#!/usr/bin/env bash
# reMarkable Backup (offizielle Cloud via rmapi)
#
# Ziel:
# - Inkrementeller Download in "current/".
# - Datierte Snapshots in "snapshots/YYYY-MM-DD_HHMMSS/".
# - Versionierung via Hardlinks (unveraenderte Dateien belegen kaum Zusatzplatz).
#
# Nutzung:
#   ./backup-official-cloud.sh /www/remarkable/notizen /
#
set -euo pipefail

BASE_DIR="${1:-/www/remarkable/notizen}"
REMOTE_DIR="${2:-/}"
TIMESTAMP="$(date +%F_%H%M%S)"

CURRENT_DIR="${BASE_DIR}/current"
SNAPSHOT_ROOT="${BASE_DIR}/snapshots"
SNAPSHOT_DIR="${SNAPSHOT_ROOT}/${TIMESTAMP}"
LATEST_LINK="${SNAPSHOT_ROOT}/latest"
LOG_DIR="${BASE_DIR}/logs"
LOCK_FILE="${BASE_DIR}/.backup.lock"

# Optional: Pfad, der ein echter Mountpoint sein muss (z. B. /www/remarkable/notizen).
# Wenn gesetzt und kein Mountpoint, wird abgebrochen (sicher gegen "auf Root-FS schreiben").
MOUNT_CHECK_PATH="${MOUNT_CHECK_PATH:-}"

# Optional: Anzahl alter Snapshots behalten (0 = unbegrenzt).
SNAPSHOT_KEEP="${SNAPSHOT_KEEP:-30}"

mkdir -p "${CURRENT_DIR}" "${SNAPSHOT_ROOT}" "${LOG_DIR}"

if [[ -n "${MOUNT_CHECK_PATH}" ]] && ! mountpoint -q "${MOUNT_CHECK_PATH}"; then
  echo "Fehler: ${MOUNT_CHECK_PATH} ist nicht gemountet. Backup abgebrochen."
  exit 1
fi

if ! command -v rmapi >/dev/null 2>&1; then
  echo "Fehler: rmapi nicht im PATH."
  exit 1
fi

if ! command -v rsync >/dev/null 2>&1; then
  echo "Fehler: rsync fehlt. Bitte installieren."
  exit 1
fi

exec 9>"${LOCK_FILE}"
if ! flock -n 9; then
  echo "Backup laeuft bereits (Lock: ${LOCK_FILE})."
  exit 1
fi

LOG_FILE="${LOG_DIR}/backup-${TIMESTAMP}.log"
exec > >(tee -a "${LOG_FILE}") 2>&1

echo "== reMarkable Backup Start =="
echo "Base: ${BASE_DIR}"
echo "Remote: ${REMOTE_DIR}"
echo "Zeit: ${TIMESTAMP}"

MGET_FLAGS=(-i)
if [[ "${BACKUP_FULL:-}" == "1" ]]; then
  MGET_FLAGS=()
fi
if [[ "${BACKUP_MIRROR_DELETE:-}" == "1" ]]; then
  MGET_FLAGS+=(-d)
fi

echo "1) Aktualisiere current/ via rmapi mget ${MGET_FLAGS[*]:-(none)} ..."
rmapi mget "${MGET_FLAGS[@]}" -o "${CURRENT_DIR}" "${REMOTE_DIR}"

# Leere Ordner anlegen (rmapi mget erstellt keine leeren Verzeichnisse)
echo "1b) Lege fehlende Ordner an ..."
rmapi find "${REMOTE_DIR}" 2>/dev/null | grep '^\[d\]' | sed 's/^\[d\] *//' | while read -r DIR; do
  LOCAL_DIR="${CURRENT_DIR}/${DIR}"
  mkdir -p "${LOCAL_DIR}"
done

echo "2) Erzeuge Snapshot: ${SNAPSHOT_DIR}"
mkdir -p "${SNAPSHOT_DIR}"

if [[ -L "${LATEST_LINK}" ]] && [[ -d "$(readlink -f "${LATEST_LINK}")" ]]; then
  PREV_SNAPSHOT="$(readlink -f "${LATEST_LINK}")"
  rsync -a --delete --link-dest="${PREV_SNAPSHOT}" "${CURRENT_DIR}/" "${SNAPSHOT_DIR}/"
else
  rsync -a --delete "${CURRENT_DIR}/" "${SNAPSHOT_DIR}/"
fi

ln -sfn "${SNAPSHOT_DIR}" "${LATEST_LINK}"

if [[ "${SNAPSHOT_KEEP}" =~ ^[0-9]+$ ]] && (( SNAPSHOT_KEEP > 0 )); then
  echo "3) Pruefe Retention (keep=${SNAPSHOT_KEEP}) ..."
  mapfile -t SNAPSHOTS < <(ls -1 "${SNAPSHOT_ROOT}" | grep -E '^[0-9]{4}-[0-9]{2}-[0-9]{2}_[0-9]{6}$' | sort)
  if (( ${#SNAPSHOTS[@]} > SNAPSHOT_KEEP )); then
    DELETE_COUNT=$(( ${#SNAPSHOTS[@]} - SNAPSHOT_KEEP ))
    for OLD in "${SNAPSHOTS[@]:0:DELETE_COUNT}"; do
      rm -rf "${SNAPSHOT_ROOT}/${OLD}"
      echo "   entfernt: ${SNAPSHOT_ROOT}/${OLD}"
    done
  fi
fi

# PDF-Konvertierung
if command -v remarkable-convert.sh >/dev/null 2>&1; then
  echo "4) Konvertiere .rmdoc zu PDF ..."
  remarkable-convert.sh "${CURRENT_DIR}"
fi

echo "== Backup fertig =="
echo "Current:  ${CURRENT_DIR}"
echo "Snapshot: ${SNAPSHOT_DIR}"