// Pure display formatters shared by main and renderer. Kept in @shared (not a
// main- or renderer-only lib) so byte/speed/ETA formatting has ONE definition on
// both sides of the IPC boundary — the renderer no longer re-parses formatted
// strings back into numbers to aggregate them (H2/H4).

/** Format a byte count as a binary-scaled size, e.g. 1048576 → '1.0 MB'. */
export function fmtBytes(bytes: number): string {
  if (bytes < 1024) return `${bytes} B`
  const units = ['KB', 'MB', 'GB', 'TB']
  let v = bytes / 1024
  let i = 0
  while (v >= 1024 && i < units.length - 1) {
    v /= 1024
    i++
  }
  return `${v.toFixed(v >= 100 ? 0 : 1)} ${units[i]}`
}

/** Format a transfer rate, e.g. 4928307 → '4.7 MB/s'. Undefined for no rate. */
export function fmtSpeed(bytesPerSec?: number): string | undefined {
  if (bytesPerSec == null) return undefined
  return `${fmtBytes(bytesPerSec)}/s`
}

/** Format a duration in seconds as M:SS or H:MM:SS. Undefined for no value. */
export function fmtEta(seconds?: number): string | undefined {
  if (seconds == null) return undefined
  const s = Math.max(0, Math.round(seconds))
  const h = Math.floor(s / 3600)
  const m = Math.floor((s % 3600) / 60)
  const r = s % 60
  if (h > 0) return `${h}:${String(m).padStart(2, '0')}:${String(r).padStart(2, '0')}`
  return `${m}:${String(r).padStart(2, '0')}`
}