#!/bin/sh
# Loops forever: sleeps until the next BACKUP_HOUR:BACKUP_MINUTE UTC, then runs backup_db.sh.
# Defaults: 02:30 UTC nightly.

set -eu

HOUR="${BACKUP_HOUR:-2}"
MINUTE="${BACKUP_MINUTE:-30}"

if [ "${BACKUP_RUN_ON_START:-0}" = "1" ]; then
  echo "[$(date -u +%FT%TZ)] BACKUP_RUN_ON_START=1 — running backup immediately"
  /app/backup_db.sh || echo "[$(date -u +%FT%TZ)] initial backup failed (continuing)"
fi

while true; do
  NOW_EPOCH=$(date -u +%s)
  TARGET=$(date -u -d "today ${HOUR}:${MINUTE}:00" +%s 2>/dev/null \
           || date -u -j -f "%H:%M:%S" "${HOUR}:${MINUTE}:00" +%s)
  if [ "$TARGET" -le "$NOW_EPOCH" ]; then
    TARGET=$((TARGET + 86400))
  fi
  SLEEP=$((TARGET - NOW_EPOCH))
  echo "[$(date -u +%FT%TZ)] next backup in ${SLEEP}s (at $(date -u -d "@${TARGET}" +%FT%TZ 2>/dev/null || date -u -r "${TARGET}" +%FT%TZ))"
  sleep "$SLEEP"
  /app/backup_db.sh || echo "[$(date -u +%FT%TZ)] backup failed (will retry tomorrow)"
done