#424

2026-10-12 14:46:19 +09:00
@@ -38,6 +38,8 @@ import NicoTagListPage from '@/pages/tags/NicoTagListPage'
 import NotFound from '@/pages/NotFound'
 import TOSPage from '@/pages/TOSPage.mdx'
 import HelpDetailPage from '@/pages/help/HelpDetailPage'
+import HelpChangesPage from '@/pages/help/HelpChangesPage'
+import HelpDiffPage from '@/pages/help/HelpDiffPage'
 import HelpListPage from '@/pages/help/HelpListPage'
 import PostDetailPage from '@/pages/posts/PostDetailPage'
 import PostHistoryPage from '@/pages/posts/PostHistoryPage'
@@ -98,6 +100,8 @@ const RouteTransitionWrapper = ({ animationMode, user, setUser }: {
 	<Route path="/wiki/:id/diff" element={<WikiDiffPage/>}/>
 	<Route path="/wiki/changes" element={<WikiHistoryPage/>}/>
 	<Route path="/help" element={<HelpListPage/>}/>
+	<Route path="/help/changes" element={<HelpChangesPage/>}/>
+	<Route path="/help/:identifier/diff" element={<HelpDiffPage/>}/>
 	<Route path="/help/:identifier" element={<HelpDetailPage/>}/>
 	<Route path="/users/settings" element={<SettingPage user={user} setUser={setUser}/>}/>
 	<Route path="/settings" element={<Navigate to="/users/settings" replace/>}/>
@@ -18,6 +18,18 @@ export type HelpSearchEntry = HelpEditionText & {
    identifier: string
    edition:    string }

+export type HelpEditionContent = HelpEditionText & { content: ComponentType }
+
+export type HelpEditionSource = HelpEditionText & { source: string }
+export type HelpChange = HelpSearchEntry & { pred: string | null }
+export type HelpDiffLine = {
+    type: 'added' | 'removed' | 'unchanged'
+    content: string }
+export type HelpDiff = {
+    from: HelpEditionSource
+    to: HelpEditionSource
+    lines: HelpDiffLine[] }
+
 const articleFiles = import.meta.glob<string> ('../../help/*/article.yml',
 					       { query: '?raw',
 						 import: 'default',
@@ -72,6 +84,18 @@ export const getHelpEditions = (
 }


+export const getHelpPublishedEditions = (
+    identifier: string,
+    language: string,
+): string[] => {
+  const currentEdition = getHelpArticle (identifier)?.languages[language]?.currentEdition
+  return currentEdition == null
+      ? []
+      : getHelpEditions (identifier, language)
+	  .filter (edition => compareEditions (edition, currentEdition) <= 0)
+}
+
+
 export const getHelpEdition = async (
    identifier: string,
    language: string,
@@ -87,28 +111,40 @@ export const getHelpEdition = async (
 }


-export const getHelpEditionText = async (
+export const getHelpEditionSource = async (
    identifier: string,
    language: string,
    edition: string,
-): Promise<HelpEditionText | null> => {
+): Promise<HelpEditionSource | null> => {
  const path = `../../help/${ identifier }/editions/${ language }/${ edition }.mdx`
  const loader = rawEditionFiles[path]

  if (!(loader))
    return null

-  const mdx = (await loader ()).replace (/^\uFEFF/, '')
+  const source = await loader ()
+  const mdx = source.replace (/^\uFEFF/, '')
  const heading = mdx.match (/^# +([^\r\n]+)(?:\r?\n|$)/)

  if (!(heading))
    throw new Error (`Help MDX の先頭に H1 がありません: ${ path }`)

-  return { title: heading[1].trim (),
+  return { source,
+	   title: heading[1].trim (),
 	   body:  mdx.slice (heading[0].length) }
 }


+export const getHelpEditionText = async (
+    identifier: string,
+    language: string,
+    edition: string,
+): Promise<HelpEditionText | null> => {
+  const content = await getHelpEditionSource (identifier, language, edition)
+  return content == null ? null : { title: content.title, body: content.body }
+}
+
+
 export const getHelpSearchEntries = async (
    language: string,
 ): Promise<HelpSearchEntry[]> => {
@@ -130,3 +166,101 @@ export const getHelpSearchEntries = async (

  return entries.filter ((entry): entry is HelpSearchEntry => entry != null)
 }
+
+
+export const getHelpEditionContent = async (
+    identifier: string,
+    language: string,
+    edition: string,
+): Promise<HelpEditionContent | null> => {
+  const [content, text] = await Promise.all ([
+      getHelpEdition (identifier, language, edition),
+      getHelpEditionText (identifier, language, edition)])
+
+  return content != null && text != null ? { content, ...text } : null
+}
+
+
+export const getHelpChanges = async (language: string): Promise<HelpChange[]> => {
+  const articles = Object.values (articleFiles).map (source =>
+      cameliseArticle (parseYAML (source)))
+  const changes = await Promise.all (articles.flatMap (article => {
+    const editions = getHelpPublishedEditions (article.identifier, language)
+    return editions.map (async (edition, index) => {
+      const text = await getHelpEditionText (article.identifier, language, edition)
+      if (text == null)
+	throw new Error (`Help edition が見つかりません: ${ article.identifier }/${ edition }`)
+
+      return { identifier: article.identifier,
+	  edition, pred: editions[index - 1] ?? null, ...text }
+    })
+  }))
+
+  return changes.sort ((a, b) =>
+      compareEditions (b.edition, a.edition)
+      || a.identifier.localeCompare (b.identifier))
+}
+
+
+const diffHelpLines = (from: string, to: string): HelpDiffLine[] => {
+  const before = from.match (/[^\n]*\n|[^\n]+$/g) ?? []
+  const after = to.match (/[^\n]*\n|[^\n]+$/g) ?? []
+  const lengths = Array.from ({ length: before.length + 1 },
+      () => new Uint32Array (after.length + 1))
+
+  for (let i = before.length - 1; i >= 0; --i)
+  {
+    for (let j = after.length - 1; j >= 0; --j)
+    {
+      lengths[i][j] =
+	  before[i] === after[j]
+	  ? lengths[i + 1][j + 1] + 1
+	  : Math.max (lengths[i + 1][j], lengths[i][j + 1])
+    }
+  }
+
+  const lines: HelpDiffLine[] = []
+  let i = 0
+  let j = 0
+  while (i < before.length || j < after.length)
+  {
+    if (i < before.length && j < after.length && before[i] === after[j])
+    {
+      lines.push ({ type: 'unchanged', content: before[i] })
+      ++i
+      ++j
+    }
+    else if (i < before.length
+	     && (j === after.length || lengths[i + 1][j] >= lengths[i][j + 1]))
+    {
+      lines.push ({ type: 'removed', content: before[i] })
+      ++i
+    }
+    else
+    {
+      lines.push ({ type: 'added', content: after[j] })
+      ++j
+    }
+  }
+  return lines
+}
+
+
+export const getHelpDiff = async (
+    identifier: string,
+    language: string,
+    from: string,
+    to: string,
+): Promise<HelpDiff | null> => {
+  const editions = getHelpPublishedEditions (identifier, language)
+  if (!(editions.includes (from)) || !(editions.includes (to)))
+    return null
+
+  const [before, after] = await Promise.all ([
+      getHelpEditionSource (identifier, language, from),
+      getHelpEditionSource (identifier, language, to)])
+  if (before == null || after == null)
+    return null
+
+  return { from: before, to: after, lines: diffHelpLines (before.source, after.source) }
+}
@@ -1,8 +1,13 @@
 import { QueryClient } from '@tanstack/react-query'
 import { match } from 'path-to-regexp'

+import { getHelpArticle,
+	 getHelpChanges,
+	 getHelpDiff,
+	 getHelpEditionContent,
+	 getHelpSearchEntries } from '@/lib/help'
 import { fetchPost, fetchPosts, fetchPostChanges } from '@/lib/posts'
-import { postsKeys, tagsKeys, wikiKeys } from '@/lib/queryKeys'
+import { helpKeys, postsKeys, tagsKeys, wikiKeys } from '@/lib/queryKeys'
 import { fetchNicoTags, fetchTagByName, fetchTag, fetchTagChanges, fetchTags } from '@/lib/tags'
 import { fetchWikiPage,
 	 fetchWikiPageByTitle,
@@ -15,12 +20,69 @@ type Prefetcher = (qc: QueryClient, url: URL) => Promise<void>
 const mPost = match<{ id: string }> ('/posts/:id')
 const mWiki = match<{ title: string }> ('/wiki/:title')
 const mTag = match<{ id: string }> ('/tags/:id')
+const mHelp = match<{ identifier: string }> ('/help/:identifier')
+const mHelpDiff = match<{ identifier: string }> ('/help/:identifier/diff')


 const boolFromQuery = (value: string | null): boolean =>
    ['1', 'true', 'on', 'yes', ''].includes ((value ?? '').toLowerCase ())


+const prefetchHelpIndex: Prefetcher = async qc => {
+  await qc.prefetchQuery ({
+      queryKey: helpKeys.index ('ja'),
+      queryFn: () => getHelpSearchEntries ('ja'),
+      staleTime: Infinity })
+}
+
+
+const prefetchHelpShow: Prefetcher = async (qc, url) => {
+  const matched = mHelp (url.pathname)
+  if (!(matched))
+    return
+
+  const { identifier } = matched.params
+  const language = 'ja'
+  const article = await qc.fetchQuery ({
+      queryKey: helpKeys.article (identifier),
+      queryFn: () => getHelpArticle (identifier),
+      staleTime: Infinity })
+  const edition = url.searchParams.get ('edition') ?? article?.languages[language]?.currentEdition
+  if (edition == null)
+    return
+
+  await qc.prefetchQuery ({
+      queryKey: helpKeys.edition (identifier, language, edition),
+      queryFn: () => getHelpEditionContent (identifier, language, edition),
+      staleTime: Infinity })
+}
+
+
+const prefetchHelpChanges: Prefetcher = async qc => {
+  await qc.prefetchQuery ({
+      queryKey: helpKeys.changes ('ja'),
+      queryFn: () => getHelpChanges ('ja'),
+      staleTime: Infinity })
+}
+
+
+const prefetchHelpDiff: Prefetcher = async (qc, url) => {
+  const matched = mHelpDiff (url.pathname)
+  const fromValues = url.searchParams.getAll ('from')
+  const toValues = url.searchParams.getAll ('to')
+  const [from] = fromValues
+  const [to] = toValues
+  if (!(matched) || fromValues.length !== 1 || toValues.length !== 1 || !(from) || !(to))
+    return
+
+  const { identifier } = matched.params
+  await qc.prefetchQuery ({
+      queryKey: helpKeys.diff (identifier, 'ja', from, to),
+      queryFn: () => getHelpDiff (identifier, 'ja', from, to),
+      staleTime: Infinity })
+}
+
+
 const prefetchWikiPagesIndex: Prefetcher = async (qc, url) => {
  const title = url.searchParams.get ('title') ?? ''

@@ -223,6 +285,13 @@ const prefetchTagChanges: Prefetcher = async (qc, url) => {


 export const routePrefetchers: { test: (u: URL) => boolean; run: Prefetcher }[] = [
+    { test: u => /^\/help\/?$/.test (u.pathname), run: prefetchHelpIndex },
+    { test: u => /^\/help\/changes\/?$/.test (u.pathname), run: prefetchHelpChanges },
+    { test: u => Boolean (mHelpDiff (u.pathname)), run: prefetchHelpDiff },
+    { test: u => {
+	const matched = mHelp (u.pathname)
+	return Boolean (matched && matched.params.identifier !== 'changes')
+      }, run: prefetchHelpShow },
    { test: u => ['/', '/posts', '/posts/search'].includes (u.pathname),
      run: prefetchPostsIndex },
    { test: u => (!(['/posts/new', '/posts/changes', '/posts/search'].includes (u.pathname))
@@ -61,3 +61,13 @@ export const wikiKeys = {
    root:   ['wiki'] as const,
    index:  (p: { title?: string }) => ['wiki', 'index', p] as const,
    show:   (title: string, p: { version?: string }) => ['wiki', title, p] as const }
+
+export const helpKeys = {
+    root:    ['help'] as const,
+    index:   (language: string) => ['help', 'index', language] as const,
+    article: (identifier: string) => ['help', 'article', identifier] as const,
+    edition: (identifier: string, language: string, edition: string) =>
+	     ['help', 'edition', identifier, language, edition] as const,
+    diff: (identifier: string, language: string, from: string, to: string) =>
+	  ['help', 'diff', identifier, language, from, to] as const,
+    changes: (language: string) => ['help', 'changes', language] as const }
@@ -1,3 +1,5 @@
+import { isAxiosError } from 'axios'
+
 import { apiGet } from '@/lib/api'

 import type { WikiPage } from '@/types'
@@ -21,8 +23,10 @@ export const fetchWikiPageByTitle = async (
  {
    return await apiGet (`/wiki/title/${ encodeURIComponent (title) }`, { params: { version } })
  }
-  catch
+  catch (error)
  {
-    return null
+    if (isAxiosError (error) && error.response?.status === 404)
+      return null
+    throw error
  }
 }
@@ -1,4 +1,52 @@
+import { useMemo } from 'react'
+import { useLocation } from 'react-router-dom'
+
+import PrefetchLink from '@/components/PrefetchLink'
+
 import type { MDXComponents } from 'mdx/types'
+import type { ComponentProps } from 'react'


-export const useMDXComponents = (): MDXComponents => ({ })
+const MDXLink = (
+    { href, children, ...props }: ComponentProps<'a'>,
+) => {
+  const location = useLocation ()
+  const url = useMemo (() => {
+    try
+    {
+      const base = new URL (location.pathname + location.search, window.location.origin)
+      return href ? new URL (href, base) : null
+    }
+    catch
+    {
+      return null
+    }
+  }, [href, location.pathname, location.search])
+  const internal = url != null
+      && url.origin === window.location.origin
+      && (url.protocol === 'http:' || url.protocol === 'https:')
+  const anchor = href?.startsWith ('#')
+      || (url?.pathname === location.pathname
+	  && url.search === location.search && Boolean (url.hash))
+  const external = url != null && !(internal)
+      && (url.protocol === 'http:' || url.protocol === 'https:')
+
+  if (internal && !(anchor) && props.download == null)
+  {
+    return (
+	<PrefetchLink to={url.pathname + url.search + url.hash} {...props}>
+	  {children}
+	</PrefetchLink>)
+  }
+
+  return (
+      <a href={href}
+	 {...props}
+	 target={external ? props.target ?? '_blank' : props.target}
+	 rel={props.rel ?? 'noopener noreferrer'}>
+	{children}
+      </a>)
+}
+
+
+export const useMDXComponents = (): MDXComponents => ({ a: MDXLink })
@@ -0,0 +1,78 @@
+import { useQuery } from '@tanstack/react-query'
+import { Helmet } from 'react-helmet-async'
+
+import PrefetchLink from '@/components/PrefetchLink'
+import PageTitle from '@/components/common/PageTitle'
+import MainArea from '@/components/layout/MainArea'
+import { SITE_TITLE } from '@/config'
+import { getHelpChanges } from '@/lib/help'
+import { helpKeys } from '@/lib/queryKeys'
+import { dateString } from '@/lib/utils'
+
+import type { FC } from 'react'
+
+
+const HelpChangesPage: FC = () => {
+  const { data: changes = [], isLoading, error } = useQuery ({
+      queryKey: helpKeys.changes ('ja'),
+      queryFn: () => getHelpChanges ('ja'),
+      staleTime: Infinity })
+
+  return (
+      <MainArea>
+	<Helmet>
+	  <title>{`ヘルプ 変更履歴 | ${ SITE_TITLE }`}</title>
+	</Helmet>
+	<PageTitle>変更履歴</PageTitle>
+
+	{isLoading
+	 ? <p className="mt-4">読み込み中...</p>
+	 : (error
+	    ? <p className="mt-4 text-red-600" role="alert">{error.message}</p>
+	    : (
+		<div className="overflow-x-auto">
+		  <table className="table-auto w-full whitespace-nowrap border-collapse">
+		    <thead className="border-b-2 border-black dark:border-white">
+		      <tr>
+			<th className="p-2 text-left">差分</th>
+			<th className="p-2 text-left">タイトル</th>
+			<th className="p-2 text-left">版</th>
+			<th className="p-2 text-left">変更</th>
+			<th className="p-2 text-left">更新日時</th>
+		      </tr>
+		    </thead>
+		    <tbody>
+		      {changes.map (entry => {
+			const path = `/help/${ encodeURIComponent (entry.identifier) }`
+			const diffQuery = new URLSearchParams ({
+			    from: entry.pred ?? '', to: entry.edition })
+			const updatedAt = `${ entry.edition.split ('.')[0] }T00:00:00`
+
+			return (
+			    <tr key={`${ entry.identifier }/${ entry.edition }`}
+				className="even:bg-gray-100 text-gray-900
+					   dark:even:bg-gray-700 dark:text-gray-100">
+			      <td className="p-2">
+				{entry.pred != null && (
+				    <PrefetchLink to={`${ path }/diff?${ diffQuery.toString () }`}>
+				      差分
+				    </PrefetchLink>)}
+			      </td>
+			      <td className="p-2">
+				<PrefetchLink to={`${ path }?edition=${ entry.edition }`}>
+				  {entry.title}
+				</PrefetchLink>
+			      </td>
+			      <td className="p-2">{entry.edition}</td>
+			      <td className="p-2">{entry.pred == null ? '新規' : '更新'}</td>
+			      <td className="p-2">{dateString (updatedAt, 'hour')}</td>
+			    </tr>)
+		      })}
+		    </tbody>
+		  </table>
+		</div>))}
+      </MainArea>)
+}
+
+
+export default HelpChangesPage
@@ -1,14 +1,16 @@
-import { useEffect, useMemo, useState } from 'react'
+import { useQuery } from '@tanstack/react-query'
+import { useMemo } from 'react'
 import { Helmet } from 'react-helmet-async'
 import { useLocation, useParams } from 'react-router-dom'

 import PrefetchLink from '@/components/PrefetchLink'
 import MainArea from '@/components/layout/MainArea'
 import { SITE_TITLE } from '@/config'
-import { getHelpArticle, getHelpEdition, getHelpEditionText, getHelpEditions } from '@/lib/help'
+import { getHelpArticle, getHelpEditionContent, getHelpEditions } from '@/lib/help'
+import { helpKeys } from '@/lib/queryKeys'
 import NotFound from '@/pages/NotFound'

-import type { FC, ComponentType } from 'react'
+import type { FC } from 'react'


 const HelpDetailPage: FC = () => {
@@ -18,9 +20,10 @@ const HelpDetailPage: FC = () => {
  // Locale 対応が入るまでは ja 固定
  const language = 'ja'

-  const article = useMemo (
-      () => getHelpArticle (identifier),
-      [identifier])
+  const { data: article, isLoading: articleLoading } = useQuery ({
+      queryKey: helpKeys.article (identifier),
+      queryFn: () => getHelpArticle (identifier),
+      staleTime: Infinity })

  const query = new URLSearchParams (location.search)
  const requestedEdition = query.get ('edition')
@@ -39,51 +42,20 @@ const HelpDetailPage: FC = () => {
      ? editions[index + 1]
      : undefined

-  const [loaded, setLoaded] = useState<{ identifier: string
-					 language: string
-					 edition: string
-					 title: string
-					 content: ComponentType | null } | null> (null)
+  const { data: current, isSuccess, isError } = useQuery ({
+      enabled: edition != null && editions.includes (edition),
+      queryKey: helpKeys.edition (identifier, language, edition ?? ''),
+      queryFn: () => getHelpEditionContent (identifier, language, edition ?? ''),
+      staleTime: Infinity })

-  useEffect (() => {
-    if (!(edition))
-      return
-
-    let active = true
-
-    void (async () => {
-      const component = await getHelpEdition (identifier, language, edition)
-      const text = await getHelpEditionText (identifier, language, edition)
-
-      if (active)
-	{
-	  setLoaded ({ identifier,
-		       language,
-		       edition,
-		       title: text?.title ?? '',
-		       content: component })
-	}
-    }) ()
-
-    return () => {
-      active = false
-    }
-  }, [identifier, language, edition])
-
-  if (!(article)
-      || !(languageMeta)
-      || !(edition)
-      || !(editions.includes (edition)))
+  if (!articleLoading
+      && (article == null
+	  || languageMeta == null
+	  || edition == null
+	  || !(editions.includes (edition))))
    return <NotFound/>

-  const current =
-      (loaded?.identifier === identifier
-       && loaded?.language === language
-       && loaded?.edition === edition)
-      ? loaded
-      : null
-
-  if (current && (!(current.content) || !(current.title)))
+  if (isError || (isSuccess && current == null))
    return <NotFound/>

  const Content = current?.content
@@ -0,0 +1,81 @@
+import { useQuery } from '@tanstack/react-query'
+import { Helmet } from 'react-helmet-async'
+import { useParams, useSearchParams } from 'react-router-dom'
+
+import PrefetchLink from '@/components/PrefetchLink'
+import PageTitle from '@/components/common/PageTitle'
+import MainArea from '@/components/layout/MainArea'
+import { SITE_TITLE } from '@/config'
+import { getHelpDiff } from '@/lib/help'
+import { helpKeys } from '@/lib/queryKeys'
+import { cn } from '@/lib/utils'
+import NotFound from '@/pages/NotFound'
+
+import type { FC } from 'react'
+
+const markers = { added: '+ ', removed: '- ', unchanged: '  ' }
+
+
+const HelpDiffPage: FC = () => {
+  const { identifier = '' } = useParams ()
+  const [searchParams] = useSearchParams ()
+  const from = searchParams.get ('from') ?? ''
+  const to = searchParams.get ('to') ?? ''
+  const validParams = Boolean (identifier && from && to)
+      && searchParams.getAll ('from').length === 1
+      && searchParams.getAll ('to').length === 1
+  const { data: diff, isLoading, isError } = useQuery ({
+      enabled: validParams,
+      queryKey: helpKeys.diff (identifier, 'ja', from, to),
+      queryFn: () => getHelpDiff (identifier, 'ja', from, to),
+      staleTime: Infinity })
+
+  if (!(validParams) || isError || (!(isLoading) && diff == null))
+    return <NotFound/>
+
+  const title = `${ diff?.to.title ?? identifier } (${ from } → ${ to })`
+  const path = `/help/${ encodeURIComponent (identifier) }`
+
+  return (
+      <MainArea>
+	<Helmet>
+	  <title>{`ヘルプ 差分: ${ title } | ${ SITE_TITLE }`}</title>
+	</Helmet>
+	<PageTitle>{title}</PageTitle>
+
+	{diff
+	 ? (
+	    <>
+	      <div className="flex flex-wrap items-center gap-3">
+		<PrefetchLink to={`${ path }?edition=${ encodeURIComponent (from) }`}>
+		  {diff.from.title} ({from})
+		</PrefetchLink>
+		<span>→</span>
+		<PrefetchLink to={`${ path }?edition=${ encodeURIComponent (to) }`}>
+		  {diff.to.title} ({to})
+		</PrefetchLink>
+	      </div>
+	      <pre className="mt-4 overflow-x-auto whitespace-pre">
+		<code>
+		  {diff.lines.map ((line, index) => {
+		    const colour = cn (
+			'block text-gray-900 dark:text-gray-100',
+			line.type === 'added' && 'bg-green-200 dark:bg-green-800',
+			line.type === 'added' && 'text-green-950 dark:text-green-50',
+			line.type === 'removed' && 'bg-red-200 dark:bg-red-800',
+			line.type === 'removed' && 'text-red-950 dark:text-red-50')
+
+		    return (
+			<span key={index} className={colour}>
+			  {markers[line.type]}{line.content.replace (/\r?\n$/, '')}
+			</span>)
+		  })}
+		</code>
+	      </pre>
+	    </>)
+	 : <div>Loading...</div>}
+      </MainArea>)
+}
+
+
+export default HelpDiffPage
@@ -1,56 +1,54 @@
+import { useQuery } from '@tanstack/react-query'
 import { useEffect, useMemo, useState } from 'react'
 import { Helmet } from 'react-helmet-async'
+import { useSearchParams } from 'react-router-dom'

 import PrefetchLink from '@/components/PrefetchLink'
+import SortHeader from '@/components/SortHeader'
 import FormField from '@/components/common/FormField'
 import PageTitle from '@/components/common/PageTitle'
 import MainArea from '@/components/layout/MainArea'
 import { SITE_TITLE } from '@/config'
 import { getHelpSearchEntries } from '@/lib/help'
+import { helpKeys } from '@/lib/queryKeys'
 import { dateString, inputClass } from '@/lib/utils'

 import type { FormEvent, FC } from 'react'

-import type { HelpSearchEntry } from '@/lib/help'
-
 type SearchConditions = { title: string; text: string }
+type HelpOrderField = 'title' | 'updated_at'
+type HelpOrder = `${ HelpOrderField }:${ 'asc' | 'desc' }`
+
+const defaultDirection: Record<HelpOrderField, 'asc' | 'desc'> = {
+    title: 'asc', updated_at: 'desc' }


 const HelpSearchPage: FC = () => {
-  const [title, setTitle] = useState ('')
-  const [text, setText] = useState ('')
-  const [conditions, setConditions] = useState<SearchConditions> ({ title: '', text: '' })
-  const [entries, setEntries] = useState<HelpSearchEntry[]> ([])
-  const [loading, setLoading] = useState (true)
-  const [error, setError] = useState<string | null> (null)
+  const [searchParams, setSearchParams] = useSearchParams ()
+  const requestedOrder = searchParams.get ('order') ?? 'updated_at:desc'
+  const order: HelpOrder =
+      ['title:asc', 'title:desc', 'updated_at:asc', 'updated_at:desc'].includes (requestedOrder)
+      ? requestedOrder as HelpOrder
+      : 'updated_at:desc'
+  const conditions = useMemo<SearchConditions> (() => ({
+      title: searchParams.get ('title') ?? '',
+      text: searchParams.get ('text') ?? '' }), [searchParams])
+  const [title, setTitle] = useState (conditions.title)
+  const [text, setText] = useState (conditions.text)
+  const { data: entries = [], isLoading: loading, error } = useQuery ({
+      queryKey: helpKeys.index ('ja'),
+      queryFn: () => getHelpSearchEntries ('ja'),
+      staleTime: Infinity })

  useEffect (() => {
-    let active = true
-
-    void (async () => {
-      try
-      {
-	if (active)
-	  setEntries (await getHelpSearchEntries ('ja'))
-      }
-      catch (err)
-      {
-	if (active)
-	  setError (err instanceof Error ? err.message : '取得に失敗しました．')
-      }
-      finally
-      {
-	if (active)
-	  setLoading (false)
-      }
-    }) ()
-
-    return () => { active = false }
-  }, [])
+    setTitle (conditions.title)
+    setText (conditions.text)
+  }, [conditions.title, conditions.text])

  const results = useMemo (() => {
    const titleQuery = conditions.title.trim ().normalize ('NFKC').toLowerCase ()
    const textQuery = conditions.text.trim ().normalize ('NFKC').toLowerCase ()
+    const [field, direction] = order.split (':')

    return (
 	entries.filter (entry => (
@@ -58,12 +56,30 @@ const HelpSearchPage: FC = () => {
 	     || entry.title.normalize ('NFKC').toLowerCase ().includes (titleQuery))
 	    && (!(textQuery)
 		|| entry.body.normalize ('NFKC').toLowerCase ().includes (textQuery))))
-	.sort ((a, b) => a.title.localeCompare (b.title, 'ja')))
-  }, [entries, conditions])
+	.sort ((a, b) => {
+	  const [dateA, revisionA = '1'] = a.edition.split ('.')
+	  const [dateB, revisionB = '1'] = b.edition.split ('.')
+	  const comparison = field === 'title'
+	      ? a.title.localeCompare (b.title, 'ja')
+	      : (dateA.localeCompare (dateB) || Number (revisionA) - Number (revisionB))
+
+	  return (direction === 'asc' ? comparison : -comparison)
+	      || a.identifier.localeCompare (b.identifier)
+	}))
+  }, [entries, conditions, order])

  const handleSearch = (ev: FormEvent<HTMLFormElement>) => {
    ev.preventDefault ()
-    setConditions ({ title, text })
+    const next = new URLSearchParams (searchParams)
+    if (title)
+      next.set ('title', title)
+    else
+      next.delete ('title')
+    if (text)
+      next.set ('text', text)
+    else
+      next.delete ('text')
+    setSearchParams (next)
  }

  return (
@@ -105,15 +121,27 @@ const HelpSearchPage: FC = () => {
 	{loading
 	 ? <p className="mt-4">読み込み中...</p>
 	 : (error
-	    ? <p className="mt-4 text-red-600" role="alert">{error}</p>
+	    ? <p className="mt-4 text-red-600" role="alert">{error.message}</p>
 	    : (
 		<div className="mt-4">
 		  <p className="mb-2 text-sm" aria-live="polite">{results.length} 件</p>
 		  <table className="table-auto w-full border-collapse">
 		    <thead className="border-b-2 border-black dark:border-white">
 		      <tr>
-			<th className="p-2 text-left">タイトル</th>
-			<th className="p-2 text-left">最終更新</th>
+			<th className="p-2 text-left">
+			  <SortHeader<HelpOrderField>
+			      by="title"
+			      label="タイトル"
+			      currentOrder={order}
+			      defaultDirection={defaultDirection}/>
+			</th>
+			<th className="p-2 text-left">
+			  <SortHeader<HelpOrderField>
+			      by="updated_at"
+			      label="最終更新"
+			      currentOrder={order}
+			      defaultDirection={defaultDirection}/>
+			</th>
 		      </tr>
 		    </thead>
 		    <tbody>
@@ -1,6 +1,4 @@
-import type { FC } from 'react'
-
-import { useQuery } from '@tanstack/react-query'
+import { useQuery, useQueryClient } from '@tanstack/react-query'
 import { useEffect, useMemo } from 'react'
 import { Helmet } from 'react-helmet-async'
 import { useLocation, useNavigate, useParams } from 'react-router-dom'
@@ -13,11 +11,14 @@ import TabGroup, { Tab } from '@/components/common/TabGroup'
 import MainArea from '@/components/layout/MainArea'
 import { SITE_TITLE } from '@/config'
 import { WikiIdBus } from '@/lib/eventBus/WikiIdBus'
+import { getHelpChanges } from '@/lib/help'
 import { fetchPosts } from '@/lib/posts'
-import { postsKeys, tagsKeys, wikiKeys } from '@/lib/queryKeys'
-import { getHelpSearchEntries } from '@/lib/help'
+import { helpKeys, postsKeys, tagsKeys, wikiKeys } from '@/lib/queryKeys'
 import { fetchTagByName } from '@/lib/tags'
 import { fetchWikiPage, fetchWikiPageByTitle } from '@/lib/wiki'
+import NotFound from '@/pages/NotFound'
+
+import type { FC } from 'react'

 import type { Tag } from '@/types'

@@ -28,28 +29,46 @@ const WikiDetailPage: FC = () => {

  const location = useLocation ()
  const navigate = useNavigate ()
-
-  void (async () => {
-    const identifier =
-	(await getHelpSearchEntries ('ja'))
-	.find (entry => (entry.title.trim ().normalize ('NFKC').toLowerCase ()
-			 === (title.trim ().normalize ('NFKC').toLowerCase ()
-			      .replace (/^ヘルプ:/, ''))))
-	.identifier
-
-    navigate (`/help/${ identifier }`, { replace: true })
-  }) ()
+  const queryClient = useQueryClient ()

  const defaultTag = useMemo (() => ({ name: title, category: 'general' } as Tag), [title])

  const query = new URLSearchParams (location.search)
  const version = query.get ('version') || undefined

-  const { data: wikiPage, isLoading: loading } = useQuery ({
+  const { data: wikiPage, isLoading: loading, isSuccess, isFetching } = useQuery ({
      enabled:  Boolean (title) && !(/^\d+$/.test (title)),
      queryKey: wikiKeys.show (title, { version }),
      queryFn:  () => fetchWikiPageByTitle (title, { version }) })

+  useEffect (() => {
+    if (!(isSuccess) || isFetching || wikiPage != null)
+      return
+
+    let active = true
+    const lookupTitle = title.trim ().normalize ('NFKC').toLowerCase ().replace (/^ヘルプ:/, '')
+
+    void queryClient.fetchQuery ({
+	queryKey: helpKeys.changes ('ja'),
+	queryFn: () => getHelpChanges ('ja'),
+	staleTime: Infinity }).then (changes => {
+      if (!(active))
+	return
+
+      const identifiers = new Set (changes
+	  .filter (entry => entry.title.trim ().normalize ('NFKC').toLowerCase () === lookupTitle)
+	  .map (entry => entry.identifier))
+      if (identifiers.size === 1)
+	navigate (`/help/${ encodeURIComponent ([...identifiers][0]) }`, { replace: true })
+    }).catch (() => {
+      // A failed Help lookup leaves the original missing Wiki URL in place.
+    })
+
+    return () => {
+      active = false
+    }
+  }, [isSuccess, isFetching, wikiPage, title, version, queryClient, navigate])
+
  const effectiveTitle = wikiPage?.title ?? title
  const deprecated = wikiPage?.deprecatedAt != null

@@ -85,19 +104,28 @@ const WikiDetailPage: FC = () => {
    if (!(/^\d+$/.test (title)))
      return

+    let active = true
    void (async () => {
      try
      {
 	const data = await fetchWikiPage (title, { })
-	navigate (`/wiki/${ encodeURIComponent(data.title) }`, { replace: true })
+	if (active)
+	  navigate (`/wiki/${ encodeURIComponent (data.title) }`, { replace: true })
      }
      catch
      {
 	;
      }
    }) ()
+
+    return () => {
+      active = false
+    }
  }, [title, navigate])

+  if (isSuccess && wikiPage == null)
+    return <NotFound/>
+
  return (
      <MainArea>
 	<Helmet>