#!/bin/sh
# ── LearnSpace SQLite backup ──────────────────────────────────────────────
# Uses VACUUM INTO for a safe, consistent snapshot (no WAL/SHM issues).
# Usage:
#   ./backup.sh                     # default paths
#   ./backup.sh /path/to/db /path/to/backups
#   KEEP=14 ./backup.sh             # keep last 14 backups (default: 7)
# ─────────────────────────────────────────────────────────────────────────

set -e

DB_PATH="${1:-${DB_PATH:-$(dirname "$0")/../data/learnspace.db}}"
BACKUP_DIR="${2:-${BACKUP_DIR:-$(dirname "$0")/../../backups}}"
KEEP="${KEEP:-7}"

if [ ! -f "$DB_PATH" ]; then
  echo "[backup] ERROR: database not found at $DB_PATH" >&2
  exit 1
fi

mkdir -p "$BACKUP_DIR"

TIMESTAMP=$(date +%Y%m%d_%H%M%S)
BACKUP_FILE="$BACKUP_DIR/learnspace_${TIMESTAMP}.db"

echo "[backup] Creating snapshot: $BACKUP_FILE"
sqlite3 "$DB_PATH" "VACUUM INTO '$BACKUP_FILE';"

# Verify backup is not empty
SIZE=$(wc -c < "$BACKUP_FILE" | tr -d ' ')
if [ "$SIZE" -lt 1024 ]; then
  echo "[backup] ERROR: backup file is suspiciously small (${SIZE} bytes)" >&2
  rm -f "$BACKUP_FILE"
  exit 1
fi

echo "[backup] OK — $(echo "scale=1; $SIZE / 1048576" | bc 2>/dev/null || echo "$SIZE bytes")"

# Rotate: keep only the last $KEEP backups
COUNT=$(ls -1 "$BACKUP_DIR"/learnspace_*.db 2>/dev/null | wc -l)
if [ "$COUNT" -gt "$KEEP" ]; then
  REMOVE=$((COUNT - KEEP))
  ls -1t "$BACKUP_DIR"/learnspace_*.db | tail -n "$REMOVE" | while read -r f; do
    echo "[backup] Removing old: $(basename "$f")"
    rm -f "$f"
  done
fi

echo "[backup] Done. Backups retained: $KEEP"