#! @perl@ -w @perlFlags@

use strict;
use Nix::Config;
use Nix::Store;
use File::Temp qw(tempdir);


my $dryRun = 0;
my $verbose = 0;
my $runEnv = 0;

my @instArgs = ();
my @buildArgs = ();
my @exprs = ();

my $shell = $ENV{SHELL} || "/bin/sh";
my $envCommand = "p=\$PATH; source \$stdenv/setup; PATH=\$PATH:\$p; exec $shell";
my @envExclude = ();


my $tmpDir = tempdir("nix-build.XXXXXX", CLEANUP => 1, TMPDIR => 1)
    or die "cannot create a temporary directory";

my $outLink = "./result";
my $drvLink = "$tmpDir/derivation";

# Ensure that the $tmpDir is deleted.
$SIG{'INT'} = sub { exit 1 };


for (my $n = 0; $n < scalar @ARGV; $n++) {
    my $arg = $ARGV[$n];

    if ($arg eq "--help") {
        print STDERR <<EOF;
Usage: nix-build [OPTION]... [FILE]...

`nix-build' builds the given Nix expressions (which
default to ./default.nix if none are given).  A symlink called
`result' is placed in the current directory.

Flags:
  --add-drv-link: create a symlink `derivation' to the store derivation
  --drv-link NAME: create symlink NAME instead of `derivation'
  --no-out-link: do not create the `result' symlink
  --out-link / -o NAME: create symlink NAME instead of `result'
  --attr / -A ATTR: select a specific attribute from the Nix expression
  
  --run-env: build dependencies of the specified derivation, then start a
      shell with the environment of the derivation
  --command: command to run with `--run-env'
  --exclude: regexp specifying dependencies to be excluded by `--run-env'

Any additional flags are passed to `nix-store'.
EOF
        exit 0;
        # '` hack
    }

    elsif ($arg eq "--add-drv-link") {
        $drvLink = "./derivation";
    }

    elsif ($arg eq "--no-out-link" or $arg eq "--no-link") {
        $outLink = "$tmpDir/result";
    }

    elsif ($arg eq "--drv-link") {
        $n++;
        die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;
        $drvLink = $ARGV[$n];
    }

    elsif ($arg eq "--out-link" or $arg eq "-o") {
        $n++;
        die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;
        $outLink = $ARGV[$n];
    }

    elsif ($arg eq "--attr" or $arg eq "-A" or $arg eq "-I") {
        $n++;
        die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;
        push @instArgs, ($arg, $ARGV[$n]);
    }

    elsif ($arg eq "--arg" || $arg eq "--argstr") {
        die "$0: `$arg' requires two arguments\n" unless $n + 2 < scalar @ARGV;
        push @instArgs, ($arg, $ARGV[$n + 1], $ARGV[$n + 2]);
        $n += 2;
    }

    elsif ($arg eq "--log-type") {
        $n++;
        die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;
        push @instArgs, ($arg, $ARGV[$n]);
        push @buildArgs, ($arg, $ARGV[$n]);
    }

    elsif ($arg eq "--option") {
        die "$0: `$arg' requires two arguments\n" unless $n + 2 < scalar @ARGV;
        push @instArgs, ($arg, $ARGV[$n + 1], $ARGV[$n + 2]);
        push @buildArgs, ($arg, $ARGV[$n + 1], $ARGV[$n + 2]);
        $n += 2;
    }

    elsif ($arg eq "--max-jobs" or $arg eq "-j" or $arg eq "--max-silent-time" or $arg eq "--log-type" or $arg eq "--cores") {
        $n++;
        die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;
        push @buildArgs, ($arg, $ARGV[$n]);
    }

    elsif ($arg eq "--dry-run") {
        push @buildArgs, "--dry-run";
        $dryRun = 1;
    }
    
    elsif ($arg eq "--show-trace") {
        push @instArgs, $arg;
    }

    elsif ($arg eq "-") {
        @exprs = ("-");
    }
    
    elsif ($arg eq "--verbose" or substr($arg, 0, 2) eq "-v") {
        push @buildArgs, $arg;
        push @instArgs, $arg;
        $verbose = 1;
    }
    
    elsif ($arg eq "--quiet") {
        push @buildArgs, $arg;
        push @instArgs, $arg;
    }
    
    elsif ($arg eq "--run-env") {
        $runEnv = 1;
    }
    
    elsif ($arg eq "--command") {
        $n++;
        die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;
        $envCommand = $ARGV[$n];
    }

    elsif ($arg eq "--exclude") {
        $n++;
        die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;
        push @envExclude, $ARGV[$n];
    }

    elsif (substr($arg, 0, 1) eq "-") {
        push @buildArgs, $arg;
    }

    else {
        push @exprs, $arg;
    }
}

@exprs = ("./default.nix") if scalar @exprs == 0;


foreach my $expr (@exprs) {

    # Instantiate.
    my @drvPaths;
    # !!! would prefer the perl 5.8.0 pipe open feature here.
    my $pid = open(DRVPATHS, "-|") || exec "$Nix::Config::binDir/nix-instantiate", "--add-root", $drvLink, "--indirect", @instArgs, $expr;
    while (<DRVPATHS>) {chomp; push @drvPaths, $_;}
    if (!close DRVPATHS) {
        die "nix-instantiate killed by signal " . ($? & 127) . "\n" if ($? & 127);
        exit 1;
    }

    if ($runEnv) {
        die "$0: ‘--run-env’ requires a single derivation\n" if scalar @drvPaths != 1;
        my $drvPath = readlink $drvPaths[0] or die "cannot read symlink `$drvPaths[0]'";
        my $drv = derivationFromPath($drvPath);

        # Build or fetch all dependencies of the derivation.
        my @inputDrvs = grep { my $x = $_; (grep { $x =~ $_ } @envExclude) == 0 } @{$drv->{inputDrvs}};
        system("$Nix::Config::binDir/nix-store -r @buildArgs @inputDrvs @{$drv->{inputSrcs}} > /dev/null") == 0
            or die "$0: failed to build all dependencies\n";

        # Set the environment.
        $ENV{'NIX_BUILD_TOP'} = $ENV{'TMPDIR'} || "/tmp";
        foreach (keys %{$drv->{env}}) {
            $ENV{$_} = $drv->{env}->{$_};
        }

        # Run a shell using the derivation's environment.  For
        # convenience, source $stdenv/setup to setup additional
        # environment variables.  Also don't lose the current $PATH
        # directories.
        exec($ENV{SHELL}, "-c", $envCommand);
        die;
    }

    foreach my $drvPath (@drvPaths) {
        my $target = readlink $drvPath or die "cannot read symlink `$drvPath'";
        print STDERR "derivation is $target\n" if $verbose;
    }

    # Build.
    my @outPaths;
    $pid = open(OUTPATHS, "-|") || exec "$Nix::Config::binDir/nix-store", "--add-root", $outLink, "--indirect", "-r",
        @buildArgs, @drvPaths;
    while (<OUTPATHS>) {chomp; push @outPaths, $_;}
    if (!close OUTPATHS) {
        die "nix-store killed by signal " . ($? & 127) . "\n" if ($? & 127);
        exit 1;
    }

    next if $dryRun;

    foreach my $outPath (@outPaths) {
        my $target = readlink $outPath or die "cannot read symlink `$outPath'";
        print "$target\n";
    }
}