#!/bin/bash
set -eu

# Author: ET de Boone, 2020

REMOTE_HOST="${REMOTE_HOST:-}"
REMOTE_PATH="${REMOTE_PATH:-}"
LOCAL_PATH="${LOCAL_PATH:-}"
SSHFS_OPTS="${SSHFS_OPTS:-}"
LOCAL_ROOT="${LOCAL_ROOT:-${HOME}/net}"

MKDIR="mkdir -pv"
RM="rm -dv"
UMOUNT="${UMOUNT:-umount}"
SSHFS="${SSHFS:-sshfs}"

usage() {
	cat <<-Usage
	Usage: $0 [options] [[REMOTE_HOST:]REMOTE_PATH LOCAL_PATH] 

	A simple wrapper around ${SSHFS} and ${UMOUNT} for (un)mounting a directory.
	Note that arguments must be supplied as Environment Variables to be omitted as arguments.

	Options:
	  -h, --help        Show this help message
	  -u, --unmount     Unmount the remote directory
	  -m, --mount       Mount the remote directory

	Arguments/Environment Variables:
	  REMOTE_HOST       Specify a remote host ${REMOTE_HOST:+(default: ${REMOTE_HOST:-})}
	  REMOTE_PATH       Specify a remote path ${REMOTE_PATH:+(default: ${REMOTE_PATH:-})}
	  LOCAL_PATH        Specify a local directory ${LOCAL_PATH:+(default: ${LOCAL_PATH:-})}

	Environment Variables:
	  UMOUNT, SSHFS     Specify used program and options. The paths will be appended (default: ${UMOUNT}, ${SSHFS})
	  SSHFS_OPTS        Specify extra options for mounting using ${SSHFS}. ${SSHFS_OPTS:+(default: ${SSHFS_OPTS:-})}
	  LOCAL_ROOT        Specify root directory to prepend to LOCAL_PATH if it is not absolute ${LOCAL_ROOT:+(default: ${LOCAL_ROOT:-})}
Usage
}

ACTION=""
while [ $# -gt 0 ];
do
	case "$1" in
		-h|--help) usage; exit 0 ;;
		-u|--unmount) ACTION="unmount";;
		-m|--mount)   ACTION="mount";;
		*) break;;
	esac
	shift
done

if [ -z "${ACTION}" ]; then
	usage
	exit 1
fi

# CLI path arguments provided, try to parse them
if [ $# -eq 2 ]; then
	ARG_REMOTE="$1"
	ARG_LOCAL="$2"

	REMOTE_HOST="${ARG_REMOTE%%:*}"
	REMOTE_PATH="${ARG_REMOTE#*:}"
	LOCAL_PATH="${ARG_LOCAL}"
fi

# Prepend LOCAL_ROOT to LOCAL_PATH if needed
if [ "${LOCAL_PATH:0:1}" != "/" ] && [ "${LOCAL_PATH:0:1}" != "." ]; then
	if [ -n "${LOCAL_ROOT}" ]; then
		LOCAL_PATH="${LOCAL_ROOT}/${LOCAL_PATH}"
	else
		echo "Error: LOCAL_ROOT is empty and LOCAL_PATH is not absolute, nor starting with a dot."
		exit 1
	fi
fi

if [ -z "${REMOTE_HOST}" ] || [ -z "${REMOTE_PATH}" ] || [ -z "${LOCAL_PATH}" ]; then
	echo "Error: REMOTE_HOST, REMOTE_PATH, and LOCAL_PATH must be specified."
	exit 1
fi

res=0
if [ "${ACTION}" = "unmount" ]; then
	${UMOUNT} "${LOCAL_PATH}"
	res=$?
	if [ $res -eq 0 ]; then
		${RM} "${LOCAL_PATH}"
	fi
elif [ "${ACTION}" = "mount" ]; then
	${MKDIR} "${LOCAL_PATH}" || { echo "Error: Failed to create directory ${LOCAL_PATH}."; exit 1; }
	${SSHFS} "${REMOTE_HOST}:${REMOTE_PATH}" "${LOCAL_PATH}" ${SSHFS_OPTS}
	res=$?
fi

exit $res