NIX_SHELL_PLUGIN_DIR=${0:a:h}

which bash > /dev/null 2>&1
if [ "$?" -ne "0" ]; then
  echo
  echo "  WARNING: bash is not installed."
  echo "  for zsh-nix-shell to work bash has to be in PATH"
  echo
fi


# extracts packages argument from args and passes them in $NIX_SHELL_PACKAGES variable.
function nix-shell() {
  local -a ARGS; ARGS=("$@")
  local NIX_SHELL_PACKAGES="${NIX_SHELL_PACKAGES}"

  # extract -p|--packages argument into NIX_SHELL_PACKAGES
  local IN_PACKAGES=0
  local PURE=0
  while [[ ${#ARGS[@]} -gt 0 ]]
  do
    key=${ARGS[1]}
    # enter "--packages packages..." mode
    if [[ $key = "-p" || $key = "--packages" ]]
    then
      IN_PACKAGES=1
      NIX_SHELL_PACKAGES+=${NIX_SHELL_PACKAGES:+ }${ARGS[2]}
      ARGS=("${ARGS[@]:1}")

    # skip "--arg name value" argument
    elif [[ $key = "--arg" ]]
    then
      IN_PACKAGES=0
      ARGS=("${ARGS[@]:2}")

    elif [[ $key = "--pure" ]]
    then
      PURE=1

    # skip all other unary arguments
    elif [[ $key == "-"* ]]
    then
      IN_PACKAGES=0
      ARGS=("${ARGS[@]:1}")

    # If we don't have any argument prefix we are either in package mode
    # or we have encountered the path argument
    elif [[ $IN_PACKAGES = 1 ]]
    then
      NIX_SHELL_PACKAGES+=" $key"
    fi
    ARGS=("${ARGS[@]:1}")
  done

  # call real nix shell
  if [[ $PURE = 1 ]]
  then
    # if you use --pure you get bash
    command nix-shell "$@"
  else
    NIX_EXECUTING_SHELL=$(readlink -f /proc/$$/exe)
    if [[ -z "$NIX_EXECUTING_SHELL" ]] && command -v lsof &> /dev/null
    then
      NIX_EXECUTING_SHELL=$(lsof -p $$ | awk '$4=="txt" {print $9}' | head -n 1)
    fi
    if [[ -z "$NIX_EXECUTING_SHELL" ]] && command -v zsh &> /dev/null
    then
      NIX_EXECUTING_SHELL="zsh"
    fi
    if [[ -z "$NIX_EXECUTING_SHELL" ]]
    then
      echo "could not determine executing shell. please install `lsof` or `zsh` directly to your PATH"
      echo "If this error persists create an issue at https://github.com/chisui/zsh-nix-shell/issues/new/choose"
      return 1
    fi
    NIX_SHELL_PACKAGES="$NIX_SHELL_PACKAGES" \
    NIX_BUILD_SHELL="$NIX_SHELL_PLUGIN_DIR/scripts/buildShellShim" \
    NIX_EXECUTING_SHELL=$NIX_EXECUTING_SHELL \
    command nix-shell "$@"
  fi
}