#!/bin/sh

# A UI for detecting and selecting all displays. Probes xrandr for connected
# displays and lets user select one to use. User may also select "manual
# selection" which opens arandr.

twoscreen() { # If multi-monitor is selected and there are two screens.
  mirror=$(printf "no\\nyes" | dmenu -i -p "Mirror displays?")

  # Mirror displays using native resolution of external display and a scaled
  # version for the internal display
  if [ "$mirror" = "yes" ]; then
    external=$(echo "$screens" | dmenu -i -p "Optimize resolution for:")
    internal=$(echo "$screens" | grep -v "$external")

    res_external=$(xrandr --query | sed -n "/^$external/,/\+/p" | \
      tail -n 1 | awk '{print $1}')

    res_internal=$(xrandr --query | sed -n "/^$internal/,/\+/p" | \
      tail -n 1 | awk '{print $1}')

    res_ext_x=$(echo "$res_external" | sed 's/x.*//')
    res_ext_y=$(echo "$res_external" | sed 's/.*x//')
    res_int_x=$(echo "$res_internal" | sed 's/x.*//')
    res_int_y=$(echo "$res_internal" | sed 's/.*x//')

    scale_x=$(echo "$res_ext_x / $res_int_x" | bc -l)
    scale_y=$(echo "$res_ext_y / $res_int_y" | bc -l)

    xrandr --output "$external" --auto --scale 1.0x1.0 \
      --output "$internal" --auto --same-as "$external" \
      --scale "$scale_x"x"$scale_y"
  else

    primary=$(echo "$screens" | dmenu -i -p "Select primary display:")
    secondary=$(echo "$screens" | grep -v ^"$primary"$)
    direction=$(printf "left\\nright" | dmenu -i -p "What side of $primary should $secondary be on?")

    xrandr --output "$primary" --auto --scale 1.0x1.0 --output "$secondary" --"$direction"-of "$primary" --auto --scale 1.0x1.0
  fi
}

morescreen() { # If multi-monitor is selected and there are more than two screens.
  primary=$(echo "$screens" | dmenu -i -p "Select primary display:")
  secondary=$(echo "$screens" | grep -v ^"$primary"$ | dmenu -i -p "Select secondary display:")
  direction=$(printf "left\\nright" | dmenu -i -p "What side of $primary should $secondary be on?")
  tertiary=$(echo "$screens" | grep -v ^"$primary"$ | grep -v ^"$secondary"$ | dmenu -i -p "Select third display:")

  xrandr --output "$primary" --auto --output "$secondary" --"$direction"-of "$primary" --auto --output "$tertiary" --"$(printf "left\\nright" | grep -v "$direction")"-of "$primary" --auto
}

multimon() { # Multi-monitor handler.
  case "$(echo "$screens" | wc -l)" in
    2) twoscreen ;;
    *) morescreen ;;
  esac ;}

onescreen() { # If only one output available or chosen.
  xrandr --output "$1" --auto --scale 1.0x1.0 $(echo "$allposs" | grep -v "\b$1" | awk '{print "--output", $1, "--off"}' | paste -sd ' ' -)
}

postrun() { # Stuff to run to clean up.
  { killall dunst ; setsid -f dunst ;} >/dev/null 2>&1 # Restart dunst to ensure proper location on screen
}

# Get all possible displays
allposs=$(xrandr -q | grep "connected")

# Get all connected screens.
screens=$(echo "$allposs" | awk '/ connected/ {print $1}')

# If there's only one screen
[ "$(echo "$screens" | wc -l)" -lt 2 ] &&
  { onescreen "$screens"; postrun; notify-send "Only one screen detected." "Using it in its optimal settings...";  exit ;}

# Get user choice including multi-monitor and manual selection:
chosen=$(printf "%s\\nmulti-monitor\\nmanual selection" "$screens" | dmenu -i -p "Select display arangement:") &&

case "$chosen" in
  "manual selection") arandr ; exit ;;
  "multi-monitor") multimon ;;
  *) onescreen "$chosen" ;;
esac

postrun