#!/usr/bin/perl -w
# wrapper to dispatch git ssh service requests
#
# Copyright (C) 2015-2016  Ian Jackson
#
#    This program is free software; you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation; either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.

use strict;

use Debian::Dgit::Infra; # must precede Debian::Dgit; - can change @INC!
use Debian::Dgit;
setup_sigwarn();

use POSIX;

open DEBUG, '>/dev/null' or die $!;
if (@ARGV && $ARGV[0] eq '-D') {
    shift @ARGV;
    open DEBUG, '>&STDERR' or die $!;
}

die unless @ARGV>=1 && @ARGV<=2 && $ARGV[0] !~ m/^-/;
our ($dispatchdir,$authrune) = @ARGV;

$authrune //= join ':',
    '@/keyrings/debian-keyring.gpg,a',
    '@/keyrings/debian-maintainers.gpg,m@/dm.txt';

our $lre = $package_re;
our $qre = '["'."']?";

# $dispatchdir/distro=DISTRO should contain
#    dgit-live          a clone of dgit (only if not using installed vsns)
#    diverts
#    repos/             }  by virtue of
#    suites             }    dgit-repos-server's defaults relating to
#    policy-hook        }    dispatch-dir
# plus files required by the authrune (by default, keyrings/ and dm.txt)
#
# diverts should be list of
#  <pat> [<divert-to>]
# where <pat> is a package name pattern which may contain * or literals.
# <divert-to> is for `git config dgit-distro.DISTRO.diverts.<divert-to>'

our ($distro,$pkg, $d);
our ($dgitlive,$repos,$suites,$diverts,$policyhook,$repo);

sub checkdivert ($) {
    my ($df) = @_;
    if (!open DIV, '<', $df) {
	$!==ENOENT or die $!;
	return undef;
    } else {
	while (<DIV>) {
	    s/^\s+//; s/\s+$//;
	    next unless m/\S/;
	    next if m/^\#/;
	    my $divert;
	    if (s/\s+(\S+)$//) { $divert=$1; }
	    s/[^-+._0-9a-zA-Z*]/\\$&/g;
	    s/\*/.*/g;
	    printf DEBUG 'DISPATCH DIVERT ^%s$ %s'."\n",
	        $_, ($divert // '(undef)');
	    if ($pkg =~ m/^$_$/) { return $divert; }
	}
	DIV->error and die $!;
	close DIV;
	return undef;
    }
}
	
sub finish () {
    close STDOUT or die $!;
    exit 0;
}

sub prl ($) {
    print @_, "\n" or die $!;
}
	
sub selectpackage ($$;$) {
    my $divertfn;
    ($distro,$pkg, $divertfn) = @_; # $distro,$pkg must have sane syntax

    $d = "$dispatchdir/distro=$distro";

    if (!stat $d) {
	die $! unless $!==ENOENT;
	die "unknown distro ($distro)\n";
    }

    $dgitlive=    "$d/dgit-live";
    $repos=       "$d/repos";
    $suites=      "$d/suites";
    $policyhook=  "$d/policy-hook";

    $authrune =~ s/\@/$d/g;

    my $divert = checkdivert("$d/diverts");
    if (defined $divert) {
	$divertfn //= sub {
	    die "diverted to $divert incompletely or too late!\n";
	};
	$divertfn->($divert);
	die;
    }

    $repo = "$repos/$pkg.git";

    print DEBUG "DISPATCH DISTRO $distro PKG $pkg\n";
}

sub hasrepo () {
    if (stat $repo) {
	-d _ or die;
	return 1;
    } else {
	$!==ENOENT or die $!;
	return 0;
    }
}

sub serve_up ($) {
    my ($repo) = @_;
    exec qw(git upload-pack --strict --timeout=1000), $repo;
    die "exec git: $!";
}

sub dispatch () {
    local ($_) = $ENV{'SSH_ORIGINAL_COMMAND'} // '';

    if (m#^: dgit ($lre) git-check ($lre) ;#) {
	selectpackage $1,$2, sub { prl "divert @_"; finish; };
	prl hasrepo;
	finish;
    } elsif (
	m#^${qre}git-([-a-z]+) ${qre}/dgit/($lre)/repos/($lre)\.git${qre}$#
	) {
	my $cmd=$1;
	selectpackage $2,$3;
	if ($cmd eq 'receive-pack') {
	    $ENV{'PERLLIB'} //= '';
	    $ENV{'PERLLIB'} =~ s#^(?=.)#:#;
	    $ENV{'PERLLIB'} =~ s#^# $ENV{DGIT_TEST_INTREE} // $dgitlive #e;
	    my $s = "$dgitlive/infra/dgit-repos-server";
	    $s = "dgit-repos-server" if !stat_exists $s;
	    exec $s, $distro, $d, $authrune, qw(--ssh);
	    die "exec $s: $!";
	} elsif ($cmd eq 'upload-pack') {
	    $repo='$repos/_empty' unless hasrepo;
	    serve_up $repo;
	} else {
	    die "unsupported git operation $cmd ($_)";
	}
    } elsif (
 m#^${qre}git-upload-pack ${qre}/dgit/($lre)/(?:repos/)?_dgit-repos-server\.git${qre}$#
	) {
	my $distro= $1;
	# if running installed packages, source code should come
	# some other way
	serve_up("$dispatchdir/distro=$1/dgit-live/.git");
    } elsif (m#^${qre}git-upload-pack\s#) {
	die "unknown repo to serve ($_).  use dgit, or for server source ".
	    "git clone here:/dgit/DISTRO/repos/_dgit-repos-server.git";
    } else {
	die "unsupported operation ($_)";
    }
}

dispatch;
