let
  nixpkgsPath_21_11 =
    "https://github.com/NixOS/nixpkgs/archive/refs/tags/21.11.tar.gz";
  nixpkgsDefault = import (builtins.fetchTarball nixpkgsPath_21_11) { };
in
{
  nixpkgs ? nixpkgsDefault
, compiler ? "default"
}:
let haskellPackages =
        if compiler == "default"
        then nixpkgs.haskellPackages
        else nixpkgs.haskell.packages.${compiler};

    mkPackage = super: pkg: path: opts: inShell:
                let orig = super.callCabal2nixWithOptions pkg path opts {};
                 in if inShell
                    # Avoid copying the source directory to nix store by using
                    # src = null.
                    then orig.overrideAttrs (oldAttrs: { src = null; })
                    else orig;

    mkPkgGit = super: gitSrc: rev: name:
      let
        src = builtins.fetchGit {
          url = gitSrc;
          rev = rev;
        };
      in super.callCabal2nix name src { };

  mkPkgGitRef = super: gitSrc: rev: ref: name:
    let
      src = builtins.fetchGit {
        url = gitSrc;
        rev = rev;
        ref = ref;
      };
    in super.callCabal2nix name src { };

    mkHaskellPackages = inShell:
        haskellPackages.override {
            overrides = self: super:
                with nixpkgs.haskell.lib;
                {
                    test-runner = mkPackage super "test-runner" ./. "" inShell;
                    streamly-targets = mkPackage super "streamly-targets" ../../targets "" false;

                    bench-report =
                      nixpkgs.haskell.lib.overrideCabal
                        (let src = fetchGit {
                            url = "git@github.com:composewell/bench-report.git";
                            rev = "3e016780cd125f6c074b70f4ffed2329e2c4ab68";
                        }; in super.callCabal2nix "bench-report" src {})
                        (old:
                          { enableLibraryProfiling = false;
                            doHaddock = false;
                          });

                    bench-show = super.callHackageDirect {
                      pkg = "bench-show";
                      ver = "0.3.2";
                      sha256 = "16b8vyzdp9b5bh34kqmbfwjsyv8wgnxxwl8kjcpgxjsh52xzyaa0";
                    } { };

#                    streamly-coreutils = let
#                      src = "git@github.com:composewell/streamly-coreutils.git";
#                      rev = "a12756efe24bbf303f2f6d66a95426c7657d297b";
#                    in mkPkgGit super src rev "streamly-coreutils";

                    streamly-coreutils =
                      nixpkgs.haskell.lib.overrideCabal
                        (let src = fetchGit {
                            url = "git@github.com:composewell/streamly-coreutils.git";
                            rev = "b1e6fc37f0e898c54378129750d3ccc1c034f611";
                        }; in super.callCabal2nix "streamly-coreutils" src {})
                        (old:
                          { librarySystemDepends =
                              if builtins.currentSystem == "x86_64-darwin"
                              then [nixpkgs.darwin.apple_sdk.frameworks.Cocoa]
                              else [];
                            #enableLibraryProfiling = false;
                            doHaddock = false;
                            doCheck = false;
                          });

                    streamly-shell = let
                      src = "https://github.com/composewell/streamly-shell.git";
                      rev = "1b3fea3239ebe47963955d81565b9d5e34567ab7";
                    in mkPkgGit super src rev "streamly-shell";

                    streamly-process = let
                      src = "https://github.com/composewell/streamly-process.git";
                      rev = "e310c8a9c6e61515373a2f5f1fb82f6e15fe452b";
                    in nixpkgs.haskell.lib.dontCheck
                      (mkPkgGit super src rev "streamly-process");

                    #streamly-process = nixpkgs.haskell.lib.dontCheck
                    #  (super.callHackageDirect {
                    #    pkg = "streamly-process";
                    #    ver = "0.1.0";
                    #    sha256 = "01nxisqfmn29fbirdsx71sfjp2rdqwrf469qyjcql2d11i1bxn94";
                    #  } { });

          #          streamly = super.callHackageDirect {
          #            pkg = "streamly";
          #            ver = "0.8.0";
          #            sha256 = "0vy2lkljizlhpbpbybmg9jcmj2g4s1aaqd2dzy5c0y0n4rgwxask";
          #          } { };
                  streamly =
                    nixpkgs.haskell.lib.overrideCabal
                      #(super.callHackageDirect
                      #  { pkg = "streamly";
                      #    ver = "0.8.2";
                      #    sha256 = "sha256-CjFq9SCdbgLZa7NqOE4OtC8OaFg4vK8VmIDjGU5rGko=";
                      #  } {})
                      (let src = fetchGit {
                          url = "git@github.com:composewell/streamly.git";
                          rev = "14ee0b70363cf925e9cc067bf1df4ecbd047ac38";
                      }; in super.callCabal2nix "streamly" src {})
                      (old:
                        { librarySystemDepends =
                            if builtins.currentSystem == "x86_64-darwin"
                            then [nixpkgs.darwin.apple_sdk.frameworks.Cocoa]
                            else [];
                          #enableLibraryProfiling = false;
                          doHaddock = false;
                        });

                  streamly-core =
                    nixpkgs.haskell.lib.overrideCabal
                      (let src = fetchGit {
                          url = "git@github.com:composewell/streamly.git";
                          rev = "14ee0b70363cf925e9cc067bf1df4ecbd047ac38";
                      }; in super.callCabal2nix "streamly-core" "${src}/core" {})
                      (old:
                        { librarySystemDepends =
                            if builtins.currentSystem == "x86_64-darwin"
                            then [nixpkgs.darwin.apple_sdk.frameworks.Cocoa]
                            else [];
                          #enableLibraryProfiling = false;
                          doHaddock = false;
                        });

                };
        };

    drv = mkHaskellPackages true;

    shell = drv.shellFor {
        packages = p:
          [ p.test-runner
          ];
        # Use a better prompt
        shellHook = ''
          export CABAL_DIR="$(pwd)/.cabal.nix"
          if test -n "$PS_SHELL"
          then
            export PS1="$PS_SHELL\[$bldred\](nix)\[$txtrst\] "
          fi
        '';
    };
in if nixpkgs.lib.inNixShell
   then shell
   else (mkHaskellPackages false).test-runner