import type { CSSProperties, ReactElement, ReactNode } from 'react'
import type { RewriteTool } from './BlockTools'
import type { DiffTree, FoldedRuns, PlacedRemoved } from './diffView'
import type { GridSlots } from './PropertyGrid'
import type { ChatState, ChatView, QaState } from './qa'
import type { PendingImage } from './qaImages'
import type { ReadableStore } from './store'
import type { BlockMarks, BlockView, ChangedBlock } from './types'
import { ChevronDown, ChevronRight, ChevronsUpDown, EyeOff } from 'lucide-react'
import { createContext, Fragment, memo, useContext, useMemo, useState } from 'react'
import { AskThread, REWRITE_THREAD } from './AskThread'
import { BlockTools } from './BlockTools'
import { CodeEditor } from './CodeEditor'
import { DiffText } from './DiffText'
import { removedTitle } from './diffView'
import { KindIcon } from './kindIcons'
import { PropertyGrid, PropertyItems, PropertyTable } from './PropertyGrid'
import { chatOf, EMPTY_CHAT, sameChat, unfinished } from './qa'
import { shallowEqual, staticStore, useStore } from './store'
import { TextPreview } from './TextPreview'
import { foldsByCard, listId, tableId } from './viewState'

/** 块树里改代码的那部分状态：哪些块在编辑。页面上的块树才有；定义卡片浮窗里的块树没有，卡片只读，不画右上角的按钮 */
export interface EditState {
  version: number
  editing: ReadonlySet<string>
  /** 刚点了「编辑」、要把光标放进去的块 */
  focusId: string | null
}

/** 函数、类落在几棵调用树里，开着哪一块的弹框。定义浮窗没有，跟问 AI 一样不画这排按钮。 */
export interface CallTreeState {
  counts: ReadonlyMap<string, number>
  openAnchor?: string
}

/**
 * 块树要画的、会变的状态：一份不可变的快照，放在 BlockTreeHandle.state 里。每张卡片只订阅自己用到的那部分（useStore），
 * 一处变了只重画受影响的卡片。
 */
export interface BlockTreeState {
  /** 能编辑（页面上的块树）；定义卡片浮窗里没有 */
  edit?: EditState
  /** 调用树。只读的树没有 */
  callTree?: CallTreeState
  /** 眼下折叠着的块 id、属性行 id 和子行 id（propertyRowId、propertyItemId）：用户的选择叠在默认上，见 collapsedIds */
  collapsed: ReadonlySet<string>
  /** collapsed 按卡片分好的（见 foldsByCard）：卡片和它的属性表只看自己那份 */
  folds: ReadonlyMap<string, ReadonlySet<string>>
  /** 按筛选不画的块（连同子孙），见 applyFilter */
  hidden: ReadonlySet<string>
  /** 本来被筛掉、跳到定义时临时显示的块 */
  temporary: ReadonlySet<string>
  /** 被正在编辑的祖先盖住、不画的块（它们的代码在祖先的编辑框里），见 coveredByEditing */
  covered: ReadonlyMap<string, string>
  /** 代码差异：新增、修改的块和删掉的块；侧栏开着「未提交的更改」或审查工单、基准里有这个文件时才有 */
  diff?: DiffTree
  /** 「只看改动」开着时折起来的连着没变的块（见 foldUnchanged） */
  folded?: FoldedRuns
}

/**
 * 一棵块树：会变的状态（state，卡片按自己那部分订阅）和动作。整页一份、不跟着状态变，卡片拿到的回调一直是同一个，
 * 卡片照 memo 跳过重画。
 */
export interface BlockTreeHandle {
  state: ReadableStore<BlockTreeState>
  onToggleFold: (id: string) => void
  /** 一次记下几块、几行折叠还是展开（点子行展开一块、同一行里别的收起） */
  onSetFolds: (folds: Record<string, boolean>) => void
  /** 「只看改动」时点开一段折起来的块（按第一块的 id） */
  onOpenRun: (id: string) => void
  /** 编辑：点「编辑 / 预览」、光标放进去之后。和 state.edit 同时有 */
  edit?: { onToggleEdit: (id: string) => void, onFocused: () => void }
  /** 打开一块的调用树弹框。和 state.callTree 同时有 */
  onOpenCall?: (anchor: string) => void
  /** 问 AI；文件不在工作区文件夹里（问答没地方存）时 state 里 available 是 false */
  qa?: QaTree
  /** 按注释规范重写；同问 AI */
  rewrite?: RewriteTree
}

/** 重写注释的状态（块按自己的记号订阅）和动作；profile 下拉是自己的，和问 AI 的互不影响 */
export interface RewriteTree {
  store: ReadableStore<ChatState>
  /** 点了块右上角的按钮：按技能命令重写这块（开新会话），展开它的重写记录 */
  onRewrite: (anchor: string) => void
  /** 在输入框里说的修改意见，接着这块最近一次重写的会话说；images 是贴的图片 */
  onAsk: (anchor: string, request: string, images: PendingImage[]) => void
  onStop: (askId: string) => void
  onDelete: (anchor: string, entryId: string) => void
  onOpen: (anchor: string) => void
  onClose: (anchor: string) => void
  /** 换重写注释用的 profile（所有块共用），`id` 同 [下拉项的 id](vscode/webview-ui/src/codeReader/types.ts#ProfileOption.id) */
  onSelectProfile: (id: string) => void
}

/** 问 AI 的状态（块按自己的记号订阅）和动作 */
export interface QaTree {
  store: ReadableStore<QaState>
  onToggle: (anchor: string) => void
  onClose: (anchor: string) => void
  /** images 是贴进输入框的图片，随问题一起发 */
  onAsk: (anchor: string, question: string, images: PendingImage[]) => void
  onStop: (askId: string) => void
  onDelete: (anchor: string, entryId: string) => void
  /** 换「问 AI」用的 profile（所有块共用），id 同 ProfileOption.id */
  onSelectProfile: (id: string) => void
}

const BlockTreeContext = createContext<BlockTreeHandle | null>(null)

function useBlockTree(): BlockTreeHandle {
  const tree = useContext(BlockTreeContext)
  if (!tree)
    throw new Error('块树外面没有 BlockTree')
  return tree
}

/** 一棵块树：blocks 是顶层的块，tree 是它的状态和动作（见 BlockTreeHandle）。 */
export function BlockTree({ blocks, tree }: { blocks: BlockView[], tree: BlockTreeHandle }): ReactElement {
  return (
    <BlockTreeContext value={tree}>
      <BlockLevel blocks={blocks} />
    </BlockTreeContext>
  )
}

/** 块树的状态：folds 由 collapsed 按卡片分好（见 foldsByCard），和 previous 里一样的那几份沿用。 */
export function treeState(state: Omit<BlockTreeState, 'folds'>, previous?: BlockTreeState): BlockTreeState {
  return { ...state, folds: foldsByCard(state.collapsed, previous?.folds) }
}

const NO_FOLDS: ReadonlySet<string> = new Set()
const NO_REMOVED: readonly PlacedRemoved[] = []
/** 没有问 AI、重写注释的块树（定义卡片浮窗）：一直不能用 */
const NO_CHAT: ReadableStore<ChatState> = staticStore(EMPTY_CHAT)

/**
 * 块下面有没有画出来的子块（删掉的子块也算）：子块都被筛掉、被盖住时不留空的一层、不给折叠箭头。
 * 挂在卡片子行上的子块（BlockSlot）画在卡片属性表里，不算。
 */
function hasShownChildren(block: BlockView, state: BlockTreeState): boolean {
  return block.children.some(child => !child.slot && shown(child, state)) || (!state.covered.has(block.id) && state.diff?.removed.has(block.id) === true)
}

const CHANGE_NAMES = { add: '新增', mod: '修改', del: '删除' } as const

/** 标差异时卡片左边外侧的改动色条（没变的留一条透明的，同一层照样对齐）；不标差异时原样。 */
function ChangeRow({ diff, change, children }: { diff: boolean, change: keyof typeof CHANGE_NAMES | undefined, children: ReactNode }): ReactElement {
  if (!diff)
    return <>{children}</>
  return (
    <div className="cr-change-row flex gap-[5px]">
      <span className="cr-change-bar" data-change={change} data-tooltip={change && CHANGE_NAMES[change]} />
      <div className="min-w-0 flex-1">{children}</div>
    </div>
  )
}

/** 「只看改动」时连着没变的几块折成的一条「… N 块没变」，点开恢复这几块。 */
function UnchangedStrip({ count, onOpen }: { count: number, onOpen: () => void }): ReactElement {
  return (
    <ChangeRow diff change={undefined}>
      <button type="button" className="cr-unchanged flex h-[22px] w-full items-center gap-1.5 rounded px-2.5 text-xs" onClick={onOpen}>
        <ChevronsUpDown size={12} strokeWidth={1.8} className="shrink-0" aria-hidden />
        {`… ${count} 块没变`}
        <span className="cr-link">点开</span>
      </button>
    </ChangeRow>
  )
}

/** 块画不画：被筛掉的、被正在编辑的祖先盖住的都不画。 */
function shown(block: BlockView, state: BlockTreeState): boolean {
  return !state.hidden.has(block.id) && !state.covered.has(block.id)
}

/**
 * 块的种类色写在哪：内置种类按 data-kind 取 CSS 里的配色；库规则认领的块（带 badge）按规则给的颜色，
 * 暗色、亮色两个都写在 style 上，CSS 按主题挑一个（见 [data-badge]）。
 */
export function kindProps(block: Pick<BlockView, 'kind' | 'badge'> | undefined): { 'data-kind'?: string, 'data-badge'?: '', 'style'?: CSSProperties } {
  if (!block)
    return {}
  if (!block.badge)
    return { 'data-kind': block.kind }
  const { dark, light } = block.badge.color
  return { 'data-kind': block.kind, 'data-badge': '', 'style': { '--kind-dark': dark, '--kind-light': light } as CSSProperties }
}

/** 一块画成什么样要的块树状态：只选这一块自己的，别的块变了它不重画。 */
interface BlockShape {
  /** 画不画：被筛掉的、被正在编辑的祖先盖住的、「只看改动」折起来的不画 */
  shown: boolean
  /** 「只看改动」时从这块起折起来的一段有几块 */
  run?: number
  /** 子块那一层画不画 */
  open: boolean
  /** 标差异 */
  diff: boolean
  change?: ChangedBlock
  /** 页面上正是差异算的那一版：卡片里的标记这时才画 */
  current: boolean
  editing: boolean
  /** 这张卡片里折叠着的（见 foldsByCard） */
  folds: ReadonlySet<string>
  hasChildren: boolean
  temporary: boolean
  focus: boolean
  /** 编辑框每来一份新文档都要对一次内容；不在编辑的卡片不跟着版本重画 */
  version?: number
  /** 调用树：扩展端标了能看调用树（BlockView.callTree）的块才有棵数 */
  calls?: number
  callOpen: boolean
}

function shapeOf(block: BlockView, state: BlockTreeState): BlockShape {
  const editing = state.edit?.editing.has(block.id) ?? false
  return {
    shown: shown(block, state) && !state.folded?.folded.has(block.id),
    run: state.folded?.runs.get(block.id),
    open: hasShownChildren(block, state) && !state.collapsed.has(block.id),
    diff: state.diff !== undefined,
    change: state.diff?.changes.get(block.id),
    current: state.diff?.current ?? false,
    editing,
    folds: state.folds.get(block.id) ?? NO_FOLDS,
    // 点父卡片子行才展开的子块：画出来就是展开着的，箭头收起整张
    hasChildren: block.slot !== undefined || hasShownChildren(block, state),
    temporary: state.temporary.has(block.id),
    focus: state.edit?.focusId === block.id,
    version: editing ? state.edit?.version : undefined,
    calls: state.callTree && block.callTree ? state.callTree.counts.get(block.anchor) ?? 0 : undefined,
    callOpen: state.callTree?.openAnchor === block.anchor,
  }
}

/** 一块的问 AI：能问（文件在工作区文件夹里）时按钮展开没有；对话区展开着或说过时才有，没展开又没说过的块不画。 */
interface AskShape {
  asking?: boolean
  chat?: ChatView
}

const NO_ASK: AskShape = {}

function askOf(anchor: string, state: ChatState): AskShape {
  if (!state.available)
    return NO_ASK
  const chat = chatOf(state, anchor)
  return { asking: chat.open, ...((chat.open || chat.history.length > 0) && { chat }) }
}

/**
 * 一块的重写注释：能写注释的块才有按钮。重写过、记录收着时点了先展开记录（好接着说）；展开着、或还没重写过时点了按技能命令重写。
 * 展开着又正在写、排着队时不能再点。重写记录同问 AI 的对话区。
 */
interface RewriteShape {
  tool?: Omit<RewriteTool, 'onRewrite'>
  chat?: ChatView
}

const NO_REWRITE: RewriteShape = {}

function rewriteOf(block: BlockView, state: ChatState): RewriteShape {
  if (!state.available)
    return NO_REWRITE
  const chat = chatOf(state, block.anchor)
  return {
    ...(block.commentTarget && {
      tool: {
        fresh: block.commentTarget.kind === 'insert',
        rewriting: chat.open && chat.asks.some(unfinished),
        reopen: !chat.open && (chat.asks.length > 0 || chat.history.length > 0),
      },
    }),
    ...((chat.open || chat.history.length > 0) && { chat }),
  }
}

function sameChatIn(a: ChatView | undefined, b: ChatView | undefined): boolean {
  return a === b || (a !== undefined && b !== undefined && sameChat(a, b))
}

function sameAsk(a: AskShape, b: AskShape): boolean {
  return a.asking === b.asking && sameChatIn(a.chat, b.chat)
}

function sameRewrite(a: RewriteShape, b: RewriteShape): boolean {
  return shallowEqual(a.tool, b.tool) && sameChatIn(a.chat, b.chat)
}

/**
 * 一块：「只看改动」折起来的一段、卡片、下面的问答区和重写记录、子块那一层。块树、问 AI、重写注释三份状态里只订阅这一块自己的，
 * 都没变就不重画；子块那一层的各块、卡片的内容各自 memo，这一块重画了它们也不跟着重画。
 */
const BlockItem = memo(({ block }: { block: BlockView }): ReactElement => {
  const tree = useBlockTree()
  const { qa, rewrite } = tree
  const shape = useStore(tree.state, state => shapeOf(block, state), shallowEqual)
  const ask = useStore(qa?.store ?? NO_CHAT, state => askOf(block.anchor, state), sameAsk)
  const rewriting = useStore(rewrite?.store ?? NO_CHAT, state => rewriteOf(block, state), sameRewrite)
  const { anchor } = block
  return (
    <>
      {shape.run !== undefined && <UnchangedStrip count={shape.run} onOpen={() => tree.onOpenRun(block.id)} />}
      {shape.shown && (
        <>
          <ChangeRow diff={shape.diff} change={shape.change?.change}>
            <BlockCard block={block} shape={shape} ask={ask} rewrite={rewriting} />
          </ChangeRow>
          {/* 输入框、展开状态跟着块的记号走，文档刷新块 id 变了也不丢 */}
          {qa && ask.chat && (
            <AskThread
              key={anchor}
              history={ask.chat.history}
              asks={ask.chat.asks}
              open={ask.chat.open}
              profiles={ask.chat.profiles}
              onSelectProfile={qa.onSelectProfile}
              onAsk={(question, images) => qa.onAsk(anchor, question, images)}
              onStop={qa.onStop}
              onDelete={entryId => qa.onDelete(anchor, entryId)}
              onClose={() => qa.onClose(anchor)}
            />
          )}
          {/* 重写记录紧跟在问答区后面；样子和问答区一样，输入框里说的是对这段注释的修改意见 */}
          {rewrite && rewriting.chat && (
            <AskThread
              key={`rewrite ${anchor}`}
              wording={REWRITE_THREAD}
              history={rewriting.chat.history}
              asks={rewriting.chat.asks}
              open={rewriting.chat.open}
              profiles={rewriting.chat.profiles}
              onSelectProfile={rewrite.onSelectProfile}
              onAsk={(request, images) => rewrite.onAsk(anchor, request, images)}
              onStop={rewrite.onStop}
              onDelete={entryId => rewrite.onDelete(anchor, entryId)}
              onClose={() => rewrite.onClose(anchor)}
            />
          )}
          {shape.open && <BlockLevel blocks={block.children} owner={block} />}
        </>
      )}
    </>
  )
})
BlockItem.displayName = 'BlockItem'

/**
 * 一层代码块：左边一条竖线标出这一层，每块的子块紧跟在它下面、再往右缩进一层。被筛掉、被盖住的块不画，不留空位，竖线跟着变短。
 * owner 是这一层所属的块（顶层没有，记在 data-owner 上，钉住卡片时按它算卡片连同子块管到哪、套着几层），悬停它时竖线换成它的种类色。
 * 标差异时每张卡片左边外侧一条改动色条，删掉的块收成一行放回原来的位置（见 RemovedCard）；「只看改动」时连着没变的块折成一条（UnchangedStrip）。
 * slotted：这一层是画在卡片属性表某一行下面的子块（BlockSlot），blocks 只有那几块。
 */
export function BlockLevel({ blocks, owner, slotted = false }: { blocks: BlockView[], owner?: BlockView, slotted?: boolean }): ReactElement {
  const tree = useBlockTree()
  // 挂在卡片子行上的子块画在卡片属性表里（slotted 的那一层），这一层不画；删掉的块都放回卡片后面这一层
  const listed = useMemo(() => slotted ? blocks : blocks.filter(block => !block.slot), [blocks, slotted])
  const removed = useStore(tree.state, state => slotted ? NO_REMOVED : state.diff?.removed.get(owner?.id ?? '') ?? NO_REMOVED)
  const listedIds = new Set(listed.map(block => block.id))
  // 删掉的块排在它原来前面那块后面；那块被筛掉了也照排，不跟着消失；那块画在卡片里时排到这一层最后
  const removedAfter = (id: string | undefined): ReactElement[] => removed
    .filter(item => item.after === id)
    .map(item => <RemovedCard key={item.id} placed={item} />)
  const removedElsewhere = removed
    .filter(item => item.after !== undefined && !listedIds.has(item.after))
    .map(item => <RemovedCard key={item.id} placed={item} />)
  return (
    <div className="cr-level flex gap-2" {...kindProps(owner)} data-owner={owner?.id}>
      <div className="flex w-3 shrink-0 justify-center">
        <div className="cr-guide w-px" />
      </div>
      <div className="flex min-w-0 flex-1 flex-col gap-2">
        {removedAfter(undefined)}
        {listed.map(block => (
          <Fragment key={block.id}>
            <BlockItem block={block} />
            {removedAfter(block.id)}
          </Fragment>
        ))}
        {removedElsewhere}
      </div>
    </div>
  )
}

/**
 * 预览状态的内容：函数、类、枚举、导入、常量、变量块和库规则的卡片是属性表，其余是一行译文；
 * 译文下面依次接着拆开的各项（跨几行写的字面量，排法同变量初始值下面的）、摊开实参的表（跨几行写的调用）、说明、几行属性（「注释」一行）。
 * folds 是这张卡片里折叠着的（见 foldsByCard）；标差异时 marks 是这块自己的内容改了哪些（页面上正是差异算的那一版才给）。
 */
const BlockPreview = memo(({ block, folds, marks }: { block: BlockView, folds: ReadonlySet<string>, marks?: BlockMarks }): ReactElement => {
  const tree = useBlockTree()
  const slots = useMemo(() => cardSlots(block, folds, tree), [block, folds, tree])
  if ('properties' in block)
    return <PropertyGrid blockId={block.id} rows={block.properties} collapsed={folds} onToggleFold={tree.onToggleFold} marks={marks?.rows} slots={slots} />
  const folding = { collapsed: folds, onToggleFold: tree.onToggleFold }
  return (
    <>
      {marks?.translation ? <DiffText diff={marks.translation} /> : <TextPreview text={block.translation} />}
      {block.items && (
        <div className="mt-[3px]">
          <PropertyItems parentId={listId(block.id)} items={block.items} folding={folding} marks={marks?.items} />
        </div>
      )}
      {block.table && (
        <div className="mt-[3px]">
          <PropertyTable parentId={tableId(block.id)} columns={block.table.columns} items={block.table.items} marks={marks?.table} folding={folding} />
        </div>
      )}
      {marks?.doc ? <DiffText diff={marks.doc} className="mt-0.5" /> : block.doc && <TextPreview text={block.doc} className="mt-0.5" />}
      {block.rows && (
        <div className="mt-[3px]">
          <PropertyGrid blockId={block.id} rows={block.rows} collapsed={folds} onToggleFold={tree.onToggleFold} marks={marks?.rows} />
        </div>
      )}
    </>
  )
})
BlockPreview.displayName = 'BlockPreview'

/**
 * 挂在卡片子行上的子块（BlockSlot）怎么画：一行下面展开着的几块画成一层块（同块树）；点那个子行的第一格展开它、
 * 同一行里别的收起，展开着的再点收起。卡片没有挂在子行上的子块时没有。
 */
function cardSlots(block: BlockView, folds: ReadonlySet<string>, tree: BlockTreeHandle): GridSlots | undefined {
  const blocks = block.children.filter(child => child.slot)
  if (blocks.length === 0)
    return undefined
  return {
    blocks,
    render: list => <BlockLevel blocks={list} owner={block} slotted />,
    onToggle: (child) => {
      if (!folds.has(child.id)) {
        tree.onSetFolds({ [child.id]: true })
        return
      }
      const others = blocks.filter(other => other !== child && other.slot?.row === child.slot?.row)
      tree.onSetFolds({ ...Object.fromEntries(others.map(other => [other.id, true])), [child.id]: false })
    },
  }
}

/**
 * 一块的卡片：折叠箭头、种类图标、预览内容或源码、右上角的一排图标按钮（BlockTools，只读的块树没有）。
 * 卡片上记着块记号（data-anchor），说明里不带路径的引用靠它认自己写在哪块（见 commentLinkOf）。
 */
function BlockCard({ block, shape, ask, rewrite }: { block: BlockView, shape: BlockShape, ask: AskShape, rewrite: RewriteShape }): ReactElement {
  const tree = useBlockTree()
  const { edit, onOpenCall } = tree
  const { anchor } = block
  const collapsed = shape.folds.has(block.id)
  const toggled = block.slot !== undefined
  const Chevron = collapsed && !toggled ? ChevronRight : ChevronDown
  const { change } = shape
  const { tool } = rewrite
  return (
    <div
      className="cr-block relative flex items-start gap-2.5 rounded-lg py-2 pr-2.5 pl-2"
      {...kindProps(block)}
      data-id={block.id}
      data-anchor={anchor}
      data-line={block.startLine}
      data-editing={shape.editing ? '' : undefined}
      data-change={change?.change}
    >
      {change?.outermost && <span className="cr-added-badge">新增</span>}
      {shape.hasChildren
        ? (
            <button
              type="button"
              className="flex h-5 w-3.5 shrink-0 items-center justify-center rounded-sm text-[var(--vscode-descriptionForeground)] hover:text-[var(--vscode-foreground)]"
              aria-label={toggled ? '收起' : collapsed ? '展开子块' : '折叠子块'}
              aria-expanded={toggled || !collapsed}
              onClick={() => tree.onToggleFold(block.id)}
            >
              <Chevron size={14} strokeWidth={1.8} />
            </button>
          )
        : <span className="w-3.5 shrink-0" />}
      <KindIcon concepts={block.concepts} />
      <div className="min-w-0 flex-1">
        {edit && shape.version !== undefined
          ? (
              <CodeEditor
                block={block}
                version={shape.version}
                autoFocus={shape.focus}
                onAutoFocused={edit.onFocused}
                onExit={() => edit.onToggleEdit(block.id)}
              />
            )
          : <BlockPreview block={block} folds={shape.folds} marks={shape.current ? change?.marks : undefined} />}
      </div>
      {shape.temporary && (
        <span className="cr-temporary flex h-5 shrink-0 items-center gap-1 rounded px-1.5 text-[11px] whitespace-nowrap">
          <EyeOff size={12} strokeWidth={1.8} aria-hidden />
          已被筛选隐藏，临时显示
        </span>
      )}
      {edit && (
        <BlockTools
          editing={shape.editing}
          onToggleEdit={() => edit.onToggleEdit(block.id)}
          asking={ask.asking}
          onToggleAsk={tree.qa && ask.asking !== undefined ? () => tree.qa?.onToggle(anchor) : undefined}
          rewrite={tree.rewrite && tool && { ...tool, onRewrite: () => tool.reopen ? tree.rewrite?.onOpen(anchor) : tree.rewrite?.onRewrite(anchor) }}
          callTree={onOpenCall && shape.calls !== undefined ? { anchor, count: shape.calls, open: shape.callOpen, onOpen: () => onOpenCall(anchor) } : undefined}
        />
      )}
    </div>
  )
}

/**
 * 删掉的一块，放在原来的位置：红色虚线边、半透明，没有编辑、问 AI 按钮。默认收成一行「已删除 · 种类 名字」，
 * 点箭头或这一行展开，下面是旧内容（整张划掉，名字不能跳定义）；子块不画。
 */
function RemovedCard({ placed }: { placed: PlacedRemoved }): ReactElement {
  const tree = useBlockTree()
  const [open, setOpen] = useState(false)
  const folds = useStore(tree.state, state => state.folds.get(placed.id) ?? NO_FOLDS)
  const { block, kindName } = placed.removed
  const title = removedTitle(block)
  const Chevron = open ? ChevronDown : ChevronRight
  const toggle = (): void => setOpen(value => !value)
  // 旧块的 id 是旧版本里的位置，换成页面上认删掉的块用的 id，属性行的 id 才不和现在的块撞上
  const old = useMemo(() => ({ ...block, id: placed.id }), [block, placed.id])
  return (
    <ChangeRow diff change="del">
      <div className="cr-block cr-removed flex items-start gap-2.5 rounded-lg py-2 pr-2.5 pl-2" {...kindProps(block)} data-id={placed.id}>
        <button
          type="button"
          className="flex h-5 w-3.5 shrink-0 items-center justify-center rounded-sm text-[var(--vscode-descriptionForeground)] hover:text-[var(--vscode-foreground)]"
          aria-label={open ? '收起删掉的内容' : '展开删掉的内容'}
          aria-expanded={open}
          onClick={toggle}
        >
          <Chevron size={14} strokeWidth={1.8} />
        </button>
        <KindIcon concepts={block.concepts} />
        <div className="min-w-0 flex-1">
          <div className="cr-removed-head cursor-pointer truncate text-[12.5px] leading-5" onClick={toggle}>
            <span className="cr-removed-label">已删除 · </span>
            {kindName}
            {title && <span className="cr-removed-title">{` ${title}`}</span>}
          </div>
          {open && (
            <div className="cr-removed-old mt-1">
              <BlockPreview block={old} folds={folds} />
            </div>
          )}
        </div>
      </div>
    </ChangeRow>
  )
}