feat: give the rooms a line to the church broker
The first piece of turning these machines into connected endpoints. classroom-mqtt is one small service per room that subscribes, validates what arrives, and hands the work to commands that already exist. Nothing in the room depends on it. A broker that is down, a network that is missing, a machine with no broker configured at all — each is a service sitting quietly, not a classroom that fails. Nothing waits for it at boot and the shipped default is off, so every existing classroom upgrades into this release with messaging disabled until a broker exists. The room is the hostname, which is already how these machines are named. Topics carry no product name because the broker is the church's and these are just rooms: classroom/notify/all, classroom/notify/<room>, and a retained classroom/status/<room> so anyone asking later can be told which rooms are up without waiting for them to say so again. Notifications are events and are never retained; status is state and is. Stale messages cannot come back, which is the property that matters most and has two halves. The session is clean, so a broker never hands over a backlog from while the room was off. And retained notifications are refused on arrival, because otherwise one would replay into every room at every reboot forever. The honest limit is written down: MQTT only flags a retained message when it is replayed to a new subscription, so a retained publish delivered live is indistinguishable from an ordinary one and is shown once — which is right, since it is live at that moment, and the replay is the actual hazard. Delivery reuses the session-aware sender rather than a second copy of it. classroom-notify-test grew into the real thing, so it is now classroom-notify with the sample sender a wrapper over it, and its 36 tests came along. The broker password lives in device.conf, so that file stops being world readable: 0640 root:classroom, which everything that reads it already satisfies. Transport logic is kept free of any broker library so it can be tested without one — 40 checks on room identity, the topic contract and which payloads become notifications. Separately verified against a real mosquitto: connect, subscribe, retained status, per-room and all-room delivery, urgency, duplicate and expired and malformed messages ignored, the broker killed with the daemon surviving, reconnect, and a stale retained notification left on the broker not reaching the screen when a room boots. Co-Authored-By: Claude Opus 5 <[email protected]>
This commit is contained in:
ekklesia
co-authored by
Claude Opus 5
Claude Opus 5
parent
c3106edd30
commit
dfd42f6fdf
Executable
+214
@@ -0,0 +1,214 @@
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#!/bin/bash
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set -euo pipefail
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# Puts a notification on the classroom screen, from anywhere.
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#
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# classroom-notify "Title" "Body text"
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# classroom-notify --critical "Parent Call" "Room 3 needs a parent."
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# classroom-notify --urgency=low "DVD" "Disc ejected."
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# sudo classroom-notify --dry-run
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#
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# Used by classroom-notify-test to send a sample, and by classroom-mqtt
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# to put messages from the church broker on the screen.
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#
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# The classroom desktop runs as the classroom user, and mako is attached
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# to that user's D-Bus session. An administrator over SSH sits in a
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# different session where nothing owns org.freedesktop.Notifications, so
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# a plain notify-send there asks D-Bus to start a second mako, which has
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# no display to open and times out with NoReply. Find the running desktop
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# session and deliver into it instead.
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CLASSROOM_USER=classroom
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urgency=normal
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dry_run=false
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while [[ $# -gt 0 ]]; do
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case "$1" in
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--critical)
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urgency=critical
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shift
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;;
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--low)
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urgency=low
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shift
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;;
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--urgency=*)
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urgency="${1#--urgency=}"
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case "$urgency" in
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low|normal|critical) ;;
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*) urgency=normal ;;
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esac
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shift
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;;
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--dry-run)
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dry_run=true
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shift
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;;
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--)
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shift
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break
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;;
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-*)
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echo "classroom-notify: unknown option $1" >&2
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echo "usage: classroom-notify-test [--low|--critical] [--dry-run] [title] [body]" >&2
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exit 2
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;;
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*)
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break
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;;
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esac
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done
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title="${1:-DVD Ready}"
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body="${2:-A disc is ready to play.}"
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fail() {
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echo "classroom-notify: $1" >&2
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exit 1
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}
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# Another process's environment, or nothing. Reading this needs ptrace
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# access, which root has on the endpoint but not, for instance, inside a
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# container with CAP_SYS_PTRACE dropped — so every caller has to cope
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# with getting nothing back.
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read_environ() {
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{ tr '\0' '\n' < "/proc/$1/environ"; } 2>/dev/null || true
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}
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environ_value() {
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printf '%s\n' "$1" | sed -n "s/^$2=//p" | head -n 1
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}
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# sway holds its own wayland-N.lock open, so the display name can be read
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# back off the process instead of being guessed at.
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display_from_lock() {
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local link target
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for link in "/proc/$1/fd"/*; do
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target="$(readlink "$link" 2>/dev/null || true)"
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case "$target" in
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*/wayland-*.lock)
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target="${target%.lock}"
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echo "${target##*/}"
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return 0
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;;
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esac
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done
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return 0
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}
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classroom_uid="$(id -u "$CLASSROOM_USER" 2>/dev/null || true)"
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[[ -n "$classroom_uid" ]] ||
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fail "there is no $CLASSROOM_USER user on this machine."
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current_uid="$(id -u)"
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runner=()
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session="this session"
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source_note="inherited from this session"
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if [[ "$current_uid" == "$classroom_uid" &&
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-n "${WAYLAND_DISPLAY:-}" &&
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-n "${DBUS_SESSION_BUS_ADDRESS:-}" ]]; then
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# Already inside the classroom desktop session.
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sway_pid="n/a"
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runtime_dir="${XDG_RUNTIME_DIR:-}"
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bus="$DBUS_SESSION_BUS_ADDRESS"
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wayland_display="$WAYLAND_DISPLAY"
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else
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session="the $CLASSROOM_USER desktop session"
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sway_pid="$(pgrep -u "$CLASSROOM_USER" -x sway | head -n 1 || true)"
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[[ -n "$sway_pid" ]] ||
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fail "no classroom desktop session is running: there is no sway process for user $CLASSROOM_USER."
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# Checked before anything that needs to look inside the session, so
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# an administrator gets told what to do rather than a permission
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# error from somewhere further down.
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if [[ "$current_uid" != "$classroom_uid" && "$current_uid" != "0" ]]; then
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fail "run this as root (sudo classroom-notify) or as the $CLASSROOM_USER user."
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fi
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environment_block="$(read_environ "$sway_pid")"
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if [[ -n "$environment_block" ]]; then
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source_note="read from sway (pid $sway_pid)"
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else
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source_note="sway's environment was unreadable; using session defaults"
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fi
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runtime_dir="$(environ_value "$environment_block" XDG_RUNTIME_DIR)"
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runtime_dir="${runtime_dir:-/run/user/$classroom_uid}"
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[[ -d "$runtime_dir" ]] ||
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fail "the classroom session runtime directory $runtime_dir does not exist."
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bus="$(environ_value "$environment_block" DBUS_SESSION_BUS_ADDRESS)"
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bus="${bus:-unix:path=$runtime_dir/bus}"
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case "$bus" in
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unix:path=*)
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bus_socket="${bus#unix:path=}"
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bus_socket="${bus_socket%%,*}"
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[[ -S "$bus_socket" ]] ||
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fail "the classroom session bus socket $bus_socket does not exist. Is the desktop session fully up?"
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;;
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esac
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wayland_display="$(environ_value "$environment_block" WAYLAND_DISPLAY)"
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if [[ -z "$wayland_display" ]]; then
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wayland_display="$(display_from_lock "$sway_pid")"
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fi
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environment=(
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"XDG_RUNTIME_DIR=$runtime_dir"
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"DBUS_SESSION_BUS_ADDRESS=$bus"
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)
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# notify-send only needs the bus. The display is passed through for
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# the sake of anything else in the session, and its absence is not
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# worth refusing to send over.
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if [[ -n "$wayland_display" ]]; then
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environment+=("WAYLAND_DISPLAY=$wayland_display")
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fi
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if [[ "$current_uid" == "$classroom_uid" ]]; then
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runner=(env "${environment[@]}")
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else
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runner=(runuser -u "$CLASSROOM_USER" -- env "${environment[@]}")
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fi
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fi
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# Deliver to the mako that is already running. Sending into a session
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# without one would have D-Bus start a second mako, which is exactly the
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# failure this script exists to avoid.
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pgrep -u "$CLASSROOM_USER" -x mako >/dev/null 2>&1 ||
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fail "mako is not running in the classroom session, and this will not start it. Check with: pgrep -u $CLASSROOM_USER -a mako"
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if [[ "$dry_run" == true ]]; then
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echo "Would notify $session:"
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echo " sway pid: $sway_pid"
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echo " session environment: $source_note"
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echo " XDG_RUNTIME_DIR: $runtime_dir"
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echo " DBUS_SESSION_BUS_ADDRESS: $bus"
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echo " WAYLAND_DISPLAY: ${wayland_display:-(not resolved)}"
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echo " urgency: $urgency"
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echo " title: $title"
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echo " body: $body"
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exit 0
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fi
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"${runner[@]}" notify-send \
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--app-name="Ekklesia Classroom" \
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--urgency="$urgency" \
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-- \
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"$title" "$body"
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echo "Sent $urgency notification to $session: $title"
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