{ stdenv, lib, fetchurl, fetchsvn,
  jansson, libedit, libxml2, libxslt, ncurses, openssl, sqlite,
  utillinux, dmidecode, libuuid, newt,
  lua, speex,
  srtp, wget, curl, iksemel, pkgconfig
}:

let
  common = {version, sha256, externals}: stdenv.mkDerivation {
    inherit version;
    pname = "asterisk";

    buildInputs = [ jansson libedit libxml2 libxslt ncurses openssl sqlite
                    dmidecode libuuid newt
                    lua speex
                    srtp wget curl iksemel ];
    nativeBuildInputs = [ utillinux pkgconfig ];

    patches = [
      # We want the Makefile to install the default /var skeleton
      # under ${out}/var but we also want to use /var at runtime.
      # This patch changes the runtime behavior to look for state
      # directories in /var rather than ${out}/var.
      ./runtime-vardirs.patch
    ];

    # Disable MD5 verification for pjsip
    postPatch = ''
      sed -i 's|$(verify_tarball)|true|' third-party/pjproject/Makefile
    '';

    src = fetchurl {
      url = "https://downloads.asterisk.org/pub/telephony/asterisk/old-releases/asterisk-${version}.tar.gz";
      inherit sha256;
    };

    # The default libdir is $PREFIX/usr/lib, which causes problems when paths
    # compiled into Asterisk expect ${out}/usr/lib rather than ${out}/lib.

    # Copy in externals to avoid them being downloaded;
    # they have to be copied, because the modification date is checked.
    # If you are getting a permission denied error on this dir,
    # you're likely missing an automatically downloaded dependency
    preConfigure = ''
      mkdir externals_cache

      ${lib.concatStringsSep "\n"
        (lib.mapAttrsToList (dst: src: "cp -r --no-preserve=mode ${src} ${dst}") externals)}

      ${lib.optionalString (externals ? "addons/mp3") "bash contrib/scripts/get_mp3_source.sh || true"}

      chmod -w externals_cache
    '';
    configureFlags = [
      "--libdir=\${out}/lib"
      "--with-lua=${lua}/lib"
      "--with-pjproject-bundled"
      "--with-externals-cache=$(PWD)/externals_cache"
    ];

    preBuild = ''
      make menuselect.makeopts
      ${lib.optionalString (externals ? "addons/mp3") ''
        substituteInPlace menuselect.makeopts --replace 'format_mp3 ' ""
      ''}
    '';

    postInstall = ''
      # Install sample configuration files for this version of Asterisk
      make samples
    '';

    meta = with stdenv.lib; {
      description = "Software implementation of a telephone private branch exchange (PBX)";
      homepage = https://www.asterisk.org/;
      license = licenses.gpl2;
      maintainers = with maintainers; [ auntie DerTim1 yorickvp ];
    };
  };

  pjproject_2_7_1 = fetchurl {
    url = https://www.pjsip.org/release/2.7.1/pjproject-2.7.1.tar.bz2;
    sha256 = "09ii5hgl5s7grx4fiimcl3s77i385h7b3kwpfa2q0arbl1ibryjr";
  };

  pjproject_2_8 = fetchurl {
    url = https://www.pjsip.org/release/2.8/pjproject-2.8.tar.bz2;
    sha256 = "0ybg0113rp3fk49rm2v0pcgqb28h3dv1pdy9594w2ggiz7bhngah";
  };

  mp3-202 = fetchsvn {
    url = http://svn.digium.com/svn/thirdparty/mp3/trunk;
    rev = "202";
    sha256 = "1s9idx2miwk178sa731ig9r4fzx4gy1q8xazfqyd7q4lfd70s1cy";
  };

in rec {
  # Supported releases (as of 2018-11-20).
  #
  # Series  Type       Rel. Date   Sec. Fixes  EOL
  # 13.x    LTS        2014-10-24  2020-10-24  2021-10-24
  # 15.x    Standard   2017-10-03  2018-10-03  2019-10-03
  asterisk-stable = asterisk_15;
  # 16.x    LTS        2018-10-09  2022-10-09  2023-10-09
  asterisk-lts = asterisk_16;
  asterisk = asterisk_16;

  asterisk_13 = common {
    version = "13.24.1";
    sha256 = "1mclpk7knqjl6jr6mpvhb17wsjah4bk2xqhb3shpx1j4z19xkmm3";
    externals = {
      "externals_cache/pjproject-2.7.1.tar.bz2" = pjproject_2_7_1;
      "addons/mp3" = mp3-202;
    };
  };

  asterisk_15 = common {
    version = "15.7.0";
    sha256 = "1ngs73h4lz94b4f3shy1yb5laqy0z03zf451xa1nihrgp1h3ilyv";
    externals = {
      "externals_cache/pjproject-2.8.tar.bz2" = pjproject_2_8;
      "addons/mp3" = mp3-202;
    };
  };

  asterisk_16 = common {
    version = "16.1.1";
    sha256 = "19bfvqmxphk2608jx7jghfy7rdbj1qj5vw2fyb0fq4xjvx919wmv";
    externals = {
      "externals_cache/pjproject-2.8.tar.bz2" = pjproject_2_8;
      "addons/mp3" = mp3-202;
    };
  };

  #asterisk-git = common {
  #  version = "15-pre";
  #  sha256 = "...";
  #  externals = {
  #    "externals_cache/pjproject-2.5.5.tar.bz2" = pjproject-255;
  #    # Note that these sounds are included with the release tarball. They are
  #    # provided here verbatim for the convenience of anyone wanting to build
  #    # Asterisk from other sources. Include in externals.
  #    "sounds/asterisk-core-sounds-en-gsm-1.5.tar.gz" = fetchurl {
  #      url = http://downloads.asterisk.org/pub/telephony/sounds/releases/asterisk-core-sounds-en-gsm-1.5.tar.gz;
  #      sha256 = "01xzbg7xy0c5zg7sixjw5025pvr4z64kfzi9zvx19im0w331h4cd";
  #    };
  #    "sounds/asterisk-moh-opsound-wav-2.03.tar.gz" = fetchurl {
  #      url = http://downloads.asterisk.org/pub/telephony/sounds/releases/asterisk-moh-opsound-wav-2.03.tar.gz;
  #      sha256 = "449fb810d16502c3052fedf02f7e77b36206ac5a145f3dacf4177843a2fcb538";
  #    };
  #    # TODO: Sounds for other languages could be added here
  #  }
  #}.overrideDerivation (_: {src = fetchgit {...}})

}