feat(#11): "What just happened" synthesized event rail

Implemented by claude via .agents/dev dispatch.
This commit is contained in:
2026-07-04 00:00:34 -04:00
parent 75ca5f4deb
commit 2d49a8bd00
5 changed files with 748 additions and 1 deletions

318
frontend/src/lib/events.ts Normal file
View File

@@ -0,0 +1,318 @@
// "What just happened" event synthesis for the live page.
// Pure functions only — no React, no side effects — so everything is unit-testable.
// Mirrors the gapHistory/battles precedent: successive LiveStreamData snapshots
// in, typed events out; the page owns the buffer, this module owns the diffing.
import type {
LiveDriverData,
LiveRCMessage,
LiveSessionMeta,
LiveStreamData,
} from '../types'
export const MAX_EVENTS = 30
export type LiveEventKind =
| 'overtake'
| 'position-gain'
| 'position-loss'
| 'pit-in'
| 'pit-out'
| 'personal-best'
| 'fastest-lap'
| 'retirement'
| 'track-status'
| 'race-control'
export interface LiveEvent {
id: string
kind: LiveEventKind
lap: number
timestamp: string
headline: string
detail?: string
racingNumbers: string[]
}
/**
* Identity of the running session, used to reset the event buffer when a new
* session starts. LiveSessionMeta carries no numeric session key, so the
* meeting + session name/type triple stands in for one.
*/
export function sessionSignature(session: LiveSessionMeta | null | undefined): string {
if (!session) return ''
return [session.MeetingName, session.SessionName, session.SessionType].join('|')
}
/**
* Prepend freshly diffed events onto the newest-first buffer, dropping any
* whose id is already present (re-renders and replayed diffs must not
* duplicate) and evicting the oldest events beyond `cap`.
*/
export function appendEvents(
buffer: ReadonlyArray<LiveEvent>,
incoming: ReadonlyArray<LiveEvent>,
cap = MAX_EVENTS,
): LiveEvent[] {
const seen = new Set(buffer.map((event) => event.id))
const fresh = incoming.filter((event) => {
if (seen.has(event.id)) return false
seen.add(event.id)
return true
})
if (fresh.length === 0) return [...buffer]
// Within one diff the array is oldest-first; reverse so the last-produced
// event ends up at the top of the newest-first rail.
return [...fresh.reverse(), ...buffer].slice(0, cap)
}
const TRACK_STATUS_HEADLINES: Record<string, string> = {
'1': 'Green flag — track clear',
'2': 'Yellow flag',
'4': 'Safety Car deployed',
'5': 'Red flag — session stopped',
'6': 'Virtual Safety Car deployed',
'7': 'Virtual Safety Car ending',
}
const RC_CATEGORIES = new Set(['flag', 'safetycar', 'drs'])
/**
* Diff two successive live snapshots into a chronological list of synthesized
* events. Callers are expected to feed genuinely consecutive snapshots of the
* same session; diffing across a session boundary is the caller's job to
* prevent (see sessionSignature).
*/
export function diffSnapshots(prev: LiveStreamData, next: LiveStreamData): LiveEvent[] {
if (!prev || !next || prev === next) return []
const events: LiveEvent[] = []
const lap = next.CurrentLap || 0
const timestamp = next.Clock || ''
const code = (racingNumber: string): string =>
next.DriverInfo?.[racingNumber]?.Tla ||
prev.DriverInfo?.[racingNumber]?.Tla ||
`#${racingNumber}`
diffTrackStatus(prev, next, lap, timestamp, events)
diffRaceControl(prev, next, events)
const prevDrivers = prev.Drivers ?? {}
const nextDrivers = next.Drivers ?? {}
const numbers = Object.keys(nextDrivers).filter((number) => prevDrivers[number])
// Racing numbers whose position loss is already explained by an overtake
// event, so we don't also report a generic "drops to Pn".
const overtakenNumbers = new Set<string>()
for (const number of numbers) {
const before = prevDrivers[number]
const after = nextDrivers[number]
if (!before.Retired && after.Retired) {
events.push({
id: `ret:${number}`,
kind: 'retirement',
lap,
timestamp,
headline: `${code(number)} retires`,
detail: before.Position > 0 ? `Was running P${before.Position}` : undefined,
racingNumbers: [number],
})
}
if (!before.InPit && after.InPit && !after.Retired) {
const fromPosition = before.Position > 0 ? ` from P${before.Position}` : ''
events.push({
id: `pit-in:${number}:l${lap}`,
kind: 'pit-in',
lap,
timestamp,
headline: `${code(number)} pits${fromPosition}`,
racingNumbers: [number],
})
}
if (before.InPit && !after.InPit && !after.Retired) {
const compound = next.Tyres?.[number]?.Compound || ''
const stops = Math.max(0, (next.Stints?.[number]?.length ?? 0) - 1)
const parts = [compound, stops > 0 ? `${ordinal(stops)} stop` : ''].filter(Boolean)
const rejoined = after.Position > 0 ? ` P${after.Position}` : ''
events.push({
id: `pit-out:${number}:l${lap}`,
kind: 'pit-out',
lap,
timestamp,
headline: `${code(number)} rejoins${rejoined}${parts.length > 0 ? ` (${parts.join(', ')})` : ''}`,
racingNumbers: [number],
})
}
diffBestLap(number, before, after, code, lap, timestamp, events)
}
// Position gains, with overtake attribution via position swaps.
for (const number of numbers) {
const before = prevDrivers[number]
const after = nextDrivers[number]
if (before.Position <= 0 || after.Position <= 0) continue
if (after.Position >= before.Position) continue
if (after.InPit || after.Retired) continue
const overtaken = numbers.find((other) => {
if (other === number) return false
const otherBefore = prevDrivers[other]
const otherAfter = nextDrivers[other]
return (
otherBefore.Position === after.Position &&
otherAfter.Position > otherBefore.Position &&
!otherAfter.InPit &&
!otherAfter.Retired
)
})
if (overtaken) {
overtakenNumbers.add(overtaken)
events.push({
id: `overtake:${number}:${overtaken}:p${after.Position}:l${lap}`,
kind: 'overtake',
lap,
timestamp,
headline: `${code(number)} overtakes ${code(overtaken)} for P${after.Position}`,
detail: before.Position - after.Position > 1 ? `Up from P${before.Position}` : undefined,
racingNumbers: [number, overtaken],
})
} else {
events.push({
id: `pos:${number}:${before.Position}-${after.Position}:l${lap}`,
kind: 'position-gain',
lap,
timestamp,
headline: `${code(number)} moves up to P${after.Position} (from P${before.Position})`,
racingNumbers: [number],
})
}
}
// Position losses not already explained by an overtake or a pit visit.
for (const number of numbers) {
const before = prevDrivers[number]
const after = nextDrivers[number]
if (before.Position <= 0 || after.Position <= 0) continue
if (after.Position <= before.Position) continue
if (overtakenNumbers.has(number)) continue
if (after.InPit || after.PitOut || after.Retired || before.InPit) continue
events.push({
id: `pos:${number}:${before.Position}-${after.Position}:l${lap}`,
kind: 'position-loss',
lap,
timestamp,
headline: `${code(number)} drops to P${after.Position} (from P${before.Position})`,
racingNumbers: [number],
})
}
return events
}
function diffTrackStatus(
prev: LiveStreamData,
next: LiveStreamData,
lap: number,
timestamp: string,
events: LiveEvent[],
): void {
if (!prev.TrackStatus || !next.TrackStatus) return
if (prev.TrackStatus === next.TrackStatus) return
events.push({
id: `track:${next.TrackStatus}:l${lap}`,
kind: 'track-status',
lap,
timestamp,
headline: TRACK_STATUS_HEADLINES[next.TrackStatus] ?? `Track status ${next.TrackStatus}`,
racingNumbers: [],
})
}
function diffRaceControl(prev: LiveStreamData, next: LiveStreamData, events: LiveEvent[]): void {
const prevMessages = prev.RCMessages ?? []
const seen = new Set(prevMessages.map(rcMessageKey))
for (const message of next.RCMessages ?? []) {
if (!message.Message || seen.has(rcMessageKey(message))) continue
if (!RC_CATEGORIES.has((message.Category || '').toLowerCase())) continue
events.push({
id: `rc:${rcMessageKey(message)}`,
kind: 'race-control',
lap: message.Lap || 0,
timestamp: message.Time || '',
headline: humanizeRaceControl(message.Message),
racingNumbers: carNumbersIn(message.Message),
})
}
}
function diffBestLap(
number: string,
before: LiveDriverData,
after: LiveDriverData,
code: (racingNumber: string) => string,
lap: number,
timestamp: string,
events: LiveEvent[],
): void {
if (!after.LastLapTime) return
const isNewLap = after.LastLapTime !== before.LastLapTime
if (after.LastLapOB && (isNewLap || !before.LastLapOB)) {
events.push({
id: `ob:${number}:${after.LastLapTime}`,
kind: 'fastest-lap',
lap,
timestamp,
headline: `${code(number)} sets the fastest lap — ${after.LastLapTime}`,
racingNumbers: [number],
})
return
}
if (after.LastLapPB && !after.LastLapOB && (isNewLap || !before.LastLapPB)) {
events.push({
id: `pb:${number}:${after.LastLapTime}`,
kind: 'personal-best',
lap,
timestamp,
headline: `${code(number)} sets a personal best — ${after.LastLapTime}`,
racingNumbers: [number],
})
}
}
function rcMessageKey(message: LiveRCMessage): string {
return `${message.Time}:${message.Message}`
}
/** "SAFETY CAR DEPLOYED" -> "Safety car deployed", keeping known acronyms upper-cased. */
export function humanizeRaceControl(message: string): string {
const lower = message.trim().toLowerCase()
if (!lower) return ''
const sentence = lower.charAt(0).toUpperCase() + lower.slice(1)
return sentence.replace(/\b(drs|vsc|sc|fia)\b/gi, (acronym) => acronym.toUpperCase())
}
function carNumbersIn(message: string): string[] {
const numbers: string[] = []
for (const match of message.matchAll(/CAR (\d+)/gi)) {
if (!numbers.includes(match[1])) numbers.push(match[1])
}
return numbers
}
function ordinal(n: number): string {
const rem10 = n % 10
const rem100 = n % 100
if (rem10 === 1 && rem100 !== 11) return `${n}st`
if (rem10 === 2 && rem100 !== 12) return `${n}nd`
if (rem10 === 3 && rem100 !== 13) return `${n}rd`
return `${n}th`
}