{ lib, pkgs }:
let
  inherit (pkgs) buildPackages callPackage;

  hocon-generator = buildPackages.rustPlatform.buildRustPackage {
    name = "hocon-generator";
    version = "0.1.0";
    src = ./src;

    passthru.updateScript = ./update.sh;

    cargoLock.lockFile = ./src/Cargo.lock;
  };

  hocon-validator = pkgs.writers.writePython3Bin "hocon-validator" {
    libraries = [ pkgs.python3Packages.pyhocon ];
  } ''
    from sys import argv
    from pyhocon import ConfigFactory

    if not len(argv) == 2:
        print("USAGE: hocon-validator <file>")

    ConfigFactory.parse_file(argv[1])
  '';
in {
  # https://github.com/lightbend/config/blob/main/HOCON.md
  format = { generator ? hocon-generator, validator ? hocon-validator
      # `include classpath("")` is not implemented in pyhocon.
      # In the case that you need this functionality,
      # you will have to disable pyhocon validation.
    , doCheck ? true }:
    let
      hoconLib = {
        mkInclude = value:
          let
            includeStatement =
              if lib.isAttrs value && !(lib.isDerivation value) then
                {
                  required = false;
                  type = null;
                  _type = "include";
                } // value
              else {
                value = toString value;
                required = false;
                type = null;
                _type = "include";
              };
          in assert lib.assertMsg (lib.elem includeStatement.type [
            "file"
            "url"
            "classpath"
            null
          ]) ''
            Type of HOCON mkInclude is not of type 'file', 'url' or 'classpath':
            ${(lib.generators.toPretty { }) includeStatement}
          '';
          includeStatement;

        mkAppend = value: {
          inherit value;
          _type = "append";
        };

        mkSubstitution = value:
          if lib.isString value then {
            inherit value;
            optional = false;
            _type = "substitution";
          } else
            assert lib.assertMsg (lib.isAttrs value) ''
              Value of invalid type provided to `hocon.lib.mkSubstition`: ${
                lib.typeOf value
              }
            '';
            assert lib.assertMsg (value ? "value") ''
              Argument to `hocon.lib.mkSubstition` is missing a `value`:
              ${builtins.toJSON value}
            ''; {
              value = value.value;
              optional = value.optional or false;
              _type = "substitution";
            };
      };

    in {
      type = let
        type' = with lib.types;
          let atomType = nullOr (oneOf [ bool float int path str ]);
          in (oneOf [ atomType (listOf atomType) (attrsOf type') ]) // {
            description = "HOCON value";
          };
      in type';

      lib = hoconLib;

      generate = name: value:
        let
          # TODO: remove in 24.11
          # Backwards compatibility for generators in the following locations:
          #  - nixos/modules/services/networking/jibri/default.nix (__hocon_envvar)
          #  - nixos/modules/services/networking/jicofo.nix (__hocon_envvar, __hocon_unquoted_string)
          #  - nixos/modules/services/networking/jitsi-videobridge.nix (__hocon_envvar)
          replaceOldIndicators = value:
            if lib.isAttrs value then
              (if value ? "__hocon_envvar" then
                lib.warn ''
                  Use of `__hocon_envvar` has been deprecated, and will
                  be removed in the future.

                  Please use `(pkgs.formats.hocon {}).lib.mkSubstitution` instead.
                '' (hoconLib.mkSubstitution value.__hocon_envvar)
              else if value ? "__hocon_unquoted_string" then
                lib.warn ''
                  Use of `__hocon_unquoted_string` has been deprecated, and will
                  be removed in the future.

                  Please make use of the freeform options of
                  `(pkgs.formats.hocon {}).format` instead.
                '' {
                  value = value.__hocon_unquoted_string;
                  _type = "unquoted_string";
                }
              else
                lib.mapAttrs (_: replaceOldIndicators) value)
            else if lib.isList value then
              map replaceOldIndicators value
            else
              value;

          finalValue = replaceOldIndicators value;
        in callPackage
        ({ stdenvNoCC, hocon-generator, hocon-validator, writeText }:
          stdenvNoCC.mkDerivation rec {
            inherit name;

            dontUnpack = true;

            json = builtins.toJSON finalValue;
            passAsFile = [ "json" ];

            strictDeps = true;
            nativeBuildInputs = [ hocon-generator ];
            buildPhase = ''
              runHook preBuild
              hocon-generator < $jsonPath > output.conf
              runHook postBuild
            '';

            inherit doCheck;
            nativeCheckInputs = [ hocon-validator ];
            checkPhase = ''
              runHook preCheck
              hocon-validator output.conf
              runHook postCheck
            '';

            installPhase = ''
              runHook preInstall
              mv output.conf $out
              runHook postInstall
            '';

            passthru.json = writeText "${name}.json" json;
          }) {
            hocon-generator = generator;
            hocon-validator = validator;
          };
    };
}