/** Shared date/time formatting helpers used across Calendar, Home, Knowledge, etc. */

function _isSameDay(a: Date, b: Date): boolean {
  return a.getFullYear() === b.getFullYear() &&
    a.getMonth() === b.getMonth() &&
    a.getDate() === b.getDate()
}

/** "9:30 AM" */
export function fmtTime(dt: string): string {
  return new Date(dt).toLocaleTimeString(undefined, { hour: "numeric", minute: "2-digit" })
}

/** "Mon, Jan 15" or "Mon, Jan 15, 9:30 AM" */
export function fmtDateTime(dt: string, allDay: boolean): string {
  const d = new Date(dt)
  const datePart = d.toLocaleDateString(undefined, { weekday: "short", month: "short", day: "numeric" })
  if (allDay) return datePart
  return `${datePart}, ${d.toLocaleTimeString(undefined, { hour: "numeric", minute: "2-digit" })}`
}

/**
 * "Today 9:30 AM" / "Tomorrow 9:30 AM" / "Mon, Jan 15 9:30 AM"
 * For all-day events returns "Today" / "Tomorrow" / "Mon, Jan 15"
 */
export function fmtRelativeDateTime(dt: string, allDay: boolean): string {
  try {
    const d = new Date(dt)
    const now = new Date()
    const tomorrow = new Date(now)
    tomorrow.setDate(now.getDate() + 1)

    const timeStr = allDay ? "" : ` ${d.toLocaleTimeString(undefined, { hour: "numeric", minute: "2-digit" })}`

    if (_isSameDay(d, now)) return `Today${timeStr}`
    if (_isSameDay(d, tomorrow)) return `Tomorrow${timeStr}`
    return d.toLocaleDateString(undefined, { weekday: "short", month: "short", day: "numeric" }) + timeStr
  } catch {
    return dt
  }
}

/**
 * Label-only: "Today" / "Tomorrow" / "Mon, Jan 15"
 */
export function fmtDayLabel(dt: string): string {
  try {
    const d = new Date(dt)
    const now = new Date()
    const tomorrow = new Date(now)
    tomorrow.setDate(now.getDate() + 1)
    if (_isSameDay(d, now)) return "Today"
    if (_isSameDay(d, tomorrow)) return "Tomorrow"
    return d.toLocaleDateString(undefined, { weekday: "short", month: "short", day: "numeric" })
  } catch {
    return dt
  }
}

/** "Jan 15" or "Jan 15, 9:30 AM" — compact, no weekday */
export function fmtCompact(dt: string, allDay: boolean): string {
  const d = new Date(dt)
  if (allDay) return d.toLocaleDateString(undefined, { month: "short", day: "numeric" })
  return d.toLocaleString(undefined, { month: "short", day: "numeric", hour: "numeric", minute: "2-digit" })
}