{ lib, stdenv, fetchurl, linkFarm, dub, ldc, removeReferencesTo, }:

# See https://nixos.org/manual/nixpkgs/unstable#dlang for more detailed usage information

{
# A lockfile generated by `dub-to-nix` from the source of the package.
# Can be either a path to the file, or an attrset already parsed with `lib.importJSON`.
dubLock,
# The build type to pass to `dub build` as a value for the `--build=` flag.
dubBuildType ? "release",
# The flags to pass to `dub build` and `dub test`.
dubFlags ? [ ],
# The flags to pass to `dub build`.
dubBuildFlags ? [ ],
# The flags to pass to `dub test`.
dubTestFlags ? [ ],
# The D compiler to be used by `dub`.
compiler ? ldc, ... }@args:

let
  makeDubDep = { pname, version, sha256, }: {
    inherit pname version;
    src = fetchurl {
      name = "dub-${pname}-${version}.zip";
      url = "mirror://dub/${pname}/${version}.zip";
      inherit sha256;
    };
  };

  lockJson = if lib.isPath dubLock then lib.importJSON dubLock else dubLock;

  lockedDeps = lib.mapAttrsToList
    (pname: { version, sha256 }: makeDubDep { inherit pname version sha256; })
    lockJson.dependencies;

  # a directory with multiple single element registries
  # one big directory with all .zip files leads to version parsing errors
  # when the name of a package is a prefix of the name of another package
  dubRegistryBase = linkFarm "dub-registry-base" (map (dep: {
    name = "${dep.pname}/${dep.pname}-${dep.version}.zip";
    path = dep.src;
  }) lockedDeps);

  combinedFlags = "--skip-registry=all --compiler=${lib.getExe compiler} ${
      toString dubFlags
    }";
  combinedBuildFlags =
    "${combinedFlags} --build=${dubBuildType} ${toString dubBuildFlags}";
  combinedTestFlags = "${combinedFlags} ${toString dubTestFlags}";
in stdenv.mkDerivation (builtins.removeAttrs args [ "dubLock" ] // {
  strictDeps = args.strictDeps or true;

  nativeBuildInputs = args.nativeBuildInputs or [ ]
    ++ [ dub compiler removeReferencesTo ];

  configurePhase = args.configurePhase or ''
    runHook preConfigure

    export DUB_HOME="$NIX_BUILD_TOP/.dub"
    mkdir -p $DUB_HOME

    # register dependencies
    ${lib.concatMapStringsSep "\n" (dep: ''
      dub fetch ${dep.pname}@${dep.version} --cache=user --skip-registry=standard --registry=file://${dubRegistryBase}/${dep.pname}
    '') lockedDeps}

    runHook postConfigure
  '';

  buildPhase = args.buildPhase or ''
    runHook preBuild

    dub build ${combinedBuildFlags}

    runHook postBuild
  '';

  doCheck = args.doCheck or false;

  checkPhase = args.checkPhase or ''
    runHook preCheck

    dub test ${combinedTestFlags}

    runHook postCheck
  '';

  preFixup = ''
    ${args.preFixup or ""}

    find "$out" -type f -exec remove-references-to -t ${compiler} '{}' +
  '';

  disallowedReferences = [ compiler ];

  meta = { platforms = dub.meta.platforms; } // args.meta or { };
})