#!/usr/bin/env bash
#
# Performs a standard screen lock, with an extra bit of style. Before locking
# the screen, takes a screenshot of the current display and programatically
# blurs and desaturates the image, using that for the lock screen background. A
# mighty neat effect. 
#
# Requirements: i3-lock imagemagick [scrot] [xbacklight]
#


#
# Generates the command to execute for taking a screenshot and applying affects
# for use as the lockscreen wallpaper. Note that this does not execute the
# command. It only generates it.
#
# @param out_file Path to save the lockscreen wallpaper to
#
function gen_wallpaper_cmd {
  # Return early if argument 1 not specified
  [[ -z ${1} ]] && return

  out_file=${1}
  tmp_file="/tmp/i3lock$(date '+%s')screen.jpg"

  screenshot_cmd=""
  if [[ $(which import 2>/dev/null) ]]; then
    screenshot_cmd="$(which import) -window root ${tmp_file}"
  elif [[ $(which scrot 2>/dev/null) ]]; then
    screenshot_cmd="$(which scrot) -d0 ${tmp_file}"
  fi

  # Generate the wallpaper gen command
  if [[ ${screenshot_cmd} != "" ]]; then
    # Generate the lockscreen background/screenshot (blurred and slightly less
    # saturated)
    out=${screenshot_cmd}
    # Add the image blur command
    out=${out}' && '
    out=${out}"convert ${tmp_file} -blur 0x4 -modulate 110,50 ${out_file}"
    # Add command to clean up the original screenshot file
    out="${out} && "
    out="${out} rm ${tmp_file}"
    echo "${out}"
  fi
  # Else we echo nothing, indicating no screenshotter was found
}


#
# Locks the screen using i3lock command. Sets 
#
# @param bg Path to image to be used for the lockscreen wallpaper
#
function lock_screen {
  # Return early if argument 1 not specified
  [[ -z ${1} ]] && return

  bg=${1}
  dim=0
  [[ $(which xbacklight) ]] && dim=1

  if [[ ${dim} == 1 ]]; then
    # Get the previous brightness so we can return to it.
    prev_bright=$(xbacklight | cut -d '.' -f 1)

    # Dim the screen, backgrounded so it continues fading after lock
    xbacklight -set 3% -time 2000 -steps 150&
  fi

  # Lock, but remain in foreground so the unlock processes aren't executed yet
  i3lock -i "${bg}" -n

  # Resume original brightness
  [[ ${dim} == 1 ]] && xbacklight -set ${prev_bright}% -time 2000 -steps 150
}


#
# La fonction primaire
#
function main {
  blurry_wallpaper='/tmp/i3lockwall.png'
  # Get the program path that will screenshot for the background image
  lock_wallpaper_cmd=$(gen_wallpaper_cmd ${blurry_wallpaper})

  if [[ ${lock_wallpaper_cmd} == "" ]]; then
    echo "Screenshot command not found (scrot or import). Exiting."
    exit 1
  fi

  # Execute in a subshell, or the double amperstands (&&) will fail. Seems I've
  # discovered a querk of bash.
  bash -c "${lock_wallpaper_cmd}"

  # Execute the lock screen with the new fancy wallpaper
  lock_screen ${blurry_wallpaper}

  # Cleanup the original screenshot and blurred counterpart
  rm "${bg}"
}


# Enter the script here
main ${ARGV}