import { useEffect, useMemo, useRef, useState } from 'react'
import {
  addTagToVerse,
  getCommentaryForVerse,
  getDictionaryEntriesForTerms,
  getLibraryState,
  getTranslationNotesForVerses,
  getTranslations,
  searchVerses,
} from './studyClient'
import {
  createSession,
  defaultTranslationId,
  hostedWorkspaceEnabled,
  loadWorkspaceSnapshot,
  saveWorkspaceSnapshot,
  timelineId,
  timelineLimit,
} from './workspace'
import type { DragEvent, MouseEvent as ReactMouseEvent, ReactNode } from 'react'
import type { CommentaryEntry, DictionaryEntry, TranslationResource, Verse } from './types'
import type {
  StrongDisplayMode,
  StudySession,
  StudySettings,
  ThemeMode,
  TimelineEntry,
  ViewMode,
} from './workspace'
import './App.css'

const tagColors = ['#2f6f5e', '#735c0f', '#8a3ffc', '#b42318', '#245ba7']
const pageSize = 34
type PageMotion = 'idle' | 'turn-forward' | 'turn-back'

function reference(verse: Verse) {
  return `${verse.book} ${verse.chapter}:${verse.verse}`
}

function replaceChangedVerses(verses: Verse[], hydrate: (verse: Verse) => Verse) {
  let changed = false
  const next = verses.map((verse) => {
    const hydrated = hydrate(verse)
    if (hydrated !== verse) changed = true
    return hydrated
  })
  return changed ? next : verses
}

function formatTimelineTime(value: string) {
  return new Date(value).toLocaleTimeString([], { hour: 'numeric', minute: '2-digit' })
}

function abbreviateBook(book: string) {
  const abbreviations: Record<string, string> = {
    Genesis: 'Gen',
    Exodus: 'Ex',
    Leviticus: 'Lev',
    Numbers: 'Num',
    Deuteronomy: 'Deut',
    Joshua: 'Josh',
    Judges: 'Judg',
    Ruth: 'Ruth',
    '1 Samuel': '1 Sam',
    '2 Samuel': '2 Sam',
    '1 Kings': '1 Kgs',
    '2 Kings': '2 Kgs',
    '1 Chronicles': '1 Chr',
    '2 Chronicles': '2 Chr',
    Ezra: 'Ezra',
    Nehemiah: 'Neh',
    Esther: 'Est',
    Job: 'Job',
    Psalms: 'Ps',
    Proverbs: 'Prov',
    Ecclesiastes: 'Eccl',
    'Song of Solomon': 'Song',
    Isaiah: 'Isa',
    Jeremiah: 'Jer',
    Lamentations: 'Lam',
    Ezekiel: 'Ezek',
    Daniel: 'Dan',
    Hosea: 'Hos',
    Joel: 'Joel',
    Amos: 'Amos',
    Obadiah: 'Ob',
    Jonah: 'Jon',
    Micah: 'Mic',
    Nahum: 'Nah',
    Habakkuk: 'Hab',
    Zephaniah: 'Zeph',
    Haggai: 'Hag',
    Zechariah: 'Zech',
    Malachi: 'Mal',
    Matthew: 'Matt',
    Mark: 'Mark',
    Luke: 'Luke',
    John: 'John',
    Acts: 'Acts',
    Romans: 'Rom',
    '1 Corinthians': '1 Cor',
    '2 Corinthians': '2 Cor',
    Galatians: 'Gal',
    Ephesians: 'Eph',
    Philippians: 'Phil',
    Colossians: 'Col',
    '1 Thessalonians': '1 Th',
    '2 Thessalonians': '2 Th',
    '1 Timothy': '1 Tim',
    '2 Timothy': '2 Tim',
    Titus: 'Titus',
    Philemon: 'Phlm',
    Hebrews: 'Heb',
    James: 'Jas',
    '1 Peter': '1 Pet',
    '2 Peter': '2 Pet',
    '1 John': '1 Jn',
    '2 John': '2 Jn',
    '3 John': '3 Jn',
    Jude: 'Jude',
    Revelation: 'Rev',
  }

  return abbreviations[book] ?? book.slice(0, 4)
}

function dictionaryTermsForVerse(verse: Verse) {
  const stopWords = new Set([
    'a',
    'an',
    'and',
    'are',
    'as',
    'at',
    'be',
    'but',
    'by',
    'for',
    'from',
    'he',
    'her',
    'him',
    'his',
    'i',
    'in',
    'is',
    'it',
    'of',
    'on',
    'or',
    'that',
    'the',
    'their',
    'them',
    'they',
    'this',
    'to',
    'unto',
    'was',
    'were',
    'with',
    'ye',
    'you',
  ])
  const strongSurfaces = verse.strongs.map((entry) => entry.surface)
  const textWords = [...verse.text.matchAll(/[A-Za-z][A-Za-z'-]*/g)].map((match) => match[0])
  const unique = new Map<string, string>()

  for (const term of [...strongSurfaces, ...textWords]) {
    const normalized = term.toLowerCase().replace(/[^a-z0-9\s'-]/g, '').trim()
    if (!normalized || stopWords.has(normalized) || normalized.length < 3) continue
    unique.set(normalized, term)
  }

  return [...unique.values()].slice(0, 28)
}

function App() {
  const [railOpen, setRailOpen] = useState(false)
  const [sessionModalOpen, setSessionModalOpen] = useState(false)
  const [aboutModalOpen, setAboutModalOpen] = useState(false)
  const [timelineModalOpen, setTimelineModalOpen] = useState(false)
  const [settingsModalOpen, setSettingsModalOpen] = useState(false)
  const [notesDrawerOpen, setNotesDrawerOpen] = useState(false)
  const [notesPinned, setNotesPinned] = useState(false)
  const [pageMotion, setPageMotion] = useState<PageMotion>('idle')
  const [viewMode, setViewMode] = useState<ViewMode>('notes')
  const [query, setQuery] = useState('')
  const [themeMode, setThemeMode] = useState<ThemeMode>('light')
  const [libraryVerses, setLibraryVerses] = useState<Verse[]>([])
  const [verses, setVerses] = useState<Verse[]>([])
  const [translations, setTranslations] = useState<TranslationResource[]>([])
  const [selectedId, setSelectedId] = useState<number | null>(null)
  const [pageStartId, setPageStartId] = useState<number | null>(null)
  const [selectedStrong, setSelectedStrong] = useState<string | null>(null)
  const [strongDisplay, setStrongDisplay] = useState<StrongDisplayMode>('highlight')
  const [tagInput, setTagInput] = useState('')
  const [noteDraft, setNoteDraft] = useState('')
  const [sessions, setSessions] = useState<StudySession[]>([])
  const [activeSessionId, setActiveSessionId] = useState('')
  const [newSessionTitle, setNewSessionTitle] = useState('New KJV Study')
  const [newSessionBaseTranslation, setNewSessionBaseTranslation] = useState(defaultTranslationId)
  const [newSessionFootnotes, setNewSessionFootnotes] = useState(true)
  const [newSessionStrongs, setNewSessionStrongs] = useState(true)
  const [newSessionCommentary, setNewSessionCommentary] = useState(true)
  const [newSessionDictionary, setNewSessionDictionary] = useState(true)
  const [newSessionTimeline, setNewSessionTimeline] = useState(true)
  const [lemmaFontSize, setLemmaFontSize] = useState(17)
  const [linkedFontSize, setLinkedFontSize] = useState(15)
  const [originalCollapsed, setOriginalCollapsed] = useState(false)
  const [linkedCollapsed, setLinkedCollapsed] = useState(false)
  const [definitionCollapsed, setDefinitionCollapsed] = useState(false)
  const [studyNotesCollapsed, setStudyNotesCollapsed] = useState(false)
  const [commentaryCollapsed, setCommentaryCollapsed] = useState(false)
  const [dictionaryCollapsed, setDictionaryCollapsed] = useState(false)
  const [showOriginalLine, setShowOriginalLine] = useState(true)
  const [showLinkedLine, setShowLinkedLine] = useState(true)
  const [showDefinitionPanel, setShowDefinitionPanel] = useState(true)
  const [showCommentaryPanel, setShowCommentaryPanel] = useState(true)
  const [showDictionaryPanel, setShowDictionaryPanel] = useState(true)
  const [splitPercent, setSplitPercent] = useState(50)
  const [commentaryEntries, setCommentaryEntries] = useState<CommentaryEntry[]>([])
  const [dictionaryEntries, setDictionaryEntries] = useState<DictionaryEntry[]>([])
  const [marginResourcesLoading, setMarginResourcesLoading] = useState(false)
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState<string | null>(null)
  const restoredSessionId = useRef('')
  const pageMotionTimeout = useRef<number | null>(null)
  const notesDragOpenTimeout = useRef<number | null>(null)
  const remoteWorkspaceSaveTimeout = useRef<number | null>(null)
  const readerRef = useRef<HTMLElement | null>(null)
  const hydratedNoteChapters = useRef(new Set<string>())
  const workspaceHydrated = useRef(false)

  function applyStudySettings(settings?: Partial<StudySettings>) {
    if (!settings) return

    setLemmaFontSize(settings.lemmaFontSize ?? 17)
    setLinkedFontSize(settings.linkedFontSize ?? 15)
    setOriginalCollapsed(settings.originalCollapsed ?? false)
    setLinkedCollapsed(settings.linkedCollapsed ?? false)
    setDefinitionCollapsed(settings.definitionCollapsed ?? false)
    setStudyNotesCollapsed(settings.studyNotesCollapsed ?? false)
    setCommentaryCollapsed(settings.commentaryCollapsed ?? false)
    setDictionaryCollapsed(settings.dictionaryCollapsed ?? false)
    setShowOriginalLine(settings.showOriginalLine ?? true)
    setShowLinkedLine(settings.showLinkedLine ?? true)
    setShowDefinitionPanel(settings.showDefinitionPanel ?? true)
    setShowCommentaryPanel(settings.showCommentaryPanel ?? true)
    setShowDictionaryPanel(settings.showDictionaryPanel ?? true)
    setSplitPercent(settings.splitPercent ?? 50)
    setNotesPinned(settings.notesPinned ?? false)
    setThemeMode(settings.themeMode ?? 'light')
  }

  async function loadLibrary(translationId = activeSession?.baseTranslation ?? defaultTranslationId) {
    setError(null)
    const state = await getLibraryState(translationId)
    setLibraryVerses(state.verses)
    setVerses(state.verses)
    const firstId = state.verses[0]?.id ?? null
    setSelectedId((current) => current ?? firstId)
    setPageStartId((current) => current ?? firstId)
  }

  function patchActiveSession(patch: Partial<StudySession>) {
    if (!activeSessionId) return
    const updatedAt = new Date().toISOString()
    setSessions((current) =>
      current.map((session) =>
        session.id === activeSessionId ? { ...session, ...patch, updatedAt } : session,
      ),
    )
  }

  function recordTimeline(
    entry: Omit<TimelineEntry, 'id' | 'at'>,
    patch: Partial<StudySession> = {},
  ) {
    if (!activeSessionId) return
    const at = new Date().toISOString()
    const nextEntry: TimelineEntry = { id: timelineId(), at, ...entry }

    setSessions((current) =>
      current.map((session) =>
        session.id === activeSessionId
          ? {
              ...session,
              selectedId,
              pageStartId,
              viewMode,
              strongDisplay,
              noteDraft,
              ...patch,
              updatedAt: at,
              timeline:
                session.timelineEnabled === false
                  ? session.timeline
                  : [nextEntry, ...session.timeline].slice(0, timelineLimit),
            }
          : session,
      ),
    )
  }

  function playPageTurnSound() {
    if (!window.AudioContext) return

    try {
      const audio = new window.AudioContext()
      const oscillator = audio.createOscillator()
      const gain = audio.createGain()

      oscillator.type = 'triangle'
      oscillator.frequency.setValueAtTime(120, audio.currentTime)
      oscillator.frequency.exponentialRampToValueAtTime(42, audio.currentTime + 0.08)
      gain.gain.setValueAtTime(0.0001, audio.currentTime)
      gain.gain.exponentialRampToValueAtTime(0.06, audio.currentTime + 0.012)
      gain.gain.exponentialRampToValueAtTime(0.0001, audio.currentTime + 0.11)
      oscillator.connect(gain)
      gain.connect(audio.destination)
      oscillator.start()
      oscillator.stop(audio.currentTime + 0.12)
      window.setTimeout(() => audio.close().catch(() => null), 180)
    } catch {
      // Page sound is intentionally best-effort.
    }
  }

  function triggerPageMotion(direction: PageMotion) {
    if (pageMotionTimeout.current) window.clearTimeout(pageMotionTimeout.current)
    setPageMotion('idle')
    window.requestAnimationFrame(() => {
      setPageMotion(direction)
      playPageTurnSound()
      pageMotionTimeout.current = window.setTimeout(() => setPageMotion('idle'), 520)
    })
  }

  async function runSearch(nextQuery = query) {
    setError(null)
    const trimmed = nextQuery.trim()
    setSelectedStrong(/^[gh]\d+$/i.test(trimmed) ? trimmed.toUpperCase() : null)
    const results = await searchVerses(nextQuery, activeSession?.baseTranslation ?? defaultTranslationId)
    setVerses(results)
    const firstResult = results[0]
    setSelectedId(firstResult?.id ?? null)
    setPageStartId(firstResult ? findPageStartId(firstResult) : null)
    recordTimeline(
      {
        type: 'search',
        label: trimmed ? `Search: ${trimmed}` : 'Cleared search',
        detail: `${results.length} matches`,
      },
      {
        selectedId: firstResult?.id ?? null,
        pageStartId: firstResult ? findPageStartId(firstResult) : null,
      },
    )
  }

  async function addTag() {
    const label = tagInput.trim()
    if (!selectedId || !label) return

    const color = tagColors[Math.abs(label.length) % tagColors.length]
    const updated = await addTagToVerse(
      selectedId,
      label,
      color,
      activeSession?.baseTranslation ?? defaultTranslationId,
    )

    setLibraryVerses((current) =>
      current.map((verse) => (verse.id === updated.id ? updated : verse)),
    )
    setVerses((current) =>
      current.map((verse) => (verse.id === updated.id ? updated : verse)),
    )
    setTagInput('')
  }

  const studySettingsSnapshot = useMemo<StudySettings>(
    () => ({
      lemmaFontSize,
      linkedFontSize,
      originalCollapsed,
      linkedCollapsed,
      definitionCollapsed,
      studyNotesCollapsed,
      commentaryCollapsed,
      dictionaryCollapsed,
      showOriginalLine,
      showLinkedLine,
      showDefinitionPanel,
      showCommentaryPanel,
      showDictionaryPanel,
      splitPercent,
      notesPinned,
      themeMode,
    }),
    [
      commentaryCollapsed,
      definitionCollapsed,
      dictionaryCollapsed,
      lemmaFontSize,
      linkedCollapsed,
      linkedFontSize,
      notesPinned,
      originalCollapsed,
      showCommentaryPanel,
      showDefinitionPanel,
      showDictionaryPanel,
      showLinkedLine,
      showOriginalLine,
      splitPercent,
      studyNotesCollapsed,
      themeMode,
    ],
  )

  useEffect(() => {
    let cancelled = false

    async function restoreWorkspace() {
      const workspace = await loadWorkspaceSnapshot()
      const selectedSession =
        workspace.sessions.find((session) => session.id === workspace.activeSessionId) ?? workspace.sessions[0]

      if (cancelled) return
      applyStudySettings(workspace.studySettings)
      setSessions(workspace.sessions)
      setActiveSessionId(workspace.activeSessionId)
      getTranslations().then(setTranslations).catch((reason) => setError(String(reason)))

      loadLibrary(selectedSession.baseTranslation)
        .catch((reason) => setError(String(reason)))
        .finally(() => {
          if (!cancelled) {
            setLoading(false)
            window.setTimeout(() => {
              workspaceHydrated.current = true
            }, 0)
          }
        })
    }

    restoreWorkspace().catch((reason) => {
      if (!cancelled) {
        setError(String(reason))
        setLoading(false)
      }
    })

    return () => {
      cancelled = true
    }
  }, [])

  useEffect(() => {
    if (!workspaceHydrated.current || !sessions.length || !activeSessionId) {
      return
    }

    if (remoteWorkspaceSaveTimeout.current) {
      window.clearTimeout(remoteWorkspaceSaveTimeout.current)
    }

    remoteWorkspaceSaveTimeout.current = window.setTimeout(() => {
      saveWorkspaceSnapshot({
        sessions,
        activeSessionId,
        studySettings: studySettingsSnapshot,
      }).catch((reason) => {
        console.warn(
          hostedWorkspaceEnabled()
            ? 'Unable to save hosted workspace.'
            : 'Unable to save local workspace.',
          reason,
        )
      })
      remoteWorkspaceSaveTimeout.current = null
    }, 650)

    return () => {
      if (remoteWorkspaceSaveTimeout.current) {
        window.clearTimeout(remoteWorkspaceSaveTimeout.current)
        remoteWorkspaceSaveTimeout.current = null
      }
    }
  }, [
    activeSessionId,
    sessions,
    studySettingsSnapshot,
  ])

  useEffect(() => {
    if (restoredSessionId.current === activeSessionId) return
    const activeSession = sessions.find((session) => session.id === activeSessionId)
    if (!activeSession) return

    restoredSessionId.current = activeSessionId
    setViewMode(activeSession.viewMode)
    setStrongDisplay(activeSession.strongDisplay)
    setNoteDraft(activeSession.noteDraft)
    loadLibrary(activeSession.baseTranslation).catch((reason) => setError(String(reason)))
    setSelectedId((current) => activeSession.selectedId ?? current)
    setPageStartId((current) => activeSession.pageStartId ?? current)
    setSelectedStrong(null)
  }, [activeSessionId, sessions])

  const selectedVerse = useMemo(
    () =>
      libraryVerses.find((verse) => verse.id === selectedId) ??
      verses.find((verse) => verse.id === selectedId) ??
      verses[0],
    [libraryVerses, selectedId, verses],
  )
  const selectedStrongEntry = useMemo(() => {
    if (!selectedVerse?.strongs.length) return null
    return (
      selectedVerse.strongs.find((entry) => entry.strong === selectedStrong) ??
      selectedVerse.strongs[0]
    )
  }, [selectedStrong, selectedVerse])
  const activeSession = useMemo(
    () => sessions.find((session) => session.id === activeSessionId) ?? sessions[0],
    [activeSessionId, sessions],
  )
  const activeTranslation = useMemo(
    () =>
      translations.find((translation) => translation.id === activeSession?.baseTranslation) ??
      translations.find((translation) => translation.id === defaultTranslationId),
    [activeSession?.baseTranslation, translations],
  )

  useEffect(() => {
    let cancelled = false

    async function loadMarginResources() {
      if (!selectedVerse) {
        setCommentaryEntries([])
        setDictionaryEntries([])
        return
      }

      setMarginResourcesLoading(true)
      try {
        const [nextCommentary, nextDictionary] = await Promise.all([
          activeSession?.commentaryEnabled === false
            ? Promise.resolve([])
            : getCommentaryForVerse(selectedVerse),
          activeSession?.dictionaryEnabled === false
            ? Promise.resolve([])
            : getDictionaryEntriesForTerms(dictionaryTermsForVerse(selectedVerse)),
        ])

        if (cancelled) return
        setCommentaryEntries(nextCommentary)
        setDictionaryEntries(nextDictionary)
      } catch (reason) {
        if (!cancelled) setError(String(reason))
      } finally {
        if (!cancelled) setMarginResourcesLoading(false)
      }
    }

    loadMarginResources()
    return () => {
      cancelled = true
    }
  }, [activeSession?.commentaryEnabled, activeSession?.dictionaryEnabled, selectedVerse])

  const pageAnchors = useMemo(() => {
    const source = libraryVerses.length ? libraryVerses : verses
    const anchors: Verse[] = []
    let index = 0

    while (index < source.length) {
      const book = source[index].book
      let bookVerseIndex = 0

      while (index < source.length && source[index].book === book) {
        if (bookVerseIndex % pageSize === 0) {
          anchors.push(source[index])
        }
        bookVerseIndex += 1
        index += 1
      }
    }

    return anchors
  }, [libraryVerses, verses])
  const pageVerses = useMemo(() => {
    if (!selectedVerse) return []
    const source = libraryVerses.length ? libraryVerses : verses
    const pageStartIndex = source.findIndex((verse) => verse.id === pageStartId)
    const selectedIndex = source.findIndex((verse) => verse.id === selectedVerse.id)
    const start = Math.max(0, pageStartIndex >= 0 ? pageStartIndex : selectedIndex)
    const book = source[start]?.book
    return source
      .slice(start, start + pageSize)
      .filter((verse) => verse.book === book)
  }, [libraryVerses, pageStartId, selectedVerse, verses])

  useEffect(() => {
    if (!activeSession?.baseTranslation || pageVerses.length === 0) return
    const chapterKeys = [
      ...new Set(
        pageVerses.map(
          (verse) => `${activeSession.baseTranslation}:${verse.book}:${verse.chapter}`,
        ),
      ),
    ]
    const unloadedChapterKeys = chapterKeys.filter(
      (chapterKey) => !hydratedNoteChapters.current.has(chapterKey),
    )
    if (unloadedChapterKeys.length === 0) return
    for (const chapterKey of unloadedChapterKeys) hydratedNoteChapters.current.add(chapterKey)

    let cancelled = false
    getTranslationNotesForVerses(activeSession.baseTranslation, pageVerses)
      .then((notesByVerse) => {
        if (cancelled || notesByVerse.size === 0) return
        const hydrate = (verse: Verse) => {
          const notes = notesByVerse.get(String(verse.id))
          if (!notes) return verse
          if (
            (verse.footnotes?.length ?? 0) === notes.footnotes.length &&
            (verse.studyNotes?.length ?? 0) === notes.studyNotes.length
          ) {
            return verse
          }
          return { ...verse, footnotes: notes.footnotes, studyNotes: notes.studyNotes }
        }
        setLibraryVerses((current) => replaceChangedVerses(current, hydrate))
        setVerses((current) => replaceChangedVerses(current, hydrate))
      })
      .catch((reason) => setError(String(reason)))

    return () => {
      cancelled = true
    }
  }, [activeSession?.baseTranslation, pageVerses])

  const pageRange = pageVerses.length
    ? `${reference(pageVerses[0])} - ${reference(pageVerses[pageVerses.length - 1])}`
    : 'No page loaded'
  const selectedFootnotes = selectedVerse?.footnotes ?? []
  const selectedStudyNotes = selectedVerse?.studyNotes ?? []
  const pageFootnotes = useMemo(
    () => pageVerses.flatMap((verse) => verse.footnotes ?? []),
    [pageVerses],
  )
  const books = useMemo(
    () => Array.from(new Set(libraryVerses.map((verse) => verse.book))),
    [libraryVerses],
  )
  const visibleBookTabs = useMemo(() => {
    if (!selectedVerse || !books.length) return []
    const visibleCount = 24
    const selectedIndex = Math.max(0, books.indexOf(selectedVerse.book))
    const halfWindow = Math.floor(visibleCount / 2)
    const maxStart = Math.max(0, books.length - visibleCount)
    const start = Math.min(Math.max(0, selectedIndex - halfWindow), maxStart)

    return books.slice(start, start + visibleCount)
  }, [books, selectedVerse])
  const chapters = useMemo(() => {
    if (!selectedVerse) return []
    return Array.from(
      new Set(
        libraryVerses
          .filter((verse) => verse.book === selectedVerse.book)
          .map((verse) => verse.chapter),
      ),
    )
  }, [libraryVerses, selectedVerse])
  const verseNumbers = useMemo(() => {
    if (!selectedVerse) return []
    return libraryVerses
      .filter(
        (verse) =>
          verse.book === selectedVerse.book && verse.chapter === selectedVerse.chapter,
      )
      .map((verse) => verse.verse)
  }, [libraryVerses, selectedVerse])

  function searchStrong(strong: string) {
    setQuery(strong)
    setSelectedStrong(strong)
    recordTimeline({
      type: 'strong',
      label: `Strong's ${strong}`,
      reference: selectedVerse ? reference(selectedVerse) : undefined,
      detail: 'Opened matching verses search',
    })
    runSearch(strong).catch((reason) => setError(String(reason)))
  }

  function jumpTo(book: string, chapter: number, verse: number) {
    const next =
      libraryVerses.find(
        (entry) =>
          entry.book === book && entry.chapter === chapter && entry.verse === verse,
      ) ??
      libraryVerses.find((entry) => entry.book === book && entry.chapter === chapter) ??
      libraryVerses.find((entry) => entry.book === book)

    if (!next) return
    const currentBookIndex = selectedVerse ? books.indexOf(selectedVerse.book) : -1
    const nextBookIndex = books.indexOf(next.book)
    triggerPageMotion(nextBookIndex >= currentBookIndex ? 'turn-forward' : 'turn-back')
    setQuery('')
    setSelectedStrong(null)
    setVerses(libraryVerses)
    setSelectedId(next.id)
    const nextPageStartId = findPageStartId(next)
    setPageStartId(nextPageStartId)
    recordTimeline(
      {
        type: 'navigation',
        label: reference(next),
        reference: reference(next),
        detail: 'Jumped from selector',
      },
      { selectedId: next.id, pageStartId: nextPageStartId },
    )
  }

  async function changeTranslation(translationId: string) {
    const translation =
      translations.find((item) => item.id === translationId) ??
      translations.find((item) => item.id === defaultTranslationId)
    const state = await getLibraryState(translationId)
    const firstVerse = state.verses[0] ?? null

    setQuery('')
    setSelectedStrong(null)
    setLibraryVerses(state.verses)
    setVerses(state.verses)
    setSelectedId(firstVerse?.id ?? null)
    setPageStartId(firstVerse?.id ?? null)
    patchActiveSession({
      baseTranslation: translationId,
      selectedId: firstVerse?.id ?? null,
      pageStartId: firstVerse?.id ?? null,
    })
    recordTimeline(
      {
        type: 'setting',
        label: `Translation: ${translation?.abbreviation ?? translationId}`,
        detail: translation?.title,
      },
      {
        baseTranslation: translationId,
        selectedId: firstVerse?.id ?? null,
        pageStartId: firstVerse?.id ?? null,
      },
    )
  }

  function shiftPage(direction: -1 | 1) {
    if (!selectedVerse) return
    const currentStartIndex = pageAnchors.findIndex((verse) => verse.id === pageStartId)
    const selectedPageStartId = findPageStartId(selectedVerse)
    const selectedIndex = pageAnchors.findIndex((verse) => verse.id === selectedPageStartId)
    const index = currentStartIndex >= 0 ? currentStartIndex : selectedIndex
    const next =
      pageAnchors[Math.min(pageAnchors.length - 1, Math.max(0, index + direction))]

    if (!next) return
    triggerPageMotion(direction > 0 ? 'turn-forward' : 'turn-back')
    setPageStartId(next.id)
    setSelectedId(next.id)
    setSelectedStrong(null)
    recordTimeline(
      {
        type: 'navigation',
        label: direction > 0 ? 'Next page' : 'Previous page',
        reference: reference(next),
      },
      { selectedId: next.id, pageStartId: next.id },
    )
  }

  function findPageStartId(verse: Verse) {
    const source = libraryVerses.length ? libraryVerses : verses
    const index = source.findIndex((entry) => entry.id === verse.id)
    if (index < 0) return pageStartId ?? verse.id

    let anchor = source[index]
    for (const pageAnchor of pageAnchors) {
      const anchorIndex = source.findIndex((entry) => entry.id === pageAnchor.id)
      if (anchorIndex > index) break
      if (pageAnchor.book === verse.book) {
        anchor = pageAnchor
      }
    }

    return anchor.id
  }

  function selectVerse(verse: Verse) {
    setSelectedId(verse.id)
    setSelectedStrong(null)
    recordTimeline(
      {
        type: 'verse',
        label: reference(verse),
        reference: reference(verse),
      },
      { selectedId: verse.id },
    )
  }

  function selectStrong(verse: Verse, strong: string) {
    setSelectedId(verse.id)
    setSelectedStrong(strong)
    recordTimeline(
      {
        type: 'strong',
        label: strong,
        reference: reference(verse),
      },
      { selectedId: verse.id },
    )
  }

  function setStrongDisplayMode(nextStrongDisplay: StrongDisplayMode) {
    setStrongDisplay(nextStrongDisplay)
    recordTimeline(
      {
        type: 'setting',
        label: `Strong's display: ${nextStrongDisplay}`,
      },
      { strongDisplay: nextStrongDisplay },
    )
  }

  function recordDisplaySetting(label: string) {
    recordTimeline({
      type: 'setting',
      label,
    })
  }

  function changeThemeMode(nextThemeMode: ThemeMode) {
    setThemeMode(nextThemeMode)
    recordDisplaySetting(`Theme: ${nextThemeMode}`)
  }

  function beginSplitResize(event: ReactMouseEvent<HTMLDivElement>) {
    event.preventDefault()
    const reader = readerRef.current
    if (!reader) return

    const resize = (moveEvent: MouseEvent) => {
      const rect = reader.getBoundingClientRect()
      const next = ((moveEvent.clientX - rect.left) / rect.width) * 100
      setSplitPercent(Math.min(68, Math.max(36, next)))
    }

    const stop = () => {
      window.removeEventListener('mousemove', resize)
      window.removeEventListener('mouseup', stop)
      recordDisplaySetting('Adjusted Bible and study margin split')
    }

    window.addEventListener('mousemove', resize)
    window.addEventListener('mouseup', stop, { once: true })
  }

  function updateNoteDraft(value: string) {
    setNoteDraft(value)
    patchActiveSession({ noteDraft: value })
  }

  function appendNoteClip(value: string) {
    const clip = value.trim()
    if (!clip) return
    const nextValue = noteDraft.trim() ? `${noteDraft.trim()}\n\n${clip}` : clip
    updateNoteDraft(nextValue)
  }

  function startTextDrag(event: DragEvent<HTMLElement>, value: string) {
    event.dataTransfer.setData('text/plain', value)
    event.dataTransfer.effectAllowed = 'copy'
  }

  function scheduleNotesDragOpen() {
    if (notesPinned || notesDragOpenTimeout.current) return
    notesDragOpenTimeout.current = window.setTimeout(() => {
      setNotesDrawerOpen(true)
      notesDragOpenTimeout.current = null
    }, 550)
  }

  function clearNotesDragOpen() {
    if (!notesDragOpenTimeout.current) return
    window.clearTimeout(notesDragOpenTimeout.current)
    notesDragOpenTimeout.current = null
  }

  function renameActiveSession(title: string) {
    patchActiveSession({ title })
  }

  function startNewSession() {
    const nextSession = {
      ...createSession(
        newSessionTitle.trim() || `Study Session ${sessions.length + 1}`,
        newSessionBaseTranslation,
      ),
      footnotesEnabled: newSessionFootnotes,
      strongsEnabled: newSessionStrongs,
      commentaryEnabled: newSessionCommentary,
      dictionaryEnabled: newSessionDictionary,
      timelineEnabled: newSessionTimeline,
    }
    setSessions((current) => [nextSession, ...current])
    setActiveSessionId(nextSession.id)
    loadLibrary(nextSession.baseTranslation).catch((reason) => setError(String(reason)))
    setSessionModalOpen(false)
  }

  function setActiveSessionOption(patch: Partial<StudySession>) {
    patchActiveSession(patch)
    if (patch.strongsEnabled === false) {
      setStrongDisplay('off')
    }
    if (
      typeof patch.strongsEnabled === 'boolean' ||
      typeof patch.footnotesEnabled === 'boolean' ||
      typeof patch.commentaryEnabled === 'boolean' ||
      typeof patch.dictionaryEnabled === 'boolean'
    ) {
      recordTimeline({ type: 'setting', label: 'Updated session resources' }, patch)
    }
  }

  function exportActiveSession() {
    if (!activeSession) return
    const blob = new Blob([JSON.stringify(activeSession, null, 2)], {
      type: 'application/json',
    })
    const url = URL.createObjectURL(blob)
    const link = document.createElement('a')
    link.href = url
    link.download = `${activeSession.title.toLowerCase().replace(/[^a-z0-9]+/g, '-') || 'study-session'}.json`
    link.click()
    URL.revokeObjectURL(url)
  }

  function restoreTimelineEntry(entry: TimelineEntry) {
    if (!entry.reference) return
    const [bookPart, rest] = entry.reference.split(/ (?=\d+:\d+$)/)
    const [chapter, verse] = rest?.split(':').map(Number) ?? []
    if (!bookPart || !chapter || !verse) return

    const next = libraryVerses.find(
      (entryVerse) =>
        entryVerse.book === bookPart &&
        entryVerse.chapter === chapter &&
        entryVerse.verse === verse,
    )
    if (!next) return

    triggerPageMotion(next.id >= (selectedVerse?.id ?? next.id) ? 'turn-forward' : 'turn-back')
    setQuery('')
    setSelectedStrong(null)
    setVerses(libraryVerses)
    setSelectedId(next.id)
    if (!pageVerses.some((pageVerse) => pageVerse.id === next.id)) {
      setPageStartId(findPageStartId(next))
    }
  }

  function recordFootnote(referenceText: string, text: string) {
    recordTimeline({
      type: 'footnote',
      label: `Footnote ${referenceText}`,
      reference: selectedVerse ? reference(selectedVerse) : undefined,
      detail: text,
    })
  }

  function renderVerseText(verse: Verse) {
    if (!activeSession?.strongsEnabled || !verse.strongs.length || strongDisplay === 'off') return verse.text

    const parts: ReactNode[] = []
    let cursor = 0
    const lowerText = verse.text.toLowerCase()
    const sortedLinks = [...verse.strongs].sort((left, right) => left.position - right.position)

    sortedLinks.forEach((entry) => {
      const surface = entry.surface.trim()
      if (!surface) return

      const index = lowerText.indexOf(surface.toLowerCase(), cursor)
      if (index < 0) return
      if (index > cursor) {
        parts.push(verse.text.slice(cursor, index))
      }

      const linkedText = verse.text.slice(index, index + surface.length)
      const isActive = entry.strong === selectedStrong
      const showCode = strongDisplay === 'numbers' || isActive
      parts.push(
        <span
          key={`${verse.id}-${entry.strong}-${entry.position}`}
          className={[
            'strong-token',
            strongDisplay,
            isActive ? 'active' : '',
          ].filter(Boolean).join(' ')}
          role="button"
          tabIndex={0}
          title={`${entry.surface}: ${entry.strong}`}
          onClick={(event) => {
            event.stopPropagation()
            selectStrong(verse, entry.strong)
          }}
          onKeyDown={(event) => {
            if (event.key === 'Enter' || event.key === ' ') {
              event.preventDefault()
              selectStrong(verse, entry.strong)
            }
          }}
        >
          <span className="strong-surface">{linkedText}</span>
          {showCode ? (
            <sup className="strong-code">{entry.strong}</sup>
          ) : null}
        </span>,
      )
      cursor = index + surface.length
    })

    if (cursor < verse.text.length) {
      parts.push(verse.text.slice(cursor))
    }

    return parts.length ? parts : verse.text
  }

  function renderOriginalLanguageLine() {
    if (!showOriginalLine || !selectedVerse?.strongs.length) return null
    const isHebrew = selectedVerse.strongs.some((entry) => entry.strong.startsWith('H'))
    const direction = isHebrew ? 'rtl' : 'ltr'

    return (
      <section className="original-language-verse" aria-label="Original language lemma line">
        <header
          className="margin-section-header"
          role="button"
          tabIndex={0}
          onClick={() => {
            setOriginalCollapsed((current) => !current)
            recordDisplaySetting('Toggled original language accordion')
          }}
          onKeyDown={(event) => {
            if (event.key === 'Enter' || event.key === ' ') {
              event.preventDefault()
              setOriginalCollapsed((current) => !current)
              recordDisplaySetting('Toggled original language accordion')
            }
          }}
        >
          <button
            type="button"
            className="collapse-button"
          >
            {isHebrew ? 'Hebrew Lemma Line' : 'Greek Lemma Line'}
          </button>
          <button
            type="button"
            className="mini-settings"
            onClick={(event) => {
              event.stopPropagation()
              setSettingsModalOpen(true)
            }}
          >
            Aa
          </button>
        </header>
        {!originalCollapsed ? (
          <p className="lemma-line-text" dir={direction} style={{ fontSize: `${lemmaFontSize}px` }}>
            {selectedVerse.strongs.map((entry) => (
              <span
                key={`${entry.strong}-${entry.position}-lemma`}
                className={entry.strong === selectedStrongEntry?.strong ? 'lemma-word active' : 'lemma-word'}
                role="button"
                tabIndex={0}
                title={`${entry.surface}: ${entry.strong}`}
                onClick={() => selectStrong(selectedVerse, entry.strong)}
                onKeyDown={(event) => {
                  if (event.key === 'Enter' || event.key === ' ') {
                    event.preventDefault()
                    selectStrong(selectedVerse, entry.strong)
                  }
                }}
              >
                {entry.lemma || entry.surface}
              </span>
            ))}
          </p>
        ) : null}
      </section>
    )
  }

  function renderLinkedEnglishLine() {
    if (!showLinkedLine || !selectedVerse?.strongs.length) return null

    return (
      <section className="english-strong-line" aria-label="English Strong's line">
        <header
          className="margin-section-header"
          role="button"
          tabIndex={0}
          onClick={() => {
            setLinkedCollapsed((current) => !current)
            recordDisplaySetting('Toggled English linked text accordion')
          }}
          onKeyDown={(event) => {
            if (event.key === 'Enter' || event.key === ' ') {
              event.preventDefault()
              setLinkedCollapsed((current) => !current)
              recordDisplaySetting('Toggled English linked text accordion')
            }
          }}
        >
          <button
            type="button"
            className="collapse-button"
          >
            English Linked Text
          </button>
          <button
            type="button"
            className="mini-settings"
            onClick={(event) => {
              event.stopPropagation()
              setSettingsModalOpen(true)
            }}
          >
            Aa
          </button>
        </header>
        {!linkedCollapsed ? (
          <p className="linked-line-text" style={{ fontSize: `${linkedFontSize}px` }}>
            {selectedVerse.strongs.map((entry) => (
              <span
                key={`${entry.strong}-${entry.position}-english`}
                className={entry.strong === selectedStrongEntry?.strong ? 'linked-word active' : 'linked-word'}
                role="button"
                tabIndex={0}
                title={`${entry.surface}: ${entry.strong}`}
                onClick={() => selectStrong(selectedVerse, entry.strong)}
                onKeyDown={(event) => {
                  if (event.key === 'Enter' || event.key === ' ') {
                    event.preventDefault()
                    selectStrong(selectedVerse, entry.strong)
                  }
                }}
              >
                {entry.surface}
              </span>
            ))}
          </p>
        ) : null}
      </section>
    )
  }

  function renderStudyNotesSection() {
    if (activeSession?.footnotesEnabled === false) return null

    return (
      <article className="resource-card study-notes-card" aria-label="Translation study notes">
        <header
          className="margin-section-header"
          role="button"
          tabIndex={0}
          onClick={() => {
            setStudyNotesCollapsed((current) => !current)
            recordDisplaySetting('Toggled translation study notes accordion')
          }}
          onKeyDown={(event) => {
            if (event.key === 'Enter' || event.key === ' ') {
              event.preventDefault()
              setStudyNotesCollapsed((current) => !current)
              recordDisplaySetting('Toggled translation study notes accordion')
            }
          }}
        >
          <button type="button" className="collapse-button">Translation Study Notes</button>
          <span>{selectedStudyNotes.length ? `${selectedStudyNotes.length} notes` : 'None'}</span>
        </header>
        {!studyNotesCollapsed ? (
          selectedStudyNotes.length ? (
            <div className="translation-note-list">
              {selectedStudyNotes.map((note) => (
                <p
                  key={note.id}
                  draggable
                  onDragStart={(event) => startTextDrag(event, `${note.reference} ${note.text}`)}
                >
                  <strong>{note.reference}</strong>
                  <span>{note.text}</span>
                </p>
              ))}
            </div>
          ) : (
            <p className="resource-disabled">No translation study notes for the selected verse.</p>
          )
        ) : null}
      </article>
    )
  }

  function renderCommentarySection() {
    if (!showCommentaryPanel) return null

    if (activeSession?.commentaryEnabled === false) {
      return (
        <article className="resource-card">
          <header className="margin-section-header">
            <button type="button" className="collapse-button">Commentary</button>
            <span>Off</span>
          </header>
          <p className="resource-disabled">Commentary is disabled for this session.</p>
        </article>
      )
    }

    return (
      <article className="resource-card commentary-card" aria-label="Commentary">
        <header
          className="margin-section-header"
          role="button"
          tabIndex={0}
          onClick={() => {
            setCommentaryCollapsed((current) => !current)
            recordDisplaySetting('Toggled commentary accordion')
          }}
          onKeyDown={(event) => {
            if (event.key === 'Enter' || event.key === ' ') {
              event.preventDefault()
              setCommentaryCollapsed((current) => !current)
              recordDisplaySetting('Toggled commentary accordion')
            }
          }}
        >
          <button type="button" className="collapse-button">Commentary</button>
          <span>{commentaryEntries.length ? 'MHCC' : marginResourcesLoading ? 'Loading' : 'None'}</span>
        </header>
        {!commentaryCollapsed ? (
          commentaryEntries.length ? (
            <div className="commentary-list">
              {commentaryEntries.map((entry) => (
                <section
                  key={entry.id}
                  draggable
                  onDragStart={(event) =>
                    startTextDrag(event, `${entry.reference}\n${entry.text}\n- ${entry.source}`)
                  }
                >
                  <h3>{entry.reference}</h3>
                  <p>{entry.text}</p>
                  <small>{entry.source}</small>
                </section>
              ))}
            </div>
          ) : (
            <p className="resource-disabled">
              {marginResourcesLoading ? 'Loading commentary...' : 'No commentary matched this verse.'}
            </p>
          )
        ) : null}
      </article>
    )
  }

  function renderDictionarySection() {
    if (!showDictionaryPanel) return null

    if (activeSession?.dictionaryEnabled === false) {
      return (
        <article className="resource-card">
          <header className="margin-section-header">
            <button type="button" className="collapse-button">Dictionary</button>
            <span>Off</span>
          </header>
          <p className="resource-disabled">Dictionary lookup is disabled for this session.</p>
        </article>
      )
    }

    return (
      <article className="resource-card dictionary-card" aria-label="Dictionary">
        <header
          className="margin-section-header"
          role="button"
          tabIndex={0}
          onClick={() => {
            setDictionaryCollapsed((current) => !current)
            recordDisplaySetting('Toggled dictionary accordion')
          }}
          onKeyDown={(event) => {
            if (event.key === 'Enter' || event.key === ' ') {
              event.preventDefault()
              setDictionaryCollapsed((current) => !current)
              recordDisplaySetting('Toggled dictionary accordion')
            }
          }}
        >
          <button type="button" className="collapse-button">Dictionary</button>
          <span>{dictionaryEntries.length ? `${dictionaryEntries.length} terms` : marginResourcesLoading ? 'Loading' : 'None'}</span>
        </header>
        {!dictionaryCollapsed ? (
          dictionaryEntries.length ? (
            <div className="dictionary-list">
              {dictionaryEntries.slice(0, 6).map((entry) => (
                <section
                  key={entry.id}
                  draggable
                  onDragStart={(event) =>
                    startTextDrag(
                      event,
                      `${entry.term}\n${entry.definitions
                        .map((definition) => `${definition.sourceName}: ${definition.text}`)
                        .join('\n\n')}`,
                    )
                  }
                >
                  <h3>{entry.term}</h3>
                  {entry.definitions.slice(0, 2).map((definition) => (
                    <p key={`${entry.id}-${definition.source}`}>
                      <strong>{definition.sourceName}</strong>
                      {definition.text}
                    </p>
                  ))}
                </section>
              ))}
            </div>
          ) : (
            <p className="resource-disabled">
              {marginResourcesLoading ? 'Loading dictionary...' : 'No dictionary terms matched this verse.'}
            </p>
          )
        ) : null}
      </article>
    )
  }

  function renderBiblePage(label = activeTranslation?.abbreviation ?? 'Bible') {
    if (!selectedVerse) return null
    return (
      <article className="bible-page" aria-label={`${label} Bible page`}>
        <header>
          <span>{label}</span>
          <strong>{reference(selectedVerse)}</strong>
          <span>{verses.length} verses loaded</span>
        </header>
        <div className="page-columns">
          {pageVerses.map((verse) => (
            <p
              key={verse.id}
              className={verse.id === selectedVerse.id ? 'page-verse selected' : 'page-verse'}
              draggable
              onDragStart={(event) => startTextDrag(event, `${reference(verse)} ${verse.text}`)}
              onClick={() => selectVerse(verse)}
            >
              <sup>{verse.verse}</sup>
              {renderVerseText(verse)}
            </p>
          ))}
        </div>
      </article>
    )
  }

  function renderPageTurner() {
    return (
      <nav className="page-turner" aria-label="Page navigation">
        <button type="button" onClick={() => shiftPage(-1)}>
          Previous page
        </button>
        <div className="page-position">
          <span>{pageRange}</span>
          <div className="chapter-tabs" aria-label="Chapter selector">
            {chapters.map((chapter) => (
              <button
                key={chapter}
                type="button"
                className={chapter === selectedVerse?.chapter ? 'active' : ''}
                style={{ fontSize: `${Math.max(8, Math.min(11, 13 - chapters.length / 20))}px` }}
                onClick={() => selectedVerse && jumpTo(selectedVerse.book, chapter, 1)}
              >
                {chapter}
              </button>
            ))}
          </div>
        </div>
        <button type="button" onClick={() => shiftPage(1)}>
          Next page
        </button>
      </nav>
    )
  }

  function renderStudyMargin() {
    if (!selectedVerse) return null
    return (
      <aside className="study-margin" aria-label="Study margin">
        <div className="panel-header">
          <h2>Study Margin</h2>
          <span>
            {activeSession?.strongsEnabled === false
              ? 'links off'
              : `${selectedVerse.strongs.length} links`}
          </span>
        </div>
        <p className="margin-reference">{reference(selectedVerse)}</p>
        {activeSession?.strongsEnabled === false ? (
          <p className="resource-disabled">Strong's links are disabled for this session.</p>
        ) : (
          <div className="margin-resource-grid">
            {renderOriginalLanguageLine()}
            {renderLinkedEnglishLine()}
            {showDefinitionPanel && selectedStrongEntry ? (
              <article className="strong-focus" aria-label="Strong's definition">
                <header
                  className="margin-section-header"
                  role="button"
                  tabIndex={0}
                  onClick={() => {
                    setDefinitionCollapsed((current) => !current)
                    recordDisplaySetting('Toggled Strong definition accordion')
                  }}
                  onKeyDown={(event) => {
                    if (event.key === 'Enter' || event.key === ' ') {
                      event.preventDefault()
                      setDefinitionCollapsed((current) => !current)
                      recordDisplaySetting('Toggled Strong definition accordion')
                    }
                  }}
                >
                  <button
                    type="button"
                    className="collapse-button"
                  >
                    Definition
                  </button>
                  <span>{selectedStrongEntry.language}</span>
                </header>
                {!definitionCollapsed ? (
                  <>
                    <div>
                      <strong>{selectedStrongEntry.strong}</strong>
                      <span>{selectedStrongEntry.language}</span>
                    </div>
                    <h4>{selectedStrongEntry.lemma}</h4>
                    <p className="translit">{selectedStrongEntry.transliteration}</p>
                    <p>{selectedStrongEntry.definition}</p>
                    <button type="button" onClick={() => searchStrong(selectedStrongEntry.strong)}>
                      Show matching verses
                    </button>
                  </>
                ) : null}
              </article>
            ) : null}
          </div>
        )}
        <div className="margin-resource-grid">
          {renderStudyNotesSection()}
          {renderCommentarySection()}
          {renderDictionarySection()}
        </div>
      </aside>
    )
  }

  function renderFootnoteStrip() {
    if (activeSession?.footnotesEnabled === false) {
      return (
        <section className="footnote-strip">
          <strong>Footnotes</strong>
          <span>Footnotes are disabled for this session.</span>
        </section>
      )
    }

    const visibleFootnotes = selectedFootnotes.length ? selectedFootnotes : pageFootnotes.slice(0, 4)
    return (
      <section className="footnote-strip">
        <strong>Footnotes</strong>
        {visibleFootnotes.length ? (
          <div className="footnote-list">
            {visibleFootnotes.map((note) => (
              <p
                key={note.id}
                role="button"
                tabIndex={0}
                onClick={() => recordFootnote(note.reference, note.text)}
                draggable
                onDragStart={(event) => startTextDrag(event, `${note.reference} ${note.text}`)}
                onKeyDown={(event) => {
                  if (event.key === 'Enter' || event.key === ' ') {
                    event.preventDefault()
                    recordFootnote(note.reference, note.text)
                  }
                }}
              >
                <span>{note.reference}</span>
                {note.text}
              </p>
            ))}
          </div>
        ) : (
          <span>No footnotes for the selected verse.</span>
        )}
      </section>
    )
  }

  function renderBookTabs() {
    if (!selectedVerse) return null

    return (
      <nav className={`book-tabs ${pageMotion}`} aria-label="Bible book tabs">
        {visibleBookTabs.map((book) => (
          <button
            key={book}
            type="button"
            className={book === selectedVerse.book ? 'active' : ''}
            title={book}
            onClick={() => jumpTo(book, 1, 1)}
          >
            {abbreviateBook(book)}
          </button>
        ))}
      </nav>
    )
  }

  function renderTimelineModal() {
    if (!timelineModalOpen) return null

    return (
      <div className="modal-backdrop" role="presentation" onMouseDown={() => setTimelineModalOpen(false)}>
        <section
          className="modal-panel timeline-modal"
          role="dialog"
          aria-modal="true"
          aria-label="Study timeline"
          onMouseDown={(event) => event.stopPropagation()}
        >
          <header>
            <div>
              <span className="eyebrow">Timeline</span>
              <h2>{activeSession?.title ?? 'Study Session'}</h2>
            </div>
            <button type="button" className="close-button" onClick={() => setTimelineModalOpen(false)}>
              Close
            </button>
          </header>
          {activeSession?.timeline.length ? (
            <div className="timeline-canvas">
              <ol>
                {[...activeSession.timeline].reverse().map((entry) => (
                  <li key={entry.id}>
                    <span className="timeline-dot" />
                    <button
                      type="button"
                      disabled={!entry.reference}
                      onClick={() => {
                        restoreTimelineEntry(entry)
                        setTimelineModalOpen(false)
                      }}
                    >
                      <time>{formatTimelineTime(entry.at)}</time>
                      <strong>{entry.label}</strong>
                      {entry.reference ? <span>{entry.reference}</span> : null}
                      {entry.detail ? <small>{entry.detail}</small> : null}
                    </button>
                  </li>
                ))}
              </ol>
            </div>
          ) : (
            <div className="empty-timeline">
              <span className="note-helper-figure" aria-hidden="true">
                <span className="helper-head" />
                <span className="helper-body" />
                <span className="helper-notebook" />
                <span className="helper-pencil" />
              </span>
              <p>This session has not recorded timeline events yet.</p>
            </div>
          )}
        </section>
      </div>
    )
  }

  function renderSessionModal() {
    if (!sessionModalOpen) return null

    return (
      <div className="modal-backdrop" role="presentation" onMouseDown={() => setSessionModalOpen(false)}>
        <section
          className="modal-panel session-modal"
          role="dialog"
          aria-modal="true"
          aria-label="Session management"
          onMouseDown={(event) => event.stopPropagation()}
        >
          <header>
            <div>
              <span className="eyebrow">Session</span>
              <h2>Manage Study Session</h2>
            </div>
            <button type="button" className="close-button" onClick={() => setSessionModalOpen(false)}>
              Close
            </button>
          </header>

          <div className="modal-grid">
            <section className="modal-section">
              <h3>Current Session</h3>
              <label>
                Active session
                <select value={activeSessionId} onChange={(event) => setActiveSessionId(event.target.value)}>
                  {sessions.map((session) => (
                    <option key={session.id} value={session.id}>
                      {session.title}
                    </option>
                  ))}
                </select>
              </label>
              <label>
                Session title
                <input
                  value={activeSession?.title ?? ''}
                  onChange={(event) => renameActiveSession(event.target.value)}
                />
              </label>
              <dl className="session-facts">
                <div>
                  <dt>Translation</dt>
                  <dd>{activeTranslation?.abbreviation ?? activeSession?.baseTranslation ?? 'n/a'}</dd>
                </div>
                <div>
                  <dt>Current page</dt>
                  <dd>{pageRange}</dd>
                </div>
                <div>
                  <dt>Timeline</dt>
                  <dd>{activeSession?.timeline.length ?? 0} events</dd>
                </div>
                <div>
                  <dt>Started</dt>
                  <dd>{activeSession ? new Date(activeSession.createdAt).toLocaleString() : 'Not started'}</dd>
                </div>
              </dl>
              <div className="resource-toggles">
                <label>
                  <input
                    type="checkbox"
                    checked={activeSession?.strongsEnabled ?? true}
                    onChange={(event) => setActiveSessionOption({ strongsEnabled: event.target.checked })}
                  />
                  Strong's links
                </label>
                <label>
                  <input
                    type="checkbox"
                    checked={activeSession?.footnotesEnabled ?? true}
                    onChange={(event) => setActiveSessionOption({ footnotesEnabled: event.target.checked })}
                  />
                  Footnotes
                </label>
                <label>
                  <input
                    type="checkbox"
                    checked={activeSession?.commentaryEnabled ?? true}
                    onChange={(event) => setActiveSessionOption({ commentaryEnabled: event.target.checked })}
                  />
                  Commentary
                </label>
                <label>
                  <input
                    type="checkbox"
                    checked={activeSession?.dictionaryEnabled ?? true}
                    onChange={(event) => setActiveSessionOption({ dictionaryEnabled: event.target.checked })}
                  />
                  Dictionary
                </label>
                <label>
                  <input
                    type="checkbox"
                    checked={activeSession?.timelineEnabled ?? true}
                    onChange={(event) => setActiveSessionOption({ timelineEnabled: event.target.checked })}
                  />
                  Record timeline
                </label>
              </div>
              <button type="button" onClick={exportActiveSession}>
                Export session
              </button>
            </section>

            <section className="modal-section">
              <h3>New Session</h3>
              <label>
                Session title
                <input value={newSessionTitle} onChange={(event) => setNewSessionTitle(event.target.value)} />
              </label>
              <label>
                Base translation
                <select
                  value={newSessionBaseTranslation}
                  onChange={(event) => setNewSessionBaseTranslation(event.target.value)}
                >
                  {translations.map((translation) => (
                    <option key={translation.id} value={translation.id}>
                      {translation.shortTitle}
                    </option>
                  ))}
                </select>
              </label>
              <div className="resource-toggles">
                <label>
                  <input
                    type="checkbox"
                    checked={newSessionStrongs}
                    onChange={(event) => setNewSessionStrongs(event.target.checked)}
                  />
                  Include Strong's links
                </label>
                <label>
                  <input
                    type="checkbox"
                    checked={newSessionFootnotes}
                    onChange={(event) => setNewSessionFootnotes(event.target.checked)}
                  />
                  Include footnotes
                </label>
                <label>
                  <input
                    type="checkbox"
                    checked={newSessionCommentary}
                    onChange={(event) => setNewSessionCommentary(event.target.checked)}
                  />
                  Include commentary
                </label>
                <label>
                  <input
                    type="checkbox"
                    checked={newSessionDictionary}
                    onChange={(event) => setNewSessionDictionary(event.target.checked)}
                  />
                  Include dictionary
                </label>
                <label>
                  <input
                    type="checkbox"
                    checked={newSessionTimeline}
                    onChange={(event) => setNewSessionTimeline(event.target.checked)}
                  />
                  Record timeline
                </label>
              </div>
              <button type="button" onClick={startNewSession}>
                Create session
              </button>
            </section>
          </div>
        </section>
      </div>
    )
  }

  function renderAboutModal() {
    if (!aboutModalOpen) return null

    return (
      <div className="modal-backdrop" role="presentation" onMouseDown={() => setAboutModalOpen(false)}>
        <section
          className="modal-panel about-modal"
          role="dialog"
          aria-modal="true"
          aria-label="About Libre Study"
          onMouseDown={(event) => event.stopPropagation()}
        >
          <header>
            <div>
              <span className="eyebrow">About</span>
              <h2>Libre Study</h2>
            </div>
            <button type="button" className="close-button" onClick={() => setAboutModalOpen(false)}>
              Close
            </button>
          </header>
          <p>
            Libre Study is a free Bible study application built by Christ IT. The project
            started in July 2026 as an open study tool focused on readable Bible pages,
            linked study data, notes, and reusable public Bible packages.
          </p>
          <dl className="about-list">
            <div>
              <dt>Project</dt>
              <dd>Christ IT / Libre Study</dd>
            </div>
            <div>
              <dt>Current Bible package</dt>
              <dd>
                {activeTranslation
                  ? `${activeTranslation.title}. ${activeTranslation.licenseName}`
                  : 'LibreBible translation package loaded from the local catalog.'}
              </dd>
            </div>
            <div>
              <dt>Software stack</dt>
              <dd>Tauri, TypeScript, React, SQLite, Rust, Vite.</dd>
            </div>
            <div>
              <dt>Source data catalog</dt>
              <dd>LibreBible packages are maintained separately so this app and future sites can consume the same resources.</dd>
            </div>
          </dl>
          <div className="about-links">
            <a href="https://christit.com">ChristIT.com</a>
            <a href="https://git.christit.com/libre-study/libre-study">Libre Study Git</a>
            <a href="https://git.christit.com/libre-study/libre-bible-data">LibreBible Data Git</a>
          </div>
        </section>
      </div>
    )
  }

  function renderSettingsModal() {
    if (!settingsModalOpen) return null

    return (
      <div className="modal-backdrop" role="presentation" onMouseDown={() => setSettingsModalOpen(false)}>
        <section
          className="modal-panel settings-modal"
          role="dialog"
          aria-modal="true"
          aria-label="Study display settings"
          onMouseDown={(event) => event.stopPropagation()}
        >
          <header>
            <div>
              <span className="eyebrow">Settings</span>
              <h2>Study Display</h2>
            </div>
            <button type="button" className="close-button" onClick={() => setSettingsModalOpen(false)}>
              Close
            </button>
          </header>
          <div className="settings-grid">
            <section className="modal-section">
              <h3>Theme</h3>
              <div className="segmented-control" aria-label="Theme mode">
                <button
                  type="button"
                  className={themeMode === 'light' ? 'active' : ''}
                  onClick={() => changeThemeMode('light')}
                >
                  Light
                </button>
                <button
                  type="button"
                  className={themeMode === 'dark' ? 'active' : ''}
                  onClick={() => changeThemeMode('dark')}
                >
                  Dark
                </button>
              </div>
            </section>

            <section className="modal-section">
              <h3>Original Language Line</h3>
              <label>
                Text size
                <input
                  type="range"
                  min="13"
                  max="26"
                  value={lemmaFontSize}
                  onChange={(event) => setLemmaFontSize(Number(event.target.value))}
                />
                <span>{lemmaFontSize}px</span>
              </label>
              <label className="checkbox-row">
                <input
                  type="checkbox"
                  checked={showOriginalLine}
                  onChange={(event) => {
                    setShowOriginalLine(event.target.checked)
                    recordDisplaySetting(
                      event.target.checked
                        ? 'Show original language line'
                        : 'Hide original language line',
                    )
                  }}
                />
                Show original language line
              </label>
            </section>

            <section className="modal-section">
              <h3>English Strong's Line</h3>
              <label>
                Text size
                <input
                  type="range"
                  min="12"
                  max="23"
                  value={linkedFontSize}
                  onChange={(event) => setLinkedFontSize(Number(event.target.value))}
                />
                <span>{linkedFontSize}px</span>
              </label>
              <label className="checkbox-row">
                <input
                  type="checkbox"
                  checked={showLinkedLine}
                  onChange={(event) => {
                    setShowLinkedLine(event.target.checked)
                    recordDisplaySetting(
                      event.target.checked ? 'Show English linked text' : 'Hide English linked text',
                    )
                  }}
                />
                Show English linked text
              </label>
            </section>

            <section className="modal-section">
              <h3>Definition Panel</h3>
              <label className="checkbox-row">
                <input
                  type="checkbox"
                  checked={showDefinitionPanel}
                  onChange={(event) => {
                    setShowDefinitionPanel(event.target.checked)
                    recordDisplaySetting(
                      event.target.checked ? 'Show Strong definition' : 'Hide Strong definition',
                    )
                  }}
                />
                Show expanded definition
              </label>
            </section>

            <section className="modal-section">
              <h3>Reference Panels</h3>
              <label className="checkbox-row">
                <input
                  type="checkbox"
                  checked={showCommentaryPanel}
                  onChange={(event) => {
                    setShowCommentaryPanel(event.target.checked)
                    recordDisplaySetting(
                      event.target.checked ? 'Show commentary panel' : 'Hide commentary panel',
                    )
                  }}
                />
                Show commentary
              </label>
              <label className="checkbox-row">
                <input
                  type="checkbox"
                  checked={showDictionaryPanel}
                  onChange={(event) => {
                    setShowDictionaryPanel(event.target.checked)
                    recordDisplaySetting(
                      event.target.checked ? 'Show dictionary panel' : 'Hide dictionary panel',
                    )
                  }}
                />
                Show dictionary
              </label>
            </section>
          </div>
        </section>
      </div>
    )
  }

  function renderNotesDrawer() {
    if (!selectedVerse) return null

    return (
      <aside
        className={[
          'notes-drawer',
          notesDrawerOpen || notesPinned ? 'open' : '',
          notesPinned ? 'pinned' : '',
        ].filter(Boolean).join(' ')}
        aria-label="Notes drawer"
        onDragEnter={(event) => {
          event.preventDefault()
          scheduleNotesDragOpen()
        }}
        onDragLeave={clearNotesDragOpen}
        onDragOver={(event) => event.preventDefault()}
        onDrop={(event) => {
          event.preventDefault()
          clearNotesDragOpen()
          appendNoteClip(event.dataTransfer.getData('text/plain'))
          setNotesDrawerOpen(true)
        }}
      >
        <button
          type="button"
          className="notes-drawer-grip"
          aria-label={notesDrawerOpen || notesPinned ? 'Close notes drawer' : 'Open notes drawer'}
          onClick={() => {
            if (notesPinned) return
            setNotesDrawerOpen((current) => !current)
          }}
        >
          <span>N</span>
          <span>O</span>
          <span>T</span>
          <span>E</span>
          <span>S</span>
        </button>
        <div className="notes-workspace">
          <header>
            <div>
              <span className="eyebrow">Notes</span>
              <h2>Study Notes</h2>
            </div>
            <button
              type="button"
              className="pin-notes"
              onClick={() => {
                const nextPinned = !notesPinned
                setNotesPinned(nextPinned)
                setNotesDrawerOpen(nextPinned)
                recordDisplaySetting(nextPinned ? 'Pinned notes drawer' : 'Unpinned notes drawer')
              }}
            >
              {notesPinned ? 'Unpin' : 'Pin'}
            </button>
          </header>
          <textarea
            value={noteDraft}
            onChange={(event) => updateNoteDraft(event.target.value)}
            placeholder="Write sermon notes, study observations, or drag clippings here later."
          />
          <div className="tag-editor">
            <input
              value={tagInput}
              onChange={(event) => setTagInput(event.target.value)}
              onKeyDown={(event) => {
                if (event.key === 'Enter') {
                  addTag().catch((reason) => setError(String(reason)))
                }
              }}
              placeholder="prophecy, sermon, doctrine"
            />
            <button type="button" onClick={() => addTag().catch((reason) => setError(String(reason)))}>
              Tag verse
            </button>
          </div>
          <div className="reader-tags">
            {selectedVerse.tags.map((tag) => (
              <span key={tag.id} style={{ backgroundColor: tag.color }}>
                {tag.label}
              </span>
            ))}
          </div>
          <div className="notes-quick-panels">
            <button
              type="button"
              className="note-helper"
              onClick={() => setTimelineModalOpen(true)}
              aria-label="Open study timeline"
            >
              <span className="note-helper-figure" aria-hidden="true">
                <span className="helper-head" />
                <span className="helper-body" />
                <span className="helper-notebook" />
                <span className="helper-pencil" />
              </span>
              <span>
                <strong>Study timeline</strong>
                <small>{activeSession?.timeline.length ?? 0} events recorded</small>
              </span>
            </button>
            <button type="button" className="note-placeholder">
              <strong>Study tools</strong>
              <small>Placeholder</small>
            </button>
          </div>
        </div>
      </aside>
    )
  }

  const splitTemplate = `${splitPercent}fr 6px ${100 - splitPercent}fr`

  return (
    <main
      className={[
        'app-shell',
        railOpen ? 'menu-open' : '',
        notesPinned ? 'notes-pinned' : '',
        themeMode === 'dark' ? 'theme-dark' : 'theme-light',
      ].filter(Boolean).join(' ')}
    >
      <aside
        className="tool-rail"
        aria-label="Main tools"
        onMouseEnter={() => setRailOpen(true)}
        onMouseLeave={() => setRailOpen(false)}
        onFocus={() => setRailOpen(true)}
        onBlur={(event) => {
          if (!event.currentTarget.contains(event.relatedTarget)) setRailOpen(false)
        }}
      >
        <button type="button" className="menu-button" title="Menu" onClick={() => setRailOpen((current) => !current)}>
          <span />
          <span />
          <span />
        </button>
        <div className="app-identity" aria-label="Libre Study">
          <span className="brand-mark">LS</span>
          <span className="rail-copy">
            <strong>Libre Study</strong>
            <small>Free Bible study by Christ IT</small>
          </span>
        </div>
        <p className="rail-description">
          A readable Bible page, study margin, notes workspace, and linked public Bible data.
        </p>
        <button type="button" title="Session management" onClick={() => setSessionModalOpen(true)}>
          <span className="rail-icon">S</span>
          <span className="rail-copy"><strong>Sessions</strong><small>Save, export, and configure</small></span>
        </button>
        <button type="button" title="Settings" onClick={() => setSettingsModalOpen(true)}>
          <span className="rail-icon">A</span>
          <span className="rail-copy"><strong>Settings</strong><small>Study display controls</small></span>
        </button>
        <button type="button" className="rail-bottom" title="About Libre Study" onClick={() => setAboutModalOpen(true)}>
          <span className="rail-icon">?</span>
          <span className="rail-copy"><strong>About</strong><small>Project, licenses, and links</small></span>
        </button>
      </aside>

      <section className="reader" ref={readerRef}>
        {loading ? (
          <div className="status-panel">Loading local library...</div>
        ) : error ? (
          <div className="status-panel error">{error}</div>
        ) : selectedVerse ? (
          <>
            <header
              className="top-bar"
              style={{ gridTemplateColumns: splitTemplate }}
            >
              <div className="bible-top-tools">
                <div className="page-controls" aria-label="Page selectors">
                  <label>
                    Translation
                    <select
                      value={activeSession?.baseTranslation ?? defaultTranslationId}
                      onChange={(event) =>
                        changeTranslation(event.target.value).catch((reason) => setError(String(reason)))
                      }
                    >
                      {translations.map((translation) => (
                        <option key={translation.id} value={translation.id}>
                          {translation.abbreviation}
                        </option>
                      ))}
                    </select>
                  </label>
                  <label>
                    Book
                    <select
                      value={selectedVerse.book}
                      onChange={(event) => jumpTo(event.target.value, 1, 1)}
                    >
                      {books.map((book) => (
                        <option key={book} value={book}>
                          {book}
                        </option>
                      ))}
                    </select>
                  </label>
                  <label>
                    Chapter
                    <select
                      value={selectedVerse.chapter}
                      onChange={(event) =>
                        jumpTo(selectedVerse.book, Number(event.target.value), 1)
                      }
                    >
                      {chapters.map((chapter) => (
                        <option key={chapter} value={chapter}>
                          {chapter}
                        </option>
                      ))}
                    </select>
                  </label>
                  <label>
                    Verse
                    <select
                      value={selectedVerse.verse}
                      onChange={(event) =>
                        jumpTo(
                          selectedVerse.book,
                          selectedVerse.chapter,
                          Number(event.target.value),
                        )
                      }
                    >
                      {verseNumbers.map((verse) => (
                        <option key={verse} value={verse}>
                          {verse}
                        </option>
                      ))}
                    </select>
                  </label>
                  <label>
                    Strong's
                    <select
                      value={strongDisplay}
                      onChange={(event) =>
                        setStrongDisplayMode(event.target.value as StrongDisplayMode)
                      }
                    >
                      <option value="off">Off</option>
                      <option value="highlight">Highlight</option>
                      <option value="numbers">Numbers</option>
                    </select>
                  </label>
                </div>
                <form
                  className="search-box"
                  onSubmit={(event) => {
                    event.preventDefault()
                    runSearch().catch((reason) => setError(String(reason)))
                  }}
                >
                  <input
                    id="search"
                    value={query}
                    onChange={(event) => setQuery(event.target.value)}
                    placeholder={`Search ${activeTranslation?.abbreviation ?? 'Bible'}, reference, or Strong's`}
                  />
                  <button type="submit">Go</button>
                </form>
              </div>
              <div className="split-spacer" aria-hidden="true" />
              <div className="study-top-tools" aria-label="Study margin tools">
                <button type="button" onClick={() => setSettingsModalOpen(true)}>
                  Margin settings
                </button>
              </div>
            </header>

            <div
              className={`study-desk ${viewMode}`}
              style={{ gridTemplateColumns: splitTemplate }}
            >
              {viewMode === 'compare' ? (
                <div className="page-system compare-system" aria-label="Compare translations">
                  <div className="compare-pages">
                    {renderBiblePage()}
                    <article className="bible-page compare-placeholder" aria-label="Second translation placeholder">
                      <header>
                        <span>Second Translation</span>
                        <strong>Not loaded</strong>
                      </header>
                      <div>
                        <h2>Add another translation to compare side by side.</h2>
                        <p>
                          This pane is reserved for the next LibreBible translation package.
                          It will use the same book, chapter, and verse position as the KJV page.
                        </p>
                      </div>
                    </article>
                  </div>
                </div>
              ) : (
                <>
                  <div className={`page-system ${viewMode} ${pageMotion}`}>
                    {renderBiblePage()}
                    {renderFootnoteStrip()}
                    {renderPageTurner()}
                    {renderBookTabs()}
                  </div>
                  <div
                    className="split-resizer"
                    role="separator"
                    aria-label="Resize Bible and study margin"
                    aria-orientation="vertical"
                    onMouseDown={beginSplitResize}
                  />
                  {renderStudyMargin()}
                </>
              )}
            </div>
          </>
        ) : (
          <div className="status-panel">No verses matched that search.</div>
        )}
      </section>
      {renderSessionModal()}
      {renderAboutModal()}
      {renderSettingsModal()}
      {renderTimelineModal()}
      {renderNotesDrawer()}
    </main>
  )
}

export default App