function eventIdSet(chapter) {
  return new Set(
    Array.isArray(chapter && chapter.events)
      ? chapter.events.map((event) => event.hotspotId)
      : [],
  )
}

function normalizeCompletedIds(chapter, completedIds) {
  const knownIds = eventIdSet(chapter)
  const seen = new Set()
  return (Array.isArray(completedIds) ? completedIds : []).filter((id) => {
    if (!knownIds.has(id) || seen.has(id)) return false
    seen.add(id)
    return true
  })
}

function getPeopleProgress(chapter, completedIds) {
  const knownIds = eventIdSet(chapter)
  const completed = new Set(normalizeCompletedIds(chapter, completedIds))
  const people = Array.isArray(chapter && chapter.people) ? chapter.people : []

  return people
    .map((person) => {
      const personEventIds = (Array.isArray(person.eventIds)
        ? person.eventIds
        : []
      ).filter((id) => knownIds.has(id))
      const completedForPerson = personEventIds.filter((id) => completed.has(id))
      const remaining = personEventIds.length - completedForPerson.length
      if (!personEventIds.length) return null

      let markerStatus = '看看'
      let statusAria = `${person.name}有1处故事细节，可以看看发生了什么`
      if (remaining === 0) {
        markerStatus = '看过'
        statusAria = `${person.name}这一处已经看过`
      } else if (completedForPerson.length > 0) {
        markerStatus = '再看看'
        statusAria = `${person.name}还有${remaining}处细节，可以再看看`
      } else if (remaining > 1) {
        markerStatus = `${remaining}处`
        statusAria = `${person.name}有${remaining}处故事细节`
      }

      return {
        ...person,
        eventIds: personEventIds,
        completed: remaining === 0,
        completedEvents: completedForPerson.length,
        remaining,
        markerStatus,
        statusAria,
      }
    })
    .filter(Boolean)
}

function selectNextPerson(people, activeInstanceId) {
  const active = people.find(
    (person) => person.instanceId === activeInstanceId && person.remaining > 0,
  )
  if (active) return active

  const partiallyCompleted = people.find(
    (person) => person.completedEvents > 0 && person.remaining > 0,
  )
  return partiallyCompleted || people.find((person) => person.remaining > 0) || null
}

function getChapterProgress(
  chapter,
  completedIds,
  activeInstanceId = '',
  chapterFinished = false,
) {
  const normalizedIds = normalizeCompletedIds(chapter, completedIds)
  const totalEvents = Array.isArray(chapter && chapter.events)
    ? chapter.events.length
    : 0
  const completedCount = normalizedIds.length
  const remainingCount = Math.max(0, totalEvents - completedCount)
  const complete = totalEvents > 0 && remainingCount === 0
  const people = getPeopleProgress(chapter, normalizedIds)
  const nextPerson = complete
    ? null
    : selectNextPerson(people, activeInstanceId)
  const repeatPerson = Boolean(
    nextPerson
      && (
        nextPerson.completedEvents > 0
        || (
          activeInstanceId
          && nextPerson.instanceId === activeInstanceId
        )
      ),
  )

  let nextStepLabel = '下一步'
  let nextStepText = '看看画中的人物和手边物件，跟着这一回往下走。'
  let continueLabel = '完成后继续'
  if (complete) {
    nextStepLabel = chapterFinished ? '本回已收好' : '4处线索已经看过'
    nextStepText = chapterFinished
      ? '这一回已经收进画册，也可以再次打开情感互动。'
      : '情感互动已经开启，点右侧按钮打开这一页。'
    continueLabel = '4处线索看完，打开情感互动'
  } else if (nextPerson && repeatPerson) {
    nextStepText = `还差${remainingCount}处。再看看${nextPerson.name}的手边。`
    continueLabel = `下一步：再看看${nextPerson.name}`
  } else if (nextPerson) {
    const multiEventNote = nextPerson.remaining > 1
      ? ` ${nextPerson.name}身边还有${nextPerson.remaining}处细节。`
      : ''
    nextStepText = `还差${remainingCount}处。接着看看${nextPerson.name}。${multiEventNote}`
    continueLabel = `下一步：看看${nextPerson.name}`
  }

  const emotionStatusText = complete
    ? (
      chapterFinished
        ? '本回已收进画册，可再次打开'
        : `${totalEvents}处线索已经看过，可以打开`
    )
    : `还差${remainingCount}处线索，看完后开启`

  return {
    completedIds: normalizedIds,
    completedCount,
    totalEvents,
    remainingCount,
    complete,
    people,
    nextPerson,
    nextAction: complete ? 'complete' : (repeatPerson ? 'repeat' : 'next'),
    nextStepLabel,
    nextStepText,
    continueLabel,
    emotionStatusText,
  }
}

module.exports = {
  normalizeCompletedIds,
  getPeopleProgress,
  getChapterProgress,
}