#! @perl@ -w @perlFlags@

use utf8;
use strict;
use Nix::Config;
use Nix::Store;
use Nix::Utils;
use File::Basename;
use Cwd;

binmode STDERR, ":encoding(utf8)";

my $dryRun = 0;
my $verbose = 0;
my $runEnv = $0 =~ /nix-shell$/;
my $pure = 0;
my $fromArgs = 0;
my $packages = 0;

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

my $shell = $ENV{SHELL} || "/bin/sh";
my $envCommand = ""; # interactive shell
my @envExclude = ();

my $myName = $runEnv ? "nix-shell" : "nix-build";

my $inShebang = 0;
my $script;

my $tmpDir = mkTempDir($myName);

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

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


# Heuristic to see if we're invoked as a shebang script, namely, if we
# have a single argument, it's the name of an executable file, and it
# starts with "#!".
if ($runEnv && scalar @ARGV == 1) {
    $script = $ARGV[0];
    if (-f $script && -x $script) {
        open SCRIPT, "<$script" or die "$0: cannot open ‘$script’: $!\n";
        my $first = <SCRIPT>;
        if ($first =~ /^\#\!/) {
            $inShebang = 1;
            @ARGV = ();
            while (<SCRIPT>) {
                chomp;
                if (/^\#\!\s*nix-shell (.*)$/) {
                    @ARGV = split / /, $1;
                }
            }
        }
        close SCRIPT;
    }
}


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

    if ($arg eq "--help") {
        exec "man $myName" or die;
    }

    elsif ($arg eq "--version") {
        print "$myName (Nix) $Nix::Config::version\n";
        exit 0;
    }

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

    elsif ($arg eq "--no-out-link" || $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" || $arg eq "-o") {
        $n++;
        die "$0: ‘$arg’ requires an argument\n" unless $n < scalar @ARGV;
        $outLink = $ARGV[$n];
    }

    elsif ($arg eq "--attr" || $arg eq "-A" || $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" || $arg eq "-j" || $arg eq "--max-silent-time" || $arg eq "--log-type" || $arg eq "--cores" || $arg eq "--timeout" || $arg eq '--add-root') {
        $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 ($arg eq "--verbose" || substr($arg, 0, 2) eq "-v") {
        push @buildArgs, $arg;
        push @instArgs, $arg;
        $verbose = 1;
    }

    elsif ($arg eq "--quiet" || $arg eq "--repair") {
        push @buildArgs, $arg;
        push @instArgs, $arg;
    }

    elsif ($arg eq "--check") {
        push @buildArgs, $arg;
    }

    elsif ($arg eq "--run-env") { # obsolete
        $runEnv = 1;
    }

    elsif ($arg eq "--command") {
        $n++;
        die "$0: ‘$arg’ requires an argument\n" unless $n < scalar @ARGV;
        $envCommand = "$ARGV[$n]\nexit";
    }

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

    elsif ($arg eq "--pure") { $pure = 1; }
    elsif ($arg eq "--impure") { $pure = 0; }

    elsif ($arg eq "--expr" || $arg eq "-E") {
        $fromArgs = 1;
        push @instArgs, "--expr";
    }

    elsif ($arg eq "--packages" || $arg eq "-p") {
        $packages = 1;
    }

    elsif ($inShebang && $arg eq "-i") {
        $n++;
        die "$0: ‘$arg’ requires an argument\n" unless $n < scalar @ARGV;
        my $interpreter = $ARGV[$n];
        # Überhack to support Perl. Perl examines the shebang and
        # executes it unless it contains the string "perl" or "indir",
        # or (undocumented) argv[0] does not contain "perl". Exploit
        # the latter by doing "exec -a".
        my $execArgs = $interpreter =~ /perl/ ? "-a PERL" : "";
        $envCommand = "exec $execArgs $interpreter $script";
    }

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

    else {
        push @exprs, $arg;
    }
}

if ($packages) {
    push @instArgs, "--expr";
    @exprs = (
        'with import <nixpkgs> { }; runCommand "shell" { buildInputs = [ '
        . (join " ", map { "($_)" } @exprs) . ']; } ""');
} elsif (!$fromArgs) {
    @exprs = ("shell.nix") if scalar @exprs == 0 && $runEnv && -e "shell.nix";
    @exprs = ("default.nix") if scalar @exprs == 0;
}

$ENV{'IN_NIX_SHELL'} = 1 if $runEnv;


foreach my $expr (@exprs) {

    # Instantiate.
    my @drvPaths;
    if ($expr !~ /^\/.*\.drv$/) {
        # If we're in a #! script, interpret filenames relative to the
        # script.
        $expr = dirname(Cwd::abs_path($script)) . "/" . $expr
            if $inShebang && $expr !~ /^\//;

        # !!! 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;
        }
    } else {
        push @drvPaths, $expr;
    }

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

        # Build or fetch all dependencies of the derivation.
        my @inputDrvs = grep { my $x = $_; (grep { $x =~ $_ } @envExclude) == 0 } @{$drv->{inputDrvs}};
        system("$Nix::Config::binDir/nix-store", "-r", "--no-output", "--no-gc-warning", @buildArgs, @inputDrvs, @{$drv->{inputSrcs}}) == 0
            or die "$0: failed to build all dependencies\n";

        # Set the environment.
        my $tmp = $ENV{"TMPDIR"} // $ENV{"XDG_RUNTIME_DIR"} // "/tmp";
        if ($pure) {
            foreach my $name (keys %ENV) {
                next if grep { $_ eq $name } ("HOME", "USER", "LOGNAME", "DISPLAY", "PATH", "TERM", "IN_NIX_SHELL", "TZ", "PAGER");
                delete $ENV{$name};
            }
            # NixOS hack: prevent /etc/bashrc from sourcing /etc/profile.
            $ENV{'__ETC_PROFILE_SOURCED'} = 1;
        }
        $ENV{'NIX_BUILD_TOP'} = $ENV{'TMPDIR'} = $ENV{'TEMPDIR'} = $ENV{'TMP'} = $ENV{'TEMP'} = $tmp;
        $ENV{'NIX_STORE'} = $Nix::Config::storeDir;
        $ENV{$_} = $drv->{env}->{$_} foreach keys %{$drv->{env}};

        # Run a shell using the derivation's environment.  For
        # convenience, source $stdenv/setup to setup additional
        # environment variables and shell functions.  Also don't lose
        # the current $PATH directories.
        my $rcfile = "$tmpDir/rc";
        writeFile(
            $rcfile,
            "rm -rf '$tmpDir'; " .
            'unset BASH_ENV; ' .
            '[ -n "$PS1" ] && [ -e ~/.bashrc ] && source ~/.bashrc; ' .
            ($pure ? '' : 'p=$PATH; ' ) .
            'dontAddDisableDepTrack=1; ' .
            '[ -e $stdenv/setup ] && source $stdenv/setup; ' .
            'if [ "$(type -t runHook)" = function ]; then runHook shellHook; fi; ' .
            ($pure ? '' : 'PATH=$PATH:$p; unset p; ') .
            'set +e; ' .
            '[ -n "$PS1" ] && PS1="\n\[\033[1;32m\][nix-shell:\w]$\[\033[0m\] "; ' .
            'unset NIX_ENFORCE_PURITY; ' .
            'unset NIX_INDENT_MAKE; ' .
            'shopt -u nullglob; ' .
            'unset TZ; ' . (defined $ENV{'TZ'} ? "export TZ='${ENV{'TZ'}}'; " : '') .
            $envCommand);
        $ENV{BASH_ENV} = $rcfile;
        exec($ENV{NIX_BUILD_SHELL} // "bash", "--rcfile", $rcfile);
        die;
    }

    # Ugly hackery to make "nix-build -A foo.all" produce symlinks
    # ./result, ./result-dev, and so on, rather than ./result,
    # ./result-2-dev, and so on.  This combines multiple derivation
    # paths into one "/nix/store/drv-path!out1,out2,..." argument.
    my $prevDrvPath = "";
    my @drvPaths2;
    foreach my $drvPath (@drvPaths) {
        my $p = $drvPath; my $output = "out";
        if ($drvPath =~ /(.*)!(.*)/) {
            $p = $1; $output = $2;
        } else {
            $p = $drvPath;
        }
        my $target = readlink $p or die "cannot read symlink ‘$p’";
        print STDERR "derivation is $target\n" if $verbose;
        if ($target eq $prevDrvPath) {
            push @drvPaths2, (pop @drvPaths2) . "," . $output;
        } else {
            push @drvPaths2, $target . "!" . $output;
            $prevDrvPath = $target;
        }
    }

    # Build.
    my @outPaths;
    my $pid = open(OUTPATHS, "-|") || exec "$Nix::Config::binDir/nix-store", "--add-root", $outLink, "--indirect", "-r",
        @buildArgs, @drvPaths2;
    while (<OUTPATHS>) {chomp; push @outPaths, $_;}
    if (!close OUTPATHS) {
        die "nix-store killed by signal " . ($? & 127) . "\n" if ($? & 127);
        exit ($? >> 8 || 1);
    }

    next if $dryRun;

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