#!/usr/bin/env bash
set -euo pipefail

log() { echo "[$(date -Is)] $*" >&2; }

sleep_until_next_rotate() {
  local rotate_at="${ROTATE_AT:-03:00}"
  local target_h target_m
  IFS=: read -r target_h target_m <<<"$rotate_at"
  target_h=$((10#$target_h))
  target_m=$((10#$target_m))

  local now_h now_m now_s target_s wait_s
  now_h=$(date +%H)
  now_m=$(date +%M)
  now_h=$((10#$now_h))
  now_m=$((10#$now_m))
  now_s=$((now_h * 3600 + now_m * 60))
  target_s=$((target_h * 3600 + target_m * 60))

  if ((now_s < target_s)); then
    wait_s=$((target_s - now_s))
  else
    wait_s=$((86400 - now_s + target_s))
  fi

  log "Next rotation at ${rotate_at} (${TZ:-UTC}) in ${wait_s}s"
  sleep "$wait_s"
}

log "Starting gluetun PIA WireGuard rotator (TZ=${TZ:-UTC}, ROTATE_AT=${ROTATE_AT:-03:00})"

log "Running rotation on startup"
/usr/local/bin/rotate.sh

while true; do
  sleep_until_next_rotate
  log "Running scheduled daily rotation"
  /usr/local/bin/rotate.sh
done