{ }:

with {
  # Look here for information about how pin version of nixpkgs
  #  → https://nixos.wiki/wiki/FAQ/Pinning_Nixpkgs
  pkgs = import (builtins.fetchGit {
    name = "nixpkgs-2020-10-24";
    url = "https://github.com/nixos/nixpkgs-channels/";
    ref = "refs/heads/nixpkgs-unstable";
    rev = "502845c3e31ef3de0e424f3fcb09217df2ce6df6";
  }) { };

  isMacOS = builtins.currentSystem == "x86_64-darwin";
};

with (pkgs);

let
  darwin-frameworks =
    if isMacOS then
      with pkgs.darwin.apple_sdk.frameworks; [
        AppKit
        CoreFoundation
        CoreServices
        CoreVideo
        Foundation
        Metal
        Security
      ]
    else
      [ ];
  llvmPkg = pkgs.llvm_10;
  lldPkg = pkgs.lld_10; # this should match llvm's version
  clangPkg = pkgs.clang_10; # this should match llvm's version
  zig = import ./nix/zig.nix { inherit pkgs isMacOS; };
  inputs =
    [
      # build libraries
      rustc
      cargo
      clippy
      rustfmt
      cmake
      git
      python3
      llvmPkg
      clangPkg
      valgrind
      pkg-config
      zig
      # llb deps
      libffi
      libxml2
      xorg.libX11
      zlib
      vulkan-headers
      vulkan-loader
      vulkan-tools
      vulkan-validation-layers
      # faster builds - see https://github.com/rtfeldman/roc/blob/trunk/BUILDING_FROM_SOURCE.md#use-lld-for-the-linker
      lldPkg
      # dev tools
      rust-analyzer
      # (import ./nix/zls.nix { inherit pkgs zig; })
      ccls
    ];
in mkShell {
  buildInputs = inputs ++ darwin-frameworks;
  LLVM_SYS_100_PREFIX = "${llvmPkg}";

  APPEND_LIBRARY_PATH = stdenv.lib.makeLibraryPath [
      pkgconfig
      vulkan-headers
      vulkan-loader
      vulkan-tools
      vulkan-validation-layers
      xorg.libX11
      xorg.libXcursor
      xorg.libXrandr
      xorg.libXi
      libcxx
      libcxxabi
      libunwind
    ];

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