#! @perl@ -w @perlFlags@

use strict;
use File::Basename;
use Nix::Config;
use Nix::Store;
use DBI;


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

my ($dbh, $insertNAR, $queryNAR);
my %cacheIds;


sub initCache {
    my $dbPath = "$Nix::Config::stateDir/binary-cache-v1.sqlite";

    # Open/create the database.
    $dbh = DBI->connect("dbi:SQLite:dbname=$dbPath", "", "")
        or die "cannot open database `$dbPath'";
    $dbh->{RaiseError} = 1;
    $dbh->{PrintError} = 0;

    $dbh->do("pragma synchronous = off"); # we can always reproduce the cache
    $dbh->do("pragma journal_mode = truncate");

    # Initialise the database schema, if necessary.
    $dbh->do(<<EOF);
        create table if not exists BinaryCaches (
            id        integer primary key autoincrement not null,
            url       text unique not null
        );
EOF
    
    $dbh->do(<<EOF);
        create table if not exists NARs (
            cache            integer not null,
            storePath        text not null,
            url              text not null,
            compression      text not null,
            fileHash         text,
            fileSize         integer,
            narHash          text,
            narSize          integer,
            refs             text,
            deriver          text,
            system           text,
            timestamp        integer not null,
            primary key (cache, storePath),
            foreign key (cache) references BinaryCaches(id) on delete cascade
        );
EOF

    $insertNAR = $dbh->prepare(
        "insert or replace into NARs(cache, storePath, url, compression, fileHash, fileSize, narHash, " .
        "narSize, refs, deriver, system, timestamp) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)") or die;

    $queryNAR = $dbh->prepare("select * from NARs where cache = ? and storePath = ?") or die;
}


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) {
        my $status = $? >> 8;
        print STDERR "could not download ‘$infoUrl’ (curl returned status ", $? >> 8, ")\n"
            if $status != 22 && $status != 37;
        return undef;
    }
    my ($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; }
    }
    return undef if $storePath ne $storePath2;
    if ($storePath ne $storePath2 || !defined $url || !defined $narHash) {
        print STDERR "bad NAR info file ‘$infoUrl’\n";
        return undef;
    }
    return
        { url => $url
        , compression => ($compression || "bzip2")
        , fileHash => $fileHash
        , fileSize => $fileSize
        , narHash => $narHash
        , narSize => $narSize
        , refs => [ @refs ]
        , deriver => $deriver
        };
}


sub getCacheId {
    my ($binaryCacheUrl) = @_;
    
    my $cacheId = $cacheIds{$binaryCacheUrl};
    return $cacheId if defined $cacheId;
    
    # FIXME: not atomic.
    my @res = @{$dbh->selectcol_arrayref("select id from BinaryCaches where url = ?", {}, $binaryCacheUrl)};
    if (scalar @res == 1) {
        $cacheId = $res[0];
    } else {
        $dbh->do("insert into BinaryCaches(url) values (?)",
                 {}, $binaryCacheUrl);
        $cacheId = $dbh->last_insert_id("", "", "", "");
    }

    $cacheIds{$binaryCacheUrl} = $cacheId;
    return $cacheId;
}


sub cachedGetInfoFrom {
    my ($storePath, $pathHash, $binaryCacheUrl) = @_;

    my $cacheId = getCacheId($binaryCacheUrl);

    # Look up $storePath in the SQLite cache.
    $queryNAR->execute($cacheId, basename($storePath));
    my $res = $queryNAR->fetchrow_hashref();
    return 
        { url => $res->{url}
        , compression => $res->{compression}
        , fileHash => $res->{fileHash}
        , fileSize => $res->{fileSize}
        , narHash => $res->{narHash}
        , narSize => $res->{narSize}
        , refs => [ split " ", $res->{refs} ]
        , deriver => $res->{deriver}
        } if defined $res;

    # Not found, so do an HTTP request to get the info.
    my $info = getInfoFrom($storePath, $pathHash, $binaryCacheUrl);

    # Cache the result.
    $insertNAR->execute(
        $cacheId, basename($storePath), $info->{url}, $info->{compression}, $info->{fileHash}, $info->{fileSize},
        $info->{narHash}, $info->{narSize}, join(" ", @{$info->{refs}}),
        $info->{deriver}, $info->{system}, time())
        if defined $info;
    
    return $info;
}


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

    my $pathHash = substr(basename($storePath), 0, 32);

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

    return undef;
}


sub downloadBinary {
    my ($storePath) = @_;
    
    my $pathHash = substr(basename($storePath), 0, 32);

    cache: foreach my $binaryCacheUrl (@binaryCacheUrls) {
        my $info = cachedGetInfoFrom($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 $storePath") != 0) {
                die "download of `$info->{url}' failed" . ($! ? ": $!" : "") . "\n" unless $? == 0;
                next;
            }
            # The hash in the manifest can be either in base-16 or
            # base-32.  Handle both.
            $info->{narHash} =~ /^sha256:(.*)$/ or die "invalid hash";
            my $hash = $1;
            my $hash2 = hashPath("sha256", 1, $storePath);
            die "hash mismatch in downloaded path ‘$storePath’; expected $hash, got $hash2\n"
                if $hash ne $hash2;
            return 1;
        }
    }

    return 0;
}


initCache();


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 $info->{deriver} ? "$Nix::Config::storeDir/$info->{deriver}" : "", "\n";
                print scalar @{$info->{refs}}, "\n";
                print "$Nix::Config::storeDir/$_\n" foreach @{$info->{refs}};
                print $info->{fileSize} || 0, "\n";
                print $info->{narSize} || 0, "\n";
            } else {
                print "0\n";
            }
        }

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

        flush STDOUT;
    }

}

elsif ($ARGV[0] eq "--substitute") {
    my $storePath = $ARGV[1] or die;
    if (!downloadBinary($storePath)) {
        print STDERR "could not download ‘$storePath’ from any binary cache\n";
    }
}

else {
    die;
}