#!/bin/sh
# Runs backup_db.sh at each time in BACKUP_TIMES (comma-separated HH:MM list).
# Times are interpreted in the container's local TZ (set via TZ env; default
# Africa/Nairobi in the Dockerfile). Defaults: 02:30, 08:30, 14:30, 20:30 local.
#
# Back-compat: legacy BACKUP_TIMES_UTC or BACKUP_HOUR/BACKUP_MINUTE are still honored.

set -eu

if [ -n "${BACKUP_TIMES:-}" ]; then
  TIMES="$BACKUP_TIMES"
elif [ -n "${BACKUP_TIMES_UTC:-}" ]; then
  TIMES="$BACKUP_TIMES_UTC"
elif [ -n "${BACKUP_HOUR:-}" ] || [ -n "${BACKUP_MINUTE:-}" ]; then
  TIMES="$(printf '%02d:%02d' "${BACKUP_HOUR:-2}" "${BACKUP_MINUTE:-30}")"
else
  TIMES="02:30,08:30,14:30,20:30"
fi

TS_FMT='+%FT%T%z'
echo "[$(date "$TS_FMT")] TZ=${TZ:-UTC}  backup schedule: ${TIMES}"

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

# Compute epoch for "today HH:MM local" on both GNU and BSD date.
slot_to_epoch_today() {
  HM="$1"
  date -d "today ${HM}:00" +%s 2>/dev/null \
    || date -j -f "%H:%M:%S" "${HM}:00" +%s
}

while true; do
  NOW_EPOCH=$(date +%s)
  NEXT=""
  # Find the smallest TARGET > NOW across all configured slots (rolling to tomorrow if needed).
  OLDIFS="$IFS"
  IFS=','
  for HM in $TIMES; do
    HM="$(echo "$HM" | tr -d ' ')"
    [ -z "$HM" ] && continue
    T=$(slot_to_epoch_today "$HM")
    if [ "$T" -le "$NOW_EPOCH" ]; then
      T=$((T + 86400))
    fi
    if [ -z "$NEXT" ] || [ "$T" -lt "$NEXT" ]; then
      NEXT="$T"
    fi
  done
  IFS="$OLDIFS"

  if [ -z "$NEXT" ]; then
    echo "[$(date "$TS_FMT")] no valid times in BACKUP_TIMES='${TIMES}'; sleeping 1h"
    sleep 3600
    continue
  fi

  SLEEP=$((NEXT - NOW_EPOCH))
  NEXT_ISO=$(date -d "@${NEXT}" "$TS_FMT" 2>/dev/null || date -r "${NEXT}" "$TS_FMT")
  echo "[$(date "$TS_FMT")] next backup in ${SLEEP}s (at ${NEXT_ISO})"
  sleep "$SLEEP"
  /app/backup_db.sh || echo "[$(date "$TS_FMT")] backup failed (will retry at next slot)"
done