#!/usr/bin/env bash
# Called only under the shared lock; --check never invokes this maintenance.
clean_backup_scratch() {
  python3 "$LIB_DIR/space.py" clean "$WORKDIR" "$STAGING_ROOT" "$ARCHIVE_DIR" "$ARCHIVE_PREFIX" "$RESTORE_ROOT"
}

available_space() {
  local value
  value=$(df -PB1 -- "$1" | awk 'END{print $4}') || return 1
  [[ $value =~ ^(0|[1-9][0-9]{0,17})$ ]] || die "Cannot determine available space on $1"
  printf '%s\n' "$value"
}

ensure_space() {
  local path=$1 additional=${2:-0} avail name dir candidates code protected
  [[ $additional =~ ^(0|[1-9][0-9]{0,15})$ ]] || die 'Invalid or excessive space request'
  local required=$((MIN_FREE_GB * 1024 * 1024 * 1024 + additional))
  avail=$(available_space "$path")
  (( avail < required )) || return 0
  echo "-- Space recovery: need $required bytes, available $avail on $path"
  echo "-- Space policy: keep $SPACE_KEEP_LOCAL uploaded local set(s) under pressure; normal retention keeps $RETENTION_KEEP_LAST"
  if [[ $ENABLE_UPLOAD == true && $(stat -c %d "$path") == "$(stat -c %d "$ARCHIVE_DIR")" ]]; then
    check_remote
    candidates=$(python3 "$LIB_DIR/space.py" eligible "$ARCHIVE_DIR" "$ARCHIVE_PREFIX" "$SPACE_KEEP_LOCAL")
    if [[ -n $candidates ]]; then
      protected=$(python3 "$LIB_DIR/space.py" protected "$ARCHIVE_DIR" "$ARCHIVE_PREFIX" "$SPACE_KEEP_LOCAL")
      [[ -n $protected ]] || die 'No protected local backup; refusing space recovery'
      while IFS= read -r name; do
        echo "-- Space recovery: validating protected local copy: $name"
        if helper verify "$ARCHIVE_DIR/$name" >/dev/null; then continue; else code=$?; fi
        (( code < 128 )) || return "$code"
        echo "WARNING: Protected local copy is damaged; keeping all candidates: $name"
        candidates=''
        break
      done <<< "$protected"
    fi
    while IFS= read -r name; do
      [[ -n $name ]] || continue
      avail=$(available_space "$path")
      (( avail < required )) || return 0
      dir="$ARCHIVE_DIR/$name"
      # A manually selected local restore source is never a cleanup candidate.
      [[ -z ${LOCAL_RUN:-} || $(realpath -m "$LOCAL_RUN") != "$dir" ]] || continue
      echo "-- Space recovery: verifying offsite copy before local removal: $name"
      if helper verify "$dir" >/dev/null &&
         remote_metadata_check "$dir" "${RCLONE_REMOTE_BASE%/}/$name" --exclude /UPLOADED &&
         remote_identity_check "$dir" "${RCLONE_REMOTE_BASE%/}/$name"; then
        python3 "$LIB_DIR/space.py" remove "$dir"
        echo "-- Space recovery: removed local copy $name; offsite copy with matching file sizes retained"
      else
        code=$?
        (( code < 128 )) || return "$code"
        echo "WARNING: Keeping $name: local/offsite verification failed"
      fi
      avail=$(available_space "$path")
      if (( avail >= required )); then
        echo "-- Space recovery complete: available $avail bytes, required $required"
        return 0
      fi
    done <<< "$candidates"
  fi
  avail=$(available_space "$path")
  (( avail < required )) || return 0
  python3 "$LIB_DIR/space.py" inventory "$ARCHIVE_DIR" "$ARCHIVE_PREFIX" "$SPACE_KEEP_LOCAL" ||
    echo 'WARNING: Local archive inventory incomplete; no further cleanup attempted'
  die "Insufficient space after safe cleanup on $path: need $required bytes, available $avail, deficit $((required - avail)) bytes; protected backups/recovery data retained. See SPEICHER.md: resolve pending uploads or move backup workspace to a larger filesystem."
}

prepare_backup_space() {
  if [[ -f $WORKDIR/restore-test/.owner ]]; then
    local cleanup_script="$LIB_DIR/../usr-local-sbin/app-restore-test.sh"
    [[ -f $cleanup_script ]] || cleanup_script=/usr/local/sbin/app-restore-test.sh
    APP_BACKUP_INHERIT_LOCK=1 bash "$cleanup_script" --config "$CONFIG_FILE" --cleanup
  fi
  clean_backup_scratch
  local i stats bytes count total=0 db_size
  # Dry-run obeys the exact copy exclusions. No dump, copy or service stop.
  for i in "${!LABELS[@]}"; do
    check_source_path "${SOURCES[i]}"
    exclusions "${LABELS[i]}"
    stats=$(rsync -aHAX --dry-run --stats --numeric-ids "${EXCLUDES[@]}" -- "${SOURCES[i]}/" "$STAGING_ROOT/.space-estimate/" 8>&- 9>&-)
    bytes=$(awk '/^Total file size:/ {gsub(/,/, "", $4); print $4}' <<< "$stats")
    count=$(awk '/^Number of files:/ {gsub(/,/, "", $4); print $4}' <<< "$stats")
    [[ $bytes =~ ^[0-9]+$ && $count =~ ^[0-9]+$ ]] || die 'Cannot estimate source allocation'
    total=$((total + bytes + count * 8192))
  done
  for i in "${!DB_NAMES[@]}"; do
    secure_file "${DB_CNFS[i]}"
    db_size=$("$DB_CLIENT_BIN" --defaults-extra-file="${DB_CNFS[i]}" --database="${DB_NAMES[i]}" --batch --skip-column-names --execute='SELECT COALESCE(SUM(data_length+index_length),0) FROM information_schema.tables WHERE table_schema=DATABASE()')
    [[ $db_size =~ ^[0-9]+$ ]] || die 'Cannot estimate database size'
    total=$((total + db_size * 3 + 67108864))
  done
  # Account for SQL expansion, tar metadata and growth between inventory/copy.
  total=$((total * 12 / 10 + 67108864))
  echo "-- Estimated snapshot budget: $total bytes (+ archive overlap and free-space reserve)"
  if [[ $(stat -c %d "$STAGING_ROOT") == "$(stat -c %d "$ARCHIVE_DIR")" ]]; then
    ensure_space "$STAGING_ROOT" "$((total * 2))"
  else
    ensure_space "$STAGING_ROOT" "$total"
    ensure_space "$ARCHIVE_DIR" "$total"
  fi
}