#!/bin/bash

### README
#############################################
# A basic wallpaper rotator, fetching pictures from https://unsplash.com
#
## Install
#
# Dependencies:
# * [feh image viewer](https://feh.finalrewind.org/)
# * [wget](https://www.gnu.org/software/wget/)
# Both should be available in the packages of your OS.
#
# Save this file to a directory listed in your PATH, as: `~/bin`
#
#   wget https://gist.githubusercontent.com/Em-AK/e54653c3ca390d7eaf6bc89dc46cc1c2/raw/wallpaper > ~/bin/wallpaper
#
# Make the file executable
#
#   chmod +x ~/bin/wallpaper
#
# Edit the value of STORAGE_DIR in the script below to specify where you want
# to store your saved wallpapers. Or create the default directory:
#
#   mkdir -p ~/images/unsplash
#
## Usage
#
#   wallpaper [-rsl]
#
# options:
#   -r : set a random wallpaper from unsplash.com. The file is saved in a
#        temporary location (see TMP_PICTURE_PATH). This file is erased every
#        time a new remote picture is fetched.
#        This option fallsback to the behaviour of option -l if unsplash.com is
#        not reachable in PING_TIMEOUT (default 2) seconds.
#   -s : save the current wallpaper in the local storage.
#   -l : set a random wallpaper from the local storage.
#
# `wallpaper` (no option) is equivalent to `wallpaper -r`
#
## Extra
#
# You can add a crontab job to change your wallpaper periodically with `crontab -e`
# For example this job will rotate your wallpaper every hour at 42min
#
#   42 * * * * /home/emak/bin/wallpaper

### Constants
#############################################
     STORAGE_DIR="$HOME/images/unsplash"
TMP_PICTURE_PATH="$HOME/.wallpaper.jpg"
 UNSPLASH_DOMAIN="unsplash.com"
    PING_TIMEOUT=2
 NEW_PICTURE_URL="https://source.unsplash.com/random/1920x1080"

### Functions
#############################################
function download_random_remote {
  wget $NEW_PICTURE_URL -O $1
}

function set_wallpaper {
  DISPLAY=:0 feh --bg-fill $1
}

function set_random_local_wallpaper {
  DISPLAY=:0
  shuf -ezn 1 $STORAGE_DIR/* | xargs -0 -n1 feh --bg-fill
}

function try_remote {
  ping $UNSPLASH_DOMAIN -c 1 -w $PING_TIMEOUT &> /dev/null
  if [ $? -ne 0 ]; then
    set_random_local_wallpaper
  else
    download_random_remote $TMP_PICTURE_PATH
    set_wallpaper $TMP_PICTURE_PATH
  fi
}

function save_temp_to_store {
  filename="photo-$(sha1sum $TMP_PICTURE_PATH | cut -d ' ' -f 1).jpg"
  cp $TMP_PICTURE_PATH $STORAGE_DIR/$filename
}

### Main
#############################################
if (($# == 0)); then
  # when no argument is given
  try_remote
else
  while getopts ":lrs" option
  do
    case "$option" in
      # -l local
      # set a random wallpaper from local
      l)
        set_random_local_wallpaper
        ;;

      # -r remote
      # set a random wallpaper from remote
      r)
        try_remote
        ;;

      # -s save/store
      # save temporary wallpaper to store
      s)
        save_temp_to_store
        ;;

      \?)
        echo "Invalid option: -$OPTARG" >&2
        ;;
    esac
  done
fi