#!/bin/sh
# QueueMed — MySQL backup helper.
#
# Dumps the configured MySQL database into /app/data/backups (or $BACKUP_DIR)
# with a timestamped filename, then prunes everything but the 7 most recent
# backups. Designed to run inside the `app` container — schedule from the host
# with `docker compose exec app /app/scripts/backup-db.sh` (cron, systemd, …).
#
# Required environment variables (already wired through docker-compose.yml):
#   MYSQL_HOST       – hostname of the MySQL service     (default: db)
#   MYSQL_DATABASE   – database name to dump             (default: queuemed)
#   MYSQL_USER       – MySQL user                        (default: queuemed)
#   MYSQL_PASSWORD   – MySQL password                    (required)
# Optional:
#   BACKUP_DIR       – override backup destination       (default: /app/data/backups)
#   BACKUP_KEEP      – number of backups to retain       (default: 7)

set -eu

MYSQL_HOST="${MYSQL_HOST:-db}"
MYSQL_DATABASE="${MYSQL_DATABASE:-queuemed}"
MYSQL_USER="${MYSQL_USER:-queuemed}"
BACKUP_DIR="${BACKUP_DIR:-/app/data/backups}"
BACKUP_KEEP="${BACKUP_KEEP:-7}"

if [ -z "${MYSQL_PASSWORD:-}" ]; then
  echo "[backup-db] MYSQL_PASSWORD is not set, aborting." >&2
  exit 1
fi

mkdir -p "$BACKUP_DIR"

TIMESTAMP="$(date -u +%Y%m%dT%H%M%SZ)"
OUT_FILE="$BACKUP_DIR/${MYSQL_DATABASE}-${TIMESTAMP}.sql.gz"
TMP_FILE="${OUT_FILE}.partial"

echo "[backup-db] dumping ${MYSQL_DATABASE} from ${MYSQL_HOST} -> ${OUT_FILE}"

# --single-transaction keeps the dump consistent without locking InnoDB tables.
# --quick streams rows row-by-row to keep memory bounded for large tables.
mysqldump \
  --host="$MYSQL_HOST" \
  --user="$MYSQL_USER" \
  --password="$MYSQL_PASSWORD" \
  --single-transaction \
  --quick \
  --routines \
  --triggers \
  --no-tablespaces \
  --default-character-set=utf8mb4 \
  "$MYSQL_DATABASE" | gzip -9 > "$TMP_FILE"

mv "$TMP_FILE" "$OUT_FILE"

echo "[backup-db] backup written: $OUT_FILE ($(wc -c < "$OUT_FILE") bytes)"

# ── Rotate: keep only the last $BACKUP_KEEP backups ─────────────────────────
# `ls -1t` sorts by mtime descending; everything after the first $BACKUP_KEEP
# entries is removed. Filenames are constrained to our prefix to avoid eating
# unrelated files that might share the directory.
cd "$BACKUP_DIR"
ls -1t "${MYSQL_DATABASE}"-*.sql.gz 2>/dev/null \
  | awk -v keep="$BACKUP_KEEP" 'NR > keep' \
  | while IFS= read -r old; do
      echo "[backup-db] pruning old backup: $old"
      rm -f -- "$old"
    done

echo "[backup-db] done."