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

UUID="bdd2a016-b6db-493d-ad0a-e8dd8a93dfbd"
NAME="usb_safe"
MNT="/mnt/usb_safe"

DEV_BY_UUID="/dev/disk/by-uuid/${UUID}"
MAPPER="/dev/mapper/${NAME}"

die() { echo "Error: $*" >&2; exit 1; }

need_cmd() {
  command -v "$1" >/dev/null 2>&1 || die "Missing command: $1"
}

resolve_blockdev() {
  local target
  target="$(readlink -f "$DEV_BY_UUID")" || return 1
  [[ -b "$target" ]] || return 1
  echo "$target"
}

is_mapped() { [[ -e "$MAPPER" ]]; }
is_mounted() { mountpoint -q "$MNT"; }

show_busy() {
  echo "Mount appears busy. Processes using $MNT:"
  if command -v lsof >/dev/null 2>&1; then
    sudo lsof +f -- "$MNT" || true
  else
    echo "(Install lsof: sudo apt install lsof)"
    sudo fuser -vm "$MNT" || true
  fi
}

do_open() {
  need_cmd cryptsetup
  need_cmd mount
  need_cmd mountpoint
  need_cmd readlink

  [[ -e "$DEV_BY_UUID" ]] || die "UUID device not found: $DEV_BY_UUID (is the drive plugged in?)"

  local dev
  dev="$(resolve_blockdev)" || die "Could not resolve block device for UUID: $UUID"

  if is_mapped; then
    echo "Mapper already exists: $MAPPER"
  else
    sudo cryptsetup open "$dev" "$NAME"
  fi

  if [[ ! -d "$MNT" ]]; then
    sudo mkdir -p "$MNT"
  fi

  if is_mounted; then
    echo "Already mounted: $MNT"
  else
    sudo mount "$MAPPER" "$MNT"
  fi

  sudo sync
  echo "OK: unlocked and mounted at $MNT"
}

do_close() {
  need_cmd cryptsetup
  need_cmd umount
  need_cmd mountpoint
  need_cmd readlink

  if is_mounted; then
    sudo sync
    if ! sudo umount "$MNT"; then
      show_busy
      die "Unmount failed"
    fi
  fi

  if is_mapped; then
    sudo cryptsetup close "$NAME"
  fi

  if [[ -e "$DEV_BY_UUID" ]]; then
    local dev
    dev="$(resolve_blockdev)" || true
    if [[ -n "${dev:-}" ]] && command -v udisksctl >/dev/null 2>&1; then
      sudo udisksctl power-off -b "$dev" || true
    fi
  fi

  echo "OK: unmounted, closed, and powered off (if supported)"
}

do_status() {
  echo "UUID device: $DEV_BY_UUID"
  if [[ -e "$DEV_BY_UUID" ]]; then
    echo "Resolved:   $(readlink -f "$DEV_BY_UUID")"
  else
    echo "Resolved:   (not present)"
  fi

  echo -n "Mapper:     "
  if is_mapped; then echo "OPEN ($MAPPER)"; else echo "CLOSED"; fi

  echo -n "Mount:      "
  if is_mounted; then echo "MOUNTED ($MNT)"; else echo "NOT MOUNTED"; fi
}

usage() {
  cat <<EOF
Usage: $0 {open|close|status}

open   - unlock LUKS by UUID and mount to $MNT
close  - sync, unmount, close mapper, power-off block device (best-effort)
status - show current state
EOF
}

main() {
  case "${1:-}" in
    open)   do_open ;;
    close)  do_close ;;
    status) do_status ;;
    *) usage; exit 2 ;;
  esac
}

main "$@"