{}:

let
  splitSystem = builtins.split "-" builtins.currentSystem;
  currentArch = builtins.elemAt splitSystem 0;
  currentOS = builtins.elemAt splitSystem 2;
in
  with {
    # Look here for information about how pin version of nixpkgs
    #  → https://nixos.wiki/wiki/FAQ/Pinning_Nixpkgs
    pkgs = import (
      builtins.fetchGit {
        # name = "nixpkgs-2021-04-23";
        url = "https://github.com/nixos/nixpkgs/";
        ref = "refs/heads/nixpkgs-unstable";
        rev = "8d0340aee5caac3807c58ad7fa4ebdbbdd9134d6";
      }
    ) {};

    isMacOS = currentOS == "darwin";
    isLinux = currentOS == "linux";
    isAarch64 = currentArch == "aarch64";
  };

  with (pkgs);

  let
    darwin-inputs =
      if isMacOS then
        with pkgs.darwin.apple_sdk.frameworks; [
          AppKit
          CoreFoundation
          CoreServices
          CoreVideo
          Foundation
          Metal
          Security
        ]
      else
        [];

    linux-inputs =
      if isLinux then
        [
          valgrind
          vulkan-headers
          vulkan-loader
          vulkan-tools
          vulkan-validation-layers
          xorg.libX11
          xorg.libXcursor
          xorg.libXrandr
          xorg.libXi
          xorg.libxcb
        ]
      else
        [];

    llvmPkgs = pkgs.llvmPackages_10;
    zig = import ./nix/zig.nix { inherit pkgs isMacOS isAarch64; };
    inputs = [
      # build libraries
      rustc
      cargo
      clippy
      rustfmt
      cmake
      git
      python3
      llvmPkgs.llvm
      llvmPkgs.clang
      pkg-config
      zig
      # lib deps
      llvmPkgs.libcxx
      llvmPkgs.libcxxabi
      libffi
      libunwind
      libxml2
      ncurses
      zlib
      libiconv
      # faster builds - see https://github.com/rtfeldman/roc/blob/trunk/BUILDING_FROM_SOURCE.md#use-lld-for-the-linker
      llvmPkgs.lld
      # dev tools
      # rust-analyzer
      # (import ./nix/zls.nix { inherit pkgs zig; })
    ];

  in
    mkShell (
      {
        buildInputs = inputs ++ darwin-inputs ++ linux-inputs;

        # Additional Env vars
        LLVM_SYS_100_PREFIX = "${llvmPkgs.llvm}";
        LD_LIBRARY_PATH = stdenv.lib.makeLibraryPath
          (
            [
              pkg-config
              stdenv.cc.cc.lib
              llvmPkgs.libcxx
              llvmPkgs.libcxxabi
              libunwind
              libffi
              ncurses
              zlib
            ] ++ linux-inputs
          );

        # Aliases don't work cross shell, so we do this
        shellHook = ''
          export PATH="$PATH:$PWD/nix/bin"
        '';
      }
    )