signal-bot/scripts/install_service.sh

#!/bin/bash

# ============================================================================
# Install, start and verify the signal-bot user service.
#
# A *user* unit, not a system one: the bot runs as whoever registered the
# Signal account and reads that user's .env. Lingering is what makes it start
# at boot with nobody logged in -- without it, "survives reboots" is a lie the
# unit file cannot tell you about, so this script checks and fails loudly.
# ============================================================================

set -euo pipefail

REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
readonly REPO_ROOT
SCRIPT_NAME="$(basename "$0")"
readonly SCRIPT_NAME
readonly UNIT_NAME="signal-bot.service"
readonly UNIT_DIR="${XDG_CONFIG_HOME:-$HOME/.config}/systemd/user"
readonly TEMPLATE="${REPO_ROOT}/scripts/${UNIT_NAME}"
readonly DEFAULT_PORT=8137

VERIFY_ONLY="false"

# shellcheck source=scripts/lib_signal.sh
source "${REPO_ROOT}/scripts/lib_signal.sh"

usage() {
	echo "Usage: $SCRIPT_NAME [--verify-only]"
	echo "  --verify-only   Check the running service without reinstalling it."
	exit 0
}

die() {
	echo "Error: $1" >&2
	exit 1
}

# The port the bot will actually bind: .env wins, code default otherwise.
bot_port() {
	local port=""
	if [[ -f "${REPO_ROOT}/.env" ]]; then
		port="$(sed -n 's/^BIND_PORT=[[:space:]]*//p' "${REPO_ROOT}/.env" | tail -1)"
	fi
	printf '%s' "${port:-$DEFAULT_PORT}"
}

validate_requirements() {
	command -v systemctl >/dev/null || die "systemctl not found; this needs systemd"
	[[ -f "${REPO_ROOT}/.env" ]] ||
		die "no ${REPO_ROOT}/.env -- run scripts/register_bot.sh first"
	[[ -x "${REPO_ROOT}/run.sh" ]] || die "no executable ${REPO_ROOT}/run.sh"
	[[ -f "$TEMPLATE" ]] || die "no unit template at $TEMPLATE"
}

# Without linger, a user unit dies at logout and never starts at boot.
require_linger() {
	if [[ "$(loginctl show-user "$USER" --property=Linger --value)" == "yes" ]]; then
		echo "== linger enabled: the bot starts at boot with nobody logged in"
		return 0
	fi
	echo "== enabling linger for $USER"
	if ! sudo -n loginctl enable-linger "$USER" 2>/dev/null; then
		echo "Error: linger is off and sudo needs a password here." >&2
		echo "       Without it the bot will NOT come back after a reboot." >&2
		echo "       Run this, then re-run with --verify-only:" >&2
		echo >&2
		echo "         sudo loginctl enable-linger $USER" >&2
		return 1
	fi
}

install_unit() {
	mkdir -p "$UNIT_DIR"
	sed "s|@REPO_ROOT@|${REPO_ROOT}|g" "$TEMPLATE" > "${UNIT_DIR}/${UNIT_NAME}"
	systemctl --user daemon-reload
	systemctl --user enable "$UNIT_NAME" >/dev/null
	systemctl --user restart "$UNIT_NAME"
	echo "== installed and started ${UNIT_DIR}/${UNIT_NAME}"
}

# Report what actually happened, not that the commands returned 0.
verify() {
	local port="$1"
	if ! systemctl --user is-active --quiet "$UNIT_NAME"; then
		echo "Error: ${UNIT_NAME} is not active." >&2
		systemctl --user --no-pager --lines=20 status "$UNIT_NAME" >&2 || true
		return 1
	fi
	signal_wait_for_url "http://127.0.0.1:${port}/healthz" "signal-bot" 60
	echo "== active, and answering on http://127.0.0.1:${port}/healthz"
	echo "== enabled at boot: $(systemctl --user is-enabled "$UNIT_NAME")"
}

main() {
	validate_requirements
	local port
	port="$(bot_port)"

	if [[ "$VERIFY_ONLY" != "true" ]]; then
		require_linger
		install_unit
	fi

	verify "$port"
	echo "== logs:  journalctl --user -u ${UNIT_NAME} -f"
}

while [[ $# -gt 0 ]]; do
	case $1 in
	--verify-only)
		VERIFY_ONLY="true"
		shift
		;;
	-h | --help) usage ;;
	*)
		echo "Unknown option: $1" >&2
		exit 1
		;;
	esac
done

main "$@"