#! /usr/bin/env perl

use strict;
use File::Basename;
use Fcntl;
use IO::File;
use Net::Amazon::S3;
use Net::Amazon::S3::Client;
use Nix::Config;
use Nix::Store;
use Hydra::Model::DB;
use Hydra::Helper::Nix;

my $cfg = getHydraConfig()->{s3backup};
my @config = defined $cfg ? ref $cfg eq "ARRAY" ? @$cfg : ($cfg) : ();

exit 0 unless @config;

my $lockfile = Hydra::Model::DB::getHydraPath . "/.hydra-s3backup.lock";
my $lockhandle = IO::File->new;
open($lockhandle, ">", $lockfile) or die "Opening $lockfile: $!";
flock($lockhandle, Fcntl::LOCK_EX) or die "Write-locking $lockfile: $!";

my $client = Net::Amazon::S3::Client->new( s3 => Net::Amazon::S3->new( retry => 1 ) );
my $db = Hydra::Model::DB->new();

my $gcRootsDir = getGCRootsDir;
opendir DIR, $gcRootsDir or die;
my @roots = readdir DIR;
closedir DIR;

my @actual_roots = ();
foreach my $link (@roots) {
    next if $link eq "." || $link eq "..";
    push @actual_roots, $Nix::Config::storeDir . "/" . $link;
}

# Don't delete a nix-cache-info file, if present
my %closure = ( "nix-cache-info" => undef );
foreach my $path (computeFSClosure(0, 0, @actual_roots)) {
    my $hash = substr basename($path), 0, 32;
    $closure{"$hash.narinfo"} = undef;
    $closure{"$hash.nar"} = undef;
}

foreach my $bucket_config (@config) {
    my $bucket = $client->bucket( name => $bucket_config->{name} );
    my $prefix = exists $bucket_config->{prefix} ? $bucket_config->{prefix} : "";

    my $cache_stream = $bucket->list({ prefix => $prefix });
    until ($cache_stream->is_done) {
        foreach my $object ($cache_stream->items) {
            $object->delete unless exists $closure{basename($object->key)};
        }
    }
}

1;
