#!/usr/bin/env python

# This program makes Debian and RPM repositories for MongoDB, by
# downloading our tarballs of statically linked executables and
# insinuating them into Linux packages.  It must be run on a
# Debianoid, since Debian provides tools to make RPMs, but RPM-based
# systems don't provide debian packaging crud.

# Notes:
#
# * Almost anything that you want to be able to influence about how a
# package construction must be embedded in some file that the
# packaging tool uses for input (e.g., debian/rules, debian/control,
# debian/changelog; or the RPM specfile), and the precise details are
# arbitrary and silly.  So this program generates all the relevant
# inputs to the packaging tools.
#
# * Once a .deb or .rpm package is made, there's a separate layer of
# tools that makes a "repository" for use by the apt/yum layers of
# package tools.  The layouts of these repositories are arbitrary and
# silly, too.
#
# * Before you run the program on a new host, these are the
# prerequisites:
#
# apt-get install dpkg-dev rpm debhelper fakeroot ia32-libs createrepo git-core
# echo "Now put the dist gnupg signing keys in ~root/.gnupg"

import argparse
import errno
from glob import glob
import os
import re
import shutil
import subprocess
import sys
import tempfile
import time

# The MongoDB names for the architectures we support.
ARCH_CHOICES=["x86_64", "arm64"]

# Made up names for the flavors of distribution we package for.
DISTROS=["suse", "debian","redhat","ubuntu", "amazon"]


class Spec(object):
    def __init__(self, ver, gitspec = None, rel = None):
        self.ver = ver
        self.gitspec = gitspec
        self.rel = rel

    # Commit-triggerd version numbers can be in the form: 3.0.7-pre-, or 3.0.7-5-g3b67ac
    # Patch builds version numbers are in the form: 3.5.5-64-g03945fa-patch-58debcdb3ff1223c9d00005b
    #
    def is_nightly(self):
        return bool(re.search("-$", self.version())) or bool(re.search("\d-\d+-g[0-9a-f]+$", self.version()))

    def is_patch(self):
        return bool(re.search("\d-\d+-g[0-9a-f]+-patch-[0-9a-f]+$", self.version()))

    def is_rc(self):
        return bool(re.search("-rc\d+$", self.version()))

    def is_pre_release(self):
        return self.is_rc() or self.is_nightly()

    def version(self):
        return self.ver

    def patch_id(self):
        if self.is_patch():
            return re.sub(r'.*-([0-9a-f]+$)', r'\1', self.version())
        else:
            return "none"

    def metadata_gitspec(self):
        """Git revision to use for spec+control+init+manpage files.
           The default is the release tag for the version being packaged."""
        if(self.gitspec):
          return self.gitspec
        else:
          return 'r' + self.version()

    def version_better_than(self, version_string):
        # FIXME: this is wrong, but I'm in a hurry.
        # e.g., "1.8.2" < "1.8.10", "1.8.2" < "1.8.2-rc1"
        return self.ver > version_string

    def suffix(self):
        return "-org" if int(self.ver.split(".")[1])%2==0 else "-org-unstable"

    def prelease(self):
      # NOTE: This is only called for RPM packages, and only after
      # pversion() below has been called. If you want to change this format
      # and want DEB packages to match, make sure to update pversion()
      # below
      #
      # "N" is either passed in on the command line, or "1"
      if self.rel:
          corenum = self.rel
      else:
          corenum = 1

      # Version suffix for RPM packages:
      # 1) RC's - "0.N.rcX"
      # 2) Nightly (snapshot) - "0.N.latest"
      # 3) Patch builds - "0.N.patch.<patch_id>"
      # 4) Standard release - "N"
      if self.is_rc():
          return "0.%s.%s" % (corenum, re.sub('.*-','',self.version()))
      elif self.is_nightly():
          return "0.%s.latest" % (corenum)
      elif self.is_patch():
          return "0.%s.patch.%s" % (corenum, self.patch_id())
      else:
          return str(corenum)

    def pversion(self, distro):
        # Note: Debian packages have funny rules about dashes in
        # version numbers, and RPM simply forbids dashes.  pversion
        # will be the package's version number (but we need to know
        # our upstream version too).

        # For RPM packages this just returns X.Y.X because of the
        # aforementioned rules, and prelease (above) adds a suffix later,
        # so detect this case early
        if re.search("(suse|redhat|fedora|centos|amazon)", distro.name()):
            return re.sub("-.*", "", self.version())

        # For DEB packages, this code sets the full version. If you change
        # this format and want RPM packages to match make sure you change
        # prelease above as well
        if re.search("^(debian|ubuntu)", distro.name()):
            if self.is_nightly():
                ver = re.sub("-.*", "-latest", self.ver)
            elif self.is_patch():
                ver = re.sub("-.*", "", self.ver) + "-patch-" + self.patch_id()
            else:
                ver = self.ver

            return re.sub("-", "~", ver)

        raise Exception("BUG: unsupported platform?")

    def branch(self):
        """Return the major and minor portions of the specified version.
        For example, if the version is "2.5.5" the branch would be "2.5"
        """
        return ".".join(self.ver.split(".")[0:2])

class Distro(object):
    def __init__(self, string):
        self.n=string

    def name(self):
        return self.n

    def pkgbase(self):
        return "mongodb"

    def archname(self, arch):
        """Return the packaging system's architecture name.
        Power and x86 have different names for apt/yum (ppc64le/ppc64el
        and x86_64/amd64)
        """
        if re.search("^(debian|ubuntu)", self.n):
            if arch == "ppc64le":
                return "ppc64el"
            elif arch == "s390x":
                return "s390x"
            elif arch == "arm64":
                return "arm64"
            elif arch.endswith("86"):
              return "i386"
            else:
              return "amd64"
        elif re.search("^(suse|centos|redhat|fedora|amazon)", self.n):
            if arch == "ppc64le":
                return "ppc64le"
            elif arch == "s390x":
                return "s390x"
            elif arch.endswith("86"):
              return "i686"
            else:
              return "x86_64"
        else:
            raise Exception("BUG: unsupported platform?")

    def repodir(self, arch, build_os, spec):
        """Return the directory where we'll place the package files for
        (distro, distro_version) in that distro's preferred repository
        layout (as distinct from where that distro's packaging building
        tools place the package files).

        Examples:

        repo/apt/ubuntu/dists/precise/mongodb-org/2.5/multiverse/binary-amd64
        repo/apt/ubuntu/dists/precise/mongodb-org/2.5/multiverse/binary-i386

        repo/apt/ubuntu/dists/trusty/mongodb-org/2.5/multiverse/binary-amd64
        repo/apt/ubuntu/dists/trusty/mongodb-org/2.5/multiverse/binary-i386

        repo/apt/debian/dists/wheezy/mongodb-org/2.5/main/binary-amd64
        repo/apt/debian/dists/wheezy/mongodb-org/2.5/main/binary-i386

        repo/yum/redhat/6/mongodb-org/2.5/x86_64
        yum/redhat/6/mongodb-org/2.5/i386

        repo/zypper/suse/11/mongodb-org/2.5/x86_64
        zypper/suse/11/mongodb-org/2.5/i386

        """

        repo_directory = ""

        if spec.is_pre_release():
          repo_directory = "testing"
        else:
          repo_directory = spec.branch()

        if re.search("^(debian|ubuntu)", self.n):
            return "repo/apt/%s/dists/%s/mongodb-org/%s/%s/binary-%s/" % (self.n, self.repo_os_version(build_os), repo_directory, self.repo_component(), self.archname(arch))
        elif re.search("(redhat|fedora|centos|amazon)", self.n):
            return "repo/yum/%s/%s/mongodb-org/%s/%s/RPMS/" % (self.n, self.repo_os_version(build_os), repo_directory, self.archname(arch))
        elif re.search("(suse)", self.n):
            return "repo/zypper/%s/%s/mongodb-org/%s/%s/RPMS/" % (self.n, self.repo_os_version(build_os), repo_directory, self.archname(arch))
        else:
            raise Exception("BUG: unsupported platform?")

    def repo_component(self):
        """Return the name of the section/component/pool we are publishing into -
        e.g. "multiverse" for Ubuntu, "main" for debian."""
        if self.n == 'ubuntu':
          return "multiverse"
        elif self.n == 'debian':
          return "main"
        else:
            raise Exception("unsupported distro: %s" % self.n)

    def repo_os_version(self, build_os):
        """Return an OS version suitable for package repo directory
        naming - e.g. 5, 6 or 7 for redhat/centos, "precise," "wheezy," etc.
        for Ubuntu/Debian, 11 for suse, "2013.03" for amazon"""
        if self.n == 'suse':
            return re.sub(r'^suse(\d+)$', r'\1', build_os)
        if self.n == 'redhat':
            return re.sub(r'^rhel(\d).*$', r'\1', build_os)
        if self.n == 'amazon':
            return "2013.03"
        elif self.n == 'ubuntu':
            if build_os == 'ubuntu1204':
                return "precise"
            elif build_os == 'ubuntu1404':
                return "trusty"
            elif build_os == 'ubuntu1604':
                return "xenial"
            else:
                raise Exception("unsupported build_os: %s" % build_os)
        elif self.n == 'debian':
            if build_os == 'debian71':
                return 'wheezy'
            elif build_os == 'debian81':
                return 'jessie'
            else:
                raise Exception("unsupported build_os: %s" % build_os)
        else:
            raise Exception("unsupported distro: %s" % self.n)

    def make_pkg(self, build_os, arch, spec, srcdir):
        if re.search("^(debian|ubuntu)", self.n):
            return make_deb(self, build_os, arch, spec, srcdir)
        elif re.search("^(suse|centos|redhat|fedora|amazon)", self.n):
            return make_rpm(self, build_os, arch, spec, srcdir)
        else:
            raise Exception("BUG: unsupported platform?")

    def build_os(self, arch):
        """Return the build os label in the binary package to download (e.g. "rhel55" for redhat,
        "ubuntu1204" for ubuntu, "debian71" for debian, "suse11" for suse, etc.)"""
        # Community builds only support amd64
        if arch not in ['x86_64', 'ppc64le', 's390x', 'arm64']:
            raise Exception("BUG: unsupported architecture (%s)" % arch)

        if re.search("(suse)", self.n):
            return [ "suse11", "suse12" ]
        elif re.search("(redhat|fedora|centos)", self.n):
            return [ "rhel70", "rhel71", "rhel72", "rhel62", "rhel55" ]
        elif self.n == 'amazon':
            return [ "amazon" ]
        elif self.n == 'ubuntu':
            return [ "ubuntu1204", "ubuntu1404", "ubuntu1604", ]
        elif self.n == 'debian':
            return [ "debian71", "debian81" ]
        else:
            raise Exception("BUG: unsupported platform?")

    def release_dist(self, build_os):
        """Return the release distribution to use in the rpm - "el5" for rhel 5.x,
        "el6" for rhel 6.x, return anything else unchanged"""

        if self.n == 'amazon':
          return 'amzn1'
        else:
          return re.sub(r'^rh(el\d).*$', r'\1', build_os)

def get_args(distros, arch_choices):

    distro_choices=[]
    for distro in distros:
        for arch in arch_choices:
          distro_choices.extend(distro.build_os(arch))

    parser = argparse.ArgumentParser(description='Build MongoDB Packages')
    parser.add_argument("-s", "--server-version", help="Server version to build (e.g. 2.7.8-rc0)", required=True)
    parser.add_argument("-m", "--metadata-gitspec", help="Gitspec to use for package metadata files", required=False)
    parser.add_argument("-r", "--release-number", help="RPM release number base", type=int, required=False)
    parser.add_argument("-d", "--distros", help="Distros to build for", choices=distro_choices, required=False, default=[], action='append')
    parser.add_argument("-p", "--prefix", help="Directory to build into", required=False)
    parser.add_argument("-a", "--arches", help="Architecture to build", choices=arch_choices, default=[], required=False, action='append')
    parser.add_argument("-t", "--tarball", help="Local tarball to package", required=True, type=lambda x: is_valid_file(parser, x))

    args = parser.parse_args()

    if len(args.distros) * len(args.arches) > 1 and args.tarball:
      parser.error("Can only specify local tarball with one distro/arch combination")

    return args

def main(argv):

    distros=[Distro(distro) for distro in DISTROS]

    args = get_args(distros, ARCH_CHOICES)

    spec = Spec(args.server_version, args.metadata_gitspec, args.release_number)

    oldcwd=os.getcwd()
    srcdir=oldcwd+"/../"

    # Where to do all of our work. Use a randomly-created directory if one
    # is not passed in.
    prefix = args.prefix
    if prefix is None:
      prefix = tempfile.mkdtemp()
    print "Working in directory %s" % prefix

    os.chdir(prefix)
    try:
      # Build a package for each distro/spec/arch tuple, and
      # accumulate the repository-layout directories.
      for (distro, arch) in crossproduct(distros, args.arches):

          for build_os in distro.build_os(arch):
            if build_os in args.distros or not args.distros:

              filename = tarfile(build_os, arch, spec)
              ensure_dir(filename)
              shutil.copyfile(args.tarball,filename)

              repo = make_package(distro, build_os, arch, spec, srcdir)
              make_repo(repo, distro, build_os, spec)

    finally:
        os.chdir(oldcwd)

def crossproduct(*seqs):
    """A generator for iterating all the tuples consisting of elements
    of seqs."""
    l = len(seqs)
    if l == 0:
        pass
    elif l == 1:
        for i in seqs[0]:
            yield [i]
    else:
        for lst in crossproduct(*seqs[:-1]):
            for i in seqs[-1]:
                lst2=list(lst)
                lst2.append(i)
                yield lst2

def sysassert(argv):
    """Run argv and assert that it exited with status 0."""
    print "In %s, running %s" % (os.getcwd(), " ".join(argv))
    sys.stdout.flush()
    sys.stderr.flush()
    assert(subprocess.Popen(argv).wait()==0)

def backtick(argv):
    """Run argv and return its output string."""
    print "In %s, running %s" % (os.getcwd(), " ".join(argv))
    sys.stdout.flush()
    sys.stderr.flush()
    return subprocess.Popen(argv, stdout=subprocess.PIPE).communicate()[0]

def tarfile(build_os, arch, spec):
    """Return the location where we store the downloaded tarball for
    this package"""
    return "dl/mongodb-linux-%s-%s-%s.tar.gz" % (spec.version(), build_os, arch)

def setupdir(distro, build_os, arch, spec):
    # The setupdir will be a directory containing all inputs to the
    # distro's packaging tools (e.g., package metadata files, init
    # scripts, etc), along with the already-built binaries).  In case
    # the following format string is unclear, an example setupdir
    # would be dst/x86_64/debian-sysvinit/wheezy/mongodb-org-unstable/
    # or dst/x86_64/redhat/rhel55/mongodb-org-unstable/
    return "dst/%s/%s/%s/%s%s-%s/" % (arch, distro.name(), build_os, distro.pkgbase(), spec.suffix(), spec.pversion(distro))

def unpack_binaries_into(build_os, arch, spec, where):
    """Unpack the tarfile for (build_os, arch, spec) into directory where."""
    rootdir=os.getcwd()
    ensure_dir(where)
    # Note: POSIX tar doesn't require support for gtar's "-C" option,
    # and Python's tarfile module prior to Python 2.7 doesn't have the
    # features to make this detail easy.  So we'll just do the dumb
    # thing and chdir into where and run tar there.
    os.chdir(where)
    try:
        sysassert(["tar", "xvzf", rootdir+"/"+tarfile(build_os, arch, spec)])
        release_dir = glob('mongodb-linux-*')[0]
        for releasefile in "bin", "GNU-AGPL-3.0", "README", "THIRD-PARTY-NOTICES", "MPL-2":
            print "moving file: %s/%s" % (release_dir, releasefile)
            os.rename("%s/%s" % (release_dir, releasefile), releasefile)
        os.rmdir(release_dir)
    except Exception:
        exc=sys.exc_value
        os.chdir(rootdir)
        raise exc
    os.chdir(rootdir)

def make_package(distro, build_os, arch, spec, srcdir):
    """Construct the package for (arch, distro, spec), getting
    packaging files from srcdir and any user-specified suffix from
    suffixes"""

    sdir=setupdir(distro, build_os, arch, spec)
    ensure_dir(sdir)
    # Note that the RPM packages get their man pages from the debian
    # directory, so the debian directory is needed in all cases (and
    # innocuous in the debianoids' sdirs).
    for pkgdir in ["debian", "rpm"]:
        print "Copying packaging files from %s to %s" % ("%s/%s" % (srcdir, pkgdir), sdir)
        # FIXME: sh-dash-cee is bad. See if tarfile can do this.
        sysassert(["sh", "-c", "(cd \"%s\" && git archive %s %s/ ) | (cd \"%s\" && tar xvf -)" % (srcdir, spec.metadata_gitspec(), pkgdir, sdir)])
    # Splat the binaries under sdir.  The "build" stages of the
    # packaging infrastructure will move the files to wherever they
    # need to go.
    unpack_binaries_into(build_os, arch, spec, sdir)
    # Remove the mongoreplay binary due to libpcap dynamic
    # linkage.
    if os.path.exists(sdir + "bin/mongoreplay"):
      os.unlink(sdir + "bin/mongoreplay")
    return distro.make_pkg(build_os, arch, spec, srcdir)

def make_repo(repodir, distro, build_os, spec):
    if re.search("(debian|ubuntu)", repodir):
        make_deb_repo(repodir, distro, build_os, spec)
    elif re.search("(suse|centos|redhat|fedora|amazon)", repodir):
        make_rpm_repo(repodir)
    else:
        raise Exception("BUG: unsupported platform?")

def make_deb(distro, build_os, arch, spec, srcdir):
    # I can't remember the details anymore, but the initscript/upstart
    # job files' names must match the package name in some way; and
    # see also the --name flag to dh_installinit in the generated
    # debian/rules file.
    suffix=spec.suffix()
    sdir=setupdir(distro, build_os, arch, spec)
    if re.search("debian", distro.name()):
        os.unlink(sdir+"debian/mongod.upstart")
        if build_os == "debian71":
            os.link(sdir+"debian/init.d", sdir+"debian/%s%s-server.mongod.init" % (distro.pkgbase(), suffix))
            os.unlink(sdir+"debian/mongod.service")
        else:
            os.link(sdir+"debian/mongod.service", sdir+"debian/%s%s-server.mongod.service" % (distro.pkgbase(), suffix))
            os.unlink(sdir+"debian/init.d")
    elif re.search("ubuntu", distro.name()):
        os.unlink(sdir+"debian/init.d")
        if build_os in ("ubuntu1204", "ubuntu1404", "ubuntu1410"):
            os.link(sdir+"debian/mongod.upstart", sdir+"debian/%s%s-server.mongod.upstart" % (distro.pkgbase(), suffix))
            os.unlink(sdir+"debian/mongod.service")
        else:
            os.link(sdir+"debian/mongod.service", sdir+"debian/%s%s-server.mongod.service" % (distro.pkgbase(), suffix))
            os.unlink(sdir+"debian/mongod.upstart")
    else:
        raise Exception("unknown debianoid flavor: not debian or ubuntu?")
    # Rewrite the control and rules files
    write_debian_changelog(sdir+"debian/changelog", spec, srcdir)
    distro_arch=distro.archname(arch)
    sysassert(["cp", "-v", srcdir+"debian/%s%s.control" % (distro.pkgbase(), suffix), sdir+"debian/control"])
    sysassert(["cp", "-v", srcdir+"debian/%s%s.rules" % (distro.pkgbase(), suffix), sdir+"debian/rules"])


    # old non-server-package postinst will be hanging around for old versions
    #
    if os.path.exists(sdir+"debian/postinst"):
      os.unlink(sdir+"debian/postinst")

    # copy our postinst files
    #
    sysassert(["sh", "-c", "cp -v \"%sdebian/\"*.postinst \"%sdebian/\""%(srcdir, sdir)])

    # Do the packaging.
    oldcwd=os.getcwd()
    try:
        os.chdir(sdir)
        sysassert(["dpkg-buildpackage", "-uc", "-us", "-a" + distro_arch])
    finally:
        os.chdir(oldcwd)
    r=distro.repodir(arch, build_os, spec)
    ensure_dir(r)
    # FIXME: see if shutil.copyfile or something can do this without
    # much pain.
    sysassert(["sh", "-c", "cp -v \"%s/../\"*.deb \"%s\""%(sdir, r)])
    return r

def make_deb_repo(repo, distro, build_os, spec):
    # Note: the Debian repository Packages files must be generated
    # very carefully in order to be usable.
    oldpwd=os.getcwd()
    os.chdir(repo+"../../../../../../")
    try:
        dirs=set([os.path.dirname(deb)[2:] for deb in backtick(["find", ".", "-name", "*.deb"]).split()])
        for d in dirs:
            s=backtick(["dpkg-scanpackages", d, "/dev/null"])
            with open(d+"/Packages", "w") as f:
                f.write(s)
            b=backtick(["gzip", "-9c", d+"/Packages"])
            with open(d+"/Packages.gz", "wb") as f:
                f.write(b)
    finally:
        os.chdir(oldpwd)
    # Notes: the Release{,.gpg} files must live in a special place,
    # and must be created after all the Packages.gz files have been
    # done.
    s="""Origin: mongodb
Label: mongodb
Suite: %s
Codename: %s/mongodb-org
Architectures: amd64 arm64
Components: %s
Description: MongoDB packages
""" % (distro.repo_os_version(build_os), distro.repo_os_version(build_os), distro.repo_component())
    if os.path.exists(repo+"../../Release"):
        os.unlink(repo+"../../Release")
    if os.path.exists(repo+"../../Release.gpg"):
        os.unlink(repo+"../../Release.gpg")
    oldpwd=os.getcwd()
    os.chdir(repo+"../../")
    s2=backtick(["apt-ftparchive", "release", "."])
    try:
        with open("Release", 'w') as f:
            f.write(s)
            f.write(s2)
    finally:
        os.chdir(oldpwd)


def move_repos_into_place(src, dst):
    # Find all the stuff in src/*, move it to a freshly-created
    # directory beside dst, then play some games with symlinks so that
    # dst is a name the new stuff and dst+".old" names the previous
    # one.  This feels like a lot of hooey for something so trivial.

    # First, make a crispy fresh new directory to put the stuff in.
    i=0
    while True:
        date_suffix=time.strftime("%Y-%m-%d")
        dname=dst+".%s.%d" % (date_suffix, i)
        try:
            os.mkdir(dname)
            break
        except OSError:
            exc=sys.exc_value
            if exc.errno == errno.EEXIST:
                pass
            else:
                raise exc
        i=i+1

    # Put the stuff in our new directory.
    for r in os.listdir(src):
        sysassert(["cp", "-rv", src + "/" + r, dname])

    # Make a symlink to the new directory; the symlink will be renamed
    # to dst shortly.
    i=0
    while True:
        tmpnam=dst+".TMP.%d" % i
        try:
            os.symlink(dname, tmpnam)
            break
        except OSError: # as exc: # Python >2.5
            exc=sys.exc_value
            if exc.errno == errno.EEXIST:
                pass
            else:
                raise exc
        i=i+1

    # Make a symlink to the old directory; this symlink will be
    # renamed shortly, too.
    oldnam=None
    if os.path.exists(dst):
       i=0
       while True:
           oldnam=dst+".old.%d" % i
           try:
               os.symlink(os.readlink(dst), oldnam)
               break
           except OSError: # as exc: # Python >2.5
               exc=sys.exc_value
               if exc.errno == errno.EEXIST:
                   pass
               else:
                   raise exc

    os.rename(tmpnam, dst)
    if oldnam:
        os.rename(oldnam, dst+".old")


def write_debian_changelog(path, spec, srcdir):
    oldcwd=os.getcwd()
    os.chdir(srcdir)
    preamble=""
    try:
        s=preamble+backtick(["sh", "-c", "git archive %s debian/changelog | tar xOf -" % spec.metadata_gitspec()])
    finally:
        os.chdir(oldcwd)
    lines=s.split("\n")
    # If the first line starts with "mongodb", it's not a revision
    # preamble, and so frob the version number.
    lines[0]=re.sub("^mongodb \\(.*\\)", "mongodb (%s)" % (spec.pversion(Distro("debian"))), lines[0])
    # Rewrite every changelog entry starting in mongodb<space>
    lines=[re.sub("^mongodb ", "mongodb%s " % (spec.suffix()), l) for l in lines]
    lines=[re.sub("^  --", " --", l) for l in lines]
    s="\n".join(lines)
    with open(path, 'w') as f:
        f.write(s)

def make_rpm(distro, build_os, arch, spec, srcdir):
    # Create the specfile.
    suffix=spec.suffix()
    sdir=setupdir(distro, build_os, arch, spec)

    specfile = srcdir + "rpm/mongodb%s.spec" % suffix
    init_spec = specfile.replace(".spec", "-init.spec")

    # The Debian directory is here for the manpages so we we need to remove the service file
    # from it so that RPM packages don't end up with the Debian file.
    os.unlink(sdir + "debian/mongod.service")

    # Swap out systemd files, different systemd spec files, and init scripts as needed based on
    # underlying os version. Arranged so that new distros moving forward automatically use
    # systemd. Note: the SUSE init packages use a different init script than then other RPM
    # distros.
    #
    if distro.name() == "suse" and distro.repo_os_version(build_os) in ("10", "11"):
        os.unlink(sdir+"rpm/init.d-mongod")
        os.link(sdir+"rpm/init.d-mongod.suse", sdir+"rpm/init.d-mongod")

        os.unlink(specfile)
        os.link(init_spec, specfile)
    elif distro.name() == "redhat" and distro.repo_os_version(build_os) in ("5", "6"):
        os.unlink(specfile)
        os.link(init_spec, specfile)
    elif distro.name() == "amazon":
        os.unlink(specfile)
        os.link(init_spec, specfile)

    topdir=ensure_dir('%s/rpmbuild/%s/' % (os.getcwd(), build_os))
    for subdir in ["BUILD", "RPMS", "SOURCES", "SPECS", "SRPMS"]:
        ensure_dir("%s/%s/" % (topdir, subdir))
    distro_arch=distro.archname(arch)
    # RPM tools take these macro files that define variables in
    # RPMland.  Unfortunately, there's no way to tell RPM tools to use
    # a given file *in addition* to the files that it would already
    # load, so we have to figure out what it would normally load,
    # augment that list, and tell RPM to use the augmented list.  To
    # figure out what macrofiles ordinarily get loaded, older RPM
    # versions had a parameter called "macrofiles" that could be
    # extracted from "rpm --showrc".  But newer RPM versions don't
    # have this.  To tell RPM what macros to use, older versions of
    # RPM have a --macros option that doesn't work; on these versions,
    # you can put a "macrofiles" parameter into an rpmrc file.  But
    # that "macrofiles" setting doesn't do anything for newer RPM
    # versions, where you have to use the --macros flag instead.  And
    # all of this is to let us do our work with some guarantee that
    # we're not clobbering anything that doesn't belong to us.
    #
    # On RHEL systems, --rcfile will generally be used and
    # --macros will be used in Ubuntu.
    #
    macrofiles=[l for l in backtick(["rpm", "--showrc"]).split("\n") if l.startswith("macrofiles")]
    flags=[]
    macropath=os.getcwd()+"/macros"

    write_rpm_macros_file(macropath, topdir, distro.release_dist(build_os))
    if len(macrofiles)>0:
        macrofiles=macrofiles[0]+":"+macropath
        rcfile=os.getcwd()+"/rpmrc"
        write_rpmrc_file(rcfile, macrofiles)
        flags=["--rcfile", rcfile]
    else:
        # This hard-coded hooey came from some box running RPM
        # 4.4.2.3.  It may not work over time, but RPM isn't sanely
        # configurable.
        flags=["--macros", "/usr/lib/rpm/macros:/usr/lib/rpm/%s-linux/macros:/etc/rpm/macros.*:/etc/rpm/macros:/etc/rpm/%s-linux/macros:~/.rpmmacros:%s" % (distro_arch, distro_arch, macropath)]
    # Put the specfile and the tar'd up binaries and stuff in
    # place.
    #
    # The version of rpm and rpm tools in RHEL 5.5 can't interpolate the
    # %{dynamic_version} macro, so do it manually
    with open(specfile, "r") as spec_source:
      with open(topdir+"SPECS/" + os.path.basename(specfile), "w") as spec_dest:
        for line in spec_source:
          line = line.replace('%{dynamic_version}', spec.pversion(distro))
          line = line.replace('%{dynamic_release}', spec.prelease())
          spec_dest.write(line)

    oldcwd=os.getcwd()
    os.chdir(sdir+"/../")
    try:
        sysassert(["tar", "-cpzf", topdir+"SOURCES/mongodb%s-%s.tar.gz" % (suffix, spec.pversion(distro)), os.path.basename(os.path.dirname(sdir))])
    finally:
        os.chdir(oldcwd)
    # Do the build.

    flags.extend(["-D", "dynamic_version " + spec.pversion(distro), "-D", "dynamic_release " + spec.prelease(), "-D", "_topdir " + topdir])
    sysassert(["rpmbuild", "-ba", "--target", distro_arch] + flags + ["%s/SPECS/mongodb%s.spec" % (topdir, suffix)])
    r=distro.repodir(arch, build_os, spec)
    ensure_dir(r)
    # FIXME: see if some combination of shutil.copy<hoohah> and glob
    # can do this without shelling out.
    sysassert(["sh", "-c", "cp -v \"%s/RPMS/%s/\"*.rpm \"%s\""%(topdir, distro_arch, r)])
    return r

def make_rpm_repo(repo):
    oldpwd=os.getcwd()
    os.chdir(repo+"../")
    try:
        sysassert(["createrepo", "."])
    finally:
        os.chdir(oldpwd)


def write_rpmrc_file(path, string):
    with open(path, 'w') as f:
        f.write(string)

def write_rpm_macros_file(path, topdir, release_dist):
    with open(path, 'w') as f:
        f.write("%%_topdir	%s\n" % topdir)
        f.write("%%dist	.%s\n" % release_dist)
        f.write("%_use_internal_dependency_generator 0\n")

def ensure_dir(filename):
    """Make sure that the directory that's the dirname part of
    filename exists, and return filename."""
    dirpart = os.path.dirname(filename)
    try:
        os.makedirs(dirpart)
    except OSError: # as exc: # Python >2.5
        exc=sys.exc_value
        if exc.errno == errno.EEXIST:
            pass
        else:
            raise exc
    return filename

def is_valid_file(parser, filename):
    """Check if file exists, and return the filename"""
    if not os.path.exists(filename):
        parser.error("The file %s does not exist!" % filename)
    else:
        return filename

if __name__ == "__main__":
    main(sys.argv)