# Gets the id of the current focused window.
#
# Authors:
#   Alex Reece <awreece@gmail.com>
#

case "$OSTYPE" in
  (darwin*)
    osascript -e 'tell application "System Events" to ¬' \
              -e '  set focus_app_name to ¬' \
              -e '    name of first application process ¬' \
              -e '    whose frontmost is true' \
              -e 'tell application focus_app_name to ¬' \
              -e '  get id of front window'
    ;;
  (linux-gnu*)
    # http://stackoverflow.com/a/8688624/447288
    xprop -root -f _NET_ACTIVE_WINDOW 0x ' $0' _NET_ACTIVE_WINDOW  \
      | awk '{print $2}'
    ;;
  (*)
    return 1
    ;;
esac