#!/bin/sh
# -*- indent-tabs-mode: nil; -*-
#:
#: A ZFS management helper tool.
#:
#: :Author:    Franz Glasner
#: :Copyright: (c) 2022 Franz Glasner.
#:             All rights reserved.
#: :License:   BSD 3-Clause "New" or "Revised" License.
#:             See LICENSE for details.
#:             If you cannot find LICENSE see
#:             <https://opensource.org/licenses/BSD-3-Clause>
#: :ID:        @(#)@@PKGORIGIN@@ $HGid$
#:

set -eu

VERSION="@@VERSION@@"

USAGE='
USAGE: fzfs [ OPTIONS ] COMMAND [ COMMAND OPTIONS ] [ ARG ... ]

OPTIONS:

  -V    Print the program name and version number to stdout and exit

  -h    Print this help message to stdout and exit

COMMANDS:

  mount [-O] [-u] [-n] DATASET [MOUNTPOINT]

    Mount the ZFS dataset DATASET and all its children to mountpoint
    MOUNTPOINT

    -O        Also mount datasets at mountpoints outside of their "natural"
              and inherited mountpoints
    -N        Mount at their "natural" configured ZFS mountpoints
              (MOUNTPOINT is not required)
    -P        Do not mount the given parent DATASET but only its children
    -n        Do not really mount but show what would be mounted where
    -u        Alias of -n

  umount DATASET

    Unmount the mounted DATASET and all its children

  unmount

    Alias for `umount'"'"'

'

#
#: Implementation of the "mount" command.
#:
#: Mount a dataset and recursively all its children datasets.
#:
command_mount() {
    local _dsname _mountpoint
    local _opt_dry_run _opt_mount_outside _opt_mount_natural
    local _opt_mount_children_only

    local _name _mp _canmount _mounted _rootds_mountpoint _relative_mp _real_mp

    _opt_dry_run=""
    _opt_mount_outside=""
    _opt_mount_natural=""
    _opt_mount_children_only=""
    while getopts "ONPnu" _opt ; do
        case ${_opt} in
            O)
                _opt_mount_outside="yes"
                ;;
            N)
                _opt_mount_natural="yes"
                ;;
            P)
                _opt_mount_children_only="yes"
                ;;
            n|u)
                _opt_dry_run="yes"
                ;;
            \?|:)
                return 2;
                ;;
        esac
    done
    shift $((OPTIND-1))
    OPTIND=1

    _dsname="${1-}"
    _mountpoint="${2-}"

    if [ -z "${_dsname}" ]; then
        echo "ERROR: no dataset given" >&2
        return 2
    fi

    _rootds_mountpoint="$(zfs list -H -o mountpoint -t filesystem "${_dsname}")"  || \
        { echo "ERROR: root dataset does not exist" >&2; return 1; }

    if [ -z "${_mountpoint}" ]; then
        if [ "${_opt_mount_natural}" = "yes" ]; then
            _mountpoint="${_rootds_mountpoint}"
        else
            echo "ERROR: no mountpoint given" >&2
            return 2
        fi
    else
        if [ "${_opt_mount_natural}" = "yes" ]; then
            echo "ERROR: Cannot have a custom mountpoint when \"-O\" is given" >&2
            return 2
        fi
    fi

    # Eventually remove a trailing slash
    _mountpoint="${_mountpoint%/}"
    if [ -z "${_mountpoint}" ]; then
        echo "ERROR: would mount over the root filesystem" >&2
        return 1
    fi

    zfs list -H -o name,mountpoint,canmount,mounted -s mountpoint -t filesystem -r "${_dsname}" \
    | {
        while IFS=$'\t' read -r _name _mp _canmount _mounted ; do
            # Skip filesystems that are already mounted
            [ "${_mounted}" = "yes" ] && continue
            # Skip filesystems that must not be mounted
            [ "${_canmount}" = "off" ] && continue
            #
            # Mount only the children and skip the given parent dataset
            # if required
            #
            [ \( "${_opt_mount_children_only}" = "yes" \) -a \( "${_name}" = "${_dsname}" \) ] && continue
            case "${_mp}" in
                "none"|"legacy")
                    # Do nothing for filesystem with unset or legacy mountpoints
                    ;;
                "${_rootds_mountpoint}"|"${_rootds_mountpoint}/"*)
                    #
                    # Handle only mountpoints that have a mountpoint below
                    # the parent datasets mountpoint
                    #

                    # Determine the mountpoint relative to the parent mountpoint
                    _relative_mp="${_mp#${_rootds_mountpoint}}"
                    # Eventually remove a trailing slash
                    _relative_mp="${_relative_mp%/}"
                    # The real effective full mountpoint
                    _real_mp="${_mountpoint}${_relative_mp}"

                    #
                    # Consistency and sanity check: computed real mountpoint must
                    # be equal to the configured mountpoint when no custom mountpoint
                    # is given.
                    #
                    if [ "${_opt_mount_natural}" = "yes" ]; then
                        if [ "${_real_mp}" != "${_mp}" ]; then
                            echo "ERROR: mountpoint mismatch" >&2
                            return 1
                        fi
                    fi

                    if [ "${_opt_dry_run}" = "yes" ]; then
                        echo "Would mount ${_name} on ${_real_mp}"
                    else
                        mkdir -p "${_real_mp}" 1> /dev/null 2> /dev/null || \
                            { echo "ERROR: cannot create mountpoint ${_real_mp}" >&2; return 1; }
                        echo "Mounting ${_name} on ${_real_mp}"
                        mount -t zfs "${_name}" "${_real_mp}" || return 1
                    fi
                    ;;
                *)
                    if [ "${_opt_mount_outside}" = "yes" ]; then
                        if [ "${_opt_dry_run}" = "yes" ]; then
                            echo "Would mount ${_name} on configured ZFS dataset mountpoint ${_mp}"
                        else
                            echo "Mounting ${_name} on configured ZFS dataset mountpoint ${_mp}"
                            zfs mount "${_name}" || return 1
                        fi
                    else
                        echo "Skipping ${_name} because its configured ZFS mountpoint is not relative to given root dataset" 2>&1
                    fi
                    ;;
            esac
        done

        return 0
    }
}


#:
#: Implement the "umount" command.
#:
#: Umount a datasets and recursively all its children datasets.
#:
command_umount() {
    local _dsname

    local _name _mp _rest _rootds_mountpoint

    _dsname="${1-}"
    [ -z "${_dsname}" ] && { echo "ERROR: no dataset given" 1>&2; return 2; }

    # Just determine whether the given dataset name exists
    _rootds_mountpoint="$(zfs list -H -o mountpoint -t filesystem "${_dsname}")" || { echo "ERROR: dataset not found" 1>&2; return 1; }

    mount -t zfs -p \
    | grep -E "^${_dsname}(/|\s)" \
    | sort -n -r \
    | {
        while IFS=' '$'\t' read -r _name _mp _rest ; do
            echo "Umounting ${_name} on ${_mp}"
            umount "${_mp}" || return 1
        done
    }
    return 0
}

#
# Global option handling
#
while getopts "Vh" _opt ; do
    case ${_opt} in
        V)
            printf 'ftjail v%s (rv:%s)\n' "${VERSION}" '@@HGREVISION@@'
            exit 0
            ;;
        h)
            echo "${USAGE}"
            exit 0
            ;;
        \?)
            exit 2;
            ;;
        *)
            echo "ERROR: option handling failed" 1>&2
            exit 2
            ;;
    esac
done
#
# Reset the Shell's option handling system to prepare for handling
# command-local options.
#
shift $((OPTIND-1))
OPTIND=1

test $# -gt 0 || { echo "ERROR: no command given" 1>&2; exit 2; }

command="$1"
shift

case "${command}" in
    mount)
        command_mount "$@"
        ;;
    umount|unmount)
        command_umount "$@"
        ;;
    *)
        echo "ERROR: unknown command \`${command}'" 1>&2
        exit 2
        ;;
esac