#! @perl@ -w @perlFlags@

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


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

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


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 ATTR: select a specific attribution from the Nix expression

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 ($arg eq "--verbose" or substr($arg, 0, 2) eq "-v") {
        push @buildArgs, $arg;
        push @instArgs, $arg;
        $verbose = 1;
    }
    
    elsif ($arg eq "--quiet") {
        push @buildArgs, $arg;
        push @instArgs, $arg;
    }
    
    elsif (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;
    }

    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";
    }
}