// ── 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'
}

/**
 * An Economics balance (PLAN_REDESIGNS §11.2.2): up to two places, and a dash
 * for one the server never reported. Not `count`'s zero — "0 coins" is a claim
 * about somebody's balance, and an unknown one is not it.
 */
export function coins(value) {
  if (value === null || value === undefined || value === '') return '—'
  const n = Number(value)
  return Number.isFinite(n) ? n.toLocaleString(undefined, { maximumFractionDigits: 2 }) : '—'
}

/**
 * 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()
}

/**
 * The weapon in a kill. The server sends `weaponName` — the game's own name for
 * a gun, or the prefab name as words (`server/model/titles/weaponNames.js`) —
 * and that is what prints. A server too old to send it gets the same fallback
 * here: the `.entity` / `.weapon` ending dropped, so never "ak47u entity".
 */
export function weapon(frame) {
  if (!frame || !frame.weapon) return ''
  if (frame.weaponName) return String(frame.weaponName)
  return prefab(String(frame.weapon).trim().replace(/[._](entity|weapon|deployed)$/, ''))
}

/**
 * The NPC families whose prefab reads badly as words, by the prefix the game's
 * short names share. First match wins, so a longer prefix sits above a shorter
 * one it starts with.
 */
const NPC_FAMILIES = [
  ['scientistnpc_heavy', 'Heavy scientist'],
  ['scientistnpc', 'Scientist'],
  ['npc_bandit_guard', 'Bandit guard'],
  ['bandit_guard', 'Bandit guard'],
  ['npc_tunneldweller', 'Tunnel dweller'],
  ['npc_underwaterdweller', 'Underwater dweller'],
  ['bradleyapc', 'Bradley APC'],
  ['patrolhelicopter', 'Patrol helicopter'],
  ['ch47scientists', 'Chinook'],
  ['sentry.scientist', 'Outpost sentry'],
  ['sentry.bandit', 'Bandit Camp sentry'],
  ['autoturret', 'Auto turret'],
  ['flameturret', 'Flame turret'],
  ['guntrap', 'Shotgun trap'],
  ['sam_site', 'SAM site'],
  ['sam_static', 'SAM site'],
  ['polarbear', 'Polar bear'],
  ['simpleshark', 'Shark'],
]

/**
 * What killed somebody, when it was not a player (PLAN_FIXES F2, D185) — the
 * killfeed's `npc` attacker, which the plugin sends as a prefab short name.
 *
 * The first walk read "killed by wolf2". `prefab` keeps its light touch for a
 * weapon, where the short name is what a Rust player reads on their own console;
 * an ATTACKER is a creature or a machine, and a number stuck to its name is the
 * game's variant, not something a reader needs. So a known family is named
 * (above), and anything else has its variant digits and deploy suffixes trimmed
 * and reads as capitalised words — `wolf2` is "Wolf", `boar` is "Boar". Still no
 * table of every prefab: a new animal reads fine without one.
 */
export function attacker(name) {
  if (!name) return ''
  const text = String(name).toLowerCase()
  const family = NPC_FAMILIES.find(([prefix]) => text.startsWith(prefix))
  if (family) return family[1]

  const words = text
    .replace(/(\.deployed|_deployed|\.entity|\.prefab)$/, '')
    .replace(/\d+$/, '')
    .replace(/[_.]+/g, ' ')
    .trim()
  return words ? words[0].toUpperCase() + words.slice(1) : ''
}

/** 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
}

/**
 * The next wipe (phase 16, D130), as `Thu, Oct 1, 7:00 PM (in 6 days)` in the
 * VIEWER's locale and clock — or `null` when the server has no schedule.
 *
 * The server computes the instant from the operator's rule in the operator's
 * zone; the page only says it the reader's way. A `once` source is an operator
 * moving a wipe, and says so, because "the wipe is not when it usually is" is
 * the thing a regular needs to notice.
 */
export function nextWipe(value, now = Date.now()) {
  if (!value || !value.at) return null
  const at = toMillis(value.at)
  if (at === null) return null
  const when = new Date(at).toLocaleString(undefined, {
    weekday: 'short',
    month: 'short',
    day: 'numeric',
    hour: 'numeric',
    minute: '2-digit',
  })
  return `${when} (${ago(at, now)})${value.source === 'once' ? ' — rescheduled' : ''}`
}

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
}

/**
 * The ink that reads on a background of `hex` — black or white, whichever has
 * the higher WCAG contrast. A chat title's colour is the operator's, chosen for
 * a dark game chat, and this page is drawn in the reader's theme: yellow text on
 * a white page is unreadable, so the colour becomes the chip and the text is
 * picked for it (phase 17, D137). Anything that is not `#rrggbb` gets black on
 * the caller's fallback.
 */
export function contrastInk(hex) {
  const m = /^#([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})$/i.exec(String(hex || ''))
  if (!m) return '#000000'
  const linear = (c) => {
    const v = parseInt(c, 16) / 255
    return v <= 0.03928 ? v / 12.92 : ((v + 0.055) / 1.055) ** 2.4
  }
  const L = 0.2126 * linear(m[1]) + 0.7152 * linear(m[2]) + 0.0722 * linear(m[3])
  // Contrast against white is 1.05 / (L + 0.05); against black (L + 0.05) / 0.05.
  return (L + 0.05) / 0.05 >= 1.05 / (L + 0.05) ? '#000000' : '#ffffff'
}

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