feat: add inline mentions in comments

app/(app)/notifications/page.tsx

@@ -145,7 +145,9 @@ function NotificationRow({
       ? `/u/${selfHandle}/posts#post-${n.post_id}`
       : n.kind === "post_mention" && n.post_id && n.actor_handle
         ? `/u/${n.actor_handle}/posts#post-${n.post_id}`
-        : (n.kind === "post_comment" || n.kind === "comment_reply") &&
+        : (n.kind === "post_comment" ||
+              n.kind === "comment_reply" ||
+              n.kind === "comment_mention") &&
             n.post_id &&
             n.post_author_handle
           ? `/u/${n.post_author_handle}/posts#post-${n.post_id}`
@@ -190,6 +192,8 @@ function messageFor(n: AppNotification): string {
       return "commented on your post.";
     case "comment_reply":
       return "replied to your comment.";
+    case "comment_mention":
+      return "mentioned you in a comment.";
     default:
       return "sent you a notification.";
   }

components/notifications/notifications-provider.tsx

@@ -67,6 +67,8 @@ function messageFor(e: IncomingEvent): string {
       return `${who} commented on your post`;
     case "comment_reply":
       return `${who} replied to your comment`;
+    case "comment_mention":
+      return `${who} mentioned you in a comment`;
     default:
       return "You have a new notification";
   }

components/social/comment/comment-row.tsx

@@ -11,6 +11,7 @@
  */
 
 import { useEffect, useRef, useState } from "react";
+import Link from "next/link";
 import { HiHeart, HiOutlineHeart } from "react-icons/hi2";
 import { Pin } from "lucide-react";
 import { toast } from "sonner";
@@ -20,6 +21,26 @@ import { UserAvatar } from "@/components/ui/user-avatar";
 import { timeAgo } from "@/lib/time";
 import { CommentMenu } from "./comment-menu";
 
+// Split a comment body into text + clickable @handle links. The capturing
+// group keeps the delimiters so they can be turned into profile links.
+const MENTION_TOKEN = /(@[A-Za-z0-9_]+)/g;
+function renderBody(text: string) {
+  return text.split(MENTION_TOKEN).map((part, i) => {
+    if (part.length > 1 && part[0] === "@") {
+      return (
+        <Link
+          key={i}
+          href={`/u/${part.slice(1)}`}
+          className="font-medium text-primary hover:underline"
+        >
+          {part}
+        </Link>
+      );
+    }
+    return part;
+  });
+}
+
 export function CommentRow({
   comment,
   viewerId,
@@ -151,7 +172,7 @@ export function CommentRow({
                 @{comment.reply_to_handle}{" "}
               </span>
             ) : null}
-            {comment.body}
+            {renderBody(comment.body)}
           </p>
 
           {/* Inline action row */}

components/social/comment/post-comments-drawer.tsx

@@ -37,6 +37,7 @@ import { useMediaQuery } from "@/components/selection-toolbar/shared";
 import { Drawer, DrawerContent } from "@/components/ui/drawer";
 import { ConfirmModal } from "@/components/ui/confirm-modal";
 import { EmojiPicker } from "@/components/ui/emoji-picker";
+import { MentionTextarea } from "@/components/social/mention-textarea";
 import { CommentRow } from "./comment-row";
 import { ReportCommentModal } from "./comment-report-modal";
 
@@ -324,20 +325,15 @@ export function PostCommentsDrawer({
             ) : null}
             <div className="flex items-end gap-2">
               <EmojiPicker onSelect={insertEmoji} />
-              <textarea
+              <MentionTextarea
                 ref={inputRef}
                 value={draft}
-                onChange={(e) => setDraft(e.target.value)}
-                onKeyDown={(e) => {
-                  if (e.key === "Enter" && !e.shiftKey) {
-                    e.preventDefault();
-                    submit();
-                  }
-                }}
+                onChange={setDraft}
+                onSubmit={submit}
                 rows={1}
                 maxLength={2000}
                 placeholder={replyTo ? "Write a reply…" : "Add a comment…"}
-                className="flex-1 resize-none rounded-lg border border-border bg-background px-3 py-2 text-base sm:text-sm text-foreground outline-none focus-visible:ring-2 focus-visible:ring-primary/40 max-h-32"
+                className="w-full resize-none rounded-lg border border-border bg-background px-3 py-2 text-base sm:text-sm text-foreground outline-none focus-visible:ring-2 focus-visible:ring-primary/40 max-h-32"
               />
               <button
                 type="button"

components/social/mention-textarea.tsx

@@ -0,0 +1,238 @@
+"use client";
+
+/**
+ * MentionTextarea — a textarea with inline "@" mention autocomplete.
+ *
+ * As the user types an `@token` at the caret, a suggestion list opens above
+ * the field (prioritised following → followers → others). Picking a user (tap
+ * or ↑/↓ + Enter/Tab) replaces the token with `@handle `. The list is portaled
+ * with `pointer-events-auto` so it works inside a modal vaul drawer, and
+ * dismisses on blur — no document listener that could fight the drawer.
+ *
+ * Enter (without Shift) submits via `onSubmit` ONLY when no suggestion list is
+ * open; while the list is open, Enter/Tab pick the highlighted user. The
+ * underlying <textarea> ref is forwarded so callers can focus it / splice text
+ * (e.g. the emoji picker).
+ */
+
+import {
+  forwardRef,
+  useEffect,
+  useImperativeHandle,
+  useRef,
+  useState,
+} from "react";
+import { createPortal } from "react-dom";
+import { Loader2 } from "lucide-react";
+import { posts, type UserSummary } from "@/lib/social";
+import { UserAvatar } from "@/components/ui/user-avatar";
+
+const SUGGEST_LIMIT = 8;
+// "@" at line start or after whitespace, then up to 30 handle chars, at the
+// end of the text before the caret. Avoids matching emails (foo@bar).
+const MENTION_RE = /(^|\s)@([A-Za-z0-9_]{0,30})$/;
+
+type Mention = { start: number; query: string };
+type PanelPos = { left: number; bottom: number; width: number };
+
+export const MentionTextarea = forwardRef<
+  HTMLTextAreaElement,
+  {
+    value: string;
+    onChange: (v: string) => void;
+    /** Called on Enter (no Shift) when the suggestion list is closed. */
+    onSubmit?: () => void;
+    placeholder?: string;
+    className?: string;
+    maxLength?: number;
+    rows?: number;
+  }
+>(function MentionTextarea(
+  { value, onChange, onSubmit, placeholder, className, maxLength, rows = 1 },
+  ref,
+) {
+  const innerRef = useRef<HTMLTextAreaElement>(null);
+  useImperativeHandle(ref, () => innerRef.current as HTMLTextAreaElement, []);
+
+  const [mention, setMention] = useState<Mention | null>(null);
+  const [items, setItems] = useState<UserSummary[]>([]);
+  const [loading, setLoading] = useState(false);
+  const [active, setActive] = useState(0);
+  const [pos, setPos] = useState<PanelPos | null>(null);
+  const reqRef = useRef(0);
+  const blurTimer = useRef<number | null>(null);
+
+  // Detect the active @token from the text up to the caret.
+  function detect(el: HTMLTextAreaElement) {
+    const caret = el.selectionStart ?? 0;
+    const m = MENTION_RE.exec(el.value.slice(0, caret));
+    if (!m) {
+      setMention(null);
+      return;
+    }
+    setMention({ start: caret - m[2].length - 1, query: m[2] });
+    setActive(0);
+    const r = el.getBoundingClientRect();
+    setPos({
+      left: r.left,
+      bottom: window.innerHeight - r.top + 6,
+      width: r.width,
+    });
+  }
+
+  // Fetch suggestions (debounced) whenever the active token changes.
+  useEffect(() => {
+    if (!mention) return;
+    const token = ++reqRef.current;
+    const t = window.setTimeout(() => {
+      setLoading(true);
+      posts
+        .mentionSuggest(mention.query, { limit: SUGGEST_LIMIT, offset: 0 })
+        .then((res) => {
+          if (reqRef.current === token) setItems(res);
+        })
+        .catch(() => {
+          if (reqRef.current === token) setItems([]);
+        })
+        .finally(() => {
+          if (reqRef.current === token) setLoading(false);
+        });
+    }, 150);
+    return () => window.clearTimeout(t);
+  }, [mention]);
+
+  function select(u: UserSummary) {
+    const el = innerRef.current;
+    if (!el || !mention) return;
+    const caret = el.selectionStart ?? value.length;
+    const insert = `@${u.handle} `;
+    const next = value.slice(0, mention.start) + insert + value.slice(caret);
+    onChange(next);
+    setMention(null);
+    const newCaret = mention.start + insert.length;
+    requestAnimationFrame(() => {
+      const node = innerRef.current;
+      if (!node) return;
+      node.focus();
+      node.setSelectionRange(newCaret, newCaret);
+    });
+  }
+
+  const listOpen = !!mention && (loading || items.length > 0);
+
+  function onKeyDown(e: React.KeyboardEvent<HTMLTextAreaElement>) {
+    if (listOpen && items.length > 0) {
+      if (e.key === "ArrowDown") {
+        e.preventDefault();
+        setActive((a) => Math.min(a + 1, items.length - 1));
+        return;
+      }
+      if (e.key === "ArrowUp") {
+        e.preventDefault();
+        setActive((a) => Math.max(a - 1, 0));
+        return;
+      }
+      if (e.key === "Enter" || e.key === "Tab") {
+        e.preventDefault();
+        select(items[active] ?? items[0]);
+        return;
+      }
+      if (e.key === "Escape") {
+        e.preventDefault();
+        setMention(null);
+        return;
+      }
+    }
+    if (e.key === "Enter" && !e.shiftKey) {
+      e.preventDefault();
+      onSubmit?.();
+    }
+  }
+
+  return (
+    <div className="relative flex-1">
+      <textarea
+        ref={innerRef}
+        value={value}
+        rows={rows}
+        maxLength={maxLength}
+        placeholder={placeholder}
+        className={className}
+        autoComplete="off"
+        onChange={(e) => {
+          onChange(e.target.value);
+          detect(e.target);
+        }}
+        onKeyUp={(e) => detect(e.currentTarget)}
+        onClick={(e) => detect(e.currentTarget)}
+        onKeyDown={onKeyDown}
+        onBlur={() => {
+          // Defer so a result tap (mousedown→click) lands before close.
+          blurTimer.current = window.setTimeout(() => setMention(null), 120);
+        }}
+      />
+
+      {listOpen && pos && typeof document !== "undefined"
+        ? createPortal(
+            <div
+              role="listbox"
+              aria-label="Mention suggestions"
+              style={{
+                position: "fixed",
+                left: pos.left,
+                bottom: pos.bottom,
+                width: pos.width,
+              }}
+              // pointer-events-auto: the comments drawer is a modal vaul sheet
+              // (body gets pointer-events:none); without this the list would be
+              // click-through.
+              className="pointer-events-auto z-[101] max-h-56 overflow-y-auto overscroll-contain rounded-lg border border-border bg-card shadow-xl"
+              onTouchMove={(e) => e.stopPropagation()}
+            >
+              {items.map((u, i) => (
+                <button
+                  key={u.id ?? u.handle}
+                  type="button"
+                  role="option"
+                  aria-selected={i === active}
+                  // Keep textarea focus + cancel the pending blur-close so the
+                  // click registers before the list would otherwise close.
+                  onMouseDown={(e) => {
+                    e.preventDefault();
+                    if (blurTimer.current)
+                      window.clearTimeout(blurTimer.current);
+                  }}
+                  onMouseEnter={() => setActive(i)}
+                  onClick={() => select(u)}
+                  className={`flex w-full items-center gap-2.5 px-3 py-2 text-left transition-colors ${
+                    i === active ? "bg-muted/70" : "hover:bg-muted/60"
+                  }`}
+                >
+                  <UserAvatar
+                    src={u.avatar_url}
+                    name={u.name}
+                    className="size-8"
+                    textClassName="text-xs"
+                  />
+                  <span className="min-w-0">
+                    <span className="block truncate text-sm font-medium text-foreground">
+                      {u.name}
+                    </span>
+                    <span className="block truncate text-xs text-muted-foreground">
+                      @{u.handle}
+                    </span>
+                  </span>
+                </button>
+              ))}
+              {loading ? (
+                <div className="flex justify-center py-2">
+                  <Loader2 className="size-4 animate-spin text-muted-foreground" />
+                </div>
+              ) : null}
+            </div>,
+            document.body,
+          )
+        : null}
+    </div>
+  );
+});