#!/usr/bin/env bash
set -Eeuo pipefail

usage() {
  cat >&2 <<'EOF'
Usage: scheduled-maintenance.sh <backup|restore-latest>

Requires FRAMEFLOW_BACKUP_MOUNTPOINT and FRAMEFLOW_BACKUP_DESTINATION.
The destination must be a writable directory inside the active mount point.
EOF
  exit "${1:-2}"
}

fail() {
  echo "Scheduled maintenance failed: $1" >&2
  exit 1
}

[[ $# -eq 1 ]] || usage
case "$1" in
  backup|restore-latest) mode="$1" ;;
  --help|-h) usage 0 ;;
  *) usage ;;
esac

script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
mount_point="${FRAMEFLOW_BACKUP_MOUNTPOINT:-}"
backup_destination="${FRAMEFLOW_BACKUP_DESTINATION:-}"

[[ -n "${mount_point}" ]] || fail "FRAMEFLOW_BACKUP_MOUNTPOINT is required"
[[ -n "${backup_destination}" ]] || fail "FRAMEFLOW_BACKUP_DESTINATION is required"

for path in "${mount_point}" "${backup_destination}"; do
  [[ "${path}" == /* ]] || fail "backup paths must be absolute: ${path}"
  [[ "${path}" != "/" ]] || fail "the filesystem root cannot be used for backups"
  [[ ! "${path}" =~ [[:space:]] ]] || fail "backup paths must not contain whitespace: ${path}"
  [[ -d "${path}" ]] || fail "backup directory does not exist: ${path}"
  [[ ! -L "${path}" ]] || fail "backup paths must not be symbolic links: ${path}"
done

mount_point="$(cd "${mount_point}" && pwd -P)"
backup_destination="$(cd "${backup_destination}" && pwd -P)"
if [[ "${backup_destination}" != "${mount_point}" && "${backup_destination}" != "${mount_point}/"* ]]; then
  fail "backup destination must be inside FRAMEFLOW_BACKUP_MOUNTPOINT"
fi
[[ -w "${backup_destination}" ]] || fail "backup destination is not writable: ${backup_destination}"

command -v findmnt >/dev/null 2>&1 || fail "findmnt is required to verify the backup mount"
mounted_target="$(findmnt -rn -M "${mount_point}" -o TARGET 2>/dev/null)" \
  || fail "backup mount is not active: ${mount_point}"
[[ "${mounted_target}" == "${mount_point}" ]] \
  || fail "backup mount resolved to an unexpected target: ${mounted_target}"

case "${mode}" in
  backup)
    exec "${script_dir}/backup.sh" "${backup_destination}"
    ;;
  restore-latest)
    latest_name=""
    latest_path=""
    while IFS= read -r -d '' candidate; do
      [[ ! -L "${candidate}" ]] || continue
      candidate_name="${candidate##*/}"
      [[ "${candidate_name}" =~ ^frameflow-[0-9]{8}T[0-9]{6}Z$ ]] || continue
      if [[ -z "${latest_name}" || "${candidate_name}" > "${latest_name}" ]]; then
        latest_name="${candidate_name}"
        latest_path="${candidate}"
      fi
    done < <(find "${backup_destination}" -mindepth 1 -maxdepth 1 -type d -name 'frameflow-*' -print0)

    [[ -n "${latest_path}" ]] || fail "no timestamped FrameFlow backup was found"
    echo "Selected latest backup for restore rehearsal: ${latest_path}"
    "${script_dir}/verify-backup.sh" "${latest_path}"
    exec "${script_dir}/rehearse-restore.sh" "${latest_path}"
    ;;
esac