Add Reddit with its comment threads, and show quoted posts whole

Two changes. They share the `Segment` model, which is why they arrive
together.

## Reddit

A new adapter under /reddit, plus the thread beneath the post -- on Reddit the
conversation is usually the reason the link was shared, so a viewer that showed
only the post would be showing the wrong half.

The `.json` twin of a post URL is the post and the whole first page of comments
in one response, far better than anything the page gives up, so it is the only
layer that normally runs. Reddit refuses it to a browser it has never seen and
answers with a JavaScript challenge, which any ordinary navigation solves by
itself; the adapter navigates once and retries, and the cookie left behind
serves every later post. Below that, `shreddit-comment` elements are read from
the rendered page -- flat, each carrying its own `depth`, so `treeFromDepths`
rebuilds the nesting.

`Post.comments` is a tree rather than a flat list with depths, because folding
a comment has to take everything under it along and nesting is what makes that
free. Each comment renders as a `<details open>`, so collapsing works with the
stylesheet off and from the keyboard, and a collapsed one says how many replies
it is hiding. "Collapse all" is the only part that needs the script, so it
ships hidden and appears once the script has run. What sits behind a "load
more" is not fetched -- that is a second page and often a third -- but it is
counted and said out loud rather than quietly dropped.

Four things the payloads got wrong on the first try, each now with a fixture:
`fallback_url` is the video track alone whenever `has_audio` is true, so a post
with sound has to use `hls_url` and only a silent one gets the proxied MP4;
`scrubber_media_url` looks like a poster and is a second MP4 for the timeline
thumbnails, while the still is in `preview.images`; a gallery's pictures live
in `media_metadata` keyed and unordered, with their order only in
`gallery_data`; and `replies` is the string "" rather than an object when there
are none. Comment bodies are Markdown, rendered by a new render/markdown.ts
that escapes first and then puts back only the constructs we chose to support
-- never Reddit's own `body_html`, which would mean trusting markup a stranger
caused to be generated.

An app share link (/r/<sub>/s/<code>) is a plain 301, so one request told not
to follow it is enough. The permalink it resolves to is what the copy button
hands back, since an opaque share code is a tracking parameter by another name.

## Quoted posts

Both X and Bluesky lifted the quoted post's media out and showed it as the
quoter's own, dropping the quoted words and the quoted author entirely. A quote
of a photo post therefore rendered as somebody else's picture under the wrong
name with nothing to say so, and a quote that had a picture of its own dropped
the quoted one instead -- the two could never both appear. Half the quote posts
people share are someone answering a stranger and the other half are someone
continuing a thought from an earlier post; neither reads with only one side of
it on the page.

`Segment.quoted` now carries the whole thing -- author, words, pictures, time
and a link to it -- and renders as a post inside the post. Neither payload
carries a usable address for it: X has no permalink and it is rebuilt from the
handle and `id_str`, Bluesky has an `at://` URI nobody can open and it is
rebuilt from the handle and the record key. On Bluesky the record sits at
`embed.record` for a plain quote and at `embed.record.record` when the quoting
post has media of its own, and a quote can also point at a feed, a list or a
post since deleted, which arrive in the same slot under a different `$type` --
only `app.bsky.embed.record#viewRecord` is taken.

Two things about X's text, both visible on any post and not only a quote. It
arrives pre-escaped, so an ampersand someone typed was reaching the page as the
literal `&amp;`; it is decoded in the adapter, where the encoding comes from,
leaving the escape-on-the-way-out rule alone. And every link is a `t.co`, which
tells the reader nothing and routes them through X's click tracker to find out
-- `entities.urls` carries the real address alongside, so it is put back. The
shortlink X staples onto the end of a quote post is dropped rather than
expanded, since the post it points at is already on the page;
`display_text_range` is where that boundary is and it keeps a link the author
put there deliberately. Its indices are UTF-16 units into the escaped text, so
the slice happens before decoding and before expanding, and splitting to
codepoints first overshoots past an emoji -- checked against a post carrying
one.

A quote is context, and context that fills the screen has stopped being
context, so a segment carrying one gives up the window-filling cap on its own
media.

## Along the way

setupMedia only ever wired `document.querySelector('.media')`, the first rail
on the page. That was already wrong for a Bluesky or Threads chain with media
in more than one post, and a quoted carousel would have hit it too. It now runs
per rail.

## Verified

108 tests, typecheck and build clean. Resolved end to end against the live
platforms: Reddit self, gallery, video, link and share-link posts; X quotes
with no media, with media on the quoted side, and with media on both; Bluesky
quotes in both embed shapes, including a ten-post chain where every post quotes
a different account and all nine quotes come back under the right name.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017nMQ2eDKnqALYhAibpTKTu

src/platforms/reddit.ts

@@ -0,0 +1,466 @@
+import type { Page } from 'playwright';
+import { ResolveError, oneSegment, type Comment, type Media, type Post } from '../types.ts';
+import { readOpenGraph } from '../browser/capture.ts';
+import { stripTracking } from './url.ts';
+import type { PlatformSpec, ResolveContext } from './types.ts';
+
+const HOST = 'https://www.reddit.com';
+
+/** Path roots that are really Reddit paths, so anything else that arrives as
+ *  a single opaque segment is a `redd.it` share code. */
+const KNOWN_ROOTS = new Set(['r', 'u', 'user', 'comments', 'gallery', 'media', 'wiki']);
+
+type Listing<T> = { kind?: string; data?: { children?: Array<Thing<T>> } };
+type Thing<T> = { kind?: string; data?: T };
+
+type RedditVideo = {
+  fallback_url?: string;
+  hls_url?: string;
+  has_audio?: boolean;
+  width?: number;
+  height?: number;
+  duration?: number;
+};
+
+type MediaMeta = {
+  status?: string;
+  e?: string;
+  m?: string;
+  s?: { u?: string; gif?: string; mp4?: string; x?: number; y?: number };
+};
+
+type Link = {
+  title?: string;
+  author?: string;
+  subreddit_name_prefixed?: string;
+  created_utc?: number;
+  selftext?: string;
+  permalink?: string;
+  url?: string;
+  url_overridden_by_dest?: string;
+  domain?: string;
+  post_hint?: string;
+  is_self?: boolean;
+  is_video?: boolean;
+  is_gallery?: boolean;
+  over_18?: boolean;
+  spoiler?: boolean;
+  link_flair_text?: string | null;
+  num_comments?: number;
+  score?: number;
+  gallery_data?: { items?: Array<{ media_id?: string }> };
+  media_metadata?: Record<string, MediaMeta>;
+  secure_media?: { reddit_video?: RedditVideo } | null;
+  media?: { reddit_video?: RedditVideo } | null;
+  preview?: {
+    images?: Array<{ source?: { url?: string; width?: number; height?: number } }>;
+    reddit_video_preview?: RedditVideo;
+  };
+  crosspost_parent_list?: Link[];
+};
+
+type CommentData = {
+  author?: string;
+  body?: string;
+  created_utc?: number;
+  score?: number;
+  score_hidden?: boolean;
+  is_submitter?: boolean;
+  distinguished?: string | null;
+  replies?: Listing<CommentData> | '';
+};
+
+type MoreData = { count?: number };
+
+/** `[deleted]` and `[removed]` are the platform's own words, kept as they are. */
+function authorName(author: string | undefined): string {
+  if (!author || author.startsWith('[')) return author ?? '[unknown]';
+  return `u/${author}`;
+}
+
+function isoFrom(seconds: number | undefined): string | undefined {
+  return seconds ? new Date(seconds * 1000).toISOString() : undefined;
+}
+
+function sized(width: number | undefined, height: number | undefined) {
+  return {
+    ...(width ? { width } : {}),
+    ...(height ? { height } : {}),
+  };
+}
+
+/**
+ * Reddit's own video, which arrives in three forms at once.
+ *
+ * `fallback_url` is a plain MP4 and the nicer thing to serve — it proxies,
+ * so the viewer never talks to Reddit, and the native scrubber can seek it.
+ * But when a post has sound that MP4 is the video track alone: the audio is
+ * a separate file the DASH manifest stitches back on. So a silent post gets
+ * the MP4 and one with audio gets the HLS playlist, linked directly because
+ * proxying it would mean rewriting the manifest and every segment.
+ */
+function fromRedditVideo(video: RedditVideo, poster: string | undefined): Media[] {
+  const common = {
+    ...sized(video.width, video.height),
+    ...(video.duration ? { durationSec: video.duration } : {}),
+  };
+
+  if (video.has_audio !== false && video.hls_url) {
+    return [{ kind: 'video', url: video.hls_url, hls: true, direct: true, ...common }];
+  }
+  const url = video.fallback_url ?? video.hls_url;
+  if (!url) return [];
+  if (url === video.hls_url) {
+    return [{ kind: 'video', url, hls: true, direct: true, ...common }];
+  }
+  return [{
+    kind: 'video',
+    url,
+    ...(poster ? { poster: { url: poster } } : {}),
+    ...common,
+  }];
+}
+
+/** One entry of a gallery post. Reddit keeps the pictures somewhere other
+ *  than the order it wants them shown in, so the two have to be joined. */
+function fromGalleryItem(meta: MediaMeta | undefined): Media[] {
+  if (!meta || meta.status !== 'valid') return [];
+  const size = sized(meta.s?.x, meta.s?.y);
+
+  // An animated entry ships as a video as well; that is smaller and seekable.
+  if (meta.s?.mp4) return [{ kind: 'video', url: meta.s.mp4, ...size }];
+  const url = meta.s?.gif ?? meta.s?.u;
+  return url ? [{ kind: 'image', url, ...size }] : [];
+}
+
+export function mediaFromLink(link: Link): Media[] {
+  // A crosspost is a wrapper with nothing of its own in it.
+  const crossposted = link.crosspost_parent_list?.[0];
+  if (crossposted && !link.is_self) {
+    const inner = mediaFromLink(crossposted);
+    if (inner.length) return inner;
+  }
+
+  // `scrubber_media_url` looks like a poster and is not one: it is a second,
+  // tiny MP4 for the timeline thumbnails. The still is in the preview.
+  const still = link.preview?.images?.[0]?.source?.url;
+
+  const video = link.secure_media?.reddit_video ?? link.media?.reddit_video;
+  if (video) return fromRedditVideo(video, still);
+
+  if (link.is_gallery) {
+    const items = link.gallery_data?.items ?? [];
+    const gallery = items.flatMap((item) =>
+      fromGalleryItem(item.media_id ? link.media_metadata?.[item.media_id] : undefined));
+    if (gallery.length) return gallery;
+  }
+
+  // A GIF link is served as a video by the preview, which is the version
+  // worth having: the original is often tens of megabytes.
+  const asVideo = link.preview?.reddit_video_preview;
+  if (asVideo) return fromRedditVideo(asVideo, still);
+
+  const direct = link.url_overridden_by_dest ?? link.url;
+  if (direct && /\.(jpe?g|png|webp|gif)(\?|$)/i.test(direct)) {
+    const source = link.preview?.images?.[0]?.source;
+    return [{ kind: 'image', url: direct, ...sized(source?.width, source?.height) }];
+  }
+
+  // A link to somewhere else: the preview is all Reddit has, and it is still
+  // worth showing above the link itself.
+  const preview = link.preview?.images?.[0]?.source;
+  if (preview?.url) {
+    return [{ kind: 'image', url: preview.url, ...sized(preview.width, preview.height) }];
+  }
+
+  return [];
+}
+
+/**
+ * The words of the post: the self text, or — for a link post — the
+ * destination, which is the whole content of the post and needs to be
+ * tappable.
+ */
+function bodyOf(link: Link): string | undefined {
+  if (link.selftext?.trim()) return link.selftext;
+  const dest = link.url_overridden_by_dest;
+  if (dest && !dest.includes('redd.it') && !dest.startsWith(`${HOST}/gallery/`)) return dest;
+  return undefined;
+}
+
+export function commentsFrom(listing: Listing<CommentData> | undefined): {
+  comments: Comment[];
+  more: number;
+} {
+  const comments: Comment[] = [];
+  let more = 0;
+
+  for (const child of listing?.data?.children ?? []) {
+    if (child.kind === 'more') {
+      more += (child.data as MoreData | undefined)?.count ?? 0;
+      continue;
+    }
+    const data = child.data;
+    if (!data || data.body === undefined) continue;
+
+    const replies = data.replies && typeof data.replies === 'object'
+      ? commentsFrom(data.replies)
+      : { comments: [], more: 0 };
+
+    comments.push({
+      author: authorName(data.author),
+      ...(data.body ? { text: data.body } : {}),
+      ...(isoFrom(data.created_utc) ? { postedAt: isoFrom(data.created_utc) } : {}),
+      // Reddit hides the score on a new comment so an early downvote cannot
+      // steer the rest. Showing a placeholder 1 would be a lie.
+      ...(data.score_hidden !== true && typeof data.score === 'number' ? { score: data.score } : {}),
+      ...(data.is_submitter ? { isAuthor: true } : {}),
+      ...(data.distinguished ? { distinguished: data.distinguished } : {}),
+      replies: replies.comments,
+      ...(replies.more ? { moreReplies: replies.more } : {}),
+    });
+  }
+
+  return { comments, more };
+}
+
+export function toPost(body: [Listing<Link>, Listing<CommentData>], originalUrl: string): Post {
+  const link = body[0]?.data?.children?.[0]?.data;
+  if (!link) throw new ResolveError('Reddit returned no post', 'reddit', originalUrl);
+
+  const { comments, more } = commentsFrom(body[1]);
+  const flags = [
+    link.link_flair_text?.trim(),
+    link.over_18 ? 'NSFW' : undefined,
+    link.spoiler ? 'Spoiler' : undefined,
+  ].filter(Boolean);
+
+  return {
+    platform: 'reddit',
+    platformLabel: 'Reddit',
+    originalUrl,
+    author: {
+      // The subreddit is the identity a Reddit link carries — the poster is
+      // a detail underneath it, so it goes in the display name.
+      handle: link.subreddit_name_prefixed ?? 'reddit',
+      displayName: [authorName(link.author), ...flags].join(' · '),
+    },
+    textPosition: 'above',
+    segments: oneSegment({
+      ...(link.title ? { title: link.title } : {}),
+      ...(bodyOf(link) ? { text: bodyOf(link) } : {}),
+      media: mediaFromLink(link),
+      ...(isoFrom(link.created_utc) ? { postedAt: isoFrom(link.created_utc) } : {}),
+    }),
+    comments,
+    ...(more ? { moreComments: more } : {}),
+    ...(typeof link.num_comments === 'number' ? { commentCount: link.num_comments } : {}),
+  };
+}
+
+export type FlatComment = {
+  depth: number;
+  author: string;
+  score: number;
+  created: string;
+  text: string;
+};
+
+/**
+ * Rebuild the nesting from a flat list of comments that each know only their
+ * own depth, which is how the rendered page presents them.
+ */
+export function treeFromDepths(flat: FlatComment[]): Comment[] {
+  const roots: Comment[] = [];
+  // The comment last seen at each depth, so a reply can be attached to
+  // whatever it appeared underneath.
+  const openAt: Comment[] = [];
+
+  for (const row of flat) {
+    if (!row.text) continue;
+    const comment: Comment = {
+      author: authorName(row.author),
+      text: row.text,
+      ...(row.created && !Number.isNaN(Date.parse(row.created))
+        ? { postedAt: new Date(row.created).toISOString() }
+        : {}),
+      ...(Number.isFinite(row.score) ? { score: row.score } : {}),
+      replies: [],
+    };
+
+    const parent = openAt[row.depth - 1];
+    if (row.depth > 0 && parent) parent.replies.push(comment);
+    else roots.push(comment);
+    // Anything deeper belonged to the comment this one just replaced.
+    openAt.length = row.depth + 1;
+    openAt[row.depth] = comment;
+  }
+
+  return roots;
+}
+
+/**
+ * Reads the comment tree back out of the rendered page.
+ *
+ * The floor, for when the JSON is refused. Reddit renders every comment as a
+ * `<shreddit-comment>` carrying its own depth, flat in document order.
+ */
+async function commentsFromDom(page: Page): Promise<Comment[]> {
+  const flat = await page
+    .evaluate(() =>
+      [...document.querySelectorAll('shreddit-comment')].map((el) => ({
+        depth: Number(el.getAttribute('depth') ?? 0),
+        author: el.getAttribute('author') ?? '',
+        score: Number(el.getAttribute('score') ?? Number.NaN),
+        created: el.getAttribute('created') ?? '',
+        text: el.querySelector('[slot="comment"]')?.textContent?.trim() ?? '',
+      })))
+    .catch((): FlatComment[] => []);
+
+  return treeFromDepths(flat);
+}
+
+/** Whatever the page will admit to, when the JSON will not come. */
+async function fromPage(page: Page, originalUrl: string): Promise<Post> {
+  const attrs = await page
+    .evaluate(() => {
+      const post = document.querySelector('shreddit-post');
+      if (!post) return null;
+      const get = (name: string): string | undefined => post.getAttribute(name) ?? undefined;
+      return {
+        title: get('post-title'),
+        author: get('author'),
+        subreddit: get('subreddit-prefixed-name'),
+        created: get('created-timestamp'),
+        score: get('score'),
+        comments: get('comment-count'),
+        image: get('content-href'),
+      };
+    })
+    .catch(() => null);
+
+  const og = await readOpenGraph(page);
+  const title = attrs?.title ?? og['og:title'];
+  if (!title) throw new ResolveError('Reddit served neither the post nor its data', 'reddit', originalUrl);
+
+  const image = attrs?.image ?? og['og:image'];
+  const media: Media[] =
+    image && /\.(jpe?g|png|webp|gif)(\?|$)/i.test(image) ? [{ kind: 'image', url: image }] : [];
+
+  const count = Number(attrs?.comments);
+  return {
+    platform: 'reddit',
+    platformLabel: 'Reddit',
+    originalUrl,
+    author: {
+      handle: attrs?.subreddit ?? 'reddit',
+      displayName: authorName(attrs?.author),
+    },
+    textPosition: 'above',
+    segments: oneSegment({
+      title,
+      media,
+      ...(attrs?.created && !Number.isNaN(Date.parse(attrs.created))
+        ? { postedAt: new Date(attrs.created).toISOString() }
+        : {}),
+    }),
+    comments: await commentsFromDom(page),
+    ...(Number.isFinite(count) ? { commentCount: count } : {}),
+  };
+}
+
+/** The `.json` twin of a post URL, asked for at the size of one page. */
+function jsonUrlFor(postUrl: string): string {
+  const url = new URL(postUrl);
+  url.pathname = `${url.pathname.replace(/\/+$/, '')}/.json`;
+  url.search = '';
+  url.searchParams.set('raw_json', '1');
+  url.searchParams.set('limit', '100');
+  url.searchParams.set('sort', 'confidence');
+  return url.href;
+}
+
+function isShareLink(url: URL): boolean {
+  return url.hostname === 'redd.it' || /^\/r\/[^/]+\/s\/[^/]+/.test(url.pathname);
+}
+
+/**
+ * Share links from the app are opaque, and the post id is only on the other
+ * side of a redirect. One request that is told not to follow it is enough —
+ * far cheaper than loading the page to find out where it went.
+ */
+async function followShareLink(page: Page, originalUrl: string): Promise<string> {
+  const response = await page.request
+    .get(originalUrl, { maxRedirects: 0 })
+    .catch(() => undefined);
+  const location = response?.headers()['location'];
+  if (!location) return originalUrl;
+  try {
+    return stripTracking(new URL(location, originalUrl)).href;
+  } catch {
+    return originalUrl;
+  }
+}
+
+async function fetchJson(page: Page, url: string): Promise<[Listing<Link>, Listing<CommentData>] | undefined> {
+  const response = await page.request
+    .get(url, { headers: { Accept: 'application/json' } })
+    .catch(() => undefined);
+  if (!response?.ok()) return undefined;
+  if (!response.headers()['content-type']?.includes('json')) return undefined;
+  const body = (await response.json().catch(() => undefined)) as unknown;
+  return Array.isArray(body) && body.length >= 2 ? (body as [Listing<Link>, Listing<CommentData>]) : undefined;
+}
+
+async function resolve({ page, originalUrl }: ResolveContext): Promise<Post> {
+  let postUrl = originalUrl;
+  try {
+    if (isShareLink(new URL(originalUrl))) postUrl = await followShareLink(page, originalUrl);
+  } catch {
+    // Not a URL we can take apart; the request below will say so.
+  }
+
+  // Reddit's JSON is the whole post and the whole first page of comments in
+  // one response, which no amount of reading the page can match.
+  let body = await fetchJson(page, jsonUrlFor(postUrl));
+
+  if (!body) {
+    // A cold context gets a JavaScript challenge instead, which the page
+    // solves by itself on any ordinary navigation. Doing that once leaves the
+    // cookie behind and the JSON answers from then on, including for every
+    // later post.
+    await page.goto(postUrl, { waitUntil: 'domcontentloaded' }).catch(() => undefined);
+    await page.waitForTimeout(1500);
+    body = await fetchJson(page, jsonUrlFor(page.url() || postUrl));
+
+    if (!body) {
+      // Still refused. The page in front of us is the post, so read that.
+      await page.waitForSelector('shreddit-comment', { timeout: 5_000 }).catch(() => undefined);
+      return fromPage(page, originalUrl);
+    }
+  }
+
+  // The resolved permalink, not the share code we came in with: an opaque
+  // `/s/` link says nothing about what it points at, and handing it back is
+  // the same as handing back a tracking parameter.
+  return toPost(body, postUrl);
+}
+
+export const reddit: PlatformSpec = {
+  id: 'reddit',
+  label: 'Reddit',
+  prefix: 'reddit',
+  canonicalHost: 'www.reddit.com',
+  textPosition: 'above',
+  matchesHost: (host) => host === 'reddit.com' || host.endsWith('.reddit.com') || host === 'redd.it',
+  /** A single opaque segment is a `redd.it` share code — the rewrite rule
+   *  drops the host, so `redd.it/abc123` arrives as just `abc123`. */
+  buildOriginalUrl: (pathRest, search) => {
+    const first = pathRest.split('/')[0] ?? '';
+    if (first && !pathRest.includes('/') && !KNOWN_ROOTS.has(first)) {
+      return `https://redd.it/${first}${search}`;
+    }
+    return `${HOST}/${pathRest}${search}`;
+  },
+  resolve,
+};