/**
 * Format date for display: "Jan 15, 2026"
 */
export function formatDate(date: string | Date | null | undefined): string {
  if (!date) return '—'

  const d = new Date(date)
  if (isNaN(d.getTime())) return '—'

  return d.toLocaleDateString('en-US', {
    month: 'short',
    day: 'numeric',
    year: 'numeric',
  })
}

/**
 * Format date and time for display: "Jan 15, 2026 at 2:30 PM"
 */
export function formatDateTime(date: string | Date | null | undefined): string {
  if (!date) return '—'

  const d = new Date(date)
  if (isNaN(d.getTime())) return '—'

  return d.toLocaleDateString('en-US', {
    month: 'short',
    day: 'numeric',
    year: 'numeric',
    hour: 'numeric',
    minute: '2-digit',
    hour12: true,
  })
}

/**
 * Format date for HTML input[type="date"]: "2026-01-15"
 */
export function formatDateForInput(date: string | Date | null | undefined): string {
  if (!date) return ''

  const d = new Date(date)
  if (isNaN(d.getTime())) return ''

  const year = d.getFullYear()
  const month = String(d.getMonth() + 1).padStart(2, '0')
  const day = String(d.getDate()).padStart(2, '0')

  return `${year}-${month}-${day}`
}

/**
 * Format file size for display: "1.5 GB", "256 MB", "12 KB"
 */
export function formatFileSize(bytes: number): string {
  if (bytes === 0) return '0 B'

  const units = ['B', 'KB', 'MB', 'GB', 'TB']
  const i = Math.floor(Math.log(bytes) / Math.log(1024))

  return `${(bytes / Math.pow(1024, i)).toFixed(i > 0 ? 1 : 0)} ${units[i]}`
}

/**
 * Format relative time: "2 hours ago", "just now"
 */
export function formatRelativeTime(date: string | Date | null | undefined): string {
  if (!date) return '—'

  const d = new Date(date)
  if (isNaN(d.getTime())) return '—'

  const now = new Date()
  const diffMs = now.getTime() - d.getTime()
  const diffSeconds = Math.floor(diffMs / 1000)
  const diffMinutes = Math.floor(diffSeconds / 60)
  const diffHours = Math.floor(diffMinutes / 60)
  const diffDays = Math.floor(diffHours / 24)

  if (diffSeconds < 60) return 'just now'
  if (diffMinutes < 60) return `${diffMinutes}m ago`
  if (diffHours < 24) return `${diffHours}h ago`
  if (diffDays < 7) return `${diffDays}d ago`

  return formatDate(date)
}