#! @perl@ -w

use strict;
use IPC::Open2;

my $rootsDir = "@localstatedir@/nix/gcroots";
my $storeDir = "@storedir@";

my %alive;

my $gcOper = "--delete";
my $minAge = 0;

my @roots = ();


# Parse the command line.
for (my $i = 0; $i < scalar @ARGV; $i++) {
    my $arg = $ARGV[$i];
    if ($arg eq "--delete" || $arg eq "--print-live" || $arg eq "--print-dead") {
        $gcOper = $arg;
    }
    elsif ($arg eq "--min-age") {
        $i++;
        $minAge = undef;
        $minAge = $ARGV[$i];
        die "invalid minimum age" unless defined $minAge && $minAge =~ /^\d*$/;
    }
    else { die "unknown argument `$arg'" };
}


# Read all GC roots from the given file.
sub readRoots {
    my $fileName = shift;
    open ROOT, "<$fileName" or die "cannot open `$fileName': $!";
    while (<ROOT>) {
        chomp;
        foreach my $root (split ' ') {
            die "bad root `$root' in file `$fileName'"
                unless $root =~ /^\S+$/;
            push @roots, $root;
        }
    }
    close ROOT;
}


# Recursively finds all *.gcroot files in the given directory.
sub findRoots;
sub findRoots {
    my $followSymlinks = shift;
    my $dir = shift;

    opendir(DIR, $dir) or die "cannot open directory `$dir': $!";
    my @names = readdir DIR or die "cannot read directory `$dir': $!";
    closedir DIR;

    foreach my $name (@names) {
        next if $name eq "." || $name eq "..";
        $name = $dir . "/" . $name;
        if ($name =~ /.gcroot$/ && -f $name) {
            readRoots $name;
        }
        elsif (-d $name) {
            if ($followSymlinks || !-l $name) {
                findRoots 0, $name;
            }
        }
    }
    
}


# Find GC roots, starting at $rootsDir.
findRoots 1, $rootsDir;


# Run the collector with the roots we found.
my $pid = open2(">&1", \*WRITE, "@bindir@/nix-store --gc $gcOper --min-age $minAge")
    or die "cannot run `nix-store --gc'";

foreach my $root (@roots) {
    print WRITE "$root\n";
}

close WRITE;

waitpid $pid, 0;
$? == 0 or die "`nix-store --gc' failed";