feat: show latest particle preview in stream list

js/src/features/particles/particle-list-view.tsx

@@ -1,8 +1,14 @@
 import { useMemo } from "react";
 import { useNavigate } from "react-router-dom";
 import { Radio } from "lucide-react";
-import { useLiveParticleChildren } from "@/hooks/use-particle";
-import { parseParticlePath, type ParticlePath } from "@/lib/particle-path";
+import { useLiveParticleChildren, useLiveLatestChild } from "@/hooks/use-particle";
+import {
+  parseParticlePath,
+  particlePath,
+  type ParticlePath,
+} from "@/lib/particle-path";
+import { getInitials } from "@/lib/utils";
+import { formatDistanceToNow } from "@/lib/time-utils";
 import { Avatar, AvatarFallback } from "@/components/ui/avatar";
 import { ScrollArea } from "@/components/ui/scroll-area";
 import { Separator } from "@/components/ui/separator";
@@ -10,14 +16,42 @@ import { Progress } from "@/components/ui/progress";
 import { Small } from "@/components/ui/typography";
 import type { Particle, StreamProperties } from "@/api/types";
 
+function getMessagePreview(particle: Particle): string {
+  switch (particle.type) {
+    case "text":
+      return particle.properties.content;
+    case "media":
+      return "Clip received";
+    case "file":
+      return particle.properties.filename;
+    case "quest":
+      return particle.properties.title;
+    case "paper":
+      return particle.properties.title;
+    default:
+      return particle.type;
+  }
+}
+
 function StreamRow({
   particle,
+  networkId,
   onClick,
 }: {
   particle: Particle & { type: "stream"; properties: StreamProperties };
+  networkId: string;
   onClick: () => void;
 }) {
-  const initials = particle.properties.name.slice(0, 2).toUpperCase();
+  const streamPath = particlePath(networkId, [particle.id]);
+  const { latestChild } = useLiveLatestChild(streamPath);
+
+  const initials = latestChild
+    ? getInitials(latestChild.created_by_email)
+    : particle.properties.name.slice(0, 2).toUpperCase();
+
+  const subtitle = latestChild
+    ? getMessagePreview(latestChild)
+    : particle.properties.status;
 
   return (
     <button
@@ -31,13 +65,20 @@ function StreamRow({
         </AvatarFallback>
       </Avatar>
       <div className="min-w-0 flex-1">
-        <p className="truncate text-sm font-medium">
-          {particle.properties.name}
-        </p>
+        <div className="flex items-center justify-between gap-2">
+          <p className="truncate text-sm font-medium">
+            {particle.properties.name}
+          </p>
+          {latestChild && (
+            <Small className="text-muted-foreground shrink-0">
+              {formatDistanceToNow(latestChild.created_at.toISOString())}
+            </Small>
+          )}
+        </div>
         <div className="text-muted-foreground flex items-center gap-1">
-          <Radio className="size-3" />
-          <Small className="text-muted-foreground">
-            {particle.properties.status}
+          {!latestChild && <Radio className="size-3" />}
+          <Small className="text-muted-foreground truncate">
+            {subtitle}
           </Small>
         </div>
       </div>
@@ -73,6 +114,7 @@ export function ParticleListView({ path }: ParticleListViewProps) {
           <div key={stream.id}>
             <StreamRow
               particle={stream}
+              networkId={networkId}
               onClick={() => navigate(`/${networkId}/${stream.id}`)}
             />
             {index < streams.length - 1 && <Separator className="mx-4" />}

js/src/hooks/use-particle.ts

@@ -1,5 +1,9 @@
 import { useState, useEffect, useMemo } from "react";
-import { subscribeToParticle, subscribeToParticleChildren } from "@/lib/firestore-particles";
+import {
+  subscribeToParticle,
+  subscribeToParticleChildren,
+  subscribeToLatestChild,
+} from "@/lib/firestore-particles";
 import type { Particle } from "@/api/types";
 import {
   type ParticlePath,
@@ -80,3 +84,35 @@ export function useLiveParticleChildren(
 
   return { children, isLoading, error };
 }
+
+interface UseLiveLatestChildResult {
+  latestChild: Particle | null;
+  isLoading: boolean;
+}
+
+export function useLiveLatestChild(path: ParticlePath): UseLiveLatestChildResult {
+  const [latestChild, setLatestChild] = useState<Particle | null>(null);
+  const [isLoading, setIsLoading] = useState(true);
+
+  const collectionPath = useMemo(() => toFirestoreChildrenPath(path), [path]);
+
+  useEffect(() => {
+    setIsLoading(true);
+    setLatestChild(null);
+
+    const unsubscribe = subscribeToLatestChild(
+      collectionPath,
+      (data) => {
+        setLatestChild(data);
+        setIsLoading(false);
+      },
+      () => {
+        setIsLoading(false);
+      },
+    );
+
+    return unsubscribe;
+  }, [collectionPath]);
+
+  return { latestChild, isLoading };
+}

js/src/lib/firestore-particles.ts

@@ -7,6 +7,7 @@ import {
   updateDoc,
   query,
   orderBy,
+  limit,
   serverTimestamp,
   Timestamp,
   type DocumentData,
@@ -97,6 +98,25 @@ export function subscribeToParticleChildren(
   );
 }
 
+export function subscribeToLatestChild(
+  collectionPath: string,
+  onData: (child: Particle | null) => void,
+  onError: (error: Error) => void,
+): Unsubscribe {
+  const q = query(
+    typedCollection(collectionPath),
+    orderBy("created_at", "desc"),
+    limit(1),
+  );
+  return onSnapshot(
+    q,
+    (snap) => {
+      onData(snap.empty ? null : snap.docs[0].data());
+    },
+    onError,
+  );
+}
+
 // This creates a new particle document with the given properties and returns its ID.
 export async function createParticle<T extends ParticleType>(
   collectionPath: string,