steam-backlog-enforcer/web/src/format.ts

// Small display-formatting helpers shared across components.

/** Format an hour count with thousands separators, e.g. 67031.1 → "67,031 h". */
export function fmtHours(hours: number): string {
  if (hours <= 0) return '—'
  return `${Math.round(hours).toLocaleString('en-US')} h`
}

/** Format a possibly-missing per-game hour value, e.g. 44.3 → "44.3". */
export function fmtHoursPrecise(hours: number): string {
  if (hours <= 0) return '—'
  return hours.toFixed(1)
}

/** Format playtime minutes as hours, e.g. 320 → "5.3 h" (0 → "untouched"). */
export function fmtPlaytime(minutes: number): string {
  if (minutes <= 0) return 'untouched'
  return `${(minutes / 60).toFixed(1)} h`
}

/** Format a day count and its target date, e.g. (866) → "866 days · 2028-10-11". */
export function fmtEta(days: number | null): string {
  if (days === null) return 'N/A'
  const target = new Date()
  target.setDate(target.getDate() + days)
  return `${days.toLocaleString('en-US')} days · ${isoDate(target)}`
}

/** Render a Date as YYYY-MM-DD in local time. */
export function isoDate(date: Date): string {
  const y = date.getFullYear()
  const m = String(date.getMonth() + 1).padStart(2, '0')
  const d = String(date.getDate()).padStart(2, '0')
  return `${y}-${m}-${d}`
}

/** Whole days from today (local midnight) until the given ISO date string. */
export function daysUntil(isoDateStr: string): number {
  const target = new Date(`${isoDateStr}T00:00:00`)
  const today = new Date()
  today.setHours(0, 0, 0, 0)
  const ms = target.getTime() - today.getTime()
  return Math.ceil(ms / (1000 * 60 * 60 * 24))
}

/** Format a second count as "7h 27m" (or "44m" / "38s" when short). */
export function fmtDuration(seconds: number): string {
  const total = Math.max(0, Math.round(seconds))
  const h = Math.floor(total / 3600)
  const m = Math.floor((total % 3600) / 60)
  if (h > 0) return `${h}h ${m}m`
  if (m > 0) return `${m}m`
  return `${total}s`
}

/** Describe how long ago an ISO-8601 timestamp was, e.g. "4m ago". */
export function fmtAgo(iso: string, now: Date = new Date()): string {
  if (!iso) return 'unknown'
  const then = new Date(iso)
  const seconds = (now.getTime() - then.getTime()) / 1000
  if (Number.isNaN(seconds)) return 'unknown'
  if (seconds < 10) return 'just now'
  return `${fmtDuration(seconds)} ago`
}

// Largest first; weeks are the top unit because months vary in length.
const REMAINING_UNITS: [string, number][] = [['w', 604_800], ['d', 86_400], ['h', 3600], ['m', 60], ['s', 1]]

/** Time left as its two largest units: "2w 2d", "2d 14h", "2h 20m", "5m 7s", "45s".
 *  Rounds up, so it reads "0s" only once the time is actually up. */
export function fmtRemaining(seconds: number): string {
  const left = Math.max(0, Math.ceil(seconds))
  for (let i = 0; i < REMAINING_UNITS.length - 1; i += 1) {
    const [name, size] = REMAINING_UNITS[i]
    if (left >= size) {
      const [subName, subSize] = REMAINING_UNITS[i + 1]
      return `${Math.floor(left / size)}${name} ${Math.floor((left % size) / subSize)}${subName}`
    }
  }
  return `${left}s`
}