/**
 * Deterministic pseudo-random number in [0, 1) from id + salt.
 * Using a simple LCG hash so values are identical on server and client
 * (avoids React hydration mismatches from Math.random()).
 */
export function sp(id: number, salt: number): number {
  const n = ((id * 9301 + salt * 49297 + 1) % 233280 + 233280) % 233280
  return n / 233280
}

/**
 * Human-readable relative time string (German) for a UTC timestamp.
 * The `created_at` value from SQLite has no timezone suffix, so we append 'Z'.
 */
export function relativeTime(created_at: string): string {
  const now = Date.now()
  const created = new Date(created_at.endsWith('Z') ? created_at : created_at + 'Z').getTime()
  const diffMs = now - created
  const minutes = Math.floor(diffMs / 60000)
  const hours = Math.floor(diffMs / 3600000)
  const days = Math.floor(diffMs / 86400000)
  if (minutes < 1) return 'gerade eben'
  if (minutes < 60) return `vor ${minutes} Min.`
  if (hours < 24) return `vor ${hours} Std.`
  return `vor ${days} ${days === 1 ? 'Tag' : 'Tagen'}`
}

/**
 * Formats a German date string from year/month/day components.
 */
export function formatDate(
  year: string,
  month?: string | null,
  day?: string | null
): string {
  if (day && month) {
    const monthNames = ['Jan', 'Feb', 'März', 'Apr', 'Mai', 'Juni', 'Juli', 'Aug', 'Sept', 'Okt', 'Nov', 'Dez']
    const monthName = monthNames[parseInt(month) - 1] || month
    return `${day}. ${monthName} ${year}`
  } else if (month) {
    const monthNames = [
      'Januar', 'Februar', 'März', 'April', 'Mai', 'Juni',
      'Juli', 'August', 'September', 'Oktober', 'November', 'Dezember',
    ]
    const monthName = monthNames[parseInt(month) - 1] || `Monat ${month}`
    return `${monthName} ${year}`
  }
  return year
}