{ lib, mkCoqDerivation, coq, compcert, ITree, version ? null }:

with lib;

# A few modules that are not built and installed by default
#  but that may be useful to some users.
# They depend on ITree.
let extra_floyd_files = [
  "ASTsize.v"
  "io_events.v"
  "powerlater.v"
  ]
  # floyd/printf.v is broken in VST 2.9
  ++ optional (!versions.isGe "8.13" coq.coq-version) "printf.v"
  ++ [
  "quickprogram.v"
  ];
in

mkCoqDerivation {
  pname = "coq${coq.coq-version}-VST";
  namePrefix = [];
  displayVersion = { coq = false; };
  owner = "PrincetonUniversity";
  repo = "VST";
  inherit version;
  defaultVersion = with versions; switch coq.coq-version [
    { case = range "8.13" "8.15"; out = "2.9"; }
    { case = range "8.12" "8.13"; out = "2.8"; }
  ] null;
  release."2.9".sha256 = "sha256:1adwzbl1pprrrwrm7cm493098fizxanxpv7nyfbvwdhgbhcnv6qf";
  release."2.8".sha256 = "sha256-cyK88uzorRfjapNQ6XgQEmlbWnDsiyLve5po1VG52q0=";
  releaseRev = v: "v${v}";
  extraBuildInputs = [ ITree ];
  propagatedBuildInputs = [ compcert ];

  preConfigure = ''
    patchShebangs util
    substituteInPlace Makefile \
      --replace 'COQVERSION= ' 'COQVERSION= 8.15.1 or-else '\
      --replace 'FLOYD_FILES=' 'FLOYD_FILES= ${toString extra_floyd_files}'
  '';

  makeFlags = [
    "BITSIZE=64"
    "COMPCERT=inst_dir"
    "COMPCERT_INST_DIR=${compcert.lib}/lib/coq/${coq.coq-version}/user-contrib/compcert"
    "INSTALLDIR=$(out)/lib/coq/${coq.coq-version}/user-contrib/VST"
  ];

  postInstall = ''
    for d in msl veric floyd sepcomp progs64
    do
      cp -r $d $out/lib/coq/${coq.coq-version}/user-contrib/VST/
    done
  '';

  meta = {
    description = "Verified Software Toolchain";
    homepage = "https://vst.cs.princeton.edu/";
    inherit (compcert.meta) platforms;
  };
}