name> <url>
#-   <name> <ftp_url> with <relative_path_hdlist>
sub read_config {
    my ($urpm, %options) = @_;

    #- keep in mind if it has been called before.
    $urpm->{media} and return; $urpm->{media} ||= [];

    #- check urpmi.cfg content, if the file is old keep track
    #- of old format used.
    local (*F, $_);
    open F, $urpm->{config}; #- no filename can be allowed on some case
    while (<F>) {
	chomp; s/#.*$//; s/^\s*//; s/\s*$//;
	/^(.*?[^\\])\s+(?:(.*?[^\\])\s+)?{$/ and do { #- urpmi.cfg format extention
	    my $medium = { name => unquotespace($1), clear_url => unquotespace($2) };
	    while (<F>) {
		chomp; s/#.*$//; s/^\s*//; s/\s*$//;
		/^hdlist\s*:\s*(.*)$/ and $medium->{hdlist} = $1, next;
		/^with_hdlist\s*:\s*(.*)$/ and $medium->{with_hdlist} = $1, next;
		/^list\s*:\s*(.*)$/ and $medium->{list} = $1, next;
		/^removable\s*:\s*(.*)$/ and $medium->{removable} = $1, next;
		/^ignore\s*$/ and $medium->{ignore} = 1, next;
		/^modified\s*$/ and $medium->{modified} = 1, next;
		$_ eq '}' and last;
		$_ and $urpm->{error}("syntax error at line $. in $urpm->{config}");
	    }
	    $urpm->probe_medium($medium, %options) and push @{$urpm->{media}}, $medium;
	    next; };
	/^(.*?[^\\])\s+(.*?[^\\])\s+with\s+(.*)$/ and do { #- urpmi.cfg old format for ftp
	    my $medium = { name => unquotespace($1), clear_url => unquotespace($2), with_hdlist => unquotespace($3) };
	    $urpm->probe_medium($medium, %options) and push @{$urpm->{media}}, $medium;
	    next; };
	/^(.*?[^\\])\s+(?:(.*?[^\\])\s*)?$/ and do { #- urpmi.cfg old format (assume hdlist.<name>.cz2?)
	    my $medium = { name => unquotespace($1), clear_url => unquotespace($2) };
	    $urpm->probe_medium($medium, %options) and push @{$urpm->{media}}, $medium;
	    next; };
	$_ and $urpm->{error}("syntax error at line $. in [$urpm->{config}]");
    }
    close F;

    #- keep in mind when an hdlist/list file is used, really usefull for
    #- the next probe.
    my (%hdlists, %lists);
    foreach (@{$urpm->{media}}) {
	exists $hdlists{$_->{hdlist}} and
	  $_->{ignore} = 1, $urpm->{error}("medium \"$_->{name}\" try to use an already used hdlist, medium ignored");
	$hdlists{$_->{hdlist}} = undef;
	exists $lists{$_->{list}} and
	  $_->{ignore} = 1, $urpm->{error}("medium \"$_->{name}\" try to use an already used list, medium ignored");
	$lists{$_->{list}} = undef;
    }

    #- urpmi.cfg if old is not enough to known the various media, track
    #- directly into /var/lib/urpmi,
    foreach (glob("$urpm->{statedir}/hdlist.*")) {
	if (/\/hdlist\.((.*)\.cz2?)$/) {
	    #- check if it has already been detected above.
	    exists $hdlists{"hdlist.$1"} and next;

	    #- if not this is a new media to take care if
	    #- there is a list file.
	    if (-s "$urpm->{statedir}/list.$2") {
		if (exists $lists{"list.$2"}) {
		    $urpm->{error}("unable to take medium \"$2\" into account as list file is already used by another medium");
		} else {
		    my $medium;
		    foreach (@{$urpm->{media}}) {
			$_->{name} eq $2 and $medium = $_, last;
		    }
		    $medium and $urpm->{error}("unable to use name \"$2\" for unamed medium because it is already used"), next;

		    $medium = { name => $2, hdlist => "hdlist.$1", list => "list.$2" };
		    $urpm->probe_medium($medium, %options) and push @{$urpm->{media}}, $medium;
		}
	    } else {
		$urpm->{error}("unable to take medium \"$2\" into account as no list file [$urpm->{statedir}/list.$2] exists");
	    }
	} else {
	    $urpm->{error}("unable to determine medium of this hdlist file [$_]");
	}
    }

    #- check the presence of hdlist file and list file if necessary.
    #- TODO?: degraded mode is possible with a list file but no hdlist, the medium
    #- is no longer updatable nor removable TODO
    unless ($options{nocheck_access}) {
	foreach (@{$urpm->{media}}) {
	    $_->{ignore} and next;
	    -r "$urpm->{statedir}/$_->{hdlist}" or
	      $_->{ignore} = 1, $urpm->{error}("unable to access hdlist file of \"$_->{name}\", medium ignored");
	    $_->{list} && -r "$urpm->{statedir}/$_->{list}" or
	      $_->{ignore} = 1, $urpm->{error}("unable to access list file of \"$_->{name}\", medium ignored");
	}
    }
}

#- probe medium to be used, take old medium into account too.
sub probe_medium {
    my ($urpm, $medium, %options) = @_;
    local $_;

    my $existing_medium;
    foreach (@{$urpm->{media}}) {
	$_->{name} eq $medium->{name} and $existing_medium = $_, last;
    }
    $existing_medium and $urpm->{error}("trying to bypass existing medium \"$medium->{name}\", avoiding"), return;
    
    unless ($medium->{ignore} || $medium->{hdlist}) {
	$medium->{hdlist} = "hdlist.$medium->{name}.cz";
	-e "$urpm->{statedir}/$medium->{hdlist}" or $medium->{hdlist} = "hdlist.$medium->{name}.cz2";
	-e "$urpm->{statedir}/$medium->{hdlist}" or
	  $medium->{ignore} = 1, $urpm->{error}("unable to find hdlist file for \"$medium->{name}\", medium ignored");
    }
    unless ($medium->{ignore} || $medium->{list}) {
	$medium->{list} = "list.$medium->{name}";
	-e "$urpm->{statedir}/$medium->{list}" or
	  $medium->{ignore} = 1, $urpm->{error}("unable to find list file for \"$medium->{name}\", medium ignored");
    }

    #- there is a little more to do at this point as url is not known, inspect directly list file for it.
    unless ($medium->{url} || $medium->{clear_url}) {
	my %probe;
	local *L;
	open L, "$urpm->{statedir}/$medium->{list}";
	while (<L>) {
	    /^(.*)\/[^\/]*/ and $probe{$1} = undef;
	}
	close L;
	foreach (sort { length($a) <=> length($b) } keys %probe) {
	    if ($medium->{url}) {
		$medium->{url} eq substr($_, 0, length($medium->{url})) or
		  $medium->{ignore} || $urpm->{error}("incoherent list file for \"$medium->{name}\", medium ignored"),
		    $medium->{ignore} = 1, last;
	    } else {
		$medium->{url} = $_;
	    }
	}
	unless ($options{nocheck_access}) {
	    $medium->{url} or
	      $medium->{ignore} || $urpm->{error}("unable to inspect list file for \"$medium->{name}\", medium ignored"),
		$medium->{ignore} = 1; #, last; keeping it cause perl to exit caller loop ...
	}
    }
    $medium->{url} ||= $medium->{clear_url};
    $medium->{removable} ||= $medium->{url} =~ /^removable_([^_:]*)(?:_[^:]*)?:/ && "/dev/$1";
    $medium;
}

#- write back urpmi.cfg code to allow modification of medium listed.
sub write_config {
    my ($urpm) = @_;

    #- avoid trashing exiting configuration in this case.
    $urpm->{media} or return;

    local *F;
    open F, ">$urpm->{config}" or $urpm->{error}("unable to write config file [$urpm->{config}]");
    foreach my $medium (@{$urpm->{media}}) {
	printf F "%s %s {\n", quotespace($medium->{name}), quotespace($medium->{clear_url});
	foreach (qw(hdlist with_hdlist list removable)) {
	    $medium->{$_} and printf F "  %s: %s\n", $_, $medium->{$_};
	}
	foreach (qw(ignore modified)) {
	    $medium->{$_} and printf F "  %s\n", $_;
	}
	printf F "}\n\n";
    }
    close F;
    $urpm->{log}("write config file [$urpm->{config}]");
}

#- add a new medium, sync the config file accordingly.
sub add_medium {
    my ($urpm, $name, $url, $with_hdlist) = @_;

    #- make sure configuration has been read.
    $urpm->{media} or $urpm->read_config();

    #- if a medium with that name has already been found
    #- we have to exit now
    my ($medium);
    foreach (@{$urpm->{media}}) {
	$_->{name} eq $2 and $medium = $_;
    }
    $medium and $urpm->{error}("medium \"$medium\" already exists"), return;

    #- creating the medium info.
    $medium = { name     => $name,
		url      => $url,
		hdlist   => "hdlist.$name.cz",
		list     => "list.$name",
		modified => 1,
	      };

    #- check to see if the medium is using file protocol or removable medium.
    if (my ($prefix, $dir) = $url =~ /^(removable_.*?|file):\/(.*)/) {
	#- the directory given does not exist or may be accessible
	#- by mounting some other. try to figure out these directory and
	#- mount everything necessary.
	$urpm->try_mounting($dir, 'mount') or $urpm->{log}("unable to access medium \"$name\""), return;

	#- check if directory is somewhat normalized so that we can get back hdlist,
	#- check it that case if depslist, compss and provides file are also
	#- provided.
	if (!($with_hdlist && -e "$dir/$with_hdlist") && $dir =~ /RPMS([^\/]*)\/*$/) {
	    foreach my $rdir (qw(Mandrake/base ../Mandrake/base ..)) {
		-e "$dir/$_/hdlist$1.cz" and $with_hdlist = "$_/hdlist$1.cz", last;
		-e "$dir/$_/hdlist$1.cz2" and $with_hdlist = "$_/hdlist$1.cz2", last;
	    }
	}

	#- add some more flags for this type of medium.
	$medium->{clear_url} = $url;
	$medium->{removable} = $url =~ /^removable_([^_:]*)(?:_[^:]*)?:/ && "/dev/$1";
    }

    #- all flags once everything has been computed.
    $with_hdlist and $medium->{with_hdlist} = $with_hdlist;

    #- create an entry in media list.
    push @{$urpm->{media}}, $medium;

    #- keep in mind the database has been modified and base files need to be updated.
    $urpm->{modified} = 1;
}

sub remove_media {
    my $urpm = shift;
    my %media; @media{@_} = undef;
    my @result;

    foreach (@{$urpm->{media}}) {
	if (exists $media{$_->{name}}) {
	    $media{$_->{name}} = 1; #- keep it mind this one has been removed

	    #- remove file associated with this medium.
	    #- this is the hdlist and the list files.
	    unlink "$urpm->{statedir}/$_->{hdlist}";
	    unlink "$urpm->{statedir}/$_->{list}";
	} else {
	    push @result, $_; #- not removed so keep it
	}
    }

    #- check if some arguments does not correspond to medium name.
    foreach (keys %media) {
	if ($media{$_}) {
	    #- when a medium is removed, depslist and others need to be recomputed.
	    $urpm->{modified} = 1;
	} else {
	    $urpm->{error}("trying to remove inexistant medium \"$_\"");
	}
    }

    #- special case if there is no more media registered.
    #- there is no need to recompute the hdlist and the files
    #- can be safely removed.
    if ($urpm->{modified} && @result == 0) {
	unlink $urpm->{depslist};
	unlink $urpm->{provides};
	unlink $urpm->{compss};
    }

    #- restore newer media list.
    $urpm->{media} = \@result;
}

sub select_media {
    my $urpm = shift;
    my %media; @media{@_} = undef;

    foreach (@{$urpm->{media}}) {
	if (exists $media{$_->{name}}) {
	    $media{$_->{name}} = 1; #- keep it mind this one has been selected.

	    #- select medium by setting modified flags, do not check ignore.
	    $_->{modified} = 1;
	}
    }

    #- check if some arguments does not correspond to medium name.
    foreach (keys %media) {
	unless ($media{$_}) {
	    $urpm->{error}("trying to select inexistant medium \"$_\"");
	}
    }
}

#- update urpmi database regarding the current configuration.
#- take care of modification and try some trick to bypass
#- computational of base files.
#- allow options :
#-   all     -> all medium are rebuilded
#-   force   -> try to force rebuilding from rpms files.
#-   noclean -> keep header directory cleaned.
sub update_media {
    my ($urpm, %options) = @_; #- do not trust existing hdlist and try to recompute them.

    #- avoid trashing existing configuration in this case.
    $urpm->{media} or return;

    #- examine each medium to see if one of them need to be updated.
    #- if this is the case and if not forced, try to use a pre-calculated
    #- hdlist file else build it from rpms files.
    foreach my $medium (@{$urpm->{media}}) {
	#- take care of modified medium only or all if all have to be recomputed.
	#- but do not take care of removable media for all.
	$medium->{ignore} and next;
	$medium->{modified} ||= $options{all} && $medium->{url} !~ /removable/ or next;

	#- list of rpm files for this medium, only available for local medium where
	#- the source hdlist is not used (use force).
	my ($prefix, $dir, $error, @files);

	#- check to see if the medium is using file protocol or removable medium.
	if (($prefix, $dir) = $medium->{url} =~ /^(removable_.*?|file):\/(.*)/) {
	    #- the directory given does not exist and may be accessible
	    #- by mounting some other. try to figure out these directory and
	    #- mount everything necessary.
	    $urpm->try_mounting($dir, 'mount') or $urpm->{log}("unable to access medium \"$medium->{name}\""), next;

	    #- if the source hdlist is present and we are not forcing using rpms file
	    if (!$options{force} && $medium->{with_hdlist} && -e "$dir/$medium->{with_hdlist}") {
		unlink "$urpm->{cachedir}/partial/$medium->{hdlist}";
		system("cp", "-a", "$dir/$medium->{with_hdlist}", "$urpm->{cachedir}/partial/$medium->{hdlist}");
		
		-s "$urpm->{cachedir}/partial/$medium->{hdlist}"
		  or $error = 1, $urpm->{error}("copy of [$dir/$medium->{with_hdlist}] failed");

		#- check if the file are equals...
		unless ($error) {
		    my @sstat = stat "$urpm->{cachedir}/partial/$medium->{hdlist}";
		    my @lstat = stat "$urpm->{statedir}/$medium->{hdlist}";
		    if ($sstat[7] == $lstat[7] && $sstat[9] == $lstat[9]) {
			#- the two files are considered equal here, the medium is so not modified.
			$medium->{modified} = 0;
			unlink "$urpm->{cachedir}/partial/$medium->{hdlist}";
			next;
		    }
		}
	    } else {
		#- try to find rpm files, use recursive method, added additional
		#- / after dir to make sure it will be taken into account if this
		#- is a symlink to a directory.
		@files = split "\n", `find '$dir/' -name "*.rpm" -print`;

		#- check files contains something good!
		if (@files > 0) {
		    #- we need to rebuild from rpm files the hdlist.
		    eval {
			$urpm->{log}("building hdlist [$urpm->{cachedir}/partial/$medium->{hdlist}]");
			$urpm->{params}->build_hdlist($options{noclean}, $options{ratio} || 4, "$urpm->{cachedir}/headers",
						      "$urpm->{cachedir}/partial/$medium->{hdlist}", @files);
		    };
		    $@ and $error = 1, $urpm->{error}("unable to build hdlist: $@");
		} else {
		    $error = 1;
		    $urpm->{error}("no rpm files found from [$dir/]");
		}
	    }
	} else {
	    my $basename = $medium->{with_hdlist} =~ /^.*\/([^\/]*)$/ && $1;

	    #- try to sync (copy if needed) local copy after restored the previous one.
	    unlink "$urpm->{cachedir}/partial/$basename";
	    $options{force} or
	      system("cp", "-a", "$urpm->{statedir}/$medium->{hdlist}", "$urpm->{cachedir}/partial/$basename");
	    system("wget", "-NP", "$urpm->{cachedir}/partial", "$medium->{url}/$medium->{with_hdlist}");
	    $? == 0 or $error = 1, $urpm->{error}("wget of [<source_url>/$medium->{with_hdlist}] failed (maybe wget is missing?)");
	    unless ($error) {
		my @sstat = stat "$urpm->{cachedir}/partial/$basename";
		my @lstat = stat "$urpm->{statedir}/$medium->{hdlist}";
		if ($sstat[7] == $lstat[7] && $sstat[9] == $lstat[9]) {
		    #- the two files are considered equal here, the medium is so not modified.
		    $medium->{modified} = 0;
		    unlink "$urpm->{cachedir}/partial/$basename";
		    next;
		}

		#- the file are different, update local copy.
		rename "$urpm->{cachedir}/partial/$basename", "$urpm->{cachedir}/partial/$medium->{hdlist}";
	    }
	}

	#- build list file according to hdlist used.
	#- make sure group and other does not have any access to this file.
	unless ($error) {
	    local *LIST;
	    my $mask = umask 077;
	    open LIST, ">$urpm->{cachedir}/partial/$medium->{list}"
	      or $error = 1, $urpm->{error}("unable to write list file of \"$medium->{name}\"");
	    umask $mask;
	    if (@files) {
		foreach (@files) {
		    print LIST "$prefix:/$_\n";
		}
	    } else {
		local (*F, $_);
		open F, "parsehdlist '$urpm->{cachedir}/partial/$medium->{hdlist}' |";
		while (<F>) {
		    print LIST "$medium->{url}/$_";
		}
		close F;
	    }
	    close LIST;

	    #- check if at least something has been written into list file.
	    -s "$urpm->{cachedir}/partial/$medium->{list}"
	      or $error = 1, $urpm->{error}("nothing written in list file for \"$medium->{name}\"");
	}

	if ($error) {
	    #- an error has occured for updating the medium, we have to remove tempory files.
	    unlink "$urpm->{cachedir}/partial/$medium->{hdlist}";
	    unlink "$urpm->{cachedir}/partial/$medium->{list}";
	} else {
	    #- make sure to rebuild base files and clean medium modified state.
	    $medium->{modified} = 0;
	    $urpm->{modified} = 1;

	    #- but use newly created file.
	    unlink "$urpm->{statedir}/$medium->{hdlist}";
	    unlink "$urpm->{statedir}/$medium->{list}";
	    rename "$urpm->{cachedir}/partial/$medium->{hdlist}", "$urpm->{statedir}/$medium->{hdlist}";
	    rename "$urpm->{cachedir}/partial/$medium->{list}", "$urpm->{statedir}/$medium->{list}";
	}
    }

    #- build base files (depslist.ordered, provides, compss) according to modified global status.
    if ($urpm->{modified}) {
	#- special case if there is no more media registered.
	#- there is no need to recompute the hdlist and the files
	#- can be safely removed.
	if (@{$urpm->{media}} == 0) {
	    unlink $urpm->{depslist};
	    unlink $urpm->{provides};
	    unlink $urpm->{compss};

	    $urpm->{modified} = 0;
	}

	if (!$options{force} && @{$urpm->{media}} == 1 && $urpm->{media}[0]{with_hdlist}) {
	    #- this is a special mode where is only one hdlist using a source hdlist, in such
	    #- case we are searching for source depslist, provides and compss files.
	    #- if they are not found or if force is used, an error message is printed and
	    #- we continue using computed results.
	    my $medium = $urpm->{media}[0];
	    my $basedir = $medium->{with_hdlist} =~ /^(.*)\/[^\/]*$/ && $1;

	    foreach my $target ($urpm->{depslist}, $urpm->{provides}, $urpm->{compss}, 'END') {
		$target eq 'END' and $urpm->{modified} = 0, last; #- assume everything is ok.
		my $basename = $target =~ /^.*\/([^\/]*)$/ && $1;

		if (my ($prefix, $dir) = $medium->{url} =~ /^(removable_.*?|file):\/(.*)/) {
		    #- the directory should be existing in any cases or this is an error
		    #- so there is no need of trying to mount it.
		    if (-e "$dir/$basedir/$basename") {
			system("cp", "-f", "$dir/$basedir/$basename", $target);
			$? == 0 or $urpm->{error}("unable to copy source of [$target] from [$dir/$basedir/$basename]"), last;
		    } else {
			$urpm->{error}("source of [$target] not found as [$dir/$basedir/$basename]"), last;
		    }
		} else {
		    #- we have to use wget here instead.
		    system("wget", "-O", $target, "$medium->{url}/$basedir/$basename");
		    $? == 0 or $urpm->{error}("wget of [$medium->{url}/$basedir/$basename] failed (maybe wget is missing?)"), last;
		}
	    }
	}

	if ($urpm->{modified}) {
	    #- cleaning.
	    $urpm->{params}->clean();

	    #- if a provides exists, try to use it to speed up process
	    #- but this is not mandatory here.
	    if (-r $urpm->{provides}) {
		local *F;
		open F, $urpm->{provides} or $urpm->{error}("unable to read provides file [$urpm->{provides}]"), return;
		$urpm->{params}->read_provides_files(\*F);
		close F;
		$urpm->{log}("read (only files) provides file [$urpm->{provides}]");
	    }

	    #- compute depslist after reading each hdlist of medium
	    #- in the right order.
	    foreach my $medium (@{$urpm->{media}}) {
		$medium->{ignore} and next;
		$urpm->{log}("reading hdlist file [$urpm->{statedir}/$medium->{hdlist}]");
		$urpm->{params}->read_hdlists("$urpm->{statedir}/$medium->{hdlist}");
		$urpm->{log}("computing dependancy");
		$urpm->{params}->compute_depslist();
	    }

	    #- there has been a problem with provides not resolved on files, there
	    #- must be at least 2 linked pass on the whole process.
	    if ($urpm->{params}->get_unresolved_provides_files() > 0) {
		$urpm->{log}("found unresolved provides on files, cleaning and recomputing dependancy");
		#- cleaning.
		$urpm->{params}->clean();

		foreach my $medium (@{$urpm->{media}}) {
		    $medium->{ignore} and next;
		    $urpm->{log}("reading hdlist file [$urpm->{statedir}/$medium->{hdlist}]");
		    $urpm->{params}->read_hdlists("$urpm->{statedir}/$medium->{hdlist}");
		}
		$urpm->{log}("keeping only provides files");
		$urpm->{params}->keep_only_cleaned_provides_files();
		foreach my $medium (@{$urpm->{media}}) {
		    $medium->{ignore} and next;
		    $urpm->{log}("reading hdlist file [$urpm->{statedir}/$medium->{hdlist}]");
		    $urpm->{params}->read_hdlists("$urpm->{statedir}/$medium->{hdlist}");
		    $urpm->{log}("computing dependancy");
		    $urpm->{params}->compute_depslist();
		}
	    }

	    #- once everything has been computed, write back the files to
	    #- sync the urpmi database.
	    $urpm->write_base_files();
	    $urpm->{modified} = 0;
	}
	#- this file is written in any cases.
	$urpm->write_config();

	#- now everything is finished.
	system("sync");
    }
}

#- check for necessity of mounting some directory to get access
sub try_mounting {
    my ($urpm, $dir, $mode) = @_;

    if ($mode eq 'mount' ? !-e $dir : -e $dir) {
	my ($fdir, $pdir, $v, %fstab, @possible_mount_point) = $dir;

	#- read /etc/fstab and check for existing mount point.
	local (*F, $_);
	open F, "/etc/fstab";
	while (<F>) {
	    /^\s*\S+\s+(\/\S+)/ and $fstab{$1} = 0;
	}
	open F, "/etc/mtab";
	while (<F>) {
	    /^\s*\S+\s+(\/\S+)/ and $fstab{$1} = 1;
	}
	close F;

	#- try to follow symlink, too complex symlink graph may not
	#- be seen.
	while ($v = readlink $fdir) {
	    if ($fdir =~ /^\//) {
		$fdir = $v;
	    } else {
		while ($v =~ /^\.\.\/(.*)/) {
		    $v = $1;
		    $fdir =~ s/^(.*)\/[^\/]+\/*/$1/;
		}
		$fdir .= "/$v";
	    }
	}

	#- check the possible mount point.
	foreach (split '/', $fdir) {
	    length($_) or next;
	    $pdir .= "/$_";
	    foreach ($pdir, "$pdir/") {
		exists $fstab{$_} and push @possible_mount_point, $_;
	    }
	}

	#- try to mount or unmount according to mode.
	$mode ne 'mount' and @possible_mount_point = reverse @possible_mount_point;
	foreach (@possible_mount_point) {
	    $fstab{$_} == ($mode ne 'mount') and $fstab{$_} = ($mode eq 'mount'),
	      $urpm->{log}("${mode}ing $_"), `$mode '$_' 2>/dev/null`;
	}
    }
    $mode eq 'mount' ? -e $dir : !-e $dir;
}

#- read depslist file using rpmtools, this file is not managed directly by urpm.
sub read_depslist {
    my ($urpm) = @_;

    local *F;
    open F, $urpm->{depslist} or $urpm->{error}("unable to read depslist file [$urpm->{depslist}]"), return;
    $urpm->{params}->read_depslist(\*F);
    close F;
    $urpm->{log}("read depslist file [$urpm->{depslist}]");
    1;
}

#- read providest file using rpmtools, this file is not managed directly by urpm.
sub read_provides {
    my ($urpm) = @_;

    local *F;
    open F, $urpm->{provides} or $urpm->{error}("unable to read provides file [$urpm->{provides}]"), return;
    $urpm->{params}->read_provides(\*F);
    close F;
    $urpm->{log}("read provides file [$urpm->{provides}]");
    1;
}

#- read providest file using rpmtools, this file is not managed directly by urpm.
sub read_compss {
    my ($urpm) = @_;

    local *F;
    open F, $urpm->{compss} or $urpm->{error}("unable to read compss file [$urpm->{compss}]"), return;
    $urpm->{params}->read_compss(\*F);
    close F;
    $urpm->{log}("read compss file [$urpm->{compss}]");
    1;
}

#- write base files using rpmtools, these files are not managed directly by urpm.
sub write_base_files {
    my ($urpm) = @_;
    local *F;

    open F, ">$urpm->{depslist}" or $urpm->{error}("unable to write depslist file [$urpm->{depslist}]");
    $urpm->{params}->write_depslist(\*F);
    close F;
    $urpm->{log}("write depslist file [$urpm->{depslist}]");

    open F, ">$urpm->{provides}" or $urpm->{error}("unable to write provides file [$urpm->{provides}]");
    $urpm->{params}->write_provides(\*F);
    close F;
    $urpm->{log}("write provides file [$urpm->{provides}]");

    open F, ">$urpm->{compss}" or $urpm->{error}("unable to write compss file [$urpm->{compss}]");
    $urpm->{params}->write_compss(\*F);
    close F;
    $urpm->{log}("write compss file [$urpm->{compss}]");
}

#- relocate depslist array to use only the most recent packages,
#- reorder info hashes too in the same manner.
sub relocate_depslist {
    my ($urpm) = @_;

    $urpm->{params}->relocate_depslist;
}

#- register local packages for being installed, keep track of source.
sub register_local_packages {
    my ($urpm, @files) = @_;
    my @names;

    #- examine each rpm and build the depslist for them using current
    #- depslist and provides environment.
    foreach (@files) {
	/(.*\/)?[^\/]*\.rpm$/ or $urpm->{error}("invalid rpm file name [$_]"), next;

	my ($name) = $urpm->{params}->read_rpms($_);
	if ($name =~ /(.*)-([^-]*)-([^-]*)/) {
	    my $pkg = $urpm->{params}{info}{$1};
	    $pkg->{version} eq $2 or $urpm->{error}("mismatch version for registering rpm file"), next;
	    $pkg->{release} eq $3 or $urpm->{error}("mismatch release for registering rpm file"), next;
	    $pkg->{source} = $1 ? $_ :  "./$_";
	    push @names, $name;
	} else {
	    $urpm->{error}("rpmtools::read_rpms is too old, upgrade rpmtools package");
	}
    }

    #- compute depslist associated.
    $urpm->{params}->compute_depslist;

    #- return package names...
    @names;
}

#- search packages registered by their name by storing their id into packages hash.
sub search_packages {
    my ($urpm, $packages, $names, %options) = @_;
    my (%exact, %found, %foundi);

    foreach my $v (@$names) {
	#- it is a way of speedup, providing the name of a package directly help
	#- to find the package.
	#- this is necessary if providing a name list of package to upgrade.
	if ($urpm->{params}{info}{$v}) {
	    $exact{$v} = $urpm->{params}{info}{$v}; next;
	}

	my $qv = quotemeta $v;
	foreach (keys %{$urpm->{params}{info}}) {
	    my $info = $urpm->{params}{info}{$_};
	    my $pack = $info->{name} .'-'. $info->{version} .'-'. $info->{release};

	    $pack =~ /^$qv-[^-]+-[^-]+$/ and $exact{$v} = $info;
	    $pack =~ /^$qv-[^-]+$/ and $exact{$v} = $info;
	    $pack =~ /$qv/ and push @{$found{$v}}, $info;
	    $pack =~ /$qv/i and push @{$foundi{$v}}, $info; 
	}
    }

    my $result = 1;
    foreach (@$names) {
	my $info = $exact{$_};
	if ($info) {
	    $packages->{$info->{id}} = undef;
	} else {
	    my $l = $found{$_} || $foundi{$_};
	    if (@{$l || []} == 0) {
		my ($name, $version, $release) = /(.*)-([^-]*)-([^-]*)/;
		$urpm->{params}{info}{$1} or ($name, $version, $release) = /(.*)-([^-]*)/;
		$urpm->{params}{info}{$1} or ($name, $version, $release) = ();
		if ($name) {
		    my $ipkg;
		    foreach (0..$#{$urpm->{params}{depslist}}) {
			my $pkg = $urpm->{params}{depslist}[$_];
			if ($pkg->{name} eq $name && $pkg->{version} eq $version && $pkg->{release} eq $release) {
			    $packages->{$_} = undef;
			    $ipkg = $_;
			    last;
			}
		    }
		    defined $ipkg or ($name, $version, $release) = ();
		}
		unless ($name) {
		    $urpm->{error}(sprintf("no package named %s\n", $_)); $result = 0;
		}
	    } elsif (@$l > 1 && !$options{all}) {
		$urpm->{error}(sprintf("The following packages contain %s: %s\n", $_, join(' ', map { $_->{name} } @$l))); $result = 0; 
	    } else {
		foreach (@$l) {
		    $packages->{$_->{id}} = undef;
		}
	    }
	}
    }

    #- return true if no error have been encoutered, else false.
    $result;
}

#- compute the closure of a list, mostly internal function for filter_packages_to_upgrade.
#- limited to values in packages which should not be a reference.
#- package are identified by their id.
sub compute_closure {
    my ($urpm, $packages, $installed, $select_choices) = @_;
    my ($id, @packages) = (undef, keys %$packages);

    #- at this level, compute global closure of what is requested, regardless of
    #- choices for which all package in the choices are taken and their dependancies.
    #- allow iteration over a modifying list.
    while (defined($id = shift @packages)) {
	#- get a relocated id if possible, by this way.
	$id = $urpm->{params}{depslist}[$id]{id};

	#- avoid a package if it has already been dropped in the sense of
	#- selected directly by another way.
	foreach ($id, split ' ', $urpm->{params}{depslist}[$id]{deps}) {
	    if (/\|/) {
		my ($follow_id, @upgradable_choices);
		my @choices = map { $urpm->{params}{depslist}[$_]{id} } split /\|/, $_;
		foreach (@choices) {
		    $installed && $installed->{$_} and $follow_id = -1, last;
		    exists $packages->{$_} && ! ref $packages->{$_} and $follow_id = $_, last;
		    $installed && exists $installed->{$_} and push @upgradable_choices, $_;
		}
		unless ($follow_id) {
		    #- if there are at least one upgradable choice, use it instead
		    #- of asking the user to chose among a list.
		    if (@upgradable_choices == 1) {
			push @packages, $upgradable_choices[0];
		    } else {
			@upgradable_choices > 1 and @choices = @upgradable_choices;
			$select_choices and push @packages, $select_choices->($urpm, @choices);
			foreach (@choices) {
			    push @{$packages->{$_} ||= []}, \@choices;
			}
		    }
		}
	    } else {
		local $_ = $urpm->{params}{depslist}[$_]{id};
		if (ref $packages->{$_}) {
		    #- all the choices associated here have to be dropped, need to copy else
		    #- there could be problem with foreach on a modifying list.
		    foreach my $choices (@{$packages->{$id}}) {
			foreach (@$choices) {
			    $packages->{$_} = [ grep { $_ != $choices } @{$packages->{$_}} ];
			    @{$packages->{$_}} > 0 or delete $packages->{$_};
			}
		    }
		}
		if ($installed && $installed->{$_}) {
		    delete $packages->{$_};
		} else {
		    exists $packages->{$_} or $packages->{$_} = $installed && ! exists $installed->{$_};
		}
	    }
	}
    }
}

#- filter the packages list (assuming only the key is registered, so undefined
#- value stored) to keep only packages that need to be upgraded,
#- additionnal packages will be stored using non null values,
#- choice will have a list of other choices as values,
#- initial packages will have a 0 stored as values.
#- options allow changing some behaviour of the algorithms:
#-   complete -> perform a complete closure before trying to look for upgrade.
sub filter_packages_to_upgrade {
    my ($urpm, $packages, $select_choices, %options) = @_;
    my ($id, %closures, %installed, @packages_installed);

    #- request the primary list to rpmlib if complete mode is not activated.
    if (!$options{complete} &&
	rpmtools::get_packages_installed('', \@packages_installed,
					 [ map { $urpm->{params}{depslist}[$_]{name} } keys %$packages ])) {
	#- there are not too many packages selected here to allow
	#- take care of package up-to-date at this point,
	#- so check version and if the package does not need to
	#- updated, ignore it and his dependancies.
	foreach (@packages_installed) {
	    my $pkg = $urpm->{params}{info}{$_->{name}}; $pkg or next; #- TODO error
	    my $cmp = rpmtools::version_compare($pkg->{version}, $_->{version});
	    $installed{$pkg->{id}} = !($cmp > 0 || $cmp == 0 && rpmtools::version_compare($pkg->{release}, $_->{release}) > 0)
	      and delete $packages->{$pkg->{id}};
	}
    }

    #- select first level of packages, as in packages list will only be
    #- examined deps of each.
    #- at this level, compute global closure of what is requested, regardless of
    #- choices for which all package in the choices are taken and their dependancies.
    #- allow iteration over a modifying list.
    @closures{keys %$packages} = ();
    $urpm->compute_closure(\%closures, undef, sub { my ($urpm, @l) = @_; @l });

    #- closures has been done so that its keys are the package that may be examined.
    #- according to number of keys, get all package installed or only the necessary
    #- packages.
    #- do not take care of already examined packages.
    delete @closures{keys %installed};
    if (scalar(keys %closures) < 100) {
	rpmtools::get_packages_installed('', \@packages_installed,
					 [ map { $urpm->{params}{depslist}[$_]{name} } keys %closures ]);
    } else {
	rpmtools::get_all_packages_installed('', \@packages_installed);
    }

    #- packages installed that may be upgraded have to be examined now.
    foreach (@packages_installed) {
	my $pkg = $urpm->{params}{info}{$_->{name}}; $pkg or next; #- TODO error
	exists $closures{$pkg->{id}} or next;
	my $cmp = rpmtools::version_compare($pkg->{version}, $_->{version});
	$installed{$pkg->{id}} = !($cmp > 0 || $cmp == 0 && rpmtools::version_compare($pkg->{release}, $_->{release}) > 0)
	  and delete $packages->{$pkg->{id}};
    }

    #- recompute closure but ask for which package to select on a choices.
    #- this is necessary to have the result before the end else some dependancy may
    #- be losed or added.
    #- accept no choice allow to browse list, and to compute it with more iteration.
    %closures = (); @closures{keys %$packages} = ();
    $urpm->compute_closure(\%closures, \%installed, $select_choices);

    #- restore package to match selection done, update the values according to
    #- need upgrade (0), requested (undef), already installed (not present) or
    #- newly added (1).
    #- choices if not chosen are present as ref.
    foreach (keys %closures) {
	exists $packages->{$_} or $packages->{$_} = $closures{$_};
    }

    $packages;
}

#- filter minimal list, upgrade packages only according to rpm requires
#- satisfied, remove upgrade for package already installed or with a better
#- version, try to upgrade to minimize upgrade errors.
#- all additional package selected have a true value.
sub filter_minimal_packages_to_upgrade {
    my ($urpm, $packages, $select_choices, %options) = @_;

    #- make a subprocess here for reading filelist, this is important
    #- not to waste a lot of memory for the main program which will fork
    #- latter for each transaction.
    local (*INPUT, *OUTPUT_CHILD); pipe INPUT, OUTPUT_CHILD;
    local (*INPUT_CHILD, *OUTPUT); pipe INPUT_CHILD, OUTPUT;
    if (my $pid = fork()) {
	close INPUT_CHILD;
	close OUTPUT_CHILD;
	select((select(OUTPUT), $| = 1)[0]);

	#- internal reading from interactive mode of parsehdlist.
	#- takes a code to call with the line read, this avoid allocating
	#- memory for that.
	my $ask_child = sub {
	    my ($name, $tag, $code) = @_;
	    $code or die "no callback code for parsehdlist output";
	    print OUTPUT "$name:$tag\n";

	    local $_;
	    while (<INPUT>) {
		chomp;
		/^\s*$/ and last;
		$code->($_);
	    }
	};

	my ($db, @packages) = (rpmtools::db_open(''), keys %$packages);
	my ($id, %provides, %installed);

	#- at this level, compute global closure of what is requested, regardless of
	#- choices for which all package in the choices are taken and their dependancies.
	#- allow iteration over a modifying list.
	while (defined($id = shift @packages)) {
	    if (ref $id) {
		#- at this point we have almost only choices to resolves.
		#- but we have to check if one package here is already selected
		#- previously, if this is the case, use it instead.
		foreach (@$id) {
		    exists $packages->{$_} and $id = undef, last;
		}
		defined $id or next;

		#- propose the choice to the user now, or select the best one (as it is supposed to be).
		my @selection = $select_choices ? ($select_choices->($urpm, @$id)) : ($id->[0]);
		foreach (@selection) {
		    unshift @packages, $_;
		    exists $packages->{$_} or $packages->{$_} = 1;
		}
	    }
	    my $pkg = $urpm->{params}{depslist}[$id];

	    #- search for package that will be upgraded, and check the difference
	    #- of provides to see if something will be altered and need to be upgraded.
	    #- this is bogus as it only take care of == operator if any.
	    my %diffprovides;
	    rpmtools::db_traverse_tag($db,
				      'name', [ $pkg->{name} ],
				      [ qw(name version release sense provides) ], sub {
					  my ($p) = @_;
					  foreach (@{$p->{provides}}) {
					      s/\[\*\]//;
					      s/\[([^\]]*)\]/ $1/;
					      /^(\S*\s*\S*\s*)(\d+:)?([^\s-]*)(-?\S*)/;
					      foreach ($_, "$1$3", "$1$2$3", "$1$3$4") {
						  $diffprovides{$_} = "$p->{name}-$p->{version}-$p->{release}";
					      }
					  }
				      });
	    $ask_child->("$pkg->{name}-$pkg->{version}-$pkg->{release}", "provides", sub {
			     /^(\S*\s*\S*\s*)(\d+:)?([^\s-]*)(-?\S*)/;
			     foreach ($_, "$1$3", "$1$2$3", "$1$3$4") {
				 delete $diffprovides{$_};
			     }
			 });
	    foreach (keys %diffprovides) {
		#- check for exact match on it.
		if (/^(\S*)\s*(\S*)\s*(\d+:)?([^\s-]*)-?(\S*)/) {
		    rpmtools::db_traverse_tag($db,
					      'whatrequires', [ $1 ],
					      [ qw(name version release sense requires) ], sub{
						  my ($p) = @_;
						  foreach (@{$p->{requires}}) {
						      s/\[\*\]//;
						      s/\[([^\]]*)\]/ $1/;
						      exists $diffprovides{$_} and $provides{$p->{name}} = undef;
						  }
					      });
		}
	    }

	    #- iterate over requires of the packages, register them.
	    $provides{$pkg->{name}} = undef;
	    $ask_child->("$pkg->{name}-$pkg->{version}-$pkg->{release}", "requires", sub {
			     if ($_[0] =~ /^(\S*)\s*(\S*)\s*([^\s-]*)-?(\S*)/) {
				 exists $provides{$1} and return;
				 #- if the provides is not found, it will be resolved at next step, else
				 #- it will be resolved by searching the rpm database.
				 $provides{$1} ||= undef;
				 rpmtools::db_traverse_tag($db,
							   'whatprovides', [ $1 ],
							   [ qw (name version release) ], sub {
							       $3 and eval(rpmtools::version_compare($_[0]{version}, $3) . $2 . 0) || return;
							       $4 and eval(rpmtools::version_compare($_[0]{release}, $4) . $2 . 0) || return;
							       $provides{$1} = "$_[0]{name}-$_[0]{version}-$_[0]{release}";
							   });
			     }
			 });

	    #- at this point, all unresolved provides (requires) should be fixed by
	    #- provides files, try to minimize choice at this level.
	    foreach (keys %provides) {
		$provides{$_} and next;
		my (@choices, @upgradable_choices);
		foreach (@{$urpm->{params}{provides}{$_}}) {
		    #- prefer upgrade package that need to be upgraded, if they are present in the choice.
		    my $pkg = $urpm->{params}{info}{$_};
		    push @choices, $pkg;
		    rpmtools::db_traverse_tag($db,
					      'name', [ $_ ],
					      [ qw(name version release) ], sub {
						  my ($p) = @_;
						  my $cmp = rpmtools::version_compare($pkg->{version}, $p->{version});
						  $installed{$pkg->{id}} ||= !($cmp > 0 || $cmp == 0 && rpmtools::version_compare($pkg->{release}, $p->{release}) > 0)
					      });
		    $installed{$pkg->{id}} and delete $packages->{$pkg->{id}};
		    if (exists $packages->{$pkg->{id}} || $installed{$pkg->{id}}) {
			#- the package is already selected, or installed with a better version and release.
			@choices = @upgradable_choices = ();
			last;
		    }
		    exists $installed{$pkg->{id}} and push @upgradable_choices, $pkg;
		}
		@upgradable_choices > 0 and @choices = @upgradable_choices;
		if (@choices > 0) {
		    if (@choices == 1) {
			exists $packages->{$choices[0]{id}} or $packages->{$choices[0]{id}} = 1;
			unshift @packages, $choices[0]{id};
		    } else {
			push @packages, [ sort { $a <=> $b } map { $_->{id} } @choices ];
		    }
		}
	    }
	}

	rpmtools::db_close($db);

	#- no need to still use the child as this point, we can let him to terminate.
	close OUTPUT;
	close INPUT;
	waitpid $pid, 0;
    } else {
	close INPUT;
	close OUTPUT;
	open STDIN, "<&INPUT_CHILD";
	open STDOUT, ">&OUTPUT_CHILD";
	exec "parsehdlist", "--interactive", map { "$urpm->{statedir}/$_->{hdlist}" } grep { ! $_->{ignore} } @{$urpm->{media}}
	  or rpmtools::_exit(1);
    }
}

#- get out of package that should not be upgraded.
sub deselect_unwanted_packages {
    my ($urpm, $packages, %options) = @_;

    my %skip;
    local ($_, *F);
    open F, $urpm->{skiplist};
    while (<F>) {
	chomp; s/#.*$//; s/^\s*//; s/\s*$//;
	my $pkg = $urpm->{params}{info}{$_} or next;
	$options{force} || (exists $packages->{$pkg->{id}} && defined $packages->{$pkg->{id}}) and delete $packages->{$pkg->{id}};
    }
    close F;
}

#- select source for package selected.
#- according to keys given in the packages hash.
#- return a list of list containing the source description for each rpm,
#- match exactly the number of medium registered, ignored medium always
#- have a null list.
sub get_source_packages {
    my ($urpm, $packages) = @_;
    my ($error, @local_sources, @list, %select);
    local (*D, *F, $_);

    #- examine the local repository, which is trusted.
    opendir D, "$urpm->{cachedir}/rpms";
    while (defined($_ = readdir D)) {
	if (/([^\/]*)-([^-]*)-([^-]*)\.([^\.]*)\.rpm/) {
	    my $pkg = $urpm->{params}{info}{$1};

	    #- check version, release and id selected.
	    #- TODO arch is not checked at this point.
	    $pkg->{version} eq $2 && $pkg->{release} eq $3 or next;
	    exists $packages->{$pkg->{id}} or next;

	    #- make sure only the first matching is taken...
	    exists $select{$pkg->{id}} and next; $select{$pkg->{id}} = undef;

	    #- we have found one source for id.
	    push @local_sources, "$urpm->{cachedir}/rpms/$1-$2-$3.$4.rpm";
	} else {
	    -d "$urpm->{cachedir}/rpms/$_" and next;
	    $error = 1;
	    $urpm->{error}("unable to determine rpms cache directory $urpm->{cachedir}/rpms");
	}
    }
    closedir D;

    #- examine each medium to search for packages.
    foreach my $medium (@{$urpm->{media} || []}) {
	my @sources;

	if (-r "$urpm->{statedir}/$medium->{hdlist}" && -r "$urpm->{statedir}/$medium->{list}" && !$medium->{ignore}) {
	    open F, "$urpm->{statedir}/$medium->{list}";
	    while (<F>) {
		if (/(.*)\/([^\/]*)-([^-]*)-([^-]*)\.([^\.]*)\.rpm/) {
		    my $pkg = $urpm->{params}{info}{$2};

		    #- check version, release and id selected.
		    #- TODO arch is not checked at this point.
		    $pkg->{version} eq $3 && $pkg->{release} eq $4 or next;
		    exists $packages->{$pkg->{id}} or next;

		    #- make sure only the first matching is taken...
		    exists $select{$pkg->{id}} and next; $select{$pkg->{id}} = undef;

		    #- we have found one source for id.
		    push @sources, "$1/$2-$3-$4.$5.rpm";
		} else {
		    $error = 1;
		    $urpm->{error}("unable to parse correctly $urpm->{statedir}/$medium->{list}");
		    last;
		}
	    }
	    close F;
	}
	push @list, \@sources;
    }

    #- examine package list to see if a package has not been found.
    foreach (keys %$packages) {
	exists $select{$_} and next;

	#- try to find which one.
	my $pkg = $urpm->{params}{depslist}[$_];
	if ($pkg) {
	    if ($pkg->{source}) {
		push @local_sources, $pkg->{source};
	    } else {
		$error = 1;
		$urpm->{error}("package $pkg->{name}-$pkg->{version}-$pkg->{release} is not found, ids=($_,$pkg->{id})");
	    }
	} else {
	    $error = 1;
	    $urpm->{error}("internal error for selecting unknown package for id=$_");
	}
    }

    $error ? () : ( \@local_sources, \@list );
}

#- upload package that may need to be uploaded.
#- make sure header are available in the appropriate directory.
#- change location to find the right package in the local
#- filesystem for only one transaction.
#- try to mount/eject removable media here.
#- return a list of package ready for rpm.
sub upload_source_packages {
    my ($urpm, $local_sources, $list, $force_local, $ask_for_medium) = @_;
    my (@sources, @distant_sources, %media, %removables);

    #- make sure everything is correct on input...
    @{$urpm->{media}} == @$list or return;

    #- removable media have to be examined to keep mounted the one that has
    #- more package than other (size is better ?).
    my $examine_removable_medium = sub {
	my ($id, $device, $copy) = @_;
	my $medium = $urpm->{media}[$id];
	$media{$id} = undef;
	if (my ($prefix, $dir) = $medium->{url} =~ /^(removable_[^:]*|file):\/(.*)/) {
	    until (-e $dir) {
		#- the directory given does not exist or may be accessible
		#- by mounting some other. try to figure out these directory and
		#- mount everything necessary.
		unless ($urpm->try_mounting($dir, 'mount')) {
		    $urpm->try_mounting($dir, 'unmount'); system("eject", $device);
		    $ask_for_medium->($medium->{name}, $medium->{removable}) or last;
		}
	    }
	    if (-e $dir) {
		my @removable_sources;
		foreach (@{$list->[$id]}) {
		    /^(removable_[^:]*|file):\/(.*\/([^\/]*))/ or next;
		    -r $2 or $urpm->{error}("unable to read rpm file [$2] from medium \"$medium->{name}\"");
		    if ($copy) {
			push @removable_sources, $2;
			push @sources, "$urpm->{cachedir}/rpms/$3";
		    } else {
			push @sources, $2;
		    }
		}
		if (@removable_sources) {
		    system("cp", "-a", @removable_sources, "$urpm->{cachedir}/rpms");
		}
	    } else {
		$urpm->{error}("medium \"$medium->{name}\" is not selected");
	    }
	} else {
	    #- we have a removable device that is not removable, well...
	    $urpm->{error}("incoherent medium \"$medium->{name}\" marked removable but not really");
	}
    };
    foreach (0..$#$list) {
	@{$list->[$_]} or next;
	my $medium = $urpm->{media}[$_];
	#- examine non removable device but that may be mounted.
	if ($medium->{removable}) {
	    push @{$removables{$medium->{removable}} ||= []}, $_;
	} elsif (my ($prefix, $dir) = $medium->{url} =~ /^(removable_[^:]*|file):\/(.*)/) {
	    -e $dir || $urpm->try_mounting($dir, 'mount') or $urpm->{error}("unable to access medium \"$medium->{name}\""), next;
	}
    }
    foreach my $device (keys %removables) {
	#- here we have only removable device.
	#- if more than one media use this device, we have to sort
	#- needed package to copy first the needed rpms files.
	if (@{$removables{$device}} > 1) {
	    my @sorted_media = sort { @{$list->[$a]} <=> @{$list->[$b]} } @{$removables{$device}};

	    #- mount all except the biggest one.
	    foreach (@sorted_media[0 .. $#sorted_media-1]) {
		$examine_removable_medium->($_, $device, 'copy');
	    }
	    #- now mount the last one...
	    $removables{$device} = [ $sorted_media[-1] ];
	}

	#- mount the removable device, only one or the important one.
	$examine_removable_medium->($removables{$device}[0], $device);
    }

    #- get back all ftp and http accessible rpms file into the local cache
    #- if necessary (as used by checksig or any other reasons).
    #- we are using wget for that with an input from its stdin.
    foreach (0..$#$list) {
	exists $media{$_} and next;
	@{$list->[$_]} or next;
	foreach (@{$list->[$_]}) {
	    if (/^(removable_[^:]*|file):\/(.*)/) {
		push @sources, $2;
	    } elsif (/^([^:]*):\/(.*\/([^\/]*))/) {
		if ($force_local) {
		    push @distant_sources, $_;
		    push @sources, "$urpm->{cachedir}/rpms/$3";
		} else {
		    push @sources, $_;
		}
	    } else {
		$urpm->{error}("malformed input: [$_]");
	    }
	}
    }
    foreach (@distant_sources) {
	$urpm->{log}("retrieving [$_]");
	system "wget", "-NP", "$urpm->{cachedir}/rpms", $_;
    }

    #- return the list of rpm file that have to be installed, they are all local now.
    @$local_sources, @sources;
}

sub select_packages_to_upgrade {
    my ($urpm, $prefix, $packages, $remove_packages, $keep_files) = @_;
    my $db = rpmtools::db_open($prefix);

    #- used for package that are not correctly updated.
    #- should only be used when nothing else can be done correctly.
    my %upgradeNeedRemove = (
			     'libstdc++' => 1,
			     'compat-glibc' => 1,
			     'compat-libs' => 1,
			    );

    #- help removing package which may have different release numbering
    my %toRemove;

    #- help searching package to upgrade in regard to already installed files.
    my %installedFilesForUpgrade;

    #- help keeping memory by this set of package that have been obsoleted.
    my %obsoletedPackages;

    #- make a subprocess here for reading filelist, this is important
    #- not to waste a lot of memory for the main program which will fork
    #- latter for each transaction.
    local (*INPUT, *OUTPUT_CHILD); pipe INPUT, OUTPUT_CHILD;
    local (*INPUT_CHILD, *OUTPUT); pipe INPUT_CHILD, OUTPUT;
    if (my $pid = fork()) {
	close INPUT_CHILD;
	close OUTPUT_CHILD;
	select((select(OUTPUT), $| = 1)[0]);

	#- internal reading from interactive mode of parsehdlist.
	#- takes a code to call with the line read, this avoid allocating
	#- memory for that.
	my $ask_child = sub {
	    my ($name, $tag, $code) = @_;
	    $code or die "no callback code for parsehdlist output";
	    print OUTPUT "$name:$tag\n";

	    local $_;
	    while (<INPUT>) {
		chomp;
		/^\s*$/ and last;
		$code->($_);
	    }
	};

	#- select packages which obseletes other package, obselete package are not removed,
	#- should we remove them ? this could be dangerous !
	foreach my $pkg (values %{$urpm->{params}{info}}) {
	    $ask_child->($pkg->{name}, "obsoletes", sub {
			     #- take care of flags and version and release if present
			     if ($_[0] =~ /^(\S*)\s*(\S*)\s*([^\s-]*)-?(\S*)/ &&
				 rpmtools::db_traverse_tag($db, "name", [$1], [], undef) > 0) {
				 $3 and eval(rpmtools::version_compare($pkg->{version}, $3) . $2 . 0) or next;
				 $4 and eval(rpmtools::version_compare($pkg->{release}, $4) . $2 . 0) or next;
				 $urpm->{log}("selecting $pkg->{name}-$pkg->{version}-$pkg->{release} using obsoletes");
				 $obsoletedPackages{$1} = undef;
				 $pkg->{selected} = 1;
			     }
			 });
	}

	#- mark all files which are not in /etc/rc.d/ for packages which are already installed but which
	#- are not in the packages list to upgrade.
	#- the 'installed' property will make a package unable to be selected, look at select.
	rpmtools::db_traverse($db, [ qw(name version release files) ], sub {
				  my ($p) = @_;
				  my $otherPackage = $p->{release} !~ /mdk\w*$/ && "$p->{name}-$p->{version}-$p->{release}";
				  my $pkg = $urpm->{params}{info}{$p->{name}};

				  if ($pkg) {
				      my $version_cmp = rpmtools::version_compare($p->{version}, $pkg->{version});
				      if ($version_cmp > 0 || $version_cmp == 0 &&
					  rpmtools::version_compare($p->{release}, $pkg->{release}) >= 0) {
					  if ($otherPackage && $version_cmp <= 0) {
					      $toRemove{$otherPackage} = 0;
					      $pkg->{selected} = 1;
					      $urpm->{log}("removing $otherPackage to upgrade ...\n  to $pkg->{name}-$pkg->{version}-$pkg->{release} since it will not be updated otherwise");
					  } else {
					      $pkg->{installed} = 1;
					  }
				      } elsif ($upgradeNeedRemove{$pkg->{name}}) {
					  my $otherPackage = "$p->{name}-$p->{version}-$p->{release}";
					  $toRemove{$otherPackage} = 0;
					  $pkg->{selected} = 1;
					  $urpm->{log}("removing $otherPackage to upgrade ...\n  to $pkg->{name}-$pkg->{version}-$pkg->{release} since it will not upgrade correctly!");
				      }
				  } else {
				      if (! exists $obsoletedPackages{$p->{name}}) {
					  @installedFilesForUpgrade{grep { ($_ !~ m|^/etc/rc.d/| && $_ !~ m|\.la$| &&
									    ! -d "$prefix/$_" && ! -l "$prefix/$_") }
								      @{$p->{files}}} = ();
				      }
				  }
			      });

	#- find new packages to upgrade.
	foreach my $pkg (values %{$urpm->{params}{info}}) {
	    my $skipThis = 0;
	    my $count = rpmtools::db_traverse_tag($db, "name", [ $pkg->{name} ], [ 'name' ], sub {
						      $skipThis ||= $pkg->{installed};
						  });

	    #- skip if not installed (package not found in current install).
	    $skipThis ||= ($count == 0);

	    #- select the package if it is already installed with a lower version or simply not installed.
	    unless ($skipThis) {
		my $cumulSize;

		$pkg->{selected} = 1;

		#- keep in mind installed files which are not being updated. doing this costs in
		#- execution time but use less memory, else hash all installed files and unhash
		#- all file for package marked for upgrade.
		rpmtools::db_traverse_tag($db, "name", [ $pkg->{name} ], [ qw(name files) ], sub {
					      my ($p) = @_;
					      @installedFilesForUpgrade{grep { ($_ !~ m|^/etc/rc.d/| && $_ !~ m|\.la$| &&
										! -d "$prefix/$_" && ! -l "$prefix/$_") }
									  @{$p->{files}}} = ();
					  });

		$ask_child->($pkg->{name}, "files", sub {
				 delete $installedFilesForUpgrade{$_[0]};
			     });
	    }
	}

	#- unmark all files for all packages marked for upgrade. it may not have been done above
	#- since some packages may have been selected by depsList.
	foreach my $pkg (values %{$urpm->{params}{info}}) {
	    if ($pkg->{selected}) {
		$ask_child->($pkg->{name}, "files", sub {
				 delete $installedFilesForUpgrade{$_[0]};
			     });
	    }
	}

	#- select packages which contains marked files, then unmark on selection.
	#- a special case can be made here, the selection is done only for packages
	#- requiring locales if the locales are selected.
	#- another special case are for devel packages where fixes over the time has
	#- made some files moving between the normal package and its devel couterpart.
	#- if only one file is affected, no devel package is selected.
	foreach my $pkg (values %{$urpm->{params}{info}}) {
	    unless ($pkg->{selected}) {
		my $toSelect = 0;
		$ask_child->($pkg->{name}, "files", sub {
				 if ($_[0] !~  m|^/etc/rc.d/| &&  $_ !~ m|\.la$| && exists $installedFilesForUpgrade{$_[0]}) {
				     ++$toSelect if ! -d "$prefix/$_[0]" && ! -l "$prefix/$_[0]";
				 }
				 delete $installedFilesForUpgrade{$_[0]};
			     });
		if ($toSelect) {
		    if ($toSelect <= 1 && $pkg->{name} =~ /-devel/) {
			$urpm->{log}("avoid selecting $pkg->{name}-$pkg->{version}-$pkg->{release} as not enough files will be updated");
		    } else {
			#- default case is assumed to allow upgrade.
			my @deps = map { /\|/ and next; #- do not inspect choice
					 my $p = $urpm->{params}{depslist}[$_];
					 $p && $p->{name} =~ /locales-/ ? ($p) : () } split ' ', $pkg->{deps};
			if (@deps == 0 || @deps > 0 && (grep { !$_->{selected} && !$_->{installed} } @deps) == 0) {
			    $urpm->{log}("selecting $pkg->{name} by selection on files");
			    $pkg->{selected} = 1;
			} else {
			    $urpm->{log}("avoid selecting $pkg->{name}-$pkg->{version}-$pkg->{release} as its locales language is not already selected");
			}
		    }
		}
	    }
	}

	#- clean memory...
	%installedFilesForUpgrade = ();

	#- no need to still use the child as this point, we can let him to terminate.
	close OUTPUT;
	close INPUT;
	waitpid $pid, 0;
    } else {
	close INPUT;
	close OUTPUT;
	open STDIN, "<&INPUT_CHILD";
	open STDOUT, ">&OUTPUT_CHILD";
	exec "parsehdlist", "--interactive", map { "$urpm->{statedir}/$_->{hdlist}" } grep { ! $_->{ignore} } @{$urpm->{media}}
	  or rpmtools::_exit(1);
    }

    #- let the caller known about what we found here!
    foreach my $pkg (values %{$urpm->{params}{info}}) {
	$packages->{$pkg->{id}} = 0 if $pkg->{selected};
    }

    #- clean false value on toRemove.
    delete $toRemove{''};

    #- get filenames that should be saved for packages to remove.
    #- typically config files, but it may broke for packages that
    #- are very old when compabilty has been broken.
    #- but new version may saved to .rpmnew so it not so hard !
    if ($keep_files && keys %toRemove) {
	rpmtools::db_traverse($db, [ qw(name version release conffiles) ], sub {
				  my ($p) = @_;
				  my $otherPackage = "$p->{name}-$p->{version}-$p->{release}";
				  if (exists $toRemove{$otherPackage}) {
				      @{$keep_files}{@{$p->{conffiles} || []}} = ();
				  }
			      });
    }

    #- close db, job finished !
    rpmtools::db_close($db);
}

1;