import type { ScrollPosition } from './occurrences'
import type { DocumentMessage, Reveal } from './types'
import { useLayoutEffect } from 'react'
import { blockPath } from './filter'
import { revealPlan, scrollTopToShow, uncoveredPlan } from './reveal'
import { blockForLine } from './scrollPosition'
import { measureBlocks, pinnedHeight } from './useScrollPosition'

/** 让一块或属性表里的一行闪几下（codeReader.css 的 [data-flash]）；正在闪的同一处再跳一次时从头闪。 */
export function flash(el: HTMLElement): void {
  const running = el.getAnimations().filter(animation => animation instanceof CSSAnimation)
  if (running.length > 0) {
    for (const animation of running)
      animation.currentTime = 0
    return
  }
  const onEnd = (event: AnimationEvent): void => {
    if (event.target !== el)
      return
    el.removeAttribute('data-flash')
    el.removeEventListener('animationend', onEnd)
  }
  el.addEventListener('animationend', onEnd)
  el.setAttribute('data-flash', '')
}

/** 把 el 滚进钉住的筛选栏下面的视口。已经整个看得见就不滚。beforeScroll 在真正滚动前拿到将要落到的位置。 */
export function showInViewport(el: HTMLElement, beforeScroll?: (position: ScrollPosition) => void): void {
  const rect = el.getBoundingClientRect()
  const pinned = pinnedHeight()
  const top = scrollTopToShow(
    { top: rect.top + window.scrollY, bottom: rect.bottom + window.scrollY },
    window.scrollY,
    window.innerHeight,
    pinned,
  )
  if (top === undefined)
    return
  const position = { x: 0, y: top }
  beforeScroll?.(position)
  window.scrollTo(position.x, position.y)
}

/** 这块自己显示着的、下标就是定义处的那个名字。子块里的同名下标不算，免得闪到旁边那张卡片。 */
function nameAt(block: HTMLElement, offset: number): HTMLElement | null {
  for (const el of block.querySelectorAll<HTMLElement>('[data-offset]')) {
    if (Number(el.dataset.offset) !== offset)
      continue
    if (el.closest('.cr-block') === block)
      return el
  }
  return null
}

/**
 * 滚到 reveal 指的位置，处理完调 done：
 * ① 从文本编辑器切过来（没有 definition）：包含那一行的块顶到视口顶部（筛选栏下面），折叠着的、被筛掉的不展开；
 * ② 跳到定义：目标或它的祖先块被筛掉了，先临时露出这条路径（show）；再展开把目标折叠住的块、属性行和子行（expand）——
 *    每一步之后重新渲染、再进来一次；最后把目标滚进筛选栏下面并闪几下。
 *    属性行 / 子行是这处定义时闪那一行；这块里显示着这个名字（下标盖住定义处）就闪这个名字，不闪整张卡片；
 *    名字不在页面上才闪整块。目标被正在编辑的祖先盖住时闪那个祖先（uncoveredPlan）。
 */
export function useReveal(
  doc: DocumentMessage | null,
  reveal: Reveal | null,
  collapsed: ReadonlySet<string>,
  filtered: ReadonlySet<string>,
  covered: ReadonlyMap<string, string>,
  show: (ids: string[]) => void,
  expand: (ids: string[]) => void,
  done: () => void,
): void {
  useLayoutEffect(() => {
    if (!doc || !reveal)
      return
    if (reveal.definition === undefined) {
      const top = blockForLine(measureBlocks(), reveal.line)?.top
      if (top !== undefined)
        window.scrollTo(0, top - pinnedHeight())
      done()
      return
    }
    const found = revealPlan(doc.blocks, reveal.line, reveal.definition)
    const plan = found && uncoveredPlan(found, covered)
    const path = plan ? blockPath(plan.id) : []
    if (path.some(id => filtered.has(id))) {
      show(path)
      return
    }
    const hidden = plan?.expand.filter(id => collapsed.has(id)) ?? []
    if (hidden.length > 0) {
      expand(hidden)
      return
    }
    // 块正在编辑时页面上没有属性表，就闪整块
    const block = plan ? document.querySelector<HTMLElement>(`.cr-block[data-id="${plan.id}"]`) : null
    const row = plan?.row === undefined ? null : document.querySelector<HTMLElement>(`:is(.cr-prop-row, .cr-prop-item, .cr-table-row)[data-id="${plan.row}"]`)
    const name = row || !block ? null : nameAt(block, reveal.definition)
    const el = row ?? name ?? block
    if (el) {
      showInViewport(el)
      flash(el)
    }
    done()
  }, [doc, reveal, collapsed, filtered, covered, show, expand, done])
}