#!/usr/bin/perl

use MDK::Common;

@ARGV == 2 or die "merge_users <existing files dir> <new files dir>\n";

my ($existing_dir, $new_dir) = @ARGV;

merge('passwd', 'shadow');
merge('group', 'gshadow');

sub merge {
    my ($main, $shadow) = @_;

    my @new = cat_("$new_dir/$main");
    my %new_ids = map { (split ':')[2] => $_ } @new;

    my %names_to_have;
    foreach (cat_("$existing_dir/$main")) {
	my @l = split ':';
	next if $l[0] eq 'nobody' || $l[2] < 500;
	if (my $e = $new_ids{$l[2]}) {
	    $_ eq $e or warn "ERROR: conflicting entries:\n  $_  $e";
	} else {
	    push @new, $_;
	    $names_to_have{$l[0]} = 1;
	}
    }

    my @new_shadow = grep { !/^root:/ } cat_("$new_dir/$shadow");
    foreach (cat_("$existing_dir/$shadow")) {
	my ($name) = split ':';
	if ($name eq 'root') {
	    unshift @new_shadow, $_;
	} elsif ($names_to_have{$name}) {
	    push @new_shadow, $_;
	}
    }

    if (rename "$existing_dir/$main",  "$existing_dir/$main.old") {
	output("$existing_dir/$main", @new);
    } else {
	warn "rename $existing_dir/$main failed: $?\n";
	<STDIN>;
    }
    if (rename "$existing_dir/$shadow",  "$existing_dir/$shadow.old") {
	output("$existing_dir/$shadow", @new_shadow);
    } else {
	warn "rename $existing_dir/$shadow failed: $?\n";
	<STDIN>;
    }
}