#! /usr/bin/bash

set -euo pipefail
IFS=$'\n\t'

API_KEY="${NASA_API_KEY:-DEMO_KEY}"
if [ "${API_KEY}" = "DEMO_KEY" ]; then
    echo "No API key set! using demo key."
fi

WALLPAPERS="$(systemd-path user)"/Pictures/nasa

mkdir --parents "${WALLPAPERS}"

APOD_URL="https://api.nasa.gov/planetary/apod?api_key=${API_KEY}"
echo "Fetching data from API"
response="$(curl --silent "${APOD_URL}")"
echo "Received response from API"
# shellcheck disable=SC2005
echo "$(printf '%s' "${response}" | jq '.')"
echo "Parsing data"
picture_date="$(printf '%s' "${response}" | jq --raw-output .date)"
picture_url="$(printf '%s' "${response}" | jq --raw-output .hdurl)"

echo "Generating output filename"
extension="${picture_url##*.}"
filename="${picture_date}.${extension}"
outfile="${WALLPAPERS}/${filename}"

if [ -f "${outfile}" ]; then
    echo "Target file already exists"
else
    echo "Creating temporary file"
    tempfile="$(mktemp)"
    echo "Fetching the daily picture"
    curl \
        --location \
        --output "${tempfile}" \
        --silent \
        "${picture_url}"
    echo "Transaction-like file update"
    mv "${tempfile}" "${outfile}"
fi

echo "Updating the wallpaper image"
ln \
    --force \
    --symbolic \
    "${outfile}" \
    "${WALLPAPERS}/today"
echo "Refreshing the desktop background"
swaymsg output "*" bg "${SWAY_WALLPAPER}" fill