#!/usr/bin/env bash
# Assess whether ZFS can rewind and import an exported or faulted pool.

set -euo pipefail

usage() {
    cat <<'EOF'
Usage: sudo ./verify-zpool-recovery.sh [--directory <path>] [--apply] [pool]

Lists pools ZFS can discover, or checks whether a named pool can be recovered
with a transaction rewind. The default is a dry run and changes nothing.

Options:
    -d, --directory <path>  Search a specific directory for vdev devices.
    --apply                 Import the named pool with rewind recovery.
    -h, --help              Show this help message.

Without a pool name, the script only lists importable pools. --apply requires
a pool name and imports it with datasets left unmounted.
EOF
}

die() {
    printf 'Error: %s\n' "$*" >&2
    exit 1
}

search_directory=
apply=false
pool=

while [[ $# -gt 0 ]]; do
    case $1 in
        -d|--directory)
            [[ $# -ge 2 ]] || die "$1 requires a path."
            search_directory=$2
            shift 2
            ;;
        --apply)
            apply=true
            shift
            ;;
        -h|--help)
            usage
            exit 0
            ;;
        -*)
            die "unknown option '$1'."
            ;;
        *)
            [[ -z $pool ]] || die 'specify at most one pool name or GUID.'
            pool=$1
            shift
            ;;
    esac
done

[[ $EUID -eq 0 ]] || die 'run as root (for example, with sudo).'
command -v zpool >/dev/null 2>&1 || die "required command 'zpool' was not found."

directory_args=()
if [[ -n $search_directory ]]; then
    [[ -d $search_directory ]] || die "'$search_directory' is not a directory."
    directory_args=(-d "$search_directory")
fi

if [[ -z $pool ]]; then
    [[ $apply == false ]] || die '--apply requires a pool name or GUID.'
    printf 'Discovering importable pools. This does not modify any pool.\n\n'
    zpool import "${directory_args[@]}"
    exit 0
fi

if zpool list -H -o name "$pool" >/dev/null 2>&1; then
    die "'$pool' is already imported; inspect it with 'zpool status $pool'."
fi

if [[ $apply == false ]]; then
    printf 'Dry-run rewind recovery check for pool %s. No changes will be made.\n\n' "$pool"
    zpool import -nF "${directory_args[@]}" "$pool"
    exit 0
fi

printf '\nWARNING: this will attempt to rewind and import pool:\n  %s\n\n' "$pool"
printf 'This can discard the most recent transaction groups. Datasets will remain unmounted.\n'
read -r -p "Type exactly 'RECOVER $pool' to continue: " confirmation
[[ $confirmation == "RECOVER $pool" ]] || die 'confirmation did not match; no changes were made.'

zpool import -N -F "${directory_args[@]}" "$pool"
printf "Pool '%s' was imported without mounting datasets. Inspect it with:\n  zpool status %s\n" "$pool" "$pool"