default.nix

# CAUTION! a spelling mistake in arg string is ignored silently.
#
# To use ghc-8.6.5
# nix-shell --argstr compiler "ghc865"

{
  nixpkgs ?
    import (builtins.fetchTarball
    https://github.com/NixOS/nixpkgs/archive/refs/tags/22.05.tar.gz)
        {}
, compiler ? "ghc922"
, c2nix ? "" # cabal2nix CLI options
# TODO
#, sources ? [] # e.g. [./. ./benchmark]
#, hdeps ? [] # e.g. [time, mtl]
#, deps ? [] # e.g. [SDL2]
}:
let haskellPackages =
        if compiler == "default"
        then nixpkgs.haskellPackages
        else nixpkgs.haskell.packages.${compiler};

    # we can possibly avoid adding our package to HaskellPackages like
    # in the case of nix-shell for a single package?
    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;

    flags = "--benchmark --flag fusion-plugin" + " " + c2nix;

    mkHaskellPackages = inShell:
        haskellPackages.override {
            overrides = self: super:
                with nixpkgs.haskell.lib;
                {
                  streamly-statistics = mkPackage super "streamly-statistics" ./. flags inShell;

                  streamly-core =
                      super.callHackageDirect
                        { pkg = "streamly-core";
                          ver = "0.1.0";
                          sha256 = "hoSV6Q2+X5a7hFnJAArqNPjcMaCVyX9Vz4FcxeJ+jgI=";
                        } {};
                        #let src = fetchGit {
                        #    url = "git@github.com:composewell/streamly.git";
                        #    rev = "8240f5f870fe47623df99514aed6a542f80c9641";
                        #}; in super.callCabal2nix "streamly-core" "${src}/core" {};

                  #streamly =
                  #  nixpkgs.haskell.lib.overrideCabal
                  #    (super.callHackageDirect
                  #      { pkg = "streamly";
                  #        ver = "0.9.0";
                  #        sha256 = "sha256-eOxVb8qQjZDo1+S7CStqYSExOg2QHWkMY+zlOYqwZak=";
                  #      } {})
                  #  #  (let src = fetchGit {
                  #  #      url = "git@github.com:composewell/streamly.git";
                  #  #      rev = "96d222e45cf3aee9b6847c0d14fde967a760fee8";
                  #  #  }; in super.callCabal2nix "streamly" src {})
                  #    (old:
                  #      { librarySystemDepends =
                  #          if nixpkgs.lib.strings.hasInfix "darwin" builtins.currentSystem
                  #          then [nixpkgs.darwin.apple_sdk.frameworks.Cocoa]
                  #          else [];
                  #      });

                  #  lockfree-queue =
                  #    super.callHackageDirect
                  #      { pkg = "lockfree-queue";
                  #        ver = "0.2.4";
                  #        sha256 = "1bj9agy3x0yjbscpjgn96gpnj4lvkh39spjvy3jnrr3a42v3ynw7";
                  #      } {};

                    # unicode-data =
                    #   super.callHackageDirect
                    #     { pkg = "unicode-data";
                    #       ver = "0.3.0";
                    #       sha256 = "sha256-3R8ZmLoN/oWU0Mr/V4o/90NqiWaE8fprVULgh8/s/Uc=";
                    #     } {};

                    # tasty-bench =
                    #   super.callHackageDirect
                    #     { pkg = "tasty-bench";
                    #       ver = "0.3";
                    #       sha256 = "0na1q52zr8p1zz8hby4242yjr2zma3js4n91avl7ibsa2y51vrc4";
                    #     } {};
                };
        };

    drv = mkHaskellPackages true;

    shell = drv.shellFor {
        packages = p:
          [ p.streamly-statistics
          ];
        doBenchmark = true;
        # 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).streamly-statistics