import type { NameMap } from './displayNames'
import type { FindAnchor, FindMatch, FindResult, FindUnit } from './find'
import type { FindPainter } from './findHighlights'
import type { TextMarks } from './SegmentText'
import type { ReadableStore } from './store'
import type { OccurrencePage } from './useOccurrences'
import { useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState } from 'react'
import { findCount, findUnits, PageFind } from './find'
import { markdownText, textOf } from './findHighlights'
import { ShortcutContext } from './occurrences'
import { pageLayout } from './pageLayout'
import { useStore } from './store'
import { showInViewport } from './useReveal'
import { onMessage, postMessage } from './vscode'

/** 打字停下多久才找：大文件里每敲一个字都整份找一遍、重画一遍高亮会卡 */
const TYPING_MS = 100

const NO_UNITS: readonly FindUnit[] = []
const NO_NAMES: NameMap = new Map()
const NOTHING: FindResult = { query: '', matches: [] }

/** 查找栏要画的和它的动作，见 [FindBar](vscode/webview-ui/src/codeReader/FindBar.tsx#FindBar)。 */
export interface FindView {
  open: boolean
  query: string
  count?: string
  canMove: boolean
  focus: number
  onQuery: (query: string) => void
  onMove: (step: 1 | -1) => void
  onClose: () => void
}

/** 一次找：查的字，从哪往后找（⌘F 拿选中的字填进去时是选中的那处）。 */
interface Search {
  query: string
  from?: FindAnchor
}

/**
 * 页面上选中的一行字，和查找从哪开始（它在页面内容 `root` 里哪段字的第几个字）；没选中、选中了好几行、焦点在输入框里时没有。
 * `line` 是那块在文件里的第一行（见 [FindAnchor]）。
 */
function selectedText(root: HTMLElement | null, page: OccurrencePage | undefined): Search | undefined {
  const selection = window.getSelection()
  const query = selection?.toString() ?? ''
  const field = document.activeElement
  if (!selection || selection.rangeCount === 0 || query.trim() === '' || /[\r\n]/.test(query) || field instanceof HTMLInputElement || field instanceof HTMLTextAreaElement)
    return undefined
  const { startContainer, startOffset } = selection.getRangeAt(0)
  const holder = (startContainer instanceof Element ? startContainer : startContainer.parentElement)?.closest<HTMLElement>('[data-find]')
  const node = holder && root?.contains(holder) ? textOf(holder).nodes.find(item => item.node === startContainer) : undefined
  const block = holder?.closest<HTMLElement>('.cr-block')?.dataset.id
  if (!holder || !node || block === undefined)
    return { query }
  return { query, from: { key: holder.dataset.find, start: node.start + startOffset, line: page?.placement.of(block)?.line ?? 0 } }
}

/** 视口顶部那块（钉住的筛选栏下面）的行：查找栏刚写字、还没有当前那处时从它往后找。 */
function viewportAnchor(): FindAnchor {
  return { start: 0, line: pageLayout.anchorAt(window.scrollY + pageLayout.pinnedHeight())?.line ?? 0 }
}

/**
 * 查找栏：扩展端的「查找」命令（⌘F）发来 openFind 时打开、聚焦输入框，页面上选中了一行字时先填进去、从它那处开始找；
 * 写了字停下一会儿就在整份文件里找（见 [PageFind]），当前那处展开把它折叠住的块、属性行和子行，滚进视口；
 * 「查找下一处 / 上一处」命令（⌘G / ⇧⌘G）发来 moveFind、输入框里 Enter / Shift+Enter、栏上的按钮都在命中之间跳。
 * 高亮由 `painter` 画在页面上，块树不重画；关掉时清掉高亮，查的字留着，下次打开照旧。
 * 查找栏开着、页面有焦点时告诉扩展端 ⌘G 归这个页面（见 [ShortcutContext]）。
 * `page` 同单击高亮跳到一处出现用的页面状态，`marks` 是页面文字的标记（中文名在里面，找的时候才订阅，中文名到了不连累整页重画）。
 */
export function useFind(page: OccurrencePage | undefined, marks: ReadableStore<TextMarks>, painter: FindPainter): FindView {
  const [open, setOpen] = useState(false)
  const [query, setQuery] = useState('')
  const [search, setSearch] = useState<Search>({ query: '' })
  /** 每次 ⌘F 加一：聚焦输入框、选中里面的字 */
  const [focus, setFocus] = useState(0)
  const [result, setResult] = useState(NOTHING)
  const [find] = useState(() => new PageFind(setResult))
  const [shortcuts] = useState(() => new ShortcutContext(
    { open: false, focused: document.hasFocus() },
    facts => facts.open && facts.focused,
    available => postMessage({ type: 'findNavigation', available }),
  ))
  /** 跳过几次：每跳一次，画完后把当前那处滚进视口 */
  const [reveals, setReveals] = useState(0)
  const latest = useRef({ page, open, query, search })

  useLayoutEffect(() => {
    latest.current = { page, open, query, search }
  })

  const reachable = useCallback((unit: FindUnit) => latest.current.page?.skip(unit.block) === false, [])

  /** 跳到 match：先展开把它折叠住的，画完后滚过去 */
  const reveal = useCallback((match: FindMatch) => {
    const current = latest.current.page
    const folded = current ? find.unitOf(match).expand.filter(id => current.collapsed.has(id)) : []
    if (current && folded.length > 0)
      current.expand(folded)
    setReveals(count => count + 1)
  }, [find])

  // 开着、写了字才把整份文件的字备好；关着时不跟着新文档重算，原来那处留着，下次打开从它附近接着
  const active = open && search.query !== ''
  const names = useStore(marks, current => active ? current.names : NO_NAMES)
  const blocks = page?.blocks
  const placement = page?.placement
  const units = useMemo(() => active && blocks && placement ? findUnits(blocks, placement, names, markdownText) : NO_UNITS, [active, blocks, placement, names])

  // 先换上新的字（新一版文档、中文名到了、又打开了）再找：当前那处停在原来那处附近，不滚
  useLayoutEffect(() => {
    if (active)
      find.setUnits(units, reachable)
  }, [find, active, units, reachable])

  useLayoutEffect(() => {
    const from = search.from ?? (search.query !== '' && find.state.current === undefined ? viewportAnchor() : undefined)
    const match = find.search(search.query, reachable, from)
    if (match)
      reveal(match)
  }, [find, search, reachable, reveal])

  useEffect(() => {
    const timer = window.setTimeout(() => setSearch(previous => previous.query === query ? previous : { query }), TYPING_MS)
    return () => window.clearTimeout(timer)
  }, [query])

  // 结果变了、开关了：照着画；之后页面变了（展开、换了一版文档）由 painter 自己下一帧重画
  useLayoutEffect(() => {
    painter.show(open && result.query !== '' ? find.paint() : undefined)
  }, [painter, find, open, result])

  useLayoutEffect(() => {
    if (reveals === 0)
      return
    // 要展开的已经展开：按展开后的页面重画一遍，再滚到当前那处；它画不出来就滚到它那段字、那块
    const painted = painter.show(latest.current.open ? find.paint() : undefined)
    const { current, matches } = find.state
    const block = current === undefined ? undefined : find.unitOf(matches[current]).block
    const target = painted.current ?? painted.text ?? (block === undefined ? null : document.querySelector<HTMLElement>(`.cr-block[data-id="${block}"]`))
    if (target)
      showInViewport(target)
    painter.place()
  }, [reveals, painter, find])

  const move = useCallback((step: 1 | -1) => {
    const { open, query, search } = latest.current
    if (!open)
      return
    // 刚写的字还没找：先找，跳到它的第一处
    if (query !== search.query) {
      setSearch({ query })
      return
    }
    const match = find.move(step, reachable)
    if (match)
      reveal(match)
  }, [find, reachable, reveal])

  const close = useCallback(() => {
    const focused = document.activeElement
    if (focused instanceof HTMLElement && focused.closest('.cr-find-bar'))
      focused.blur()
    setOpen(false)
  }, [])

  useEffect(() => onMessage((msg) => {
    if (msg.type === 'openFind') {
      const selected = selectedText(painter.root, latest.current.page)
      if (selected) {
        setQuery(selected.query)
        setSearch(selected)
      }
      setOpen(true)
      setFocus(count => count + 1)
    }
    else if (msg.type === 'moveFind') {
      move(msg.step)
    }
  }), [painter, move])

  useEffect(() => shortcuts.update({ open }), [shortcuts, open])

  useEffect(() => {
    const onFocus = (): void => shortcuts.update({ focused: true })
    const onBlur = (): void => shortcuts.update({ focused: false })
    window.addEventListener('focus', onFocus)
    window.addEventListener('blur', onBlur)
    // 焦点落进页面里（⌘F 聚焦输入框）时页面一定有焦点
    document.addEventListener('focusin', onFocus)
    return () => {
      window.removeEventListener('focus', onFocus)
      window.removeEventListener('blur', onBlur)
      document.removeEventListener('focusin', onFocus)
    }
  }, [shortcuts])

  return {
    open,
    query,
    count: open ? findCount(result) : undefined,
    canMove: result.matches.length > 0,
    focus,
    onQuery: setQuery,
    onMove: move,
    onClose: close,
  }
}