xkcdlock/xkcdlock

#!/usr/bin/env rbash

# xkcd_lock v1
#
# A wrapper around i3lock to display xkcd images on the lock screen
#
# Note that 'latest' needs an internet connection for the download!
# If the download fails it falls back to a specific hard-coded image
#
# Builtin is a function to download all images.
#
# Dependencies: rbash, i3lock, xrandr, awk, curl,
#               convert (from imagick)
#
# © 2016 Björn Busse (see also: LICENSE)
# bbusse@baerlin.eu
#
# Thanks to Randall Patrick Munroe! BTC 1FhCLQK2ZXtCUQDtG98p6fVH7S6mxAsEey
# Thanks to Michael Stapelberg for an awesome window manager - i3
#
# TODO:
# - make sure we do not exceed screen boundaries in x and y
# - add tooltip overlay and xkcd number
# - parallelize downloads

[[ "$TRACE" ]] && set -x
set -eo pipefail

readonly SCRIPT_NAME=$(basename $0)

# screensaver executable
LOCK_BIN="i3lock"
# verbosity
VERBOSE=0
# "latest" or "random"
IMG_CHOICE="random"
# path to images
IMG_PATH="${HOME}/Pictures/xkcd_comics"
# default / fallback image
IMG_DEFAULT="not_really_into_pokemon.png"
# background colour
BG_COLOUR="white"

DOWNLOAD_DISCLAIMER="\nThe downloaded images will end up in your current working directory.\n\
Since we are using restricted bash, we can not change path.\n\
Use '-y' instead of '-d' to really start the download to the current working directory.\n"

log() {
    if (( 1=="${VERBOSE}" )); then
        echo "$@" >&2
    fi

    logger -p user.notice -t $SCRIPT_NAME "$@"
}

error() {
    echo "$@" >&2
    logger -p user.error -t $SCRIPT_NAME "$@"
}

# does not work with restricted bash (bash -r/rbash)
get_script_path() {
    echo $(dirname $(readlink -f $0))
}

show_help() {
    printf "\n xkcd_lock v1\n\n\
 Available options are:\n\n \
   -d  download images to current working directory\n \
   -h  show this help\n \
   -i  show specific image file - overrides '-m'\n \
   -l  lock program: one of i3lock/swaylock\n \
   -m  latest|random                                   default: random\n \
   -v  be verbose\n\n"
}

xkcd_get_latest_image() {
    if [[ -z $(which curl) ]]; then
        error "Could not find curl to get latest image"
        exit 1
    fi

    log "Looking for latest image"
    local img_url=$(curl -s http://xkcd.com/index.html | \
                    awk '/Image URL \(for hotlinking\/embedding\): / {print $5}' | \
                    awk 'BEGIN{FS="<";} {print $1}')

    if [[ -z $img_url ]]; then
        error "Can not download latest image, using fallback image"
        local img_fn="${IMG_DEFAULT}"
    else
        log "Downloading: $img_url"
        curl -sO --max-time 6 "$img_url"

        if [[ 0="$?" ]]; then
            local img_fn=$(echo "$img_url" | awk 'BEGIN{FS="/";} {print $5}')
        else
            error "Can not download latest image, using fallback image"
            local img_fn="${IMG_DEFAULT}"
        fi
    fi

    echo "$img_fn"
}

xkcd_get_img_name() {
    echo $(echo "$img_url_hotlink" | awk 'BEGIN{FS="/";} {print $5}')
}

xkcd_get_all_images() {
    VERBOSE="1"

    if [[ -z $(which curl) ]]; then
        error "Could not find curl to download images"
        exit 1
    fi

    log "Looking for latest image"
    local nimg_latest=$(curl -s http://xkcd.com/index.html | \
                        awk '/Permanent link to this comic: / {print $6}' | \
                        awk 'BEGIN{FS="/";} {print $4}')

    log "Found: $nimg_latest"

    for ((i=1; i<=$nimg_latest; i++)); do
        local img_url_hotlink=$(xkcd_get_hotlink_url $i)
        local img_name=$(xkcd_get_img_name $img_url_hotlink)

        if [[ -e "$img_name" ]]; then
            log "$img_name exists. Skipping download"
            continue
        fi

        log "Downloading ${i} ${img_url_hotlink} (${img_name})"
        local r=$(curl -sO $img_url_hotlink)
        log "Success: $r"
    done

    echo 0
}

xkcd_get_hotlink_url() {
    local url="http://xkcd.com/$i"
    local url_hotlink="$(curl -sL $url | awk '/Image URL \(for hotlinking\/embedding\): / {print $5}')"
    echo $url_hotlink
}

get_nscreens() {
    local nscreens=$(xrandr -q | awk '/ connected/ {count++} END {print count}')
    echo "$nscreens"
}

screen_get_smallest_resolution() {
    local res=$(xrandr -q | awk '/*/ {print $1}' \
                | awk 'BEGIN{FS="x";} NR==1 || $1<min {line=$0; min=$1}; END {print line}')

    echo "$res"
}

screen_get_highest_resolution() {
    local res=$(xrandr -q | awk '/*/ {print $1}' \
                          | awk 'BEGIN{FS="x";} NR==1 || $1>max {line=$0; max=$1}; END {print line}')

    echo "$res"
}

get_random_image() {
    local img_fn="$(find $IMG_PATH -type f | shuf -n 1)"

    if ! [[ -e "$img_fn" ]]; then
        error "Could not find image to display"
    fi

    echo "$img_fn"
}

resize_image() {
    local tmp_file=$(mktemp)

    log "Resizing $img_fn to $res and saving image to $tmp_file"
    convert -adaptive-resize $res $img_fn $tmp_file

    if ! [[ -e "$tmp_file" ]]; then
        error "Could not find resized image"
        exit 1
    fi

    echo "$tmp_file"
}

center_image() {
    local tmp_file=$(mktemp)

    log "Centering $tmp_file and saving image to $tmp_file"
    convert $tmp_file_r -gravity center -background $BG_COLOUR -extent $res $tmp_file

    if ! [[ -e "$tmp_file" ]]; then
        error "Could not find centered image"
        exit 1
    fi

    echo "$tmp_file"
}

prepare_image() {
    local res=$(screen_get_highest_resolution)

    local tmp_file_r=$(resize_image $img_fn $res)
    local tmp_file_c=$(center_image $tmp_file_r $res)

    echo "$tmp_file_c"
}

screen_lock() {
    local img_fn_final=$(prepare_image $img_fn)

    log "Locking screen with $img_fn"
    $LOCK_BIN -i $img_fn_final
}

main() {
    local locker=$(which $LOCK_BIN)
    local OPTIND

    while getopts "h?i:l:vm:dy" opt; do
        case "$opt" in
        d)
            printf "%s${DOWNLOAD_DISCLAIMER}"
            printf "%s\nCurrent working directory: ${PWD}\n\n"
            exit 0
            ;;
        h|\?)
            show_help
            exit 0
            ;;
        i)
            local img_fn="${OPTARG}"
            local r=$(screen_lock $img_fn)
            exit 0
            ;;
        l)
            if [[ "sway"="${OPTARG}" ]]; then
               LOCK_BIN="swaylock"
            fi
            ;;
        m)
            IMG_CHOICE="${OPTARG}"
            ;;
        v)
            VERBOSE=1
            ;;
        y)
            r=$(xkcd_get_all_images)
            exit 0
        esac
    done

    if ! [[ -d "$IMG_PATH" ]]; then
        error "Image directory does not exist: $IMG_PATH"
        exit 1
    fi

    if [[ -z $(which xrandr) ]]; then
        error "Could not find xrandr to determine screen size"
        exit 1
    fi

    if [[ -z "$locker" ]]; then
        error "Could not find screen locker: $lock_bin"
        exit 1
    fi

    if [[ -z $(which convert) ]]; then
        error "Could not find $convert_bin \nYou need imagick"
        exit 1
    fi

    case "$IMG_CHOICE" in
        "latest")   local img_fn=$(xkcd_get_latest_image);;
        "random")   local img_fn=$(get_random_image);;
    esac

    screen_lock $img_fn
}

main "$@"