#! @perl@ -w @perlFlags@

use strict;
use Nix::Config;
use Nix::Store;


my @binaryCacheUrls = split / /, ($ENV{"NIX_BINARY_CACHES"} || "");


sub getInfoFrom {
    my ($storePath, $pathHash, $binaryCacheUrl) = @_;
    my $infoUrl = "$binaryCacheUrl/$pathHash.narinfo";
    #print STDERR "checking $infoUrl...\n";
    my $s = `$Nix::Config::curl --fail --silent --location ${infoUrl}`;
    if ($? != 0) {
        #print STDERR "GOT CURL REPLY ", $? >> 8, "\n";
        return undef;
    }
    my ($storePath2, $url, $compression, $fileHash, $fileSize, $narHash, $narSize, $deriver);
    my @refs;
    foreach my $line (split "\n", $s) {
        $line =~ /^(.*): (.*)$/ or return undef;
        if ($1 eq "StorePath") { $storePath2 = $2; }
        elsif ($1 eq "URL") { $url = $2; }
        elsif ($1 eq "Compression") { $compression = $2; }
        elsif ($1 eq "FileHash") { $fileHash = $2; }
        elsif ($1 eq "FileSize") { $fileSize = int($2); }
        elsif ($1 eq "NarHash") { $narHash = $2; }
        elsif ($1 eq "NarSize") { $narSize = int($2); }
        elsif ($1 eq "References") { @refs = split / /, $2; }
        elsif ($1 eq "Deriver") { $deriver = $2; }
    }
    if ($storePath ne $storePath2 || !defined $url || !defined $narHash || !defined $narSize) {
        print STDERR "bad NAR info file ‘$infoUrl’\n";
        return undef
    }
    return
        { url => $url
        , compression => ($compression || "bzip2")
        , fileHash => $fileHash
        , fileSize => $fileSize
        , narHash => $narHash
        , narSize => $narSize
        , refs => [ map { "$Nix::Config::storeDir/$_" } @refs ]
        , deriver => "$Nix::Config::storeDir/$deriver"
        }
}


sub getInfo {
    my ($storePath) = @_;

    my $pathHash = hashString("sha256", 1, $storePath);

    cache: foreach my $binaryCacheUrl (@binaryCacheUrls) {
        my $info = getInfoFrom($storePath, $pathHash, $binaryCacheUrl);
        return $info if defined $info;
    }

    return undef;
}


sub downloadBinary {
    my ($storePath) = @_;
    
    my $pathHash = hashString("sha256", 1, $storePath);

    cache: foreach my $binaryCacheUrl (@binaryCacheUrls) {
        my $info = getInfoFrom($storePath, $pathHash, $binaryCacheUrl);
        if (defined $info) {
            my $decompressor;
            if ($info->{compression} eq "bzip2") { $decompressor = "$Nix::Config::bzip2 -d"; }
            elsif ($info->{compression} eq "xz") { $decompressor = "$Nix::Config::xz -d"; }
            else {
                print STDERR "unknown compression method ‘$info->{compression}’\n";
                next;
            }
            if (system("$Nix::Config::curl --fail --location $binaryCacheUrl/$info->{url} | $decompressor | $Nix::Config::binDir/nix-store --restore $storePath") == 0) {
                return 1;
            }
        }
    }

    return 0;
}


if ($ARGV[0] eq "--query") {

    while (<STDIN>) {
        my $cmd = $_; chomp $cmd;

        if ($cmd eq "have") {
            my $storePath = <STDIN>; chomp $storePath;
            # FIXME: want to give correct info here, but it's too slow.
            print "0\n";
            #my $info = getInfo($storePath);
            #if (defined $info) { print "1\n"; } else { print "0\n"; }
        }

        elsif ($cmd eq "info") {
            my $storePath = <STDIN>; chomp $storePath;
            my $info = getInfo($storePath);
            if (defined $info) {
                print "1\n";
                print $info->{deriver} || "", "\n";
                print scalar @{$info->{refs}}, "\n";
                print "$_\n" foreach @{$info->{refs}};
                print $info->{fileSize} || 0, "\n";
                print $info->{narSize}, "\n";
            } else {
                print "0\n";
            }
        }

        else { die "unknown command `$cmd'"; }

        flush STDOUT;
    }

}

elsif ($ARGV[0] eq "--substitute") {
    my $storePath = $ARGV[1] or die;
    exit 1 unless downloadBinary($storePath);
}

else {
    die;
}