shell.nix

with import <nixpkgs-unstable> { };

let
  # define packages to install with special handling for OSX
  basePackages = [
    git
    beam.packages.erlangR23.elixir_1_11
    nodejs-15_x
    postgresql_13
    nodePackages.node2nix
  ];

  inputs = basePackages ++ lib.optional stdenv.isLinux inotify-tools
    ++ lib.optionals stdenv.isDarwin
    (with darwin.apple_sdk.frameworks; [ CoreFoundation CoreServices ]);

  # define shell startup command
  hooks = ''
    # this allows mix to work on the local directory
    mkdir -p $PWD/.nix-mix
    mkdir -p $PWD/.nix-hex
    export MIX_HOME=$PWD/.nix-mix
    export HEX_HOME=$PWD/.nix-mix
    export PATH=$MIX_HOME/bin:$PATH
    export PATH=$HEX_HOME/bin:$PATH
    mix local.hex --if-missing
    export LANG=en_US.UTF-8
    export ERL_AFLAGS="-kernel shell_history enabled"

    # postges related
    export PGDATA="$PWD/db"
  '';

in mkShell {
  buildInputs = inputs;
  shellHook = hooks;
}