/*
This is the library of nix builders. Some rules to follow:
- Keep this code as minimal as possible. I'd rather write Haskell than Nix,
  wouldn't you?
- Try to reuse as much upstream Nix as possible.
- Path-like args such as 'srcs' should always be absolute paths.
*/
{ srcs ? "" # list of all source files, as a space-separated string
, main # the entrypoint or main module (not a path)
, root # path to git root
, packageSet # name mapped to private.${packageSet}, e.g. 'ghcWith'
, langdeps ? null # list of deps (as a string), split and passed to packageSet
, sysdeps ? null
, name # exe name
, compileLine ? "" # Target.compiler <> Target.compilerFlags
}:
with import (/. + root + "/Biz/Bild.nix") {};
with builtins;
let
  srcs_ = (lib.strings.splitString " " srcs) ++ [main];

  skip = ["_" ".direnv"];
  filter = file: type:
    if elem (baseNameOf file) skip then false
    # TODO: this means any new directory will cause a rebuild. this bad.  i
    # should recurse into the directory and match against the srcs. for now I
    # just use postUnpack to delete empty dirs
    else if type == "directory" then true
    else if type == "regular" then (builtins.elem file srcs_)
    else false;

  # clean up empty dirs
  postUnpack = "find . -type d -empty -delete";

  src = lib.sources.cleanSourceWith {inherit filter; src = lib.sources.cleanSource root;};

  langdeps_ = pkgset:
    if langdeps == null || langdeps == [] then
      []
    else
      private.selectAttrs (lib.strings.splitString " " langdeps) pkgset;
  sysdeps_ =
    if sysdeps == null || sysdeps == [] then
      []
    else
      private.selectAttrs (lib.strings.splitString " " sysdeps) private.nixpkgs.pkgs;
  BIZ_ROOT = ".";
in {
  base = stdenv.mkDerivation rec {
    inherit name src BIZ_ROOT postUnpack;
    buildInputs = [ (private.${packageSet} langdeps_) ] ++ sysdeps_;
    installPhase = "install -D ${name} $out/bin/${name}";
    buildPhase = compileLine;
  };

  python = buildPythonApplication rec {
    inherit name src BIZ_ROOT postUnpack;
    propagatedBuildInputs = [ (private.${packageSet} langdeps_) ] ++ sysdeps_;
    buildInputs = sysdeps_;
    checkInputs = [(private.pythonWith (p: with p; [black mypy pylint]))];
    checkPhase = ''
      black --quiet --exclude 'setup\.py$' --check .
      pylint --errors-only .
      mypy --strict --no-error-summary --exclude 'setup\.py$' .
      python -m ${main} test
    '';
    preBuild = ''
      # initialize possibly-empty subdirectories as python modules
      find . -type d -exec touch {}/__init__.py \;
      # generate a minimal setup.py
      cat > setup.py << EOF
      from setuptools import setup, find_packages
      setup(
          name='${name}',
          entry_points={'console_scripts':['${name} = ${main}:main']},
          version='0.0.0',
          url='git://simatime.com/biz.git',
          author='dev',
          author_email='dev@simatime.com',
          description='nil',
          packages=find_packages(),
          install_requires=[],
      )
      EOF
    '';
    pythonImportsCheck = [main]; # sanity check
  };
}