{ pkgs ? import <nixpkgs> {} }:
pkgs.mkShell {
  NIX_ENFORCE_PURITY=0;
  buildInputs = with pkgs; [
    cargo
    rustc
    rustfmt
  ];
  shellHook = ''
    function log_header {
      echo -ne "==> \e[32m\e[1m$1\e[0m\n\n"
    }
    function log_subheader {
      echo -ne "--> \e[33m\e[1m$1\e[0m\n\n"
    }
    function log {
      echo -ne "    $1\n"
    }

    echo ""
    log_header "rust_environment"
    if [ -s Cargo.toml ]; then
      log_subheader "found Cargo.toml, running 'cargo-build'"
      cargo build
      echo ""
    fi
    log_header "package versions"
    log "$(rustc --version)"
    log "$(cargo --version)"
  '';
}