/**
 * Parse `BARE_OS_REPLICATION_SYNC_WINDOWS` (UTC, `HH:MM-HH:MM` ranges, comma-separated).
 * @param {Record<string, string>} env
 * @returns {{ active: boolean, windows: string[], nowUtc: string, note?: string }}
 */
export function computeReplicationSyncWindow(env) {
  const raw = String(env.BARE_OS_REPLICATION_SYNC_WINDOWS || '').trim()
  const now = new Date()
  const pad = (n) => (n < 10 ? '0' : '') + n
  const nowUtc = `${pad(now.getUTCHours())}:${pad(now.getUTCMinutes())}`
  if (!raw) {
    return {
      active: true,
      windows: [],
      nowUtc,
      note: 'no windows; replication always allowed'
    }
  }
  const parts = raw
    .split(',')
    .map((s) => s.trim())
    .filter(Boolean)
  /** @type {string[]} */
  const windows = []
  let active = false
  const toMin = (h, m) => h * 60 + m
  const cur = toMin(now.getUTCHours(), now.getUTCMinutes())
  for (const p of parts) {
    const m = p.match(/^(\d{1,2}):(\d{2})\s*-\s*(\d{1,2}):(\d{2})$/)
    if (!m) continue
    const a = toMin(Number(m[1]), Number(m[2]))
    const b = toMin(Number(m[3]), Number(m[4]))
    windows.push(p)
    if (a <= b) {
      if (cur >= a && cur <= b) active = true
    } else {
      if (cur >= a || cur <= b) active = true
    }
  }
  if (windows.length === 0) {
    return {
      active: true,
      windows: [],
      nowUtc,
      note: 'no valid windows parsed; default allow'
    }
  }
  return { active, windows, nowUtc }
}