// ── Formatting, with no dependencies and no React ─────────────────────────
//
// Every function here is pure and takes what the API answered, so the suite next
// door can ask all of it without a DOM. That is deliberate: the client half's
// real failures are timing and resolution (see `test/build.test.js`), which a
// DOM-less runner cannot see — so the way to have any test coverage at all on
// this side is to keep the parts that CAN be tested free of React.
//
// `Intl` does the work. It is in every browser core supports, it knows the
// viewer's locale and their clock, and it is one fewer thing in a chunk an
// operator ships.

const RELATIVE = new Intl.RelativeTimeFormat(undefined, { numeric: 'auto' })

const UNITS = [
  ['year', 31536000],
  ['month', 2592000],
  ['week', 604800],
  ['day', 86400],
  ['hour', 3600],
  ['minute', 60],
  ['second', 1],
]

/**
 * "3 minutes ago", from an ISO string or an epoch-millisecond number.
 *
 * Both shapes arrive from this module's own API: `updatedAt` is an ISO string
 * the model produced, and an event's `t` is the millisecond stamp the plugin put
 * on the frame. Accepting both here is what stops every caller remembering which
 * is which.
 */
export function ago(value, now = Date.now()) {
  const at = toMillis(value)
  if (at === null) return 'never'

  const seconds = Math.round((at - now) / 1000)
  const magnitude = Math.abs(seconds)

  // Under a minute, "in 0 seconds" is what `numeric: 'auto'` produces and it is
  // not what anybody means. Say the thing.
  if (magnitude < 45) return 'just now'

  const [unit, size] = UNITS.find(([, s]) => magnitude >= s) || ['second', 1]
  return RELATIVE.format(Math.round(seconds / size), unit)
}

/**
 * The stamp on a feed row.
 *
 * **Today's rows get a time; everything older gets a date as well.** The feed can
 * be filtered to a past wipe, and a row from six weeks ago rendered as `02:03 PM`
 * reads as this afternoon — which the page walk found the moment it looked at the
 * previous wipe: three events from August, all apparently a few minutes old.
 *
 * `now` is a parameter so the boundary is testable rather than a property of the
 * machine the test runs on.
 */
export function clock(value, now = Date.now()) {
  const at = toMillis(value)
  if (at === null) return ''

  const when = new Date(at)
  const time = when.toLocaleTimeString(undefined, { hour: '2-digit', minute: '2-digit' })

  const today = new Date(now)
  const sameDay =
    when.getFullYear() === today.getFullYear() &&
    when.getMonth() === today.getMonth() &&
    when.getDate() === today.getDate()

  if (sameDay) return time
  return `${when.toLocaleDateString(undefined, { month: 'short', day: 'numeric' })} ${time}`
}

/** A date, for a wipe: the thing people actually compare wipes by. */
export function day(value) {
  const at = toMillis(value)
  if (at === null) return 'unknown'
  return new Date(at).toLocaleDateString(undefined, { year: 'numeric', month: 'short', day: 'numeric' })
}

/**
 * A session or a playtime, as `4h 12m`.
 *
 * Seconds are dropped above a minute and kept below it, because a two-hour
 * session reported to the second is noise and a forty-second one reported as
 * "0m" is wrong.
 */
export function duration(seconds) {
  const total = Number(seconds)
  if (!Number.isFinite(total) || total <= 0) return '—'
  if (total < 60) return `${Math.round(total)}s`

  const hours = Math.floor(total / 3600)
  const minutes = Math.round((total % 3600) / 60)

  if (hours === 0) return `${minutes}m`
  return minutes === 0 ? `${hours}h` : `${hours}h ${minutes}m`
}

/** Thousands separators, in the viewer's locale. */
export function count(value) {
  const n = Number(value)
  return Number.isFinite(n) ? n.toLocaleString() : '0'
}

/**
 * A prefab short name as something readable — `patrolhelicopter` stays itself,
 * `rifle.ak` becomes `rifle ak`.
 *
 * Deliberately a light touch rather than a lookup table. A table mapping every
 * Rust prefab to a pretty name is a second copy of the game's item list that
 * goes stale every wipe, and the short name is what a Rust player reads on their
 * own server console anyway.
 */
export function prefab(name) {
  if (!name) return ''
  return String(name).replace(/[_.]+/g, ' ').trim()
}

/** A steam id, shortened for a table cell, without pretending it is a name. */
export function shortId(steamId) {
  const id = String(steamId || '')
  return id.length > 10 ? `…${id.slice(-6)}` : id
}

function toMillis(value) {
  if (value === null || value === undefined || value === '') return null
  if (typeof value === 'number') return Number.isFinite(value) ? value : null

  const parsed = Date.parse(value)
  return Number.isNaN(parsed) ? null : parsed
}

export default { ago, clock, day, duration, count, prefab, shortId }