#!/bin/bash
# preinst for smartbotic-database (server)
# v1.9.5: snapshot data dir before deb upgrade (after old prerm stops the service).
set -e

DATA_DIR=/var/lib/smartbotic-database
BACKUP_ROOT="${SMARTBOTIC_DB_BACKUP_ROOT:-/var/backups/smartbotic-database}"
RETENTION="${SMARTBOTIC_DB_BACKUP_RETENTION:-3}"

case "$1" in
    upgrade)
        if [ "${SMARTBOTIC_DB_SKIP_BACKUP:-0}" = "1" ]; then
            echo "smartbotic-database: SMARTBOTIC_DB_SKIP_BACKUP=1, skipping pre-upgrade backup"
            exit 0
        fi

        if [ ! -d "$DATA_DIR" ] || [ -z "$(ls -A "$DATA_DIR" 2>/dev/null)" ]; then
            echo "smartbotic-database: $DATA_DIR is empty or missing, nothing to back up"
            exit 0
        fi

        DATA_KB=$(du -sk "$DATA_DIR" | awk '{print $1}')
        if [ -z "$DATA_KB" ] || ! [ "$DATA_KB" -gt 0 ] 2>/dev/null; then
            echo "smartbotic-database: failed to measure $DATA_DIR size" >&2
            exit 1
        fi
        REQ_KB=$((DATA_KB * 12 / 10))
        mkdir -p "$BACKUP_ROOT"
        FREE_KB=$(df -P "$BACKUP_ROOT" | awk 'NR==2 {print $4}')
        if [ -z "$FREE_KB" ] || ! [ "$FREE_KB" -gt 0 ] 2>/dev/null; then
            echo "smartbotic-database: failed to measure free space at $BACKUP_ROOT" >&2
            exit 1
        fi

        if [ "$FREE_KB" -lt "$REQ_KB" ]; then
            cat >&2 <<EOF
smartbotic-database: insufficient disk space for pre-upgrade backup
  data size       : ${DATA_KB} KB
  required (1.2x) : ${REQ_KB} KB
  free at         : ${BACKUP_ROOT} (${FREE_KB} KB)

Free up space, point SMARTBOTIC_DB_BACKUP_ROOT at a larger volume, or
override with SMARTBOTIC_DB_SKIP_BACKUP=1 apt upgrade smartbotic-database.

To restore from backup if upgrade fails:
  systemctl stop smartbotic-database
  rm -rf /var/lib/smartbotic-database/*
  cp -a ${BACKUP_ROOT}/<latest>/. /var/lib/smartbotic-database/
  chown -R smartbotic-db:smartbotic-db /var/lib/smartbotic-database
  systemctl start smartbotic-database
EOF
            exit 1
        fi

        TS=$(date -u +%Y%m%dT%H%M%SZ)
        OLD_VERSION="${2:-unknown}"
        BACKUP_DIR="$BACKUP_ROOT/pre-upgrade-${TS}-from-${OLD_VERSION}"
        BACKUP_TMP="${BACKUP_DIR}.tmp"

        echo "smartbotic-database: backing up $DATA_DIR to $BACKUP_DIR (${DATA_KB} KB)..."
        mkdir -p "$BACKUP_TMP"
        # Atomic-backup pattern: stage in .tmp, rename on success. If anything below
        # fails (including set -e unwinding), the trap wipes the partial dir so it
        # never gets mistaken for a complete backup by the retention sweep.
        trap 'rm -rf "$BACKUP_TMP"' ERR EXIT
        cp -a "$DATA_DIR/." "$BACKUP_TMP/"
        echo "$OLD_VERSION" > "$BACKUP_TMP/.from-version"
        echo "$TS" > "$BACKUP_TMP/.timestamp"
        mv "$BACKUP_TMP" "$BACKUP_DIR"
        trap - ERR EXIT

        # Retention: keep the newest $RETENTION backups, delete the rest.
        # Runs AFTER trap is cleared so a retention failure cannot wipe the final backup.
        ls -1dt "$BACKUP_ROOT"/pre-upgrade-* 2>/dev/null | tail -n +$((RETENTION + 1)) | xargs -r rm -rf

        echo "smartbotic-database: backup complete"
        ;;
    install|abort-upgrade) ;;
    *) echo "preinst called with unknown argument '$1'" >&2; exit 1 ;;
esac
exit 0