{
  description = "4r";

  inputs = {
    nixpkgs.url = github:NixOS/nixpkgs/22.05;
    utils.url = github:numtide/flake-utils;

    relude-src = {
      url = github:kowainik/relude/v1.1.0.0;
      flake = false;
    };
    doctest-src = {
      url = github:sol/doctest/0.20.0;
      flake = false;
    };
    servant-src = {
      url = github:haskell-servant/servant;
      flake = false;
    };
    polysemy-zoo-src = {
      url = github:polysemy-research/polysemy-zoo/006421384e61f4a7f66670e69af926735c91a65e;
      flake = false;
    };
    polysemy-src.url = github:polysemy-research/polysemy/v1.7.1.0;
    servant-polysemy-src = {
      url = github:AJChapman/servant-polysemy/v0.1.3;
      flake = false;
    };
  };

  outputs = inputs@{ nixpkgs, utils, ... }:
    utils.lib.eachDefaultSystem (system:
      let nixpkgs' = import nixpkgs {
            inherit system;
          };
          unwords = nixpkgs'.lib.concatStringsSep " ";
          options = [
            "-Wall"
            "-Wcompat"
            "-Wincomplete-uni-patterns"
            "-Wredundant-constraints"
            "-Wmissing-export-lists"
            "-Wincomplete-record-updates"
            "-Wmissing-deriving-strategies"
          ];
          extensions = [
            "-XNoImplicitPrelude"
            "-XNoFieldSelectors"
            "-XOverloadedRecordDot"
            "-XDuplicateRecordFields"
            "-XBangPatterns"
            "-XBinaryLiterals"
            "-XBlockArguments"
            "-XConstraintKinds"
            "-XDataKinds"
            "-XDeriveFunctor"
            "-XDeriveGeneric"
            "-XDerivingStrategies"
            "-XFlexibleContexts"
            "-XFlexibleInstances"
            "-XGADTs"
            "-XGeneralizedNewtypeDeriving"
            "-XHexFloatLiterals"
            "-XImportQualifiedPost"
            "-XInstanceSigs"
            "-XKindSignatures"
            "-XLambdaCase"
            "-XMultiParamTypeClasses"
            "-XNumericUnderscores"
            "-XOverloadedStrings"
            "-XScopedTypeVariables"
            "-XStandaloneDeriving"
            "-XTupleSections"
            "-XTypeApplications"
            "-XTypeOperators"
            "-XTypeSynonymInstances"
            "-XUndecidableInstances"
          ];
          this = ghcVersion:
            let pkgs = nixpkgs'.haskell.packages.${ghcVersion}.override {
                  overrides = (import ./nix/dependencies.nix inputs ghcVersion);
                };
                _4r-api = pkgs.mkDerivation {
                  pname = "4r-api";
                  version = "0.1.0";
                  src = ./4r-api;
                  isExecutable = false;
                  isLibrary = true;
                  libraryHaskellDepends = with pkgs; [
                    aeson
                    base
                    polysemy
                    relude
                    servant
                    servant-client
                    servant-client-polysemy
                  ];
                  doHaddock = false;
                  doHoogle = false;
                  license = nixpkgs.lib.licenses.gpl3Plus;
                  passthru = { inherit pkgs; };
                };
                _4r = pkgs.mkDerivation {
                  pname = "4r";
                  version = "0.1.0";
                  src = ./4r;
                  isExecutable = true;
                  executableHaskellDepends = with pkgs; [
                    _4r-api
                    aeson
                    ansi-terminal
                    base
                    commonmark
                    commonmark-extensions
                    cryptohash-sha512
                    http-api-data
                    http-client
                    optparse-applicative
                    polysemy
                    relude
                    servant
                    servant-client
                    servant-client-polysemy
                    unordered-containers
                  ];
                  license = nixpkgs.lib.licenses.gpl3Plus;
                  passthru = { inherit pkgs; };
                };
                _4r-feed = pkgs.mkDerivation {
                  pname = "4r-feed";
                  version = "0.1.0";
                  src = ./4r-feed;
                  isExecutable = true;
                  executableHaskellDepends = with pkgs; [
                    _4r-api
                    base
                    cache
                    clock
                    commonmark
                    commonmark-extensions
                    feed
                    http-client
                    http-media
                    http-types
                    mtl
                    polysemy
                    relude
                    servant
                    servant-client
                    servant-client-polysemy
                    servant-server
                    wai-cli
                  ];
                  license = nixpkgs.lib.licenses.gpl3Plus;
                  passthru = { inherit pkgs; };
                };
                fourmolu = nixpkgs'.writeScript "fourmolu"
                  ''
                  set -x
                  ${pkgs.fourmolu}/bin/fourmolu --mode inplace \
                    --indentation 2 --check-idempotence --import-export-comma-style leading \
                    ${unwords (map (e: "-o ${e}") (options ++ extensions))} \
                    $(find . -name '*.hs')
                  '';
             in
            { inherit _4r _4r-api _4r-feed fourmolu; };
          thisNative = this "ghc922";
       in
      {
        packages = thisNative // {
          default = thisNative._4r;
        };

        apps =
          let binaryToApp = bin: { type = "app"; program = "${bin}/bin/${bin.pname}"; };
           in
          rec {
            _4r = binaryToApp thisNative._4r;
            _4r-feed = binaryToApp thisNative._4r-feed;
            default = _4r;
            fourmolu = {
              type = "app";
              program = thisNative.fourmolu.outPath;
            };
          };

        devShells =
          let mkGhci = deriv: dir: deriv.env.overrideAttrs (_: {
                shellHook = ''
                  ghci ${unwords (options ++ extensions)} $(find ${dir} -name '*.hs')
                  exit $?
                '';
              });
           in
          {
            default = thisNative._4r.env;
            _4r = mkGhci thisNative._4r "4r";
            _4r-api = mkGhci thisNative._4r-api "4r-api";
            _4r-feed = mkGhci thisNative._4r-feed "4r-feed";
          };

          nixosModules._4r-feed = { ... }: {
            options = {};
            config =
            let name = "4r-feed";
             in
            {
              users.users.${name} = {
                group = "nobody";
                isSystemUser = true;
              };
              systemd.services.${name} = {
                enable = true;
                script =
                  ''
                  ${thisNative._4r-feed}/bin/4r-feed --host 127.0.0.1 --port 40000 --devlogging
                  '';
                after = ["i2p.service"];
                wantedBy = ["multi-user.target"];
                serviceConfig = {
                  User = name;
                  Group = "nobody";
                };
              };
            };
          };
      });
}