switch-to

#!/bin/bash 

usage() {
  printf '%s\n' "Usage: switch-to [-hcn] open_cmd
Switch focus to a particular X window, or open a new one if no matches are found.

where:
  -h, --help  - show this help text
  -n, --name  - the window title of the window to switch focus to
  -c, --class - the WM_CLASS of the window to switch focus to"
}

main() {
  # Switch focus using either window name or class
  if [[ -n "${WINDOW_NAME}" ]]; then
    wmctrl -a "${WINDOW_NAME}"
  elif [[ -n "${WM_CLASS}" ]]; then
    wmctrl -xa "${WM_CLASS}"
  fi

  # If it didn't switch, use the given cmd to open a new window
  if (( "$?" != 0 )); then
    ${OPEN_CMD}
  fi
}

# Option parsing
declare PARAMS=''
declare WINDOW_NAME
declare WM_CLASS
declare OPEN_CMD
while (( "$#" )); do
  case $1 in
    -h|--help)  # display help message
      usage
      exit 1
      ;;
    -n|--name)  # set window name
      WINDOW_NAME="$2"
      shift 2
      ;;
    -c|--class) # set WM_CLASS
      WM_CLASS="$2"
      shift 2
      ;;
    --)  # End argument parsing
      shift
      break
      ;;
    -*|--*)  # unsupported flags
      echo "Unsupported flag: $1" >&2
      usage
      exit 1
      ;;
    *)  # preserve positional arguments
      PARAMS="${PARAMS} '$1'"
      shift
      ;;
  esac
done

# set positional arguments in their proper place
eval set -- "${PARAMS}"

# parse positional args
OPEN_CMD="$1"

# validate parameters
if [[ -z "${OPEN_CMD}" ]]; then
  echo "Error: missing 'open_cmd' positional parameter" 1>&2
  usage
  exit 1
fi

if [[ -n "${WINDOW_NAME}" && -n "${WM_CLASS}" ]]; then
  echo "Error: cannot set both '--name' and '--class' flags" 1>&2
  usage
  exit 1
fi

# Freeze configuration flags
readonly WINDOW_NAME WM_CLASS OPEN_CMD

main