feat: add tweet detail page

src/components/app-shell.tsx

@@ -4,7 +4,7 @@ export function AppShell({
   active,
   children,
 }: {
-  active: 'user' | 'search'
+  active?: 'user' | 'search'
   children: React.ReactNode
 }) {
   return (

src/features/posts/components/post-card.test.tsx

@@ -80,6 +80,21 @@ describe('PostCard', () => {
     expect(screen.getByText('@yuta').closest('a')).toBeNull()
   })
 
+  it('links deliberately to the internal detail page', () => {
+    render(<PostCard post={richPost} />)
+
+    expect(
+      screen.getByRole('link', { name: '詳細・スレッド' }),
+    ).toHaveAttribute('href', '/status/123')
+  })
+
+  it('marks the focal post without linking to its current page', () => {
+    render(<PostCard current post={{ ...richPost, quotedTweet: undefined }} />)
+
+    expect(screen.queryByRole('link', { name: '詳細・スレッド' })).toBeNull()
+    expect(screen.getByRole('article')).toHaveClass('current-post')
+  })
+
   it('collapses a malformed optional timestamp without losing the post', () => {
     const { container } = render(
       <PostCard post={{ ...richPost, createdAt: 'not-a-date' }} />,

src/features/posts/components/post-card.tsx

@@ -41,15 +41,19 @@ function formattedTime(createdAt?: string): string | undefined {
 export function PostCard({
   post,
   quoted = false,
+  current = false,
 }: {
   post: Post
   quoted?: boolean
+  current?: boolean
 }) {
   const time = formattedTime(post.createdAt)
   const original = `https://x.com/${encodeURIComponent(post.author.username)}/status/${encodeURIComponent(post.id)}`
 
   return (
-    <article className={quoted ? 'post quote' : 'post'}>
+    <article
+      className={quoted ? 'post quote' : current ? 'post current-post' : 'post'}
+    >
       <header className="post-header">
         {post.author.profileImageUrl ? (
           <img
@@ -86,6 +90,11 @@ export function PostCard({
             返信 {post.replyCount ?? 0}　再投稿 {post.retweetCount ?? 0}　いいね{' '}
             {post.likeCount ?? 0}
           </span>
+          {!current ? (
+            <a href={`/status/${encodeURIComponent(post.id)}`}>
+              詳細・スレッド
+            </a>
+          ) : null}
           <a href={original} rel="noreferrer noopener" target="_blank">
             元の投稿を開く
           </a>

src/features/posts/components/post-feed.test.tsx

@@ -154,6 +154,90 @@ describe('PostFeed', () => {
     expect(screen.queryByRole('alert')).not.toBeInTheDocument()
   })
 
+  it('renders the focal post once above its deduplicated conversation', () => {
+    usePostFeed.mockReturnValue({
+      ...queryResult(),
+      data: {
+        pages: [
+          {
+            focalPost: post('2'),
+            conversationId: '1',
+            nextCursor: 'next',
+            tweets: [post('1'), post('2')],
+          },
+          {
+            conversationId: '1',
+            tweets: [post('2'), post('3')],
+          },
+        ],
+        pageParams: [undefined, { cursor: 'next', conversationId: '1' }],
+      },
+    } as never)
+
+    const { container } = render(
+      <PostFeed request={{ kind: 'thread', tweetId: '2' }} />,
+    )
+
+    expect(screen.getByText('表示中の投稿')).toBeVisible()
+    expect(screen.getAllByText('post-2')).toHaveLength(1)
+    expect(screen.getAllByRole('article')).toHaveLength(3)
+    expect(container.querySelector('.current-post')).toBeInTheDocument()
+  })
+
+  it('keeps the focal post visible when there are no other posts', () => {
+    usePostFeed.mockReturnValue({
+      ...queryResult(),
+      data: {
+        pages: [
+          {
+            focalPost: post('2'),
+            conversationId: '1',
+            tweets: [post('2')],
+          },
+        ],
+        pageParams: [undefined],
+      },
+    } as never)
+
+    render(<PostFeed request={{ kind: 'thread', tweetId: '2' }} />)
+
+    expect(screen.getByText('post-2')).toBeVisible()
+    expect(screen.getByText('会話にほかの投稿はありません。')).toBeVisible()
+  })
+
+  it('keeps the focal post and conversation across a later-page error', () => {
+    usePostFeed.mockReturnValue({
+      ...queryResult(),
+      data: {
+        pages: [
+          {
+            focalPost: post('2'),
+            conversationId: '1',
+            nextCursor: 'next',
+            tweets: [post('1'), post('2')],
+          },
+        ],
+        pageParams: [undefined],
+      },
+      error: new PostLoadError({
+        code: 'upstream',
+        message: 'X から投稿を取得できませんでした。',
+        retryable: true,
+      }),
+      hasNextPage: true,
+      isError: true,
+      isFetchNextPageError: true,
+    } as never)
+
+    render(<PostFeed request={{ kind: 'thread', tweetId: '2' }} />)
+
+    expect(screen.getByText('post-2')).toBeVisible()
+    expect(screen.getByText('post-1')).toBeVisible()
+    expect(screen.getByRole('alert')).toHaveTextContent(
+      '続きの投稿を取得できませんでした。',
+    )
+  })
+
   it('retries an initial retryable error with refetch', () => {
     const refetch = vi.fn().mockResolvedValue(undefined)
     usePostFeed.mockReturnValue({

src/features/posts/components/post-feed.tsx

@@ -1,12 +1,33 @@
 import { useEffect, useRef } from 'react'
-import { flattenPostPages } from '../page'
+import {
+  flattenConversationPages,
+  flattenPostPages,
+  focalPostFromPages,
+} from '../page'
+import type { Post } from '../types'
 import { type FeedRequest, PostLoadError, usePostFeed } from '../use-post-feed'
 import { PostCard } from './post-card'
 
+function FocalPost({ post }: { post: Post }) {
+  return (
+    <section aria-labelledby="focal-post-label" className="focal-post">
+      <p className="focal-label" id="focal-post-label">
+        表示中の投稿
+      </p>
+      <PostCard current post={post} />
+    </section>
+  )
+}
+
 export function PostFeed({ request }: { request: FeedRequest | undefined }) {
   const query = usePostFeed(request)
   const sentinel = useRef<HTMLDivElement>(null)
-  const posts = query.data ? flattenPostPages(query.data.pages) : []
+  const pages = query.data?.pages ?? []
+  const focalPost =
+    request?.kind === 'thread' ? focalPostFromPages(pages) : undefined
+  const posts = focalPost
+    ? flattenConversationPages(pages, focalPost.id)
+    : flattenPostPages(pages)
 
   useEffect(() => {
     if (
@@ -62,10 +83,21 @@ export function PostFeed({ request }: { request: FeedRequest | undefined }) {
     )
   }
   if (posts.length === 0 && !query.hasNextPage) {
-    return <p className="state">条件に一致する投稿はありません。</p>
+    return (
+      <>
+        {focalPost ? <FocalPost post={focalPost} /> : null}
+        <p className="state">
+          {focalPost
+            ? '会話にほかの投稿はありません。'
+            : '条件に一致する投稿はありません。'}
+        </p>
+      </>
+    )
   }
 
   return (
+    <>
+      {focalPost ? <FocalPost post={focalPost} /> : null}
       <section aria-live="polite" className="feed">
         {posts.map((post) => (
           <PostCard key={post.id} post={post} />
@@ -88,5 +120,6 @@ export function PostFeed({ request }: { request: FeedRequest | undefined }) {
           <p className="state">これ以上の投稿はありません。</p>
         ) : null}
       </section>
+    </>
   )
 }

src/routeTree.gen.ts

@@ -12,6 +12,7 @@ import { Route as rootRouteImport } from './routes/__root'
 import { Route as UserRouteImport } from './routes/user'
 import { Route as SearchRouteImport } from './routes/search'
 import { Route as IndexRouteImport } from './routes/index'
+import { Route as StatusTweetIdRouteImport } from './routes/status.$tweetId'
 
 const UserRoute = UserRouteImport.update({
   id: '/user',
@@ -28,35 +29,44 @@ const IndexRoute = IndexRouteImport.update({
   path: '/',
   getParentRoute: () => rootRouteImport,
 } as any)
+const StatusTweetIdRoute = StatusTweetIdRouteImport.update({
+  id: '/status/$tweetId',
+  path: '/status/$tweetId',
+  getParentRoute: () => rootRouteImport,
+} as any)
 
 export interface FileRoutesByFullPath {
   '/': typeof IndexRoute
   '/search': typeof SearchRoute
   '/user': typeof UserRoute
+  '/status/$tweetId': typeof StatusTweetIdRoute
 }
 export interface FileRoutesByTo {
   '/': typeof IndexRoute
   '/search': typeof SearchRoute
   '/user': typeof UserRoute
+  '/status/$tweetId': typeof StatusTweetIdRoute
 }
 export interface FileRoutesById {
   __root__: typeof rootRouteImport
   '/': typeof IndexRoute
   '/search': typeof SearchRoute
   '/user': typeof UserRoute
+  '/status/$tweetId': typeof StatusTweetIdRoute
 }
 export interface FileRouteTypes {
   fileRoutesByFullPath: FileRoutesByFullPath
-  fullPaths: '/' | '/search' | '/user'
+  fullPaths: '/' | '/search' | '/user' | '/status/$tweetId'
   fileRoutesByTo: FileRoutesByTo
-  to: '/' | '/search' | '/user'
+  to: '/' | '/search' | '/user' | '/status/$tweetId'
-  id: '__root__' | '/' | '/search' | '/user'
+  id: '__root__' | '/' | '/search' | '/user' | '/status/$tweetId'
   fileRoutesById: FileRoutesById
 }
 export interface RootRouteChildren {
   IndexRoute: typeof IndexRoute
   SearchRoute: typeof SearchRoute
   UserRoute: typeof UserRoute
+  StatusTweetIdRoute: typeof StatusTweetIdRoute
 }
 
 declare module '@tanstack/react-router' {
@@ -82,6 +92,13 @@ declare module '@tanstack/react-router' {
       preLoaderRoute: typeof IndexRouteImport
       parentRoute: typeof rootRouteImport
     }
+    '/status/$tweetId': {
+      id: '/status/$tweetId'
+      path: '/status/$tweetId'
+      fullPath: '/status/$tweetId'
+      preLoaderRoute: typeof StatusTweetIdRouteImport
+      parentRoute: typeof rootRouteImport
+    }
   }
 }
 
@@ -89,6 +106,7 @@ const rootRouteChildren: RootRouteChildren = {
   IndexRoute: IndexRoute,
   SearchRoute: SearchRoute,
   UserRoute: UserRoute,
+  StatusTweetIdRoute: StatusTweetIdRoute,
 }
 export const routeTree = rootRouteImport
   ._addFileChildren(rootRouteChildren)

src/routes/-feed-wiring.test.tsx

@@ -88,4 +88,31 @@ describe('post feed route wiring', () => {
       }),
     )
   })
+
+  it('turns a decimal status path into a deliberate thread request', async () => {
+    await renderRoute('/status/123')
+
+    expect(await screen.findByRole('heading', { name: '会話' })).toBeVisible()
+    await waitFor(() =>
+      expect(usePostFeed).toHaveBeenCalledWith({
+        kind: 'thread',
+        tweetId: '123',
+      }),
+    )
+    expect(
+      screen.queryByRole('link', { name: 'ユーザー', current: 'page' }),
+    ).toBeNull()
+    expect(
+      screen.queryByRole('link', { name: '検索', current: 'page' }),
+    ).toBeNull()
+  })
+
+  it('keeps an invalid status path local and idle', async () => {
+    await renderRoute('/status/not-a-tweet')
+
+    expect(await screen.findByRole('alert')).toHaveTextContent(
+      '投稿 ID を確認してください。',
+    )
+    expect(usePostFeed).toHaveBeenCalledWith(undefined)
+  })
 })

src/routes/status.$tweetId.tsx

@@ -0,0 +1,36 @@
+import { createFileRoute } from '@tanstack/react-router'
+import { AppShell } from '#/components/app-shell'
+import { PostFeed } from '#/features/posts/components/post-feed'
+import { InputError, normalizeTweetId } from '#/features/posts/inputs'
+
+export const Route = createFileRoute('/status/$tweetId')({
+  component: StatusRoute,
+})
+
+function StatusRoute() {
+  const { tweetId: rawTweetId } = Route.useParams()
+  let tweetId: string | undefined
+  let error: string | undefined
+
+  try {
+    tweetId = normalizeTweetId(rawTweetId)
+  } catch (cause) {
+    error =
+      cause instanceof InputError
+        ? cause.message
+        : '投稿 ID を確認してください。'
+  }
+
+  return (
+    <AppShell>
+      <h1>会話</h1>
+      <p className="intro">選んだ投稿と、その会話だけを表示します。</p>
+      {error ? (
+        <p className="state" role="alert">
+          {error}
+        </p>
+      ) : null}
+      <PostFeed request={tweetId ? { kind: 'thread', tweetId } : undefined} />
+    </AppShell>
+  )
+}

src/styles.css

@@ -254,6 +254,20 @@ a {
   grid-column: 1 / -1;
 }
 
+.focal-post {
+  display: grid;
+  gap: 0.5rem;
+  margin-top: 1.4rem;
+}
+
+.focal-label {
+  margin: 0;
+  color: var(--accent);
+  font-size: 0.72rem;
+  font-weight: 750;
+  letter-spacing: 0.08em;
+}
+
 .feed {
   display: grid;
   gap: 0.85rem;
@@ -268,6 +282,11 @@ a {
   background: var(--paper);
 }
 
+.current-post {
+  border-color: var(--accent);
+  box-shadow: 0 0 0 1px color-mix(in srgb, var(--accent) 25%, transparent);
+}
+
 .post-header {
   display: grid;
   grid-template-columns: auto minmax(0, 1fr) auto;
@@ -361,6 +380,7 @@ video.media {
 .post-footer {
   display: flex;
   flex-wrap: wrap;
+  align-items: center;
   justify-content: space-between;
   gap: 0.75rem 1rem;
   margin-top: 1rem;