POSIX script to update keybase package to latest nightly on Debian-based Linux

keybase-nightly.sh

#!/usr/bin/env bash

# Keybase publishes a JSON file concurrent with every nightly build upload to their public download web server,
# though they're real cute in the way they parse the timestamp as a UNIX epoch...in milliseconds :-/ That means
# we need to fuss with rounding errors in Bash built-in computations on top of using jq as a parser for the raw
# file instead of what I expected to be some quick "awk-to-humantime-to-apt" pipeline-foo. Still it came out
# fairly snappy and is solid as a rock.

# Set this up as a cron job at the interval of your choosing, it won't do anything until it sees that the
# installed version reported by apt has an older timestamp than the one in the JSON file. When that happens it
# does an unattended update and as a bonus also calls HardCode-Tray (Google it, it's good) to shove another 
# tray/panel icon up its Electron-based backside, since the one they include doesn't scale and looks like shit
# on KDE Plasma 5. (At least I think so...)

NIGHTLY_URL="https://prerelease.keybase.io/nightly"
NIGHTLY_EPOCH="$(curl -s -n ${NIGHTLY_URL}/update-linux-prod.json | jq '.publishedAt')"
((NIGHTLY_EPOCH += 500))
((NIGHTLY_EPOCH /= 1000))
NIGHTLY_DATE="$(date -ud @"${NIGHTLY_EPOCH}" +%Y%m%d%H%M%S)"
INSTALLED_DATE="$(sudo -u "$SUDO_USER" keybase version | grep -Po '(?<=^Client:\s{2}[\.\d]{5}-)\d{14}(?=\+[\d|a-f]+)')"
WORKING_DIR="/tmp/keybase_nightly"
NIGHTLY_DEB="${WORKING_DIR}/keybase_amd64_nightly_${NIGHTLY_DATE}.deb"
DARK_THEME="Papirus-Dark"
LIGHT_THEME="Papirus"

if [ "$NIGHTLY_DATE" -gt "$INSTALLED_DATE" ]; then
  echo "Installed version: $INSTALLED_DATE  Newer version found: $NIGHTLY_DATE"
  logger --tag keybase-nightly --id=$PPID "Found new Keybase client nightly release; commencing download and installation process."
  mkdir -p "${WORKING_DIR}" && wget -O "${NIGHTLY_DEB}" "${NIGHTLY_URL}"/keybase_amd64.deb
  dpkg -i "${NIGHTLY_DEB}" || (
    echo "Unable to install package, file saved to ${NIGHTLY_DEB}."
    exit 1
  )
  if [ -d /srv/local-apt-repository ]; then
    rm -f /srv/local-apt-repository/keybase_amd64_nightly*
    mv -f "${NIGHTLY_DEB}" /srv/local-apt-repository && /usr/lib/local-apt-repository/rebuild
  fi
  rm -rf "${WORKING_DIR}" || echo "Unable to delete the working directory at ${WORKING_DIR}."
  if [ -x /usr/bin/hardcode-tray ]; then
    hardcode-tray -s 22 -ct RSVGConvert -dt "${DARK_THEME}" -lt "${LIGHT_THEME}" -o keybase -a
  fi
  # sudo -u "$SUDO_USER" XDG_RUNTIME_DIR="/run/user/$(id -u "$SUDO_USER")" \
  # DBUS_SESSION_BUS_ADDRESS="unix:path=/run/user/$(id -u "$SUDO_USER")/bus" \
  # systemctl --user restart keybase.gui.service
  logger --tag keybase-nightly --id=$PPID "Successfully installed new Keybase client nightly release."
else
  echo "You already have the latest version : $INSTALLED_DATE"
  logger --tag keybase-nightly --id=$PPID "Checking Keybase client nightly version...latest nightly already installed."
fi