AGENTS.md

@@ -114,6 +114,10 @@ npm run preview
   requires a break.
 - Ruby blocks use separate `{ ... }` rules from hashes, with 2-space body
   indentation.
+- For arrays, never put whitespace or a line break immediately before `]`.
+- Keep the first element on the same line as `[` by default.
+- If an array would exceed the line limit, break after `[` and indent
+  elements by 4 spaces.
 - TypeScript and Python: use GNU-style spacing before parentheses where
   syntactically valid.
 - Never write Ruby, TypeScript, or TSX lines longer than 99 characters.

backend/AGENTS.md

@@ -83,6 +83,10 @@ service, representation, and spec.
   by 4 spaces.
 - Put one logical pair per line when the expression would otherwise become
   dense.
+- For Ruby arrays, never put whitespace or a line break immediately before `]`.
+- Keep the first element on the same line as `[` by default.
+- If an array would exceed the line limit, break after `[` and indent
+  elements by 4 spaces.
 - For Ruby blocks, use 2-space indentation for the block body.
 - Keep comments short and useful; avoid narrating obvious code.
 - Do not add production dependencies without approval.

backend/app/services/theatre_post_selector.rb

@@ -1,5 +1,10 @@
 class TheatrePostSelector
   Candidate = Struct.new(:post, :weight, :penalty, :tags, keyword_init: true)
+  ELIGIBLE_POST_URL_CONDITION =
+      ["url LIKE '%nicovideo.jp%'",
+       "url LIKE '%youtube.com/watch%'",
+       "url LIKE '%youtu.be/%'"]
+      .join(' OR ')
 
   def initialize theatre:
     @theatre = theatre
@@ -52,7 +57,7 @@ class TheatrePostSelector
   end
 
   def eligible_posts
-    posts = Post.where("url LIKE '%nicovideo.jp%'")
+    posts = Post.where(ELIGIBLE_POST_URL_CONDITION)
     posts = posts.where.not(id: theatre.current_post_id) if theatre.current_post_id
     posts
   end

backend/spec/requests/theatres_spec.rb

@@ -28,6 +28,13 @@ RSpec.describe 'Theatres API', type: :request do
     )
   end
 
+  let!(:youtube_post) do
+    Post.create!(
+      title: 'youtube post',
+      url: 'https://www.youtube.com/watch?v=yt123'
+    )
+  end
+
   let!(:other_post) do
     Post.create!(
       title: 'other post',
@@ -286,7 +293,7 @@ RSpec.describe 'Theatres API', type: :request do
           .to change { theatre.reload.current_post_id }
 
         expect(response).to have_http_status(:no_content)
-        expect([niconico_post.id, second_niconico_post.id])
+        expect([niconico_post.id, second_niconico_post.id, youtube_post.id])
           .to include(theatre.reload.current_post_id)
         expect(theatre.reload.current_post_started_at)
           .to be_within(1.second).of(Time.current)
@@ -294,10 +301,27 @@ RSpec.describe 'Theatres API', type: :request do
       end
     end
 
+    context 'when only a YouTube post is eligible' do
+      before do
+        niconico_post.destroy!
+        second_niconico_post.destroy!
+        theatre.update!(host_user: member)
+        sign_in_as(member)
+      end
+
+      it 'sets current_post to the YouTube post' do
+        do_request
+
+        expect(response).to have_http_status(:no_content)
+        expect(theatre.reload.current_post_id).to eq(youtube_post.id)
+      end
+    end
+
     context 'when current user is host and no eligible post exists' do
       before do
         niconico_post.destroy!
         second_niconico_post.destroy!
+        youtube_post.destroy!
         theatre.update!(
           host_user: member,
           current_post: other_post,

frontend/AGENTS.md

@@ -47,6 +47,10 @@ If either command cannot be run or fails, report the exact command and failure.
 - Never write a TypeScript or TSX line longer than 99 characters.
 - Aim to keep TypeScript and TSX lines within 79 characters where practical.
 - Use 4-space logical indentation in TypeScript and TSX.
+- For arrays, never put whitespace or a line break immediately before `]`.
+- Keep the first element on the same line as `[` by default.
+- If an array would exceed the line limit, break after `[` and indent
+  elements by 4 spaces.
 - In TypeScript and TSX only, replace every leading run of 8 spaces with a tab
   to reduce bytes.
 - Treat one leading tab as exactly equivalent to 8 leading spaces.

frontend/src/components/NicoViewer.tsx

@@ -14,10 +14,20 @@ import type { NiconicoMetadata, NiconicoVideoInfo, NiconicoViewerHandle } from '
 type NiconicoPlayerMessage =
     | { eventName: 'enterProgrammaticFullScreen' }
     | { eventName: 'exitProgrammaticFullScreen' }
-    | { eventName: 'loadComplete'; playerId?: string; data: { videoInfo: NiconicoVideoInfo } }
-    | { eventName: 'playerMetadataChange'; playerId?: string; data: NiconicoMetadata }
-    | { eventName: 'playerStatusChange' | 'statusChange'; playerId?: string; data?: unknown }
-    | { eventName: 'error'; playerId?: string; data?: unknown; code?: string; message?: string }
+    | { eventName: 'loadComplete'
+        playerId?:  string
+        data:       { videoInfo: NiconicoVideoInfo } }
+    | { eventName: 'playerMetadataChange'
+        playerId?:  string
+        data:       NiconicoMetadata }
+    | { eventName: 'playerStatusChange' | 'statusChange'
+        playerId?:  string
+        data?:      unknown }
+    | { eventName: 'error'
+        playerId?:  string
+        data?:      unknown
+        code?:      string
+        message?:   string }
 
 type NiconicoCommand =
     | { eventName: 'play'; sourceConnectorType: 1; playerId: string }
@@ -30,6 +40,7 @@ type NiconicoCommand =
 	data: { commentVisibility: boolean } }
 
 const EMBED_ORIGIN = 'https://embed.nicovideo.jp'
+const LOAD_COMPLETE_TIMEOUT_MS = 8_000
 
 type Props = {
     id:                 string
@@ -45,7 +56,10 @@ export default forwardRef ((props: Props, ref: ForwardedRef<NiconicoViewerHandle
 	  const { id, width, height, style = { }, onLoadComplete, onMetadataChange, onError } = props
 
 	  const iframeRef = useRef<HTMLIFrameElement> (null)
-  const playerId = useMemo (() => `nico-${ id }-${ Math.random ().toString (36).slice (2) }`, [id])
+	  const loadCompleteTimerRef = useRef<ReturnType<typeof setTimeout> | null> (null)
+	  const playerId = useMemo (
+	      () => `nico-${ id }-${ Math.random ().toString (36).slice (2) }`,
+	      [id])
 
   const [screenWidth, setScreenWidth] = useState<CSSProperties['width']> ()
   const [screenHeight, setScreenHeight] = useState<CSSProperties['height']> ()
@@ -80,6 +94,24 @@ export default forwardRef ((props: Props, ref: ForwardedRef<NiconicoViewerHandle
 	  const margedStyle: CSSProperties =
 	      { border: 'none', maxWidth: '100%', ...style, ...styleFullScreen }
 
+	  const clearLoadCompleteTimer = useCallback (() => {
+	    if (!(loadCompleteTimerRef.current))
+	      return
+
+	    clearTimeout (loadCompleteTimerRef.current)
+	    loadCompleteTimerRef.current = null
+	  }, [])
+
+	  const startLoadCompleteTimer = useCallback (() => {
+	    clearLoadCompleteTimer ()
+	    loadCompleteTimerRef.current = setTimeout (() => {
+	      onError?.({
+		  eventName: 'loadCompleteTimeout',
+		  reason:    'niconico video length was not reported by embed',
+	      })
+	    }, LOAD_COMPLETE_TIMEOUT_MS)
+	  }, [clearLoadCompleteTimer, onError])
+
   const postToPlayer = useCallback ((message: NiconicoCommand) => {
     const win = iframeRef.current?.contentWindow
     if (!(win))
@@ -163,6 +195,7 @@ export default forwardRef ((props: Props, ref: ForwardedRef<NiconicoViewerHandle
 
 	      if (data.eventName === 'loadComplete')
 		{
+		  clearLoadCompleteTimer ()
 		  onLoadComplete?.(data.data.videoInfo)
 		  return
 		}
@@ -175,6 +208,7 @@ export default forwardRef ((props: Props, ref: ForwardedRef<NiconicoViewerHandle
 
 	      if (data.eventName === 'error')
 	        {
+		  clearLoadCompleteTimer ()
 	          console.error ('niconico player error:', data)
 	          onError?.(data)
 	        }
@@ -183,7 +217,9 @@ export default forwardRef ((props: Props, ref: ForwardedRef<NiconicoViewerHandle
     addEventListener ('message', onMessage)
 
 	    return () => removeEventListener ('message', onMessage)
-  }, [onError, onLoadComplete, onMetadataChange, playerId])
+	  }, [clearLoadCompleteTimer, onError, onLoadComplete, onMetadataChange, playerId])
+
+	  useEffect (() => clearLoadCompleteTimer, [clearLoadCompleteTimer])
 
   useLayoutEffect (() => {
     if (!(fullScreen))
@@ -238,6 +274,7 @@ export default forwardRef ((props: Props, ref: ForwardedRef<NiconicoViewerHandle
 		  width={width}
 		  height={height}
 		  style={margedStyle}
+		  onLoad={startLoadCompleteTimer}
 		  allowFullScreen
 		  allow="autoplay"/>)
 })

frontend/src/components/PostEmbed.tsx

@@ -1,4 +1,4 @@
-import { useState } from 'react'
+import { useCallback, useEffect, useState } from 'react'
 import YoutubeEmbed from 'react-youtube'
 
 import NicoViewer from '@/components/NicoViewer'
@@ -8,18 +8,97 @@ import { useDialogue } from '@/components/dialogues/DialogueProvider'
 import type { FC, RefObject } from 'react'
 
 import type { NiconicoMetadata, NiconicoVideoInfo, NiconicoViewerHandle, Post } from '@/types'
+import type { YouTubePlayer } from 'react-youtube'
+
+type YouTubeEvent<T = unknown> = {
+    data:    T
+    target:  YouTubePlayer }
 
 type Props = {
     ref?:               RefObject<NiconicoViewerHandle | null>
     post:               Post
     onLoadComplete?:    (info: NiconicoVideoInfo) => void
     onMetadataChange?:  (meta: NiconicoMetadata) => void
+    onVideoReady?:      (durationMs: number) => void
+    onPlaybackChange?:  (currentTimeMs: number) => number | void
     onError?:           (data: unknown) => void }
 
 
-const PostEmbed: FC<Props> = ({ ref, post, onLoadComplete, onMetadataChange, onError }) => {
+const PostEmbed: FC<Props> = ({
+    ref,
+    post,
+    onLoadComplete,
+    onMetadataChange,
+    onVideoReady,
+    onPlaybackChange,
+    onError,
+}) => {
   const dialogue = useDialogue ()
   const [framed, setFramed] = useState (false)
+  const [youtubePlayer, setYoutubePlayer] = useState<YouTubePlayer | null> (null)
+
+  const reportYoutubePlayback = useCallback (async (player: YouTubePlayer) => {
+    const currentTime = await player.getCurrentTime ()
+    const currentTimeMs = currentTime * 1_000
+    const targetTimeMs = onPlaybackChange?.(currentTimeMs)
+
+    if (typeof targetTimeMs !== 'number')
+      return
+
+    if (Math.abs (currentTimeMs - targetTimeMs) > 5_000)
+      await player.seekTo (targetTimeMs / 1_000, true)
+  }, [onPlaybackChange])
+
+  const handleYoutubeReady = async (event: YouTubeEvent) => {
+    setYoutubePlayer (event.target)
+
+    try
+    {
+      await event.target.playVideo ()
+
+      const duration = await event.target.getDuration ()
+      const durationMs = duration * 1_000
+      onVideoReady?.(durationMs)
+
+      if (!(Number.isFinite (durationMs)) || durationMs <= 0)
+	return
+
+      await reportYoutubePlayback (event.target)
+    }
+    catch (error)
+    {
+      onError?.({ platform: 'youtube', error })
+    }
+  }
+
+  const handleYoutubeStateChange = (event: YouTubeEvent<number>) => {
+    void reportYoutubePlayback (event.target)
+  }
+
+  const handleYoutubeError = (event: YouTubeEvent<number>) => {
+    onError?.({ platform: 'youtube', code: event.data })
+  }
+
+  const handleNiconicoLoadComplete = (info: NiconicoVideoInfo) => {
+    onVideoReady?.(info.lengthInSeconds * 1_000)
+    onLoadComplete?.(info)
+  }
+
+  const handleNiconicoMetadataChange = (meta: NiconicoMetadata) => {
+    onPlaybackChange?.(meta.currentTime)
+    onMetadataChange?.(meta)
+  }
+
+  useEffect (() => {
+    if (!(youtubePlayer) || !(onPlaybackChange))
+      return
+
+    const timer = setInterval (
+	() => void reportYoutubePlayback (youtubePlayer),
+	1_000)
+
+    return () => clearInterval (timer)
+  }, [onPlaybackChange, reportYoutubePlayback, youtubePlayer])
 
   const url = new URL (post.url)
 
@@ -39,8 +118,8 @@ const PostEmbed: FC<Props> = ({ ref, post, onLoadComplete, onMetadataChange, onE
 	      id={videoId}
 	      width={640}
 	      height={360}
-	      onLoadComplete={onLoadComplete}
-	      onMetadataChange={onMetadataChange}
+	      onLoadComplete={handleNiconicoLoadComplete}
+	      onMetadataChange={handleNiconicoMetadataChange}
 	      onError={onError}/>)
     }
 
@@ -71,7 +150,10 @@ const PostEmbed: FC<Props> = ({ ref, post, onLoadComplete, onMetadataChange, onE
 	      mute:         0,
 	      loop:         1,
 	      width:        '640',
-	      height:       '360' } }}/>)
+	      height:       '360' } }}
+	      onReady={handleYoutubeReady}
+	      onStateChange={handleYoutubeStateChange}
+	      onError={handleYoutubeError}/>)
     }
   }
 

frontend/src/pages/theatres/TheatreDetailPage.tsx

@@ -21,9 +21,7 @@ import { useValidationErrors } from '@/lib/useValidationErrors'
 
 import type { FC, FormEvent, ReactNode } from 'react'
 
-import type { NiconicoMetadata,
-	      NiconicoVideoInfo,
-	      NiconicoViewerHandle,
+import type { NiconicoViewerHandle,
 	      Post,
 	      Category,
 	      Tag,
@@ -88,7 +86,9 @@ const commentBox = (
 	  {dateString (comment.createdAt)}
 	</div>),
      (
-	<div key={`${ comment.no }-post`} className="mt-1 w-full text-xs text-zinc-500 dark:text-zinc-400">
+	<div
+	    key={`${ comment.no }-post`}
+	    className="mt-1 w-full text-xs text-zinc-500 dark:text-zinc-400">
 	  {programme && (
 	      <>
 		<PrefetchLink to={`/posts/${ programme.post.id }`} className="font-bold hover:underline">
@@ -439,7 +439,7 @@ const TheatreDetailPage: FC<Props> = ({ user }: Props) => {
     void refreshProgrammes ()
   }, [refreshProgrammes, theatreInfo.postId])
 
-  const syncPlayback = (meta: NiconicoMetadata) => {
+  const syncPlaybackTime = (currentTimeMs: number): number | void => {
     if (!(theatreInfo.postStartedAt))
       return
 
@@ -447,24 +447,38 @@ const TheatreDetailPage: FC<Props> = ({ user }: Props) => {
 	currentPostElapsedMs (theatreInfo),
 	videoLength)
 
-    const drift = Math.abs (meta.currentTime - targetTime)
+    const drift = Math.abs (currentTimeMs - targetTime)
 
     if (drift > 5_000)
       embedRef.current?.seek (targetTime)
+
+    return targetTime
   }
 
   const handlePlaybackError = async () => {
     if (!(theatreInfoRef.current.hostFlg) || loadingRef.current)
       return
 
+    loadingRef.current = true
+    try
+    {
       await advancePost ()
     }
+    finally
+    {
+      loadingRef.current = false
+    }
+  }
 
-  const handleNiconicoLoadComplete = (info: NiconicoVideoInfo) => {
-    const lengthMs = info.lengthInSeconds * 1_000
-    setVideoLength (lengthMs)
+  const handleVideoReady = (durationMs: number) => {
+    const playableDurationMs =
+	Number.isFinite (durationMs)
+	? durationMs
+	: 0
 
-    if (lengthMs <= 0)
+    setVideoLength (playableDurationMs)
+
+    if (playableDurationMs <= 0)
       {
 	void handlePlaybackError ()
 	return
@@ -738,7 +752,8 @@ const TheatreDetailPage: FC<Props> = ({ user }: Props) => {
       <motion.div
 	  layout="position"
 	  transition={{ layout: { duration: .2, ease: 'easeOut' } }}
-	  className="min-h-0 flex-1 overflow-y-auto bg-zinc-50 text-zinc-950 md:overflow-hidden dark:bg-zinc-950 dark:text-zinc-50">
+	  className="min-h-0 flex-1 overflow-y-auto bg-zinc-50 text-zinc-950
+		     md:overflow-hidden dark:bg-zinc-950 dark:text-zinc-50">
 	<Helmet>
 	  <meta name="robots" content="noindex"/>
 	  {theatre && <title>{`${ theatreTitle } | ${ SITE_TITLE }`}</title>}
@@ -811,8 +826,8 @@ const TheatreDetailPage: FC<Props> = ({ user }: Props) => {
 			  key={post.id}
 			  ref={embedRef}
 			  post={post}
-			  onLoadComplete={handleNiconicoLoadComplete}
-			  onMetadataChange={syncPlayback}
+			  onVideoReady={handleVideoReady}
+			  onPlaybackChange={syncPlaybackTime}
 			  onError={handlePlaybackError}/>) : (
 		      <div className="grid min-h-72 place-items-center text-zinc-400">
 			{loading ? '次の投稿を選んでゐます……' : '上映待機中'}