#!/bin/bash
set -Eeuo pipefail

# Used to check environment variables have been set.
# In use it is called by do_chroot.sh and do_umount.sh
#
# Works safely, but not expected to be run independently.
# It mounts the FILE_SYSTEM_DIR specified in ARM_root.sh.
# If necessary, you can run do_umount.sh to unmount it.

# Define chroot mounts, without a leading /.
# Needed by do_chroot.sh.
# Used as $i in:
#    mount --bind /$i ./$i
#    umount ./$i
export CHROOT_MOUNT_SET="dev dev/pts proc sys"

#
# Check environment variables, then mount the filesystem.
#
main(){
	local CONFIG_FILE="${1}"

	check_config_file_is_specified "$CONFIG_FILE"
	check_config_file_exists "$CONFIG_FILE"
	check_config_file_is_executable "$CONFIG_FILE"

	. $CONFIG_FILE

	check_for_unset_variables "$CONFIG_FILE"
	mount_filesystem_if_not_mounted "$CONFIG_FILE"
}

check_config_file_is_specified() {
	local CONFIG_FILE="${1}"

	if [ -z "$CONFIG_FILE" ]; then
		echo "Error: CONFIG_FILE not specified."
		exit 1
	fi
}

check_config_file_exists() {
	local CONFIG_FILE="${1}"

	if [ ! -f "$CONFIG_FILE" ]; then
		cat <<-!
		Error: $CONFIG_FILE is missing.
		Expecting $CONFIG_FILE to set FILE_SYSTEM_DIR and POOL_PREFIX,
		perhaps something like:
		  export FILE_SYSTEM_DIR=/space/amd64/devuan/beowulf/tasmotizer
		  
		  # On our zfs, /space/amd64/... is the mount of rpool/amd64/...
		  # RPOOL_ROOT is specified to convert from one to the other.
		  export POOL_PREFIX=/space
		  export RPOOL_ROOT=rpool
		!
		exit 1
	fi
}

check_config_file_is_executable() {
	local CONFIG_FILE="${1}"

	if [ ! -x "$CONFIG_FILE" ]; then
		echo "Error: $CONFIG_FILE is not executable."
		exit 2
	fi
}

check_for_unset_variables() {
	local CONFIG_FILE="${1}"

	# Check for unset variables. Allow unset variables here.
	set +u;
	    if [ -z "$FILE_SYSTEM_DIR" ]; then
		echo "Error: FILE_SYSTEM_DIR was not set in $CONFIG_FILE."
		exit 3
	    fi;
	set -u

	# Check for unset variables. Allow unset variables here.
	set +u;
	    if [ -z "$POOL_PREFIX" ]; then
		echo "Error: POOL_PREFIX was not set in $CONFIG_FILE."
		exit 4
	    fi;
	set -u
	
	# Check for unset variables. Allow unset variables here.
	set +u;
	    if [ -z "$RPOOL_ROOT" ]; then
		echo "Error: RPOOL_ROOT was not set in $CONFIG_FILE."
		exit 5
	    fi;
	set -u
	
}

mount_filesystem_if_not_mounted() {
	local CONFIG_FILE="${1}"

	check_for_unset_variables $CONFIG_FILE

	# On our zfs, /space/amd64/... is the mount of rpool/amd64/...
	# Get the pool name (change POOL_PREFIX for RPOOL_ROOT).
	local RPOOL=${FILE_SYSTEM_DIR/${POOL_PREFIX}/${RPOOL_ROOT}}
	
	# Mount if not mounted
	if [ -z "$(grep "${RPOOL} "  /proc/mounts)" ]; then
		sudo zfs mount $RPOOL
	fi
}

# Entry point.
main ./ARM_root.sh