os/pkgs/toggle-kbd-layout.nix

self:
with self; ''
  set -e

  current_layout=$(${sway}/bin/swaymsg -t get_inputs | ${jq}/bin/jq -r '.[] | select(.type == "keyboard") | .xkb_active_layout_index' | head -1)
  total_layouts=$(${sway}/bin/swaymsg -t get_inputs | ${jq}/bin/jq -r '.[] | select(.type == "keyboard") | .xkb_layout_names | length' | head -1)

  next_layout_index=$(expr $current_layout + 1);

  if [ $next_layout_index -ge $total_layouts ]; then
    next_layout_index=0;
  fi

  ${sway}/bin/swaymsg input '*' xkb_switch_layout "$next_layout_index"

  echo $next_layout_index
  next_layout=$(${sway}/bin/swaymsg -t get_inputs | ${jq}/bin/jq  -r "[ .[] | select(.type == \"keyboard\") | .xkb_layout_names ][0].[$next_layout_index]")
  ${libnotify}/bin/notify-send "$next_layout"
''