#!/bin/sh
# Modem AT Command Safe Executor (Zero-dependency, Dynamic Timeout)
# Dante <dante@seckv.com>

DEVICE=""
COMMAND=""
TIMEOUT=3
BAUDRATE=115200

SMS_TO=""
SMS_MSG=""

while [ $# -gt 0 ]; do
	case "$1" in
		-d) DEVICE="$2"; shift 2 ;;
		-c) COMMAND="$2"; shift 2 ;;
		-t) TIMEOUT="$2"; shift 2 ;;
		-b) BAUDRATE="$2"; shift 2 ;;
		--sms-to) SMS_TO="$2"; shift 2 ;;
		--sms-msg) SMS_MSG="$2"; shift 2 ;;
		*) shift ;;
	esac
done

if [ -z "$DEVICE" ]; then
	echo "Usage: $0 -d <device> [-c <command>] [--sms-to <number> --sms-msg <text>]" >&2
	exit 1
fi

if [ -z "$COMMAND" ] && [ -z "$SMS_TO" ]; then
	echo "Usage: Either -c <command> or --sms-to <number> must be specified" >&2
	exit 1
fi

case "$DEVICE" in
	/dev/ttyUSB*|/dev/ttyACM*) ;;
	*)
		echo "ERROR: Invalid device path $DEVICE" >&2
		exit 2
		;;
esac

if [ ! -c "$DEVICE" ]; then
	echo "ERROR: Device $DEVICE not found" >&2
	exit 3
fi

# Dynamic Timeout auto-detection: long-running commands like AT+COPS=? or scan
if [ -n "$SMS_TO" ]; then
	[ "$TIMEOUT" -lt 15 ] && TIMEOUT=15
else
	case "$COMMAND" in
		*COPS=\?*|*COPS\?*|*QSCAN*|*GTCCINFO*|*SCAN*)
			[ "$TIMEOUT" -lt 60 ] && TIMEOUT=60
			;;
	esac
fi

LOCKFILE="/var/lock/modem_$(basename "$DEVICE").lock"
mkdir -p /var/lock

# Acquire exclusive file lock compatible with Busybox flock (-n -x FD)
exec 9>"$LOCKFILE"
locked=0
waited=0
while [ $waited -le "$TIMEOUT" ]; do
	if flock -n -x 9 2>/dev/null; then
		locked=1
		break
	fi
	sleep 1
	waited=$((waited + 1))
done

if [ $locked -eq 0 ]; then
	echo "ERROR: Device $DEVICE busy, lock timed out" >&2
	exit 4
fi

# Fast path: Prioritize native sms_tool engine if installed (zero echo loop, robust termios)
if command -v sms_tool >/dev/null 2>&1; then
	TMP_OUT="/tmp/at_sms_$$.tmp"
	TMP_DONE="/tmp/at_sms_$$.done"
	rm -f "$TMP_OUT" "$TMP_DONE"

	(
		if [ -n "$SMS_TO" ]; then
			sms_tool -d "$DEVICE" -b "$BAUDRATE" send "$SMS_TO" "$SMS_MSG" > "$TMP_OUT" 2>&1
		else
			sms_tool -d "$DEVICE" -b "$BAUDRATE" at "$COMMAND" > "$TMP_OUT" 2>&1
		fi
		echo $? > "$TMP_DONE"
	) &
	CHILD_PID=$!

	elapsed=0
	while [ $elapsed -lt "$TIMEOUT" ]; do
		if [ -f "$TMP_DONE" ] || ! kill -0 "$CHILD_PID" 2>/dev/null; then
			break
		fi
		sleep 1
		elapsed=$((elapsed + 1))
	done

	if [ ! -f "$TMP_DONE" ] && kill -0 "$CHILD_PID" 2>/dev/null; then
		kill -9 "$CHILD_PID" 2>/dev/null || true
		for p in $(pgrep -f "sms_tool.*$DEVICE" 2>/dev/null); do
			kill -9 "$p" 2>/dev/null || true
		done
		RC=124
		OUT="ERROR: Command timed out after ${TIMEOUT}s"
	else
		wait "$CHILD_PID" 2>/dev/null
		RC=$(cat "$TMP_DONE" 2>/dev/null || echo 0)
		OUT=$(cat "$TMP_OUT" 2>/dev/null)
	fi
	rm -f "$TMP_OUT" "$TMP_DONE"

	flock -u 9 2>/dev/null || true
	CLEAN_OUT=$(echo "$OUT" | tr -d "\r")
	if [ $RC -eq 0 ] && ! echo "$CLEAN_OUT" | grep -qE "ERROR|\+CME ERROR|\+CMS ERROR"; then
		if [ -z "$CLEAN_OUT" ]; then
			echo "OK"
		else
			echo "$CLEAN_OUT"
			case "$CLEAN_OUT" in
				*OK*) ;;
				*) echo "OK" ;;
			esac
		fi
		exit 0
	else
		case "$COMMAND" in
			*CFUN=1,1*|*CFUN=16*|*QPOWD*)
				if ! echo "$CLEAN_OUT" | grep -qE "ERROR|\+CME ERROR|\+CMS ERROR"; then
					[ -z "$CLEAN_OUT" ] && echo "OK" || echo "$CLEAN_OUT"
					exit 0
				fi
				;;
		esac
		echo "$CLEAN_OUT"
		exit ${RC:-1}
	fi
fi

command -v stty >/dev/null 2>&1 && stty -F "$DEVICE" "$BAUDRATE" raw -echo -echoe -echok min 0 time 2 2>/dev/null || true

OUT_FILE="/tmp/at_out_$$.tmp"
rm -f "$OUT_FILE"

(
	exec 3<>"$DEVICE"
	# Drain stale residual buffer
	dd if="$DEVICE" of=/dev/null bs=512 count=1 2>/dev/null || true
	cat <&3 > "$OUT_FILE" &
	CAT_PID=$!

	if [ -n "$SMS_TO" ]; then
		# Text mode SMS sending
		printf "AT+CMGF=1\r\n" >&3
		sleep 1
		printf "AT+CMGS=\"%s\"\r\n" "$SMS_TO" >&3
		sleep 1
		printf "%s\x1A" "$SMS_MSG" >&3

		elapsed=0
		while [ $elapsed -lt "$TIMEOUT" ]; do
			sleep 1
			elapsed=$((elapsed + 1))
			if [ -f "$OUT_FILE" ]; then
				if grep -q "\+CMGS:" "$OUT_FILE" 2>/dev/null && grep -q "OK" "$OUT_FILE" 2>/dev/null; then
					break
				elif grep -qE "\+CMS ERROR|\+CME ERROR|ERROR" "$OUT_FILE" 2>/dev/null; then
					break
				fi
			fi
		done
	else
		printf "%s\r\n" "$COMMAND" >&3

		elapsed=0
		while [ $elapsed -lt "$TIMEOUT" ]; do
			sleep 1
			elapsed=$((elapsed + 1))
			if [ -f "$OUT_FILE" ] && grep -qE "OK|ERROR|\+CME ERROR|\+CMS ERROR" "$OUT_FILE" 2>/dev/null; then
				break
			fi
		done
	fi

	kill -9 "$CAT_PID" 2>/dev/null || true
	exec 3>&-
)

flock -u 9 2>/dev/null || true

if [ -f "$OUT_FILE" ]; then
	cat "$OUT_FILE" | tr -d "\r"
	rm -f "$OUT_FILE"
fi

exit 0