################################################################
#
# Copyright (c) 2024 SUSE LLC
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 or 3 as
# published by the Free Software Foundation.
#
# 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 (see the file COPYING); if not, write to the
# Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
#
################################################################

package Build::SPDX;

our $licenseListVersion = "3.24";

our $licenses = [
  "0BSD",
  "3D-Slicer-1.0",
  "AAL",
  "Abstyles",
  "AdaCore-doc",
  "Adobe-2006",
  "Adobe-Display-PostScript",
  "Adobe-Glyph",
  "Adobe-Utopia",
  "ADSL",
  "AFL-1.1",
  "AFL-1.2",
  "AFL-2.0",
  "AFL-2.1",
  "AFL-3.0",
  "Afmparse",
  "AGPL-1.0",
  "AGPL-1.0-only",
  "AGPL-1.0-or-later",
  "AGPL-3.0",
  "AGPL-3.0-only",
  "AGPL-3.0-or-later",
  "Aladdin",
  "AMD-newlib",
  "AMDPLPA",
  "AML",
  "AML-glslang",
  "AMPAS",
  "ANTLR-PD",
  "ANTLR-PD-fallback",
  "any-OSI",
  "Apache-1.0",
  "Apache-1.1",
  "Apache-2.0",
  "APAFML",
  "APL-1.0",
  "App-s2p",
  "APSL-1.0",
  "APSL-1.1",
  "APSL-1.2",
  "APSL-2.0",
  "Arphic-1999",
  "Artistic-1.0",
  "Artistic-1.0-cl8",
  "Artistic-1.0-Perl",
  "Artistic-2.0",
  "ASWF-Digital-Assets-1.0",
  "ASWF-Digital-Assets-1.1",
  "Baekmuk",
  "Bahyph",
  "Barr",
  "bcrypt-Solar-Designer",
  "Beerware",
  "Bitstream-Charter",
  "Bitstream-Vera",
  "BitTorrent-1.0",
  "BitTorrent-1.1",
  "blessing",
  "BlueOak-1.0.0",
  "Boehm-GC",
  "Borceux",
  "Brian-Gladman-2-Clause",
  "Brian-Gladman-3-Clause",
  "BSD-1-Clause",
  "BSD-2-Clause",
  "BSD-2-Clause-Darwin",
  "BSD-2-Clause-first-lines",
  "BSD-2-Clause-FreeBSD",
  "BSD-2-Clause-NetBSD",
  "BSD-2-Clause-Patent",
  "BSD-2-Clause-Views",
  "BSD-3-Clause",
  "BSD-3-Clause-acpica",
  "BSD-3-Clause-Attribution",
  "BSD-3-Clause-Clear",
  "BSD-3-Clause-flex",
  "BSD-3-Clause-HP",
  "BSD-3-Clause-LBNL",
  "BSD-3-Clause-Modification",
  "BSD-3-Clause-No-Military-License",
  "BSD-3-Clause-No-Nuclear-License",
  "BSD-3-Clause-No-Nuclear-License-2014",
  "BSD-3-Clause-No-Nuclear-Warranty",
  "BSD-3-Clause-Open-MPI",
  "BSD-3-Clause-Sun",
  "BSD-4-Clause",
  "BSD-4-Clause-Shortened",
  "BSD-4-Clause-UC",
  "BSD-4.3RENO",
  "BSD-4.3TAHOE",
  "BSD-Advertising-Acknowledgement",
  "BSD-Attribution-HPND-disclaimer",
  "BSD-Inferno-Nettverk",
  "BSD-Protection",
  "BSD-Source-beginning-file",
  "BSD-Source-Code",
  "BSD-Systemics",
  "BSD-Systemics-W3Works",
  "BSL-1.0",
  "BUSL-1.1",
  "bzip2-1.0.5",
  "bzip2-1.0.6",
  "C-UDA-1.0",
  "CAL-1.0",
  "CAL-1.0-Combined-Work-Exception",
  "Caldera",
  "Caldera-no-preamble",
  "Catharon",
  "CATOSL-1.1",
  "CC-BY-1.0",
  "CC-BY-2.0",
  "CC-BY-2.5",
  "CC-BY-2.5-AU",
  "CC-BY-3.0",
  "CC-BY-3.0-AT",
  "CC-BY-3.0-AU",
  "CC-BY-3.0-DE",
  "CC-BY-3.0-IGO",
  "CC-BY-3.0-NL",
  "CC-BY-3.0-US",
  "CC-BY-4.0",
  "CC-BY-NC-1.0",
  "CC-BY-NC-2.0",
  "CC-BY-NC-2.5",
  "CC-BY-NC-3.0",
  "CC-BY-NC-3.0-DE",
  "CC-BY-NC-4.0",
  "CC-BY-NC-ND-1.0",
  "CC-BY-NC-ND-2.0",
  "CC-BY-NC-ND-2.5",
  "CC-BY-NC-ND-3.0",
  "CC-BY-NC-ND-3.0-DE",
  "CC-BY-NC-ND-3.0-IGO",
  "CC-BY-NC-ND-4.0",
  "CC-BY-NC-SA-1.0",
  "CC-BY-NC-SA-2.0",
  "CC-BY-NC-SA-2.0-DE",
  "CC-BY-NC-SA-2.0-FR",
  "CC-BY-NC-SA-2.0-UK",
  "CC-BY-NC-SA-2.5",
  "CC-BY-NC-SA-3.0",
  "CC-BY-NC-SA-3.0-DE",
  "CC-BY-NC-SA-3.0-IGO",
  "CC-BY-NC-SA-4.0",
  "CC-BY-ND-1.0",
  "CC-BY-ND-2.0",
  "CC-BY-ND-2.5",
  "CC-BY-ND-3.0",
  "CC-BY-ND-3.0-DE",
  "CC-BY-ND-4.0",
  "CC-BY-SA-1.0",
  "CC-BY-SA-2.0",
  "CC-BY-SA-2.0-UK",
  "CC-BY-SA-2.1-JP",
  "CC-BY-SA-2.5",
  "CC-BY-SA-3.0",
  "CC-BY-SA-3.0-AT",
  "CC-BY-SA-3.0-DE",
  "CC-BY-SA-3.0-IGO",
  "CC-BY-SA-4.0",
  "CC-PDDC",
  "CC0-1.0",
  "CDDL-1.0",
  "CDDL-1.1",
  "CDL-1.0",
  "CDLA-Permissive-1.0",
  "CDLA-Permissive-2.0",
  "CDLA-Sharing-1.0",
  "CECILL-1.0",
  "CECILL-1.1",
  "CECILL-2.0",
  "CECILL-2.1",
  "CECILL-B",
  "CECILL-C",
  "CERN-OHL-1.1",
  "CERN-OHL-1.2",
  "CERN-OHL-P-2.0",
  "CERN-OHL-S-2.0",
  "CERN-OHL-W-2.0",
  "CFITSIO",
  "check-cvs",
  "checkmk",
  "ClArtistic",
  "Clips",
  "CMU-Mach",
  "CMU-Mach-nodoc",
  "CNRI-Jython",
  "CNRI-Python",
  "CNRI-Python-GPL-Compatible",
  "COIL-1.0",
  "Community-Spec-1.0",
  "Condor-1.1",
  "copyleft-next-0.3.0",
  "copyleft-next-0.3.1",
  "Cornell-Lossless-JPEG",
  "CPAL-1.0",
  "CPL-1.0",
  "CPOL-1.02",
  "Cronyx",
  "Crossword",
  "CrystalStacker",
  "CUA-OPL-1.0",
  "Cube",
  "curl",
  "cve-tou",
  "D-FSL-1.0",
  "DEC-3-Clause",
  "diffmark",
  "DL-DE-BY-2.0",
  "DL-DE-ZERO-2.0",
  "DOC",
  "Dotseqn",
  "DRL-1.0",
  "DRL-1.1",
  "DSDP",
  "dtoa",
  "dvipdfm",
  "ECL-1.0",
  "ECL-2.0",
  "eCos-2.0",
  "EFL-1.0",
  "EFL-2.0",
  "eGenix",
  "Elastic-2.0",
  "Entessa",
  "EPICS",
  "EPL-1.0",
  "EPL-2.0",
  "ErlPL-1.1",
  "etalab-2.0",
  "EUDatagrid",
  "EUPL-1.0",
  "EUPL-1.1",
  "EUPL-1.2",
  "Eurosym",
  "Fair",
  "FBM",
  "FDK-AAC",
  "Ferguson-Twofish",
  "Frameworx-1.0",
  "FreeBSD-DOC",
  "FreeImage",
  "FSFAP",
  "FSFAP-no-warranty-disclaimer",
  "FSFUL",
  "FSFULLR",
  "FSFULLRWD",
  "FTL",
  "Furuseth",
  "fwlw",
  "GCR-docs",
  "GD",
  "GFDL-1.1",
  "GFDL-1.1-invariants-only",
  "GFDL-1.1-invariants-or-later",
  "GFDL-1.1-no-invariants-only",
  "GFDL-1.1-no-invariants-or-later",
  "GFDL-1.1-only",
  "GFDL-1.1-or-later",
  "GFDL-1.2",
  "GFDL-1.2-invariants-only",
  "GFDL-1.2-invariants-or-later",
  "GFDL-1.2-no-invariants-only",
  "GFDL-1.2-no-invariants-or-later",
  "GFDL-1.2-only",
  "GFDL-1.2-or-later",
  "GFDL-1.3",
  "GFDL-1.3-invariants-only",
  "GFDL-1.3-invariants-or-later",
  "GFDL-1.3-no-invariants-only",
  "GFDL-1.3-no-invariants-or-later",
  "GFDL-1.3-only",
  "GFDL-1.3-or-later",
  "Giftware",
  "GL2PS",
  "Glide",
  "Glulxe",
  "GLWTPL",
  "gnuplot",
  "GPL-1.0",
  "GPL-1.0+",
  "GPL-1.0-only",
  "GPL-1.0-or-later",
  "GPL-2.0",
  "GPL-2.0+",
  "GPL-2.0-only",
  "GPL-2.0-or-later",
  "GPL-2.0-with-autoconf-exception",
  "GPL-2.0-with-bison-exception",
  "GPL-2.0-with-classpath-exception",
  "GPL-2.0-with-font-exception",
  "GPL-2.0-with-GCC-exception",
  "GPL-3.0",
  "GPL-3.0+",
  "GPL-3.0-only",
  "GPL-3.0-or-later",
  "GPL-3.0-with-autoconf-exception",
  "GPL-3.0-with-GCC-exception",
  "Graphics-Gems",
  "gSOAP-1.3b",
  "gtkbook",
  "Gutmann",
  "HaskellReport",
  "hdparm",
  "Hippocratic-2.1",
  "HP-1986",
  "HP-1989",
  "HPND",
  "HPND-DEC",
  "HPND-doc",
  "HPND-doc-sell",
  "HPND-export-US",
  "HPND-export-US-acknowledgement",
  "HPND-export-US-modify",
  "HPND-export2-US",
  "HPND-Fenneberg-Livingston",
  "HPND-INRIA-IMAG",
  "HPND-Intel",
  "HPND-Kevlin-Henney",
  "HPND-Markus-Kuhn",
  "HPND-merchantability-variant",
  "HPND-MIT-disclaimer",
  "HPND-Pbmplus",
  "HPND-sell-MIT-disclaimer-xserver",
  "HPND-sell-regexpr",
  "HPND-sell-variant",
  "HPND-sell-variant-MIT-disclaimer",
  "HPND-sell-variant-MIT-disclaimer-rev",
  "HPND-UC",
  "HPND-UC-export-US",
  "HTMLTIDY",
  "IBM-pibs",
  "ICU",
  "IEC-Code-Components-EULA",
  "IJG",
  "IJG-short",
  "ImageMagick",
  "iMatix",
  "Imlib2",
  "Info-ZIP",
  "Inner-Net-2.0",
  "Intel",
  "Intel-ACPI",
  "Interbase-1.0",
  "IPA",
  "IPL-1.0",
  "ISC",
  "ISC-Veillard",
  "Jam",
  "JasPer-2.0",
  "JPL-image",
  "JPNIC",
  "JSON",
  "Kastrup",
  "Kazlib",
  "Knuth-CTAN",
  "LAL-1.2",
  "LAL-1.3",
  "Latex2e",
  "Latex2e-translated-notice",
  "Leptonica",
  "LGPL-2.0",
  "LGPL-2.0+",
  "LGPL-2.0-only",
  "LGPL-2.0-or-later",
  "LGPL-2.1",
  "LGPL-2.1+",
  "LGPL-2.1-only",
  "LGPL-2.1-or-later",
  "LGPL-3.0",
  "LGPL-3.0+",
  "LGPL-3.0-only",
  "LGPL-3.0-or-later",
  "LGPLLR",
  "Libpng",
  "libpng-2.0",
  "libselinux-1.0",
  "libtiff",
  "libutil-David-Nugent",
  "LiLiQ-P-1.1",
  "LiLiQ-R-1.1",
  "LiLiQ-Rplus-1.1",
  "Linux-man-pages-1-para",
  "Linux-man-pages-copyleft",
  "Linux-man-pages-copyleft-2-para",
  "Linux-man-pages-copyleft-var",
  "Linux-OpenIB",
  "LOOP",
  "LPD-document",
  "LPL-1.0",
  "LPL-1.02",
  "LPPL-1.0",
  "LPPL-1.1",
  "LPPL-1.2",
  "LPPL-1.3a",
  "LPPL-1.3c",
  "lsof",
  "Lucida-Bitmap-Fonts",
  "LZMA-SDK-9.11-to-9.20",
  "LZMA-SDK-9.22",
  "Mackerras-3-Clause",
  "Mackerras-3-Clause-acknowledgment",
  "magaz",
  "mailprio",
  "MakeIndex",
  "Martin-Birgmeier",
  "McPhee-slideshow",
  "metamail",
  "Minpack",
  "MirOS",
  "MIT",
  "MIT-0",
  "MIT-advertising",
  "MIT-CMU",
  "MIT-enna",
  "MIT-feh",
  "MIT-Festival",
  "MIT-Khronos-old",
  "MIT-Modern-Variant",
  "MIT-open-group",
  "MIT-testregex",
  "MIT-Wu",
  "MITNFA",
  "MMIXware",
  "Motosoto",
  "MPEG-SSG",
  "mpi-permissive",
  "mpich2",
  "MPL-1.0",
  "MPL-1.1",
  "MPL-2.0",
  "MPL-2.0-no-copyleft-exception",
  "mplus",
  "MS-LPL",
  "MS-PL",
  "MS-RL",
  "MTLL",
  "MulanPSL-1.0",
  "MulanPSL-2.0",
  "Multics",
  "Mup",
  "NAIST-2003",
  "NASA-1.3",
  "Naumen",
  "NBPL-1.0",
  "NCBI-PD",
  "NCGL-UK-2.0",
  "NCL",
  "NCSA",
  "Net-SNMP",
  "NetCDF",
  "Newsletr",
  "NGPL",
  "NICTA-1.0",
  "NIST-PD",
  "NIST-PD-fallback",
  "NIST-Software",
  "NLOD-1.0",
  "NLOD-2.0",
  "NLPL",
  "Nokia",
  "NOSL",
  "Noweb",
  "NPL-1.0",
  "NPL-1.1",
  "NPOSL-3.0",
  "NRL",
  "NTP",
  "NTP-0",
  "Nunit",
  "O-UDA-1.0",
  "OAR",
  "OCCT-PL",
  "OCLC-2.0",
  "ODbL-1.0",
  "ODC-By-1.0",
  "OFFIS",
  "OFL-1.0",
  "OFL-1.0-no-RFN",
  "OFL-1.0-RFN",
  "OFL-1.1",
  "OFL-1.1-no-RFN",
  "OFL-1.1-RFN",
  "OGC-1.0",
  "OGDL-Taiwan-1.0",
  "OGL-Canada-2.0",
  "OGL-UK-1.0",
  "OGL-UK-2.0",
  "OGL-UK-3.0",
  "OGTSL",
  "OLDAP-1.1",
  "OLDAP-1.2",
  "OLDAP-1.3",
  "OLDAP-1.4",
  "OLDAP-2.0",
  "OLDAP-2.0.1",
  "OLDAP-2.1",
  "OLDAP-2.2",
  "OLDAP-2.2.1",
  "OLDAP-2.2.2",
  "OLDAP-2.3",
  "OLDAP-2.4",
  "OLDAP-2.5",
  "OLDAP-2.6",
  "OLDAP-2.7",
  "OLDAP-2.8",
  "OLFL-1.3",
  "OML",
  "OpenPBS-2.3",
  "OpenSSL",
  "OpenSSL-standalone",
  "OpenVision",
  "OPL-1.0",
  "OPL-UK-3.0",
  "OPUBL-1.0",
  "OSET-PL-2.1",
  "OSL-1.0",
  "OSL-1.1",
  "OSL-2.0",
  "OSL-2.1",
  "OSL-3.0",
  "PADL",
  "Parity-6.0.0",
  "Parity-7.0.0",
  "PDDL-1.0",
  "PHP-3.0",
  "PHP-3.01",
  "Pixar",
  "pkgconf",
  "Plexus",
  "pnmstitch",
  "PolyForm-Noncommercial-1.0.0",
  "PolyForm-Small-Business-1.0.0",
  "PostgreSQL",
  "PPL",
  "PSF-2.0",
  "psfrag",
  "psutils",
  "Python-2.0",
  "Python-2.0.1",
  "python-ldap",
  "Qhull",
  "QPL-1.0",
  "QPL-1.0-INRIA-2004",
  "radvd",
  "Rdisc",
  "RHeCos-1.1",
  "RPL-1.1",
  "RPL-1.5",
  "RPSL-1.0",
  "RSA-MD",
  "RSCPL",
  "Ruby",
  "SAX-PD",
  "SAX-PD-2.0",
  "Saxpath",
  "SCEA",
  "SchemeReport",
  "Sendmail",
  "Sendmail-8.23",
  "SGI-B-1.0",
  "SGI-B-1.1",
  "SGI-B-2.0",
  "SGI-OpenGL",
  "SGP4",
  "SHL-0.5",
  "SHL-0.51",
  "SimPL-2.0",
  "SISSL",
  "SISSL-1.2",
  "SL",
  "Sleepycat",
  "SMLNJ",
  "SMPPL",
  "SNIA",
  "snprintf",
  "softSurfer",
  "Soundex",
  "Spencer-86",
  "Spencer-94",
  "Spencer-99",
  "SPL-1.0",
  "ssh-keyscan",
  "SSH-OpenSSH",
  "SSH-short",
  "SSLeay-standalone",
  "SSPL-1.0",
  "StandardML-NJ",
  "SugarCRM-1.1.3",
  "Sun-PPP",
  "Sun-PPP-2000",
  "SunPro",
  "SWL",
  "swrule",
  "Symlinks",
  "TAPR-OHL-1.0",
  "TCL",
  "TCP-wrappers",
  "TermReadKey",
  "TGPPL-1.0",
  "threeparttable",
  "TMate",
  "TORQUE-1.1",
  "TOSL",
  "TPDL",
  "TPL-1.0",
  "TTWL",
  "TTYP0",
  "TU-Berlin-1.0",
  "TU-Berlin-2.0",
  "UCAR",
  "UCL-1.0",
  "ulem",
  "UMich-Merit",
  "Unicode-3.0",
  "Unicode-DFS-2015",
  "Unicode-DFS-2016",
  "Unicode-TOU",
  "UnixCrypt",
  "Unlicense",
  "UPL-1.0",
  "URT-RLE",
  "Vim",
  "VOSTROM",
  "VSL-1.0",
  "W3C",
  "W3C-19980720",
  "W3C-20150513",
  "w3m",
  "Watcom-1.0",
  "Widget-Workshop",
  "Wsuipa",
  "WTFPL",
  "wxWindows",
  "X11",
  "X11-distribute-modifications-variant",
  "Xdebug-1.03",
  "Xerox",
  "Xfig",
  "XFree86-1.1",
  "xinetd",
  "xkeyboard-config-Zinoviev",
  "xlock",
  "Xnet",
  "xpp",
  "XSkat",
  "xzoom",
  "YPL-1.0",
  "YPL-1.1",
  "Zed",
  "Zeeff",
  "Zend-2.0",
  "Zimbra-1.3",
  "Zimbra-1.4",
  "Zlib",
  "zlib-acknowledgement",
  "ZPL-1.1",
  "ZPL-2.0",
  "ZPL-2.1",
];

our $license_exceptions = [
  "389-exception",
  "Asterisk-exception",
  "Asterisk-linking-protocols-exception",
  "Autoconf-exception-2.0",
  "Autoconf-exception-3.0",
  "Autoconf-exception-generic",
  "Autoconf-exception-generic-3.0",
  "Autoconf-exception-macro",
  "Bison-exception-1.24",
  "Bison-exception-2.2",
  "Bootloader-exception",
  "Classpath-exception-2.0",
  "CLISP-exception-2.0",
  "cryptsetup-OpenSSL-exception",
  "DigiRule-FOSS-exception",
  "eCos-exception-2.0",
  "Fawkes-Runtime-exception",
  "FLTK-exception",
  "fmt-exception",
  "Font-exception-2.0",
  "freertos-exception-2.0",
  "GCC-exception-2.0",
  "GCC-exception-2.0-note",
  "GCC-exception-3.1",
  "Gmsh-exception",
  "GNAT-exception",
  "GNOME-examples-exception",
  "GNU-compiler-exception",
  "gnu-javamail-exception",
  "GPL-3.0-interface-exception",
  "GPL-3.0-linking-exception",
  "GPL-3.0-linking-source-exception",
  "GPL-CC-1.0",
  "GStreamer-exception-2005",
  "GStreamer-exception-2008",
  "i2p-gpl-java-exception",
  "KiCad-libraries-exception",
  "LGPL-3.0-linking-exception",
  "libpri-OpenH323-exception",
  "Libtool-exception",
  "Linux-syscall-note",
  "LLGPL",
  "LLVM-exception",
  "LZMA-exception",
  "mif-exception",
  "Nokia-Qt-exception-1.1",
  "OCaml-LGPL-linking-exception",
  "OCCT-exception-1.0",
  "OpenJDK-assembly-exception-1.0",
  "openvpn-openssl-exception",
  "PCRE2-exception",
  "PS-or-PDF-font-exception-20170817",
  "QPL-1.0-INRIA-2004-exception",
  "Qt-GPL-exception-1.0",
  "Qt-LGPL-exception-1.1",
  "Qwt-exception-1.0",
  "RRDtool-FLOSS-exception-2.0",
  "SANE-exception",
  "SHL-2.0",
  "SHL-2.1",
  "stunnel-exception",
  "SWI-exception",
  "Swift-exception",
  "Texinfo-exception",
  "u-boot-exception-2.0",
  "UBDL-exception",
  "Universal-FOSS-exception-1.0",
  "vsftpd-openssl-exception",
  "WxWindows-exception-3.1",
  "x11vnc-openssl-exception",
];


my %known_licenses = map { lc($_) => $_} @$licenses;
my %known_license_exceptions = map { lc($_) => $_} @$license_exceptions;

sub _tokenize_license_r {
  my ($name) = @_;
  $name =~ s/^\s+//;
  my @ret;
  while (1) {
    if ($name =~ s/^\(//) {
      my $t;
      ($t, $name) = _tokenize_license_r($name);
      return unless $t && defined($name) && $name =~ s/^\s*\)//;
      push @ret, $t;
    } else {
      return unless $name =~ /^([^\s\+\(\)]+)/;
      push @ret, $1;
      $name = substr($name, length($1));
      push @ret, 'PLUS', '+' if $name =~ s/^\+//;
      $name =~ s/^\s+//;
      if ($name =~ s/^WITH\s+//i) {
	return unless $name =~ /^([^\s\+\(\)]+)/;
	push @ret, 'WITH', $1;
	$name = substr($name, length($1));
      }
    }
    $name =~ s/^\s+//;
    return \@ret, $name if $name eq '' || $name =~ /^\)/;
    if ($name =~ s/^AND(?:\s+|(?=\())//i) {
      push @ret, 'AND';
    } elsif ($name =~ s/^OR(?:\s+|(?=\())//i) {
      push @ret, 'OR';
    } else {
      return;
    }
  }
}

sub tokenize_license {
  my ($ret, $rest) = _tokenize_license_r($_[0]);
  return $ret && defined($rest) && $rest eq '' ? $ret : undef;
}

sub normalize_tokenized_license {
  my ($n, $unknown_license_cb, $unknown_exception_cb) = @_;
  my @n = ('START', @$n);
  my $l = '';
  while (@n) {
    my ($op, $t) = splice(@n, 0, 2);
    $l .= " $op " if $op ne 'START' && $op ne 'PLUS';
    if ($op eq 'PLUS') {
      $t = '+';
    } elsif ($op eq 'WITH') {
      my $nt = $known_license_exceptions{lc($t)};
      $t = $nt ? $nt : $unknown_exception_cb ? $unknown_exception_cb->($t) : undef;
    } elsif (ref $t) {
      $t = normalize_tokenized_license($t, $unknown_license_cb, $unknown_exception_cb);
      $t = "($t)" if defined $t;
    } else {
      my $plusidx = @n && $n[0] eq 'PLUS' ? 2 : 0;
      if (!$unknown_exception_cb && @n > $plusidx + 1 && $n[$plusidx] eq 'WITH' && !$known_license_exceptions{lc($n[$plusidx + 1])}) {
	# the exception is not known, encode complete license with exception
	$t .= ($plusidx ? '+' : '') . " WITH $n[$plusidx + 1]";
	splice(@n, 0, $plusidx + 2);
      } elsif ($plusidx && !$known_licenses{lc($t)}) {
	# we are not allowed to use the + suffix with license references
	$t .= '+';
	splice(@n, 0, 2);
      }
      my $nt = $known_licenses{lc($t)};
      $t = $nt ? $nt : $unknown_license_cb ? $unknown_license_cb->($t) : undef;
    }
    return undef unless defined $t;
    $l .= $t;
  }
  return $l;
}

sub normalize_license {
  my ($name, $unknown_license_cb, $unknown_exception_cb) = @_;
  $name =~ s/\s+/ /g;
  $name =~ s/ and / AND /g;
  $name =~ s/ or / OR /g;
  $name =~ s/ with / WITH /g;
  $name =~ s/\bLicenseRef-//ig;	# strip away LicenseRef- prefix
  my $n = tokenize_license($name);
  $n = $n ? normalize_tokenized_license($n, $unknown_license_cb, $unknown_exception_cb) : undef;
  return $n if defined $n;
  # parse/normalization error, encode complete string as new license
  return $unknown_license_cb ? $unknown_license_cb->($name) : undef;
}

1;
