#!/bin/sh

# stateful script to manage dual monitor setups

read_cfg() {
  if [ -f ~/.config/xrandr ]; then
    . ~/.config/xrandr
  fi
  if [ -z "${PRIMARY_MONITOR}" ]; then
    PRIMARY_MONITOR=$(get_default_monitor)
  fi
  if [ -z "${MONITOR_RELATION}" ]; then
    MONITOR_RELATION="solo"
  fi
}

show_cfg() {
  printf "PRIMARY_MONITOR=${PRIMARY_MONITOR}\n"
  printf "SECONDARY_MONITOR=${SECONDARY_MONITOR}\n"
  printf "MONITOR_RELATION=${MONITOR_RELATION}\n"
}

get_default_monitor() {
  xrandr --listmonitors | grep -v ^Monitors | head -n 1 | awk '{print $NF}'
}

apply_monitor_cfg() {
  xrandr --output ${PRIMARY_MONITOR} --auto --primary
  if [ ! -z "${SECONDARY_MONITOR}" ] && [ "${SECONDARY_MONITOR}" != "${PRIMARY_MONITOR}" ]; then
    case ${MONITOR_RELATION} in
      solo)  
        xrandr --output ${SECONDARY_MONITOR} --off ;;
      left-of|right-of|above|below)
        xrandr --output ${SECONDARY_MONITOR} --auto --${MONITOR_RELATION} ${PRIMARY_MONITOR} ;;
    esac
  else
    echo "SECONDARY_MONITOR is not set, or same as PRIMARY_MONITOR:"
    show_cfg
  fi
}

helpme() {
  printf "$0 [list | setup | primary [NAME] | secondary [NAME] | relation [NAME] | reconfigure]\n"
  printf "  commands:\n"
  printf "    list: show monitor info\n"
  printf "    setup: show current setup\n"
  printf "    primary: set primary monitorp\n"
  printf "    secondary: set secondary monitor\n"
  printf "    relation: set monitor relation\n"
  printf "    reconfigure: set monitor config based on the relation\n"
  printf "  relations:\n"
  printf "    solo: disable secondary monitor\n"
  printf "    left-of,right-of,above,below: secondary monitor has named relation to primary\n"
}

read_cfg

case "$1" in
  list)
    xrandr --listmonitors ;;
  setup)
    show_cfg ;;
  primary)
    PRIMARY_MONITOR=${2}
    show_cfg > ~/.config/xrandr
    ;;
  secondary)
    SECONDARY_MONITOR=${2}
    show_cfg > ~/.config/xrandr
    ;;
  relation)
    MONITOR_RELATION=${2}
    show_cfg > ~/.config/xrandr
    ;;
  reconfigure)
    apply_monitor_cfg ;;
  *)
    helpme
esac