ssm/sm

#!/usr/bin/env bash
shopt -s nullglob

# Utility functions
## Make setting default values a bit less awkward
default() {
	declare -n _p=$1
	
	if ! [[ "$_p" ]]; then
		_p=$2
	fi
}

## Die. Why not?
die() {
	declare code=${1:-0}

	[[ "$2" ]] && printf '%s\n' "$2"
	exit "$code"
}

## Run the command and wait for it to die
svc() {
	svc::cleanup() {
		kill -n "$service_stop_signal" "$service_pid"

		pid_wait "$service_pid" && {
			rm -f $svc_pidfile $service_ready_flag
		}
	}; trap 'svc::cleanup' TERM INT

	svc::reload() {
		kill -n "$service_reload_signal" "$service_pid"
	}; trap 'svc::reload' HUP

	"$@" &
	service_pid=$!

	while nullexec kill -n 0 "$service_pid"; do
		wait
	done
}

#cat >/dev/null << EOF
## Respawn
respawn() {
	respawn::cleanup() {
		kill -n 15 $(jobs -p)
		wait
		exit 0
	}; trap 'respawn::cleanup' TERM

	while true; do
		exec "$@" &
		job_pid=$!
		wait
	done
}
#EOF

## Run a command with its output discarded
nullexec() {
	"$@" &>/dev/null
}

## Wait for a pid to die
pid_wait() {
	declare cnt=0

	while nullexec kill -0 "$1"; do
		(( cnt >= (service_stop_timeout*10) )) && return 1
		sleep 0.1
		(( cnt++ ))
	done

	return 0
}

## See if NAME is a function
is_function() {
	declare name=$1 name_tupe

	name_type=$( type -t "$name" )

	if [[ $name_type == 'function' ]]; then
		return 0
	fi

	return 1
}

## Simple timer
timer() {
	declare cnt timeout=$1
	shift

	while ! "$@"; do
		(( cnt >= (timeout*10) )) && return 1
		sleep 0.1
		(( cnt++ ))
	done

	return 0
}

## Is a service ready?
is_ready() [[ -f "$service_ready_flag" ]]

## Wait for this service to get ready
wait_ready() {
	timer "$service_ready_timeout" is_ready
}

## Depend on other services to be started
depend() {
	declare s

	for s in "$@"; do
		if ! "$0" "$s" qstatus; then
			nullexec "$0" "$s" start || {
				failed_deps+=( "$s" )
				return 1
			}
		fi
	done
}

## Depend on other services to be ready
depend_ready() {
	declare s

	depend "$@" || return 1

	for s in "$@"; do
		"$0" "$s" wait_ready || {
			failed_deps+=( "$s" )
			return 1
		}
	done
}

# Super functions
## Start the service, write down the svc pid
super_start() {
	(( service_running )) && return 3

	[[ -f "${service_command[0]}" ]] || return 9

	depend "${service_depends[@]}" || return 7
	depend_ready "${service_depends_ready[@]}" || return 7

	if (( service_managed )); then
		if (( service_respawn )); then
			svc respawn "${service_command[@]}" &>"$service_logfile" &
		else
			svc "${service_command[@]}" &>"$service_logfile" &
		fi

		svc_pid=$!

		printf '%s' "$svc_pid" > "$svc_pidfile"
	else
		"${service_command[@]}" &
	fi

	if timer "$service_ready_timeout" ready; then
		printf '1' > "$service_ready_flag"
	else
		return 5
	fi

	return 0
}

# A separate function for oneshot services
super_oneshot() {
	(( service_enabled )) && return 3
}

## Reload the service
## Usually just sends HUP
super_reload() {
	(( service_running )) || return 3

	kill -n 1 "$service_pid"
}

## Stop the service
## Returns:
##   3: Service is not running.
super_stop() {
	(( service_running )) || return 3

	nullexec kill -n "$service_stop_signal" "$service_pid" || return 1
	pid_wait "$service_pid" || return 5

	return 0
}

# Overloadable functions
start() { super_start; }
stop() { super_stop; }
reload() { super_reload; }
restart() {
	"$0" "$service_name" stop
	"$0" "$service_name" start
}

logs() { cat "$service_logfile"; }

## Status is a bit of a special case. It's talkative.
status() {
	(( service_running )) && return 0
	return 1
}

## For use in scripts
qstatus() { nullexec status; }

## By default there is no ready check
ready() { :; }

# Code
main() {
	# Let's set some defaults
	service_managed=1

	if (( $UID )); then
		# XDG stuff
		default XDG_CONFIG_HOME "$HOME/.config"
		default XDG_RUNTIME_DIR "/run/user/$UID"

		cfgdir="$XDG_CONFIG_HOME/sm"
		rundir="$XDG_RUNTIME_DIR/sm"
		logdir="$HOME/log/sm"
	else
		cfgdir='/etc/sm'
		rundir='/run/sm'
		logdir='/var/log/sm'
	fi

	# Load custom functions
	for f in "$cfgdir/functions"/*; do
		source "$f" || die 9 "Failed to source functions from $f"
	done
	
	# Now create the needed runtime stuff
	for d in "$rundir" "$logdir"; do
		mkdir -p "$d" || die 3 "Failed to create runtime dir: $d"
	done

	# service_name is just $1
	service_name=$1
	
	# Semi-hardcoded stuff
	svc_pidfile="$rundir/$service_name.pid"

	# Get the service defaults
	[[ -f "$cfgdir/conf.d/$1" ]] && {
		source "$cfgdir/conf.d/$1" || die 5 "Failed to read service defaults: $cfgdir/conf.d/$1"
	}

	# Get the service config
	source "$cfgdir/init.d/$1" || die 7 "Failed to read the service config: $cfgdir/init.d/$1"
	
	# Legacy
	[[ "$service_args" ]] && service_command=( "${service_command[@]}" "${service_args[@]}" )
	[[ "$service_respawn" == 'true' ]] && service_respawn=1

	[[ "$service_pidfile" ]] && service_managed=0

	if ! (( service_managed )); then
		(( service_respawn )) && die 21 "Refusing to respawn a service that manages itself."
	fi

	# Service-level defaults
	default service_pidfile "$svc_pidfile"
	default service_logfile "$logdir/$service_name.log"
	default service_stop_timeout 30
	default service_ready_timeout 15
	default service_stop_signal 15
	default service_reload_signal 1
	default service_ready_flag "$rundir/$service_name.ready"

	# Let's see if there's a PID
	if [[ -f "$service_pidfile" ]]; then
		service_pid=$(<$service_pidfile)
	
		# Let's see if it's running
		if nullexec kill -0 "$service_pid"; then
			service_running=1
		fi
	fi

	# Check if action is even defined
	is_function "$2" || die 17 "Function $2 is not defined for $service_name."

	# Run pre_$action function
	if is_function "pre_$2"; then
		"pre_$2" || {
			printf 'pre_%s failed!\n' "$2"
			die 13
		}
	fi

	# Run the function
	case "$2" in
		stop)
			printf 'Stopping %s... ' "$service_name"

			stop; res=$?

			case "$res" in
				0) printf 'ok.\n';;
				3) printf 'not running.\n' "$service_name";;
				5) printf 'timed out.\n';;
				*) printf 'fail.\n';;
			esac
		;;

		start)
			printf 'Starting %s... ' "$service_name"

			start; res=$?

			case "$res" in
				0) printf 'ok.\n';;
				3) printf 'already running.\n';;
				5) printf 'readyness check timed out.\n';;
				7) printf 'dependencies failed: %s.\n' "${failed_deps[@]}";;
				9) printf 'service_command does not exist: %s.\n' "${service_command[0]}";;
				*) printf 'fail.\n';;
			esac
		;;

		reload)
			printf 'Reloading %s... ' "$service_name"

			reload; res=$?

			case "$res" in
				0) printf 'ok.\n';;
				*) printf 'fail.\n';;
			esac
		;;

		status)
			status; res=$?

			case "$res" in
				0) printf '%s is running/enabled.\n' "$service_name";;
				1) printf '%s is not running/enabled.\n' "$service_name";;
				*) printf '%s: status unknown.\n' "$service_name";;
			esac
		;;

		logs) logs;;

		*) "$2"; res=$?;;
	esac

	(( res )) && return "$res"

	# Run post_$action function
	if is_function "post_$2"; then
		"post_$2" || {
			printf 'post_%s failed!\n' "$2"
			die 15
		}
	fi
}

main "$@"