#! @perl@ -w

use strict;
use XML::Simple;
use Hydra::Schema;
use IPC::Run;
use POSIX qw(strftime);


my $db = Hydra::Schema->connect("dbi:SQLite:dbname=hydra.sqlite", "", "", {});

$db->storage->dbh->do("PRAGMA synchronous = OFF;");


sub isValidPath {
    my $path = shift;
    return system("nix-store --check-validity $path 2> /dev/null") == 0;
}


sub captureStdoutStderr {
    my $stdin = ""; my $stdout; my $stderr;
    my $res = IPC::Run::run(\@_, \$stdin, \$stdout, \$stderr);
    return ($res, $stdout, $stderr);
}

    
sub getStorePathHash {
    my ($storePath) = @_;
    my $hash = `nix-store --query --hash $storePath`
        or die "cannot get hash of $storePath";
    chomp $hash;
    die unless $hash =~ /^sha256:(.*)$/;
    $hash = $1;
    $hash = `nix-hash --to-base16 --type sha256 $hash`
        or die "cannot convert hash";
    chomp $hash;
    return $hash;    
}


sub fetchInput {
    my ($input, $alt, $inputInfo) = @_;
    my $type = $input->type;

    if ($type eq "path") {
        my $uri = $alt->value;

        my $timestamp = time;
        my $sha256;
        my $storePath;

        # Some simple caching: don't check a path more than once every N seconds.
        (my $cachedInput) = $db->resultset('Cachedpathinputs')->search(
            {srcpath => $uri, lastseen => {">", $timestamp - 60}},
            {rows => 1, order_by => "lastseen DESC"});

        if (defined $cachedInput && isValidPath($cachedInput->storepath)) {
            $storePath = $cachedInput->storepath;
            $sha256 = $cachedInput->sha256hash;
            $timestamp = $cachedInput->timestamp;
        } else {

            print "copying input ", $input->name, " from $uri\n";
            $storePath = `nix-store --add "$uri"`
                or die "cannot copy path $uri to the Nix store";
            chomp $storePath;

            $sha256 = getStorePathHash $storePath;

            ($cachedInput) = $db->resultset('Cachedpathinputs')->search(
                {srcpath => $uri, sha256hash => $sha256});

            # Path inputs don't have a natural notion of a "revision",
            # so we simulate it by using the timestamp that we first
            # saw this path have this SHA-256 hash.  So if the
            # contents of the path changes, we get a new "revision",
            # but if it doesn't change (or changes back), we don't get
            # a new "revision".
            if (!defined $cachedInput) {
                $db->txn_do(sub {
                    $db->resultset('Cachedpathinputs')->create(
                        { srcpath => $uri
                        , timestamp => $timestamp
                        , lastseen => $timestamp
                        , sha256hash => $sha256
                        , storepath => $storePath
                        });
                });
            } else {
                $timestamp = $cachedInput->timestamp;
                $db->txn_do(sub {
                    $cachedInput->lastseen(time);
                    $cachedInput->update;
                });
            }
        }

        $$inputInfo{$input->name} =
            { type => $type
            , uri => $uri
            , storePath => $storePath
            , sha256hash => $sha256
            , revision => strftime "%Y%m%d%H%M%S", gmtime($timestamp)
            };
    }

    elsif ($type eq "svn") {
        my $uri = $alt->value;

        my $sha256;
        my $storePath;

        # First figure out the last-modified revision of the URI.
        my @cmd = (["svn", "ls", "-v", "--depth", "empty", $uri],
                   "|", ["sed", 's/^ *\([0-9]*\).*/\1/']);
        my $stdout; my $stderr;
        die "cannot get head revision of Subversion repository at `$uri':\n$stderr"
            unless IPC::Run::run(@cmd, \$stdout, \$stderr);
        my $revision = $stdout; chomp $revision;
        die unless $revision =~ /^\d+$/;

        (my $cachedInput) = $db->resultset('Cachedsubversioninputs')->search(
            {uri => $uri, revision => $revision});

        if (defined $cachedInput && isValidPath($cachedInput->storepath)) {
            $storePath = $cachedInput->storepath;
            $sha256 = $cachedInput->sha256hash;
        } else {
            
            # Then download this revision into the store.
            print "checking out Subversion input ", $input->name, " from $uri revision $revision\n";
            $ENV{"NIX_HASH_ALGO"} = "sha256";
            $ENV{"PRINT_PATH"} = "1";
            (my $res, $stdout, $stderr) = captureStdoutStderr(
                "nix-prefetch-svn", $uri, $revision);
            die "cannot check out Subversion repository `$uri':\n$stderr" unless $res;

            ($sha256, $storePath) = split ' ', $stdout;

            $db->txn_do(sub {
                $db->resultset('Cachedsubversioninputs')->create(
                    { uri => $uri
                    , revision => $revision
                    , sha256hash => $sha256
                    , storepath => $storePath
                    });
            });
        }
        
        $$inputInfo{$input->name} =
            { type => $type
            , uri => $uri
            , storePath => $storePath
            , sha256hash => $sha256
            , revision => $revision
            };
    }
    
    elsif ($type eq "string") {
        die unless defined $alt->value;
        $$inputInfo{$input->name} = {type => $type, value => $alt->value};
    }
    
    else {
        die "input `" . $input->name . "' has unknown type `$type'";
    }
}


sub checkJob {
    my ($project, $jobset, $inputInfo, $nixExprPath, $jobName, $jobExpr, $extraArgs) = @_;
    
    # Instantiate the store derivation.
    (my $res, my $drvPath, my $stderr) = captureStdoutStderr(
        "nix-instantiate", $nixExprPath, "--attr", $jobName, @{$extraArgs});
    die "cannot evaluate the Nix expression for job `$jobName':\n$stderr" unless $res;
    chomp $drvPath;

    # Call nix-env --xml to get info about this job (drvPath, outPath, meta attributes, ...). 
    ($res, my $infoXml, $stderr) = captureStdoutStderr(
        qw(nix-env --query --available * --attr-path --out-path --drv-path --meta --xml --system-filter *),
        "-f", $nixExprPath, "--attr", $jobName, @{$extraArgs});
    die "cannot get information about the job `$jobName':\n$stderr" unless $res;

    my $info = XMLin($infoXml, ForceArray => 1, KeyAttr => ['attrPath', 'name'])
        or die "cannot parse XML output";

    my $job = $info->{item}->{$jobName};
    die if !defined $job;
        
    my $description = defined $job->{meta}->{description} ? $job->{meta}->{description}->{value} : "";
    die unless $job->{drvPath} eq $drvPath;
    my $outPath = $job->{outPath};

    $db->txn_do(sub {
        if (scalar($db->resultset('Builds')->search(
                { project => $project->name, jobset => $jobset->name
                , attrname => $jobName, outPath => $outPath })) > 0)
        {
            print "already scheduled/done\n";
            return;
        }

        print "adding to queue\n";
        
        my $build = $db->resultset('Builds')->create(
            { finished => 0
            , timestamp => time()
            , project => $project->name
            , jobset => $jobset->name
            , attrname => $jobName
            , description => $description
            , nixname => $job->{name}
            , drvpath => $drvPath
            , outpath => $outPath
            , system => $job->{system}
            });

        $db->resultset('Buildschedulinginfo')->create(
            { id => $build->id
            , priority => 0
            , busy => 0
            , locker => ""
            });

        foreach my $inputName (keys %{$inputInfo}) {
            my $input = $inputInfo->{$inputName};
            $db->resultset('Buildinputs')->create(
                { build => $build->id
                , name => $inputName
                , type => $input->{type}
                , uri => $input->{uri}
                , revision => $input->{revision}
                , value => $input->{value}
                , dependency => $input->{id}
                , path => ($input->{storePath} or "") # !!! temporary hack
                , sha256hash => $input->{sha256hash}
                });
        }
    });
};


sub setJobsetError {
    my ($jobset, $errorMsg) = @_;
    eval {
        $db->txn_do(sub {
            $jobset->errormsg($errorMsg);
            $jobset->errortime(time);
            $jobset->update;
        });
    };
}


sub checkJobAlternatives {
    my ($project, $jobset, $inputInfo, $nixExprPath, $jobName, $jobExpr, $extraArgs, $argsNeeded, $n) = @_;

    if ($n >= scalar @{$argsNeeded}) {
        eval {
            checkJob($project, $jobset, $inputInfo, $nixExprPath, $jobName, $jobExpr, $extraArgs);
        };
        if ($@) {
            print "error evaluating job `", $jobName, "': $@";
            setJobsetError($jobset, $@);
        }
        return;
    }

    my $argName = @{$argsNeeded}[$n];
    #print "finding alternatives for argument $argName\n";

    my ($input) = $jobset->jobsetinputs->search({name => $argName});

    my %newInputInfo = %{$inputInfo}; $inputInfo = \%newInputInfo; # clone

    if (defined $input) {
        
        foreach my $alt ($input->jobsetinputalts) {
            #print "input ", $input->name, " (type ", $input->type, ") alt ", $alt->altnr, "\n";
            fetchInput($input, $alt, $inputInfo);
            my @newArgs = @{$extraArgs};
            if (defined $inputInfo->{$argName}->{storePath}) {
                push @newArgs, "--arg", $argName,
                    "{path = builtins.storePath " . $inputInfo->{$argName}->{storePath} . ";" .
                    " rev = \"" . $inputInfo->{$argName}->{revision} . "\";}";
            } elsif (defined $inputInfo->{$argName}->{value}) {
                push @newArgs, "--argstr", $argName, $inputInfo->{$argName}->{value};
            }
            checkJobAlternatives(
                $project, $jobset, $inputInfo, $nixExprPath,
                $jobName, $jobExpr, \@newArgs, $argsNeeded, $n + 1);
        }
    }

    else {

        (my $prevBuild) = $db->resultset('Builds')->search(
            {finished => 1, project => $project->name, jobset => $jobset->name, attrname => $argName, buildStatus => 0},
            {join => 'resultInfo', order_by => "timestamp DESC", rows => 1});

        if (!defined $prevBuild) {
            # !!! reschedule?
            die "missing input `$argName'";
        }

        # The argument name matches a previously built job in this
        # jobset.  Pick the most recent build.  !!! refine the
        # selection criteria: e.g., most recent successful build.
        if (!isValidPath($prevBuild->outpath)) {
            die "input path " . $prevBuild->outpath . " has been garbage-collected";
        }
                    
        $$inputInfo{$argName} =
            { type => "build"
            , storePath => $prevBuild->outpath
            , id => $prevBuild->id
            };

        my @newArgs = @{$extraArgs};
        push @newArgs, "--arg", $argName, "{path = builtins.storePath " . $prevBuild->outpath . ";}";
        
        checkJobAlternatives(
            $project, $jobset, $inputInfo, $nixExprPath,
            $jobName, $jobExpr, \@newArgs, $argsNeeded, $n + 1);
    }
}


sub checkJobSet {
    my ($project, $jobset) = @_;
    my $inputInfo = {};

    # Fetch the input containing the Nix expression.
    (my $exprInput) = $jobset->jobsetinputs->search({name => $jobset->nixexprinput});
    die unless defined $exprInput;

    die "not supported yet" if scalar($exprInput->jobsetinputalts) != 1;

    fetchInput($exprInput, $exprInput->jobsetinputalts->first, $inputInfo);

    # Evaluate the Nix expression.
    my $nixExprPath = $inputInfo->{$jobset->nixexprinput}->{storePath} . "/" . $jobset->nixexprpath;

    print "evaluating $nixExprPath\n";

    (my $res, my $jobsXml, my $stderr) = captureStdoutStderr(
        "nix-instantiate", $nixExprPath, "--eval-only", "--strict", "--xml");
    die "cannot evaluate the Nix expression containing the jobs:\n$stderr" unless $res;

    my $jobs = XMLin($jobsXml,
                     ForceArray => ['value', 'attr'],
                     KeyAttr => ['name'],
                     SuppressEmpty => '',
                     ValueAttr => [value => 'value'])
        or die "cannot parse XML output";

    die unless defined $jobs->{attrs};

    # Iterate over the attributes listed in the Nix expression and
    # perform the builds described by them.  If an attribute is a
    # function, then fill in the function arguments with the
    # (alternative) values supplied in the jobsetinputs table.
    foreach my $jobName (keys(%{$jobs->{attrs}->{attr}})) {
        print "considering job $jobName\n";

        my @argsNeeded = ();
        
        my $jobExpr = $jobs->{attrs}->{attr}->{$jobName};

        # !!! fix the case where there is only 1 attr, XML::Simple fucks up as usual
        if (defined $jobExpr->{function}->{attrspat}) {
            foreach my $argName (keys(%{$jobExpr->{function}->{attrspat}->{attr}})) {
                #print "needs input $argName\n";
                push @argsNeeded, $argName;
            }            
        }

        eval {
            checkJobAlternatives(
                $project, $jobset, {}, $nixExprPath,
                $jobName, $jobExpr, [], \@argsNeeded, 0);
        };
        warn $@ if $@;
    }
}


sub checkJobs {

    foreach my $project ($db->resultset('Projects')->search({enabled => 1})) {
        print "considering project ", $project->name, "\n";
        foreach my $jobset ($project->jobsets->all) {
            print "considering jobset ", $jobset->name, " in ", $project->name, "\n";
            eval {
                checkJobSet($project, $jobset);
            };
            if ($@) {
                print "error evaluating jobset ", $jobset->name, ": $@";
                setJobsetError($jobset, $@);
            }
        }
    }
    
}


while (1) {
    checkJobs;
    print "sleeping...\n";
    sleep 10;
}