feat: add narrative chapter headlines and race-hub chapter strip (#21)

Generate deterministic template headlines server-side for each replay chapter
kind, expose Chapter.headline in the race-hub payload, and render a horizontal
chapter strip on the story view with active-chapter highlighting, click-to-jump,
and a 90-second tour mode built on the existing scrubber playback.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/components/ChapterStrip.tsx

@@ -0,0 +1,87 @@
+import type { Chapter } from '../types'
+import {
+  activeChapterIndex,
+  chapterKindLabel,
+  chapterLapRange,
+  chapterStartScrub,
+} from '../lib/chapters'
+import '../styles/chapters.css'
+
+interface Props {
+  chapters: Chapter[]
+  scrubTime: number | null
+  tMin: number
+  tRange: number
+  tourActive: boolean
+  tourChapterIndex: number | null
+  onChapterClick: (index: number, scrub: number) => void
+  onTourToggle: () => void
+}
+
+export function ChapterStrip({
+  chapters,
+  scrubTime,
+  tMin,
+  tRange,
+  tourActive,
+  tourChapterIndex,
+  onChapterClick,
+  onTourToggle,
+}: Props) {
+  if (chapters.length === 0) {
+    return (
+      <div className="chapter-strip" data-testid="chapter-strip">
+        <p className="chapter-strip-empty">No story chapters for this session.</p>
+      </div>
+    )
+  }
+
+  const activeIndex = activeChapterIndex(chapters, scrubTime, tMin, tRange)
+
+  return (
+    <div className="chapter-strip" data-testid="chapter-strip">
+      <div className="chapter-strip-header">
+        <span className="chapter-strip-title">Race chapters</span>
+        <div className="chapter-strip-actions">
+          <button
+            type="button"
+            className={`chapter-tour-btn ${tourActive ? 'active' : ''}`}
+            onClick={onTourToggle}
+            aria-pressed={tourActive}
+          >
+            {tourActive ? 'Exit 90s' : '90s tour'}
+          </button>
+        </div>
+      </div>
+      <div className="chapter-strip-scroll" role="list" aria-label="Race story chapters">
+        {chapters.map((chapter, index) => {
+          const scrub = chapterStartScrub(chapter, tMin, tRange) ?? index / Math.max(chapters.length - 1, 1)
+          const isActive = tourActive
+            ? tourChapterIndex === index
+            : activeIndex === index
+          const headline = chapter.headline || chapter.title
+
+          return (
+            <button
+              key={`${chapter.kind}-${chapter.start_lap}-${index}`}
+              type="button"
+              role="listitem"
+              className={`chapter-card ${isActive ? (tourActive ? 'tour-active' : 'active') : ''}`}
+              onClick={() => onChapterClick(index, scrub)}
+              aria-current={isActive ? 'true' : undefined}
+              data-testid={`chapter-card-${index}`}
+            >
+              <div className="chapter-card-top">
+                <span className={`chapter-kind chapter-kind--${chapter.kind}`}>
+                  {chapterKindLabel(chapter.kind)}
+                </span>
+                <span className="chapter-lap-range">{chapterLapRange(chapter)}</span>
+              </div>
+              <span className="chapter-headline">{headline}</span>
+            </button>
+          )
+        })}
+      </div>
+    </div>
+  )
+}

frontend/src/components/RaceStoryCanvas.tsx

@@ -1,9 +1,13 @@
 import { useEffect, useMemo, useRef, useState } from 'react'
 import { useQuery } from '@tanstack/react-query'
-import type { Driver, EnrichedResult, EnrichedGrid, PositionSample, Lap, Meeting, Session } from '../types'
+import type { Driver, EnrichedResult, EnrichedGrid, PositionSample, Lap, Meeting, Session, Chapter } from '../types'
 import { fetchReplayFrames, fetchTrackOutline } from '../api'
 import { ReplayTrackMap } from './ReplayTrackMap'
+import { ChapterStrip } from './ChapterStrip'
 import { gridDelta, gridDeltaClass, formatDuration, formatGap } from '../utils'
+import { chapterEndScrub, chapterStartScrub, chapterTourDurations } from '../lib/chapters'
+
+const CHAPTER_TOUR_MS = 90_000
 
 interface Props {
   data: {
@@ -17,6 +21,7 @@ interface Props {
     session?: Session
     meeting?: Meeting
     drivers?: Driver[]
+    chapters?: Chapter[]
   }
 }
 
@@ -32,6 +37,7 @@ export function RaceStoryCanvas({ data }: Props) {
     session,
     meeting,
     drivers = [],
+    chapters = [],
   } = data
   const hasPositions = datasets['positions']?.status === 'available'
 
@@ -40,7 +46,10 @@ export function RaceStoryCanvas({ data }: Props) {
   const [mapOpen, setMapOpen] = useState(false)
   const [isPlaying, setIsPlaying] = useState(false)
   const [playbackSpeed, setPlaybackSpeed] = useState(10)
+  const [chapterTourActive, setChapterTourActive] = useState(false)
+  const [tourChapterIndex, setTourChapterIndex] = useState<number | null>(null)
   const svgRef = useRef<SVGSVGElement>(null)
+  const tourRef = useRef({ chapterIndex: 0, startedAt: 0, durationMs: 0, startScrub: 0, endScrub: 0 })
 
   // Position Evolution Chart Logic
   const allTimes = useMemo(() => [...new Set(positions.map((p) => p.date))].sort(), [positions])
@@ -87,6 +96,85 @@ export function RaceStoryCanvas({ data }: Props) {
     return () => cancelAnimationFrame(frame)
   }, [chartTiming, isPlaying, playbackSpeed])
 
+  const stopChapterTour = () => {
+    setChapterTourActive(false)
+    setTourChapterIndex(null)
+  }
+
+  const jumpToChapter = (index: number, scrub: number) => {
+    setIsPlaying(false)
+    stopChapterTour()
+    setScrubTime(scrub)
+  }
+
+  const toggleChapterTour = () => {
+    if (chapterTourActive) {
+      stopChapterTour()
+      return
+    }
+    if (!chartTiming || chapters.length === 0) return
+    setIsPlaying(false)
+    setChapterTourActive(true)
+    setTourChapterIndex(0)
+    const startScrub = chapterStartScrub(chapters[0], chartTiming.tMin, chartTiming.tRange) ?? 0
+    setScrubTime(startScrub)
+    const durations = chapterTourDurations(chapters, CHAPTER_TOUR_MS)
+    tourRef.current = {
+      chapterIndex: 0,
+      startedAt: performance.now(),
+      durationMs: durations[0] ?? CHAPTER_TOUR_MS / chapters.length,
+      startScrub,
+      endScrub: chapterEndScrub(chapters[0], chartTiming.tMin, chartTiming.tRange) ?? startScrub,
+    }
+  }
+
+  useEffect(() => {
+    if (!chapterTourActive || !chartTiming || chapters.length === 0) return
+
+    let frame = 0
+    const tick = (now: number) => {
+      const state = tourRef.current
+      const elapsed = now - state.startedAt
+      const progress = Math.min(1, elapsed / Math.max(state.durationMs, 1))
+      const scrub = state.startScrub + (state.endScrub - state.startScrub) * progress
+      setScrubTime(scrub)
+      setTourChapterIndex(state.chapterIndex)
+
+      if (progress >= 1) {
+        const nextIndex = state.chapterIndex + 1
+        if (nextIndex >= chapters.length) {
+          stopChapterTour()
+          return
+        }
+        const durations = chapterTourDurations(chapters, CHAPTER_TOUR_MS)
+        const startScrub = chapterStartScrub(chapters[nextIndex], chartTiming.tMin, chartTiming.tRange) ?? 0
+        const endScrub = chapterEndScrub(chapters[nextIndex], chartTiming.tMin, chartTiming.tRange) ?? startScrub
+        tourRef.current = {
+          chapterIndex: nextIndex,
+          startedAt: now,
+          durationMs: durations[nextIndex] ?? CHAPTER_TOUR_MS / chapters.length,
+          startScrub,
+          endScrub,
+        }
+      }
+      frame = requestAnimationFrame(tick)
+    }
+
+    frame = requestAnimationFrame(tick)
+    return () => cancelAnimationFrame(frame)
+  }, [chapterTourActive, chartTiming, chapters])
+
+  useEffect(() => {
+    if (!chapterTourActive) return
+    const onKeyDown = (event: KeyboardEvent) => {
+      if (event.key === 'Escape') {
+        stopChapterTour()
+      }
+    }
+    window.addEventListener('keydown', onKeyDown)
+    return () => window.removeEventListener('keydown', onKeyDown)
+  }, [chapterTourActive])
+
   const replayTMs = useMemo(() => {
     const replay = replayQuery.data
     const frames = replay?.frames ?? []
@@ -210,6 +298,7 @@ export function RaceStoryCanvas({ data }: Props) {
 
     const handlePointerMove = (e: React.PointerEvent<SVGRectElement>) => {
       setIsPlaying(false)
+      stopChapterTour()
       if (!svgRef.current) return
       const rect = svgRef.current.getBoundingClientRect()
       const x = e.clientX - rect.left
@@ -373,6 +462,7 @@ export function RaceStoryCanvas({ data }: Props) {
             className={`rs-tool-btn ${isPlaying ? 'active' : ''}`}
             onClick={() => {
               setScrubTime((current) => current ?? 0)
+              stopChapterTour()
               setIsPlaying((current) => !current)
             }}
           >
@@ -404,6 +494,18 @@ export function RaceStoryCanvas({ data }: Props) {
 
   return (
     <div className="race-story-canvas">
+      {hasChartData && chartTiming && chapters.length > 0 && (
+        <ChapterStrip
+          chapters={chapters}
+          scrubTime={scrubTime}
+          tMin={chartTiming.tMin}
+          tRange={chartTiming.tRange}
+          tourActive={chapterTourActive}
+          tourChapterIndex={tourChapterIndex}
+          onChapterClick={jumpToChapter}
+          onTourToggle={toggleChapterTour}
+        />
+      )}
       <div className="rs-replay-shell">
         <div className="rs-replay-main">
           {hasChartData ? (

frontend/src/lib/chapters.ts

@@ -0,0 +1,82 @@
+import type { Chapter } from '../types'
+
+export function chapterKindLabel(kind: string): string {
+  switch (kind) {
+    case 'start':
+      return 'GO'
+    case 'safety_car':
+      return 'SC'
+    case 'virtual_safety_car':
+      return 'VSC'
+    case 'red_flag':
+      return 'RF'
+    case 'pit_phase':
+      return 'PIT'
+    case 'decisive_swing':
+      return '▲'
+    case 'finish':
+      return 'FIN'
+    default:
+      return kind.slice(0, 3).toUpperCase()
+  }
+}
+
+export function chapterLapRange(chapter: Chapter): string {
+  if (chapter.start_lap === chapter.end_lap) {
+    return `L${chapter.start_lap}`
+  }
+  return `L${chapter.start_lap}–L${chapter.end_lap}`
+}
+
+/** Normalized scrub position (0–1) for a chapter's start time on the chart axis. */
+export function chapterStartScrub(
+  chapter: Chapter,
+  tMin: number,
+  tRange: number,
+): number | null {
+  if (!chapter.start_time || tRange <= 0) return null
+  const ms = new Date(chapter.start_time).getTime()
+  if (Number.isNaN(ms)) return null
+  return Math.max(0, Math.min(1, (ms - tMin) / tRange))
+}
+
+/** Normalized scrub position (0–1) for a chapter's end time on the chart axis. */
+export function chapterEndScrub(
+  chapter: Chapter,
+  tMin: number,
+  tRange: number,
+): number | null {
+  const raw = chapter.end_time ?? chapter.start_time
+  if (!raw || tRange <= 0) return null
+  const ms = new Date(raw).getTime()
+  if (Number.isNaN(ms)) return null
+  return Math.max(0, Math.min(1, (ms - tMin) / tRange))
+}
+
+/** Index of the chapter containing the current scrub position, if any. */
+export function activeChapterIndex(
+  chapters: Chapter[],
+  scrubTime: number | null,
+  tMin: number,
+  tRange: number,
+): number | null {
+  if (scrubTime === null || chapters.length === 0 || tRange <= 0) return null
+  const chartMs = tMin + scrubTime * tRange
+  for (let i = 0; i < chapters.length; i++) {
+    const ch = chapters[i]
+    const startMs = ch.start_time ? new Date(ch.start_time).getTime() : NaN
+    const endRaw = ch.end_time ?? ch.start_time
+    const endMs = endRaw ? new Date(endRaw).getTime() : NaN
+    if (!Number.isNaN(startMs) && !Number.isNaN(endMs) && chartMs >= startMs && chartMs <= endMs) {
+      return i
+    }
+  }
+  return null
+}
+
+/** Duration in ms each chapter should play during a ~90s tour. */
+export function chapterTourDurations(chapters: Chapter[], totalMs = 90_000): number[] {
+  if (chapters.length === 0) return []
+  const perChapter = totalMs / chapters.length
+  return chapters.map(() => perChapter)
+}

frontend/src/styles/chapters.css

@@ -0,0 +1,154 @@
+.chapter-strip {
+  display: flex;
+  flex-direction: column;
+  gap: var(--s3);
+}
+
+.chapter-strip-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: var(--s4);
+}
+
+.chapter-strip-title {
+  font-size: 11px;
+  font-weight: 600;
+  letter-spacing: 0.06em;
+  text-transform: uppercase;
+  color: var(--text-3);
+}
+
+.chapter-strip-actions {
+  display: flex;
+  align-items: center;
+  gap: var(--s2);
+}
+
+.chapter-tour-btn {
+  font-family: var(--f-mono);
+  font-size: 11px;
+  padding: var(--s1) var(--s3);
+  border: 1px solid var(--border);
+  border-radius: var(--s1);
+  background: var(--surface);
+  color: var(--text-2);
+  cursor: pointer;
+  transition: background 0.15s, border-color 0.15s, color 0.15s;
+}
+
+.chapter-tour-btn:hover,
+.chapter-tour-btn.active {
+  background: var(--surface-h);
+  border-color: var(--border-2);
+  color: var(--text);
+}
+
+.chapter-strip-scroll {
+  display: flex;
+  gap: var(--s3);
+  overflow-x: auto;
+  padding-bottom: var(--s2);
+  scroll-snap-type: x mandatory;
+  -webkit-overflow-scrolling: touch;
+}
+
+.chapter-card {
+  flex: 0 0 min(240px, 72vw);
+  display: flex;
+  flex-direction: column;
+  gap: var(--s2);
+  padding: var(--s3) var(--s4);
+  border: 1px solid var(--border);
+  border-radius: var(--s2);
+  background: var(--surface);
+  text-align: left;
+  cursor: pointer;
+  scroll-snap-align: start;
+  transition: border-color 0.15s, background 0.15s, box-shadow 0.15s;
+}
+
+.chapter-card:hover {
+  background: var(--surface-h);
+  border-color: var(--border-2);
+}
+
+.chapter-card.active {
+  border-color: var(--accent, var(--red));
+  background: var(--surface-h);
+  box-shadow: 0 0 0 1px color-mix(in srgb, var(--accent, var(--red)) 35%, transparent);
+}
+
+.chapter-card.tour-active {
+  border-color: var(--yellow);
+  box-shadow: 0 0 0 1px color-mix(in srgb, var(--yellow) 40%, transparent);
+}
+
+.chapter-card-top {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: var(--s3);
+}
+
+.chapter-kind {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  min-width: 28px;
+  height: 20px;
+  padding: 0 var(--s2);
+  border-radius: var(--s1);
+  font-family: var(--f-mono);
+  font-size: 10px;
+  font-weight: 700;
+  letter-spacing: 0.04em;
+  background: var(--bg);
+  color: var(--text-2);
+  border: 1px solid var(--border);
+}
+
+.chapter-card.active .chapter-kind {
+  color: var(--text);
+  border-color: var(--border-2);
+}
+
+.chapter-kind--safety_car,
+.chapter-kind--virtual_safety_car {
+  color: var(--orange, #f90);
+}
+
+.chapter-kind--red_flag {
+  color: var(--red);
+}
+
+.chapter-kind--decisive_swing {
+  color: var(--green, #22c55e);
+}
+
+.chapter-kind--finish {
+  color: var(--yellow);
+}
+
+.chapter-lap-range {
+  font-family: var(--f-mono);
+  font-size: 10px;
+  color: var(--text-3);
+  white-space: nowrap;
+}
+
+.chapter-headline {
+  font-size: 13px;
+  line-height: 1.35;
+  color: var(--text);
+  display: -webkit-box;
+  -webkit-line-clamp: 2;
+  -webkit-box-orient: vertical;
+  overflow: hidden;
+}
+
+.chapter-strip-empty {
+  font-size: 12px;
+  color: var(--text-3);
+  padding: var(--s3) 0;
+}

frontend/src/test/ChapterStrip.test.tsx

@@ -0,0 +1,87 @@
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import { fireEvent, render, screen } from '@testing-library/react'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { ChapterStrip } from '../components/ChapterStrip'
+import type { Chapter } from '../types'
+
+const chapters: Chapter[] = [
+  {
+    kind: 'start',
+    title: 'Start',
+    headline: 'Lights out — the field charges into Turn 1',
+    start_lap: 1,
+    end_lap: 1,
+    start_time: '2025-05-25T13:00:00Z',
+    end_time: '2025-05-25T13:01:00Z',
+    driver_numbers: [],
+  },
+  {
+    kind: 'safety_car',
+    title: 'Safety Car (L12-L15)',
+    headline: 'Sainz incident brings out the Safety Car — leaders dive for the pits',
+    start_lap: 12,
+    end_lap: 15,
+    start_time: '2025-05-25T13:12:00Z',
+    end_time: '2025-05-25T13:15:00Z',
+    driver_numbers: [55],
+  },
+]
+
+const tMin = new Date('2025-05-25T13:00:00Z').getTime()
+const tMax = new Date('2025-05-25T13:20:00Z').getTime()
+const tRange = tMax - tMin
+
+function renderStrip(
+  overrides: Partial<{
+    scrubTime: number | null
+    onChapterClick: (index: number, scrub: number) => void
+  }> = {},
+) {
+  const onChapterClick = overrides.onChapterClick ?? vi.fn()
+  const queryClient = new QueryClient({ defaultOptions: { queries: { retry: false } } })
+  render(
+    <QueryClientProvider client={queryClient}>
+      <ChapterStrip
+        chapters={chapters}
+        scrubTime={overrides.scrubTime ?? null}
+        tMin={tMin}
+        tRange={tRange}
+        tourActive={false}
+        tourChapterIndex={null}
+        onChapterClick={onChapterClick}
+        onTourToggle={vi.fn()}
+      />
+    </QueryClientProvider>,
+  )
+  return { onChapterClick }
+}
+
+describe('ChapterStrip', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('renders chapter headlines and lap ranges', () => {
+    renderStrip()
+    expect(screen.getByTestId('chapter-strip')).toBeInTheDocument()
+    expect(screen.getByText('Lights out — the field charges into Turn 1')).toBeInTheDocument()
+    expect(screen.getByText('L12–L15')).toBeInTheDocument()
+  })
+
+  it('highlights the active chapter from scrub time', () => {
+    const scrub = (new Date('2025-05-25T13:13:00Z').getTime() - tMin) / tRange
+    renderStrip({ scrubTime: scrub })
+    expect(screen.getByTestId('chapter-card-1')).toHaveClass('active')
+    expect(screen.getByTestId('chapter-card-0')).not.toHaveClass('active')
+  })
+
+  it('calls click handler to jump scrubber', () => {
+    const onChapterClick = vi.fn<(index: number, scrub: number) => void>()
+    renderStrip({ onChapterClick })
+    fireEvent.click(screen.getByTestId('chapter-card-1'))
+    expect(onChapterClick).toHaveBeenCalledTimes(1)
+    const [index, scrub] = onChapterClick.mock.calls[0]
+    expect(index).toBe(1)
+    expect(scrub).toBeCloseTo(0.6, 2)
+  })
+})

frontend/src/test/chapters.test.ts

@@ -0,0 +1,63 @@
+import { describe, expect, it } from 'vitest'
+import {
+  activeChapterIndex,
+  chapterKindLabel,
+  chapterLapRange,
+  chapterStartScrub,
+  chapterTourDurations,
+} from '../lib/chapters'
+import type { Chapter } from '../types'
+
+const sampleChapters: Chapter[] = [
+  {
+    kind: 'start',
+    title: 'Start',
+    headline: 'Lights out — the field charges into Turn 1',
+    start_lap: 1,
+    end_lap: 1,
+    start_time: '2025-05-25T13:00:00Z',
+    end_time: '2025-05-25T13:01:00Z',
+    driver_numbers: [],
+  },
+  {
+    kind: 'safety_car',
+    title: 'Safety Car (L12-L15)',
+    headline: 'Sainz incident brings out the Safety Car — leaders dive for the pits',
+    start_lap: 12,
+    end_lap: 15,
+    start_time: '2025-05-25T13:12:00Z',
+    end_time: '2025-05-25T13:15:00Z',
+    driver_numbers: [55],
+  },
+]
+
+describe('chapters lib', () => {
+  it('labels chapter kinds', () => {
+    expect(chapterKindLabel('safety_car')).toBe('SC')
+    expect(chapterKindLabel('finish')).toBe('FIN')
+  })
+
+  it('formats lap ranges', () => {
+    expect(chapterLapRange(sampleChapters[0])).toBe('L1')
+    expect(chapterLapRange(sampleChapters[1])).toBe('L12–L15')
+  })
+
+  it('maps chapter start time to scrub position', () => {
+    const tMin = new Date('2025-05-25T13:00:00Z').getTime()
+    const tMax = new Date('2025-05-25T13:20:00Z').getTime()
+    const scrub = chapterStartScrub(sampleChapters[1], tMin, tMax - tMin)
+    expect(scrub).toBeCloseTo(0.6, 2)
+  })
+
+  it('finds active chapter from scrub time', () => {
+    const tMin = new Date('2025-05-25T13:00:00Z').getTime()
+    const tMax = new Date('2025-05-25T13:20:00Z').getTime()
+    const tRange = tMax - tMin
+    const scrub = (new Date('2025-05-25T13:13:00Z').getTime() - tMin) / tRange
+    expect(activeChapterIndex(sampleChapters, scrub, tMin, tRange)).toBe(1)
+  })
+
+  it('splits 90s evenly across chapters', () => {
+    expect(chapterTourDurations(sampleChapters)).toEqual([45_000, 45_000])
+  })
+})

frontend/src/types.ts

@@ -97,6 +97,7 @@ export interface RaceHub {
 export interface Chapter {
   kind: 'start' | 'safety_car' | 'virtual_safety_car' | 'red_flag' | 'pit_phase' | 'decisive_swing' | 'finish' | string
   title: string
+  headline: string
   start_lap: number
   end_lap: number
   start_time?: string