feat: add recently viewed posts backend and dashboard integration

app/api/posts/view/route.js

@@ -0,0 +1,56 @@
+import { doc, getDoc, setDoc } from "firebase/firestore";
+import { getServerDb } from "../../../../lib/firebase-admin";
+
+export async function POST(req) {
+  try {
+    const { userId, postId } = await req.json();
+
+    if (!userId || !postId) {
+      return Response.json(
+        { error: "userId and postId are required" },
+        { status: 400 }
+      );
+    }
+
+    const db = getServerDb();
+
+    // Verify the post exists
+    const postRef = doc(db, "posts", postId);
+    const postSnap = await getDoc(postRef);
+    if (!postSnap.exists()) {
+      return Response.json(
+        { error: "Post not found" },
+        { status: 404 }
+      );
+    }
+
+    // Update user's recentlyViewed list
+    const userRef = doc(db, "users", userId);
+    const userSnap = await getDoc(userRef);
+    const userData = userSnap.exists() ? userSnap.data() : {};
+    const recentlyViewed = userData.recentlyViewed || [];
+
+    // Store only post IDs (postId is already a string)
+    // Avoid duplicate entries & move to the top
+    let updatedList = recentlyViewed.filter((id) => id !== postId);
+    updatedList.unshift(postId);
+
+    // Keep only the latest 10 viewed posts
+    if (updatedList.length > 10) {
+      updatedList = updatedList.slice(0, 10);
+    }
+
+    await setDoc(userRef, { recentlyViewed: updatedList }, { merge: true });
+
+    return Response.json({
+      success: true,
+      recentlyViewed: updatedList,
+    });
+  } catch (error) {
+    console.error("Error in /api/posts/view:", error);
+    return Response.json(
+      { error: "Internal server error", details: error.message },
+      { status: 500 }
+    );
+  }
+}

app/dashboard/page.js

@@ -650,9 +650,22 @@ export default function Dashboard() {
 
   // ── Comment CRUD ──────────────────────────────────────────────────────────
   const toggleComments = (postId) => {
-    setOpenCommentsFor((prev) => (prev === postId ? null : postId));
+    const nextState = openCommentsFor === postId ? null : postId;
+    setOpenCommentsFor(nextState);
     setCommentDraft("");
     setEditingComment(null);
+
+    if (nextState && user) {
+      fetch("/api/posts/view", {
+        method: "POST",
+        headers: {
+          "Content-Type": "application/json",
+        },
+        body: JSON.stringify({ userId: user.uid, postId }),
+      }).catch((err) => {
+        console.error("Failed to update recently viewed:", err);
+      });
+    }
   };
 
   const handleAddComment = async (post) => {