#140 ぼちぼち

frontend/package-lock.json

@@ -13,6 +13,7 @@
         "@radix-ui/react-dialog": "^1.1.14",
         "@radix-ui/react-switch": "^1.2.5",
         "@radix-ui/react-toast": "^1.2.14",
+        "@tanstack/react-query": "^5.90.2",
         "axios": "^1.10.0",
         "camelcase-keys": "^9.1.3",
         "class-variance-authority": "^0.7.1",
@@ -20,6 +21,7 @@
         "humps": "^2.0.1",
         "lucide-react": "^0.511.0",
         "markdown-it": "^14.1.0",
+        "path-to-regexp": "^8.3.0",
         "react": "^19.1.0",
         "react-dom": "^19.1.0",
         "react-helmet-async": "^2.0.5",
@@ -28,7 +30,8 @@
         "react-router-dom": "^6.30.0",
         "react-youtube": "^10.1.0",
         "remark-gfm": "^4.0.1",
-        "tailwind-merge": "^3.3.0"
+        "tailwind-merge": "^3.3.0",
+        "zustand": "^5.0.8"
       },
       "devDependencies": {
         "@eslint/js": "^9.25.0",
@@ -1908,6 +1911,32 @@
         "win32"
       ]
     },
+    "node_modules/@tanstack/query-core": {
+      "version": "5.90.2",
+      "resolved": "https://registry.npmjs.org/@tanstack/query-core/-/query-core-5.90.2.tgz",
+      "integrity": "sha512-k/TcR3YalnzibscALLwxeiLUub6jN5EDLwKDiO7q5f4ICEoptJ+n9+7vcEFy5/x/i6Q+Lb/tXrsKCggf5uQJXQ==",
+      "license": "MIT",
+      "funding": {
+        "type": "github",
+        "url": "https://github.com/sponsors/tannerlinsley"
+      }
+    },
+    "node_modules/@tanstack/react-query": {
+      "version": "5.90.2",
+      "resolved": "https://registry.npmjs.org/@tanstack/react-query/-/react-query-5.90.2.tgz",
+      "integrity": "sha512-CLABiR+h5PYfOWr/z+vWFt5VsOA2ekQeRQBFSKlcoW6Ndx/f8rfyVmq4LbgOM4GG2qtxAxjLYLOpCNTYm4uKzw==",
+      "license": "MIT",
+      "dependencies": {
+        "@tanstack/query-core": "5.90.2"
+      },
+      "funding": {
+        "type": "github",
+        "url": "https://github.com/sponsors/tannerlinsley"
+      },
+      "peerDependencies": {
+        "react": "^18 || ^19"
+      }
+    },
     "node_modules/@types/axios": {
       "version": "0.14.4",
       "resolved": "https://registry.npmjs.org/@types/axios/-/axios-0.14.4.tgz",
@@ -5452,6 +5481,16 @@
       "dev": true,
       "license": "ISC"
     },
+    "node_modules/path-to-regexp": {
+      "version": "8.3.0",
+      "resolved": "https://registry.npmjs.org/path-to-regexp/-/path-to-regexp-8.3.0.tgz",
+      "integrity": "sha512-7jdwVIRtsP8MYpdXSwOS0YdD0Du+qOoF/AEPIt88PcCFrZCzx41oxku1jD88hZBwbNUIEfpqvuhjFaMAqMTWnA==",
+      "license": "MIT",
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/express"
+      }
+    },
     "node_modules/picocolors": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/picocolors/-/picocolors-1.1.1.tgz",
@@ -7186,6 +7225,35 @@
       "integrity": "sha512-Tpp60P6IUJDTuOq/5Z8cdskzJujfwqfOTkrwIwj7IRISpnkJnT6SyJ4PCPnGMoFjC9ddhal5KVIYtAt97ix05A==",
       "license": "MIT"
     },
+    "node_modules/zustand": {
+      "version": "5.0.8",
+      "resolved": "https://registry.npmjs.org/zustand/-/zustand-5.0.8.tgz",
+      "integrity": "sha512-gyPKpIaxY9XcO2vSMrLbiER7QMAMGOQZVRdJ6Zi782jkbzZygq5GI9nG8g+sMgitRtndwaBSl7uiqC49o1SSiw==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=12.20.0"
+      },
+      "peerDependencies": {
+        "@types/react": ">=18.0.0",
+        "immer": ">=9.0.6",
+        "react": ">=18.0.0",
+        "use-sync-external-store": ">=1.2.0"
+      },
+      "peerDependenciesMeta": {
+        "@types/react": {
+          "optional": true
+        },
+        "immer": {
+          "optional": true
+        },
+        "react": {
+          "optional": true
+        },
+        "use-sync-external-store": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/zwitch": {
       "version": "2.0.4",
       "resolved": "https://registry.npmjs.org/zwitch/-/zwitch-2.0.4.tgz",

frontend/package.json

@@ -15,6 +15,7 @@
     "@radix-ui/react-dialog": "^1.1.14",
     "@radix-ui/react-switch": "^1.2.5",
     "@radix-ui/react-toast": "^1.2.14",
+    "@tanstack/react-query": "^5.90.2",
     "axios": "^1.10.0",
     "camelcase-keys": "^9.1.3",
     "class-variance-authority": "^0.7.1",
@@ -22,6 +23,7 @@
     "humps": "^2.0.1",
     "lucide-react": "^0.511.0",
     "markdown-it": "^14.1.0",
+    "path-to-regexp": "^8.3.0",
     "react": "^19.1.0",
     "react-dom": "^19.1.0",
     "react-helmet-async": "^2.0.5",
@@ -30,7 +32,8 @@
     "react-router-dom": "^6.30.0",
     "react-youtube": "^10.1.0",
     "remark-gfm": "^4.0.1",
-    "tailwind-merge": "^3.3.0"
+    "tailwind-merge": "^3.3.0",
+    "zustand": "^5.0.8"
   },
   "devDependencies": {
     "@eslint/js": "^9.25.0",

frontend/src/App.tsx

@@ -1,8 +1,9 @@
 import axios from 'axios'
 import toCamel from 'camelcase-keys'
 import { useEffect, useState } from 'react'
-import { BrowserRouter, Navigate, Route, Routes } from 'react-router-dom'
+import { BrowserRouter, Navigate, Route, Routes, useLocation } from 'react-router-dom'
 
+import RouteBlockerOverlay from '@/components/RouteBlockerOverlay'
 import TopNav from '@/components/TopNav'
 import { Toaster } from '@/components/ui/toaster'
 import { API_BASE_URL } from '@/config'
@@ -25,6 +26,13 @@ import type { FC } from 'react'
 import type { User } from '@/types'
 
 
+const PostDetailRoute = ({ user }: { user: User | null }) => {
+  const location = useLocation ()
+  const key = location.pathname
+  return <PostDetailPage key={key} user={user}/>
+}
+
+
 export default (() => {
   const [user, setUser] = useState<User | null> (null)
   const [status, setStatus] = useState (200)
@@ -71,6 +79,8 @@ export default (() => {
   }
 
   return (
+      <>
+	<RouteBlockerOverlay/>
 	<BrowserRouter>
 	  <div className="flex flex-col h-screen w-screen">
 	    <TopNav user={user}/>
@@ -78,7 +88,7 @@ export default (() => {
 	      <Route path="/" element={<Navigate to="/posts" replace/>}/>
 	      <Route path="/posts" element={<PostListPage/>}/>
 	      <Route path="/posts/new" element={<PostNewPage user={user}/>}/>
-	    <Route path="/posts/:id" element={<PostDetailPage user={user}/>}/>
+	      <Route path="/posts/:id" element={<PostDetailRoute user={user}/>}/>
 	      <Route path="/tags/nico" element={<NicoTagListPage user={user}/>}/>
 	      <Route path="/wiki" element={<WikiSearchPage/>}/>
 	      <Route path="/wiki/:title" element={<WikiDetailPage/>}/>
@@ -92,5 +102,6 @@ export default (() => {
 	    </Routes>
 	  </div>
 	  <Toaster/>
-      </BrowserRouter>)
+	</BrowserRouter>
+      </>)
 }) satisfies FC

frontend/src/components/PostList.tsx

@@ -1,4 +1,4 @@
-import { Link } from 'react-router-dom'
+import PrefetchLink from '@/components/PrefetchLink'
 
 import type { FC, MouseEvent } from 'react'
 
@@ -11,7 +11,8 @@ type Props = { posts:     Post[]
 export default (({ posts, onClick }: Props) => (
     <div className="flex flex-wrap gap-6 p-4">
       {posts.map ((post, i) => (
-	  <Link to={`/posts/${ post.id }`}
+	  <PrefetchLink
+	      to={`/posts/${ post.id }`}
 	      key={post.id}
 	      className="w-40 h-40 overflow-hidden rounded-lg shadow-md hover:shadow-lg"
 	      onClick={onClick}>
@@ -21,5 +22,5 @@ export default (({ posts, onClick }: Props) => (
 		 loading={i < 12 ? 'eager' : 'lazy'}
 		 decoding="async"
 		 className="object-cover w-full h-full"/>
-	  </Link>))}
+	  </PrefetchLink>))}
     </div>)) satisfies FC<Props>

frontend/src/components/PrefetchLink.tsx

@@ -0,0 +1,87 @@
+import { useQueryClient } from '@tanstack/react-query'
+import { useMemo } from 'react'
+import { createPath, useNavigate } from 'react-router-dom'
+
+import { useOverlayStore } from '@/components/RouteBlockerOverlay'
+import { prefetchForURL } from '@/lib/prefetchers'
+import { cn } from '@/lib/utils'
+
+import type { AnchorHTMLAttributes, FC, MouseEvent, TouchEvent } from 'react'
+import type { To } from 'react-router-dom'
+
+type Props = AnchorHTMLAttributes<HTMLAnchorElement> & {
+    to:             To
+    replace?:       boolean
+    className?:     string
+    cancelOnError?: boolean }
+
+
+export default (({ to,
+		   replace,
+		   className,
+		   onMouseEnter,
+		   onTouchStart,
+		   onClick,
+		   cancelOnError = false,
+		   ...rest }: Props) => {
+  const navigate = useNavigate ()
+  const qc = useQueryClient ()
+  const url = useMemo (() => {
+    const path = (typeof to === 'string') ? to : createPath (to)
+    return (new URL (path, location.origin)).toString ()
+  }, [to])
+  const setOverlay = useOverlayStore (s => s.setActive)
+
+  const doPrefetch = async () => {
+    try
+    {
+      await prefetchForURL (qc, url)
+      return true
+    }
+    catch (e)
+    {
+      console.error ('データ取得エラー', e)
+      return false
+    }
+  }
+
+  const handleMouseEnter = async (ev: MouseEvent<HTMLAnchorElement>) => {
+    onMouseEnter?.(ev)
+    doPrefetch ()
+  }
+
+  const handleTouchStart = async (ev: TouchEvent<HTMLAnchorElement>) => {
+    onTouchStart?.(ev)
+    doPrefetch ()
+  }
+
+  const handleClick = async (ev: MouseEvent<HTMLAnchorElement>) => {
+    onClick?.(ev)
+
+    if (ev.defaultPrevented
+	|| ev.metaKey
+	|| ev.ctrlKey
+	|| ev.shiftKey
+	|| ev.altKey)
+      return
+
+    ev.preventDefault ()
+
+    setOverlay (true)
+    const ok = await doPrefetch ()
+    setOverlay (false)
+
+    if (!(ok) && cancelOnError)
+      return
+
+    navigate (to, { replace })
+  }
+
+  return (
+      <a href={typeof to === 'string' ? to : createPath (to)}
+	 onMouseEnter={handleMouseEnter}
+	 onTouchStart={handleTouchStart}
+	 onClick={handleClick}
+	 className={cn ('cursor-pointer', className)}
+	 {...rest}/>)
+}) satisfies FC<Props>

frontend/src/components/RouteBlockerOverlay.tsx

@@ -0,0 +1,46 @@
+import { useEffect } from 'react'
+import { create } from 'zustand'
+
+import type { FC } from 'react'
+
+type OverlayStore = {
+    active:     boolean
+    setActive:  (v: boolean) => void }
+
+
+export const useOverlayStore = create<OverlayStore> (set => ({
+    active:     false,
+    setActive:  v => set ({ active: v }) }))
+
+
+export default (() => {
+  const active = useOverlayStore (s => s.active)
+
+  useEffect (() => {
+    if (active)
+      {
+	document.body.style.overflow = 'hidden'
+	document.body.setAttribute ('aria-busy', 'true')
+      }
+    else
+      {
+	document.body.style.overflow = ''
+	document.body.removeAttribute ('aria-busy')
+      }
+  }, [active])
+
+  if (!(active))
+    return null
+
+  return (
+      <div
+	  role="progressbar"
+	  aria-label="Loading"
+	  className="fixed inset-0 z-[9999] bg-black/50 backdrop-blur-sm pointer-events-auto">
+	<div className="absolute inset-0 flex items-center justify-center">
+	  <div className="rounded-2xl bg-black/60 text-white px-6 py-3 text-sm">
+	    Loading...
+	  </div>
+	</div>
+      </div>)
+}) satisfies FC

frontend/src/components/TagLink.tsx

@@ -1,5 +1,6 @@
 import { Link } from 'react-router-dom'
 
+import PrefetchLink from '@/components/PrefetchLink'
 import { LIGHT_COLOUR_SHADE, DARK_COLOUR_SHADE, TAG_COLOUR } from '@/consts'
 import { cn } from '@/lib/utils'
 
@@ -9,7 +10,8 @@ import type { Tag } from '@/types'
 
 type CommonProps = { tag:         Tag
 		     withWiki?:   boolean
-		     withCount?:  boolean }
+		     withCount?:  boolean
+		     prefetch?:   boolean }
 
 type PropsWithLink =
     CommonProps & { linkFlg?: true } & Partial<ComponentProps<typeof Link>>
@@ -24,6 +26,7 @@ export default (({ tag,
 		   linkFlg   = true,
 		   withWiki  = true,
 		   withCount = true,
+		   prefetch  = false,
 		   ...props }: Props) => {
   const spanClass = cn (
       `text-${ TAG_COLOUR[tag.category] }-${ LIGHT_COLOUR_SHADE }`,
@@ -44,7 +47,15 @@ export default (({ tag,
 	    </span>)}
 	{linkFlg
 	 ? (
-	    <Link to={`/posts?${ (new URLSearchParams ({ tags: tag.name })).toString () }`}
+	    prefetch
+	    ? <PrefetchLink
+		  to={`/posts?${ (new URLSearchParams ({ tags: tag.name })).toString () }`}
+		  className={linkClass}
+		  {...props}>
+		{tag.name}
+	      </PrefetchLink>
+	    : <Link
+		  to={`/posts?${ (new URLSearchParams ({ tags: tag.name })).toString () }`}
 		  className={linkClass}
 		  {...props}>
 		{tag.name}

frontend/src/components/TagSidebar.tsx

@@ -10,16 +10,17 @@ import { API_BASE_URL } from '@/config'
 import { CATEGORIES } from '@/consts'
 import { cn } from '@/lib/utils'
 
-import type { FC } from 'react'
+import type { FC, MouseEvent } from 'react'
 
 import type { Post, Tag } from '@/types'
 
 type TagByCategory = Record<string, Tag[]>
 
-type Props = { posts: Post[] }
+type Props = { posts:     Post[]
+	       onClick?:  (event: MouseEvent<HTMLElement>) => void }
 
 
-export default (({ posts }: Props) => {
+export default (({ posts, onClick }: Props) => {
   const navigate = useNavigate ()
 
   const [tagsVsbl, setTagsVsbl] = useState (false)
@@ -64,11 +65,11 @@ export default (({ posts }: Props) => {
 	<div className={cn (!(tagsVsbl) && 'hidden', 'md:block mt-4')}>
 	  <SectionTitle>タグ</SectionTitle>
 	  <ul>
-	    {CATEGORIES.flatMap (cat => cat in tags ? (
+	    {CATEGORIES.flatMap (cat => cat in tags ?
 		tags[cat].map (tag => (
 		    <li key={tag.id} className="mb-1">
-		      <TagLink tag={tag}/>
+		      <TagLink tag={tag} prefetch onClick={onClick}/>
-		    </li>))) : [])}
+		    </li>)) : [])}
 	  </ul>
 	  <SectionTitle>関聯</SectionTitle>
 	  {posts.length > 0 && (

frontend/src/lib/posts.ts

@@ -0,0 +1,37 @@
+import axios from 'axios'
+import toCamel from 'camelcase-keys'
+
+import { API_BASE_URL } from '@/config'
+
+import type { Post } from '@/types'
+
+
+export const fetchPosts = async ({ tags, match, limit, cursor }: {
+    tags:     string
+    match:    'any' | 'all'
+    limit:    number
+    cursor?:  string }): Promise<{ posts: Post[]; nextCursor: string }> => {
+  const res = await axios.get (`${ API_BASE_URL }/posts`, {
+      params: { tags, match, limit, ...(cursor && { cursor }) } })
+
+  return toCamel (res.data as any, { deep: true }) as { posts:      Post[]
+							nextCursor: string }
+}
+
+
+export const fetchPost = async (id: string): Promise<Post> => {
+  const res = await axios.get (`${ API_BASE_URL }/posts/${ id }`, {
+      headers: { 'X-Transfer-Code': localStorage.getItem ('user_code') ?? '' } })
+
+  return toCamel (res.data as any, { deep: true }) as Post
+}
+
+
+export const toggleViewedFlg = async (id: string, viewed: boolean): Promise<void> => {
+  const url = `${ API_BASE_URL }/posts/${ id }/viewed`
+  const opt = { headers: { 'X-Transfer-Code': localStorage.getItem ('user_code') ?? '' } }
+  if (viewed)
+    await axios.post (url, { }, opt)
+  else
+    await axios.delete (url, opt)
+}

frontend/src/lib/prefetchers.ts

@@ -0,0 +1,45 @@
+import { QueryClient } from '@tanstack/react-query'
+import { match } from 'path-to-regexp'
+
+import { fetchPost, fetchPosts } from '@/lib/posts'
+
+type Prefetcher = (qc: QueryClient, url: URL) => Promise<void>
+
+const mPost = match<{ id: string }> ('/posts/:id')
+
+
+const prefetchPostsIndex: Prefetcher = async (qc, url) => {
+  const tags = url.searchParams.get ('tags') ?? ''
+  const match = url.searchParams.get ('match') === 'any' ? 'any' : 'all'
+  const limit = Number (url.searchParams.get ('limit') || 20)
+  await qc.prefetchQuery ({
+      queryKey: ['posts', 'index', { tags, match, limit }],
+      queryFn:  () => fetchPosts ({ tags, match, limit }) })
+}
+
+
+const prefetchPostShow: Prefetcher = async (qc, url) => {
+  const m = mPost (url.pathname)
+  if (!(m))
+    return
+
+  const { id } = m.params
+  await qc.prefetchQuery ({
+      queryKey: ['posts', id],
+      queryFn:  () => fetchPost (id) })
+}
+
+
+export const routePrefetchers: { test: (u: URL) => boolean; run: Prefetcher }[] = [
+    { test: u => u.pathname === '/' || u.pathname === '/posts', run: prefetchPostsIndex },
+    { test: u => Boolean (mPost (u.pathname)), run: prefetchPostShow }]
+
+
+export const prefetchForURL = async (qc: QueryClient, urlLike: string): Promise<void> => {
+  const u = new URL (urlLike, location.origin)
+  const jobs = routePrefetchers.filter (r => r.test (u)).map (r => r.run (qc, u))
+  if (jobs.length === 0)
+    return
+
+  await Promise.all (jobs)
+}

frontend/src/main.tsx

@@ -1,3 +1,4 @@
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
 import { createRoot } from 'react-dom/client'
 import { HelmetProvider } from 'react-helmet-async'
 
@@ -6,7 +7,15 @@ import App from '@/App'
 
 const helmetContext = { }
 
+const client = new QueryClient ({
+    defaultOptions: {
+	queries: { staleTime: 5 * 60 * 1000,
+		   gcTime:    30 * 60 * 1000,
+		   retry:     1 }}})
+
 createRoot (document.getElementById ('root')!).render (
     <HelmetProvider context={helmetContext}>
+      <QueryClientProvider client={client}>
 	<App/>
+      </QueryClientProvider>
     </HelmetProvider>)

frontend/src/pages/posts/PostDetailPage.tsx

@@ -1,5 +1,4 @@
-import axios from 'axios'
+import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
-import toCamel from 'camelcase-keys'
 import { useEffect, useState } from 'react'
 import { Helmet } from 'react-helmet-async'
 import { useParams } from 'react-router-dom'
@@ -12,14 +11,15 @@ import TabGroup, { Tab } from '@/components/common/TabGroup'
 import MainArea from '@/components/layout/MainArea'
 import { Button } from '@/components/ui/button'
 import { toast } from '@/components/ui/use-toast'
-import { API_BASE_URL, SITE_TITLE } from '@/config'
+import { SITE_TITLE } from '@/config'
+import { fetchPost, toggleViewedFlg } from '@/lib/posts'
 import { cn } from '@/lib/utils'
 import NotFound from '@/pages/NotFound'
 import ServiceUnavailable from '@/pages/ServiceUnavailable'
 
 import type { FC } from 'react'
 
-import type { Post, User } from '@/types'
+import type { User } from '@/types'
 
 type Props = { user: User | null }
 
@@ -27,48 +27,50 @@ type Props = { user: User | null }
 export default (({ user }: Props) => {
   const { id } = useParams ()
 
-  const [post, setPost] = useState<Post | null> (null)
+  const { data: post, isError: errorFlg, error } = useQuery ({
+      enabled:          Boolean (id),
+      queryKey:         ['posts', String (id)],
+      queryFn:          () => fetchPost (String (id)),
+      placeholderData:  undefined })
+
+  const qc = useQueryClient ()
+
   const [status, setStatus] = useState (200)
 
-  const changeViewedFlg = async () => {
+  const changeViewedFlg = useMutation ({
-    const url = `${ API_BASE_URL }/posts/${ id }/viewed`
+      mutationFn: async () => {
-    const opt = { headers: { 'X-Transfer-Code': localStorage.getItem ('user_code') || '' } }
+	const next = !(post!.viewed)
-    try
+	await toggleViewedFlg (id!, next)
-    {
+	return next
-      if (post!.viewed)
+      },
-	await axios.delete (url, opt)
+      onMutate: async () => {
-      else
+	await qc.cancelQueries ({ queryKey: ['posts', String (id)] })
-	await axios.post (url, { }, opt)
+	const prev = qc.getQueryData<any> (['posts', String (id)])
-
+	qc.setQueryData (['posts', String (id)],
-      // 通信に成功したら “閲覧済” をトグル
+			 (cur: any) => cur ? { ...cur, viewed: !(cur.viewed) } : cur)
-      setPost (post => ({ ...post!, viewed: !(post!.viewed) }))
+	return { prev }
-    }
+      },
-    catch
+      onError: (...[, , ctx]) => {
-    {
+	if (ctx?.prev)
+	  qc.setQueryData (['posts', String (id)], ctx.prev)
 	toast ({ title: '失敗……', description: '通信に失敗しました……' })
-    }
+      },
-  }
+      onSuccess: () => {
+	qc.invalidateQueries ({ queryKey: ['posts', 'index'] })
+	qc.invalidateQueries ({ queryKey: ['related', String (id)] })
+      } })
 
   useEffect (() => {
-    setPost (null)
+    if (!(errorFlg))
-
-    if (!(id))
       return
 
-    const fetchPost = async () => {
+    const code = (error as any)?.response.status ?? (error as any)?.status
-      try
+    if (code)
-      {
+      setStatus (code)
-	const res = await axios.get (`${ API_BASE_URL }/posts/${ id }`, { headers: {
+  }, [errorFlg, error])
-	    'X-Transfer-Code': localStorage.getItem ('user_code') ?? '' } })
+
-	setPost (toCamel (res.data as any, { deep: true }) as Post)
+  useEffect (() => {
-      }
+    setStatus (200)
-      catch (err)
-      {
-	if (axios.isAxiosError (err))
-	  setStatus (err.status ?? 200)
-      }
-    }
-    fetchPost ()
   }, [id])
 
   switch (status)
@@ -90,15 +92,18 @@ export default (({ user }: Props) => {
 	      <meta name="thumbnail" content={post.thumbnail || post.thumbnailBase}/>)}
 	  {post && <title>{`${ post.title || post.url } | ${ SITE_TITLE }`}</title>}
 	</Helmet>
+
 	<div className="hidden md:block">
-	  <TagDetailSidebar post={post}/>
+	  <TagDetailSidebar post={post ?? null}/>
 	</div>
+
 	<MainArea>
 	  {post
 	   ? (
 	      <>
 		<PostEmbed post={post}/>
-		<Button onClick={changeViewedFlg}
+		<Button onClick={() => changeViewedFlg.mutate ()}
+			disabled={changeViewedFlg.isPending}
 			className={cn ('text-white', viewedClass)}>
 		  {post.viewed ? '閲覧済' : '未閲覧'}
 		</Button>
@@ -112,7 +117,10 @@ export default (({ user }: Props) => {
 		      <Tab name="編輯">
 			<PostEditForm post={post}
 				      onSave={newPost => {
-					setPost (newPost)
+					qc.setQueryData (['posts', String (id)],
+							 (prev: any) => newPost ?? prev)
+					qc.invalidateQueries ({ queryKey: ['posts', 'index'] })
+					qc.invalidateQueries ({ queryKey: ['related', String (id)] })
 					toast ({ description: '更新しました．' })
 				      }}/>
 		      </Tab>)}
@@ -120,8 +128,9 @@ export default (({ user }: Props) => {
 	      </>)
 	   : 'Loading...'}
 	</MainArea>
+
 	<div className="md:hidden">
-	  <TagDetailSidebar post={post}/>
+	  <TagDetailSidebar post={post ?? null}/>
 	</div>
       </div>)
 }) satisfies FC<Props>

frontend/src/pages/posts/PostListPage.tsx

@@ -10,6 +10,7 @@ import WikiBody from '@/components/WikiBody'
 import TabGroup, { Tab } from '@/components/common/TabGroup'
 import MainArea from '@/components/layout/MainArea'
 import { API_BASE_URL, SITE_TITLE } from '@/config'
+import { fetchPosts } from '@/lib/posts'
 
 import type { Post, WikiPage } from '@/types'
 
@@ -28,13 +29,11 @@ export default () => {
   const loadMore = async (withCursor: boolean) => {
     setLoading (true)
 
-    const res = await axios.get (`${ API_BASE_URL }/posts`, {
+    const data = await fetchPosts ({
-	params: { tags:   tags.join (' '),
+	tags:   tags.join (' '),
 	match:  anyFlg ? 'any' : 'all',
-		  limit:  '20',
+	limit:  20,
-		  ...(withCursor && { cursor }) } })
+	...(withCursor && { cursor }) })
-    const data = toCamel (res.data as any, { deep: true }) as { posts:      Post[]
-								nextCursor: string }
     setPosts (posts => (
 	[...((new Map ([...(withCursor ? posts : []), ...data.posts]
 		       .map (post => [post.id, post])))
@@ -111,7 +110,13 @@ export default () => {
 	  </title>
 	</Helmet>
 
-	<TagSidebar posts={posts.slice (0, 20)}/>
+	<TagSidebar posts={posts.slice (0, 20)} onClick={() => {
+	    const statesToSave = {
+		posts, cursor,
+		scroll: containerRef.current?.scrollTop ?? 0 }
+	    sessionStorage.setItem (`posts:${ tagsQuery }`,
+				    JSON.stringify (statesToSave))
+	}}/>
 
 	<MainArea>
 	  <TabGroup>