From 830077a75f31b2272f78d774b732bebeac096666 Mon Sep 17 00:00:00 2001
From: Aditya Raut <araut7798@gmail.com>
Date: Sun, 5 Apr 2026 09:09:57 +0530
Subject: [PATCH] feat(assignments): add file attachment functionality for
 assignments and submissions

---
 .../components/CourseView/AssignmentCard.jsx  | 105 +++++++++++++++---
 .../components/CourseView/AssignmentModal.jsx |  34 ++++++
 .../components/CourseView/AssignmentsTab.jsx  |   6 +-
 .../src/components/CourseView/QuizzesTab.jsx  |  63 ++++++++---
 client/src/pages/CourseView.jsx               |  79 ++++++++++---
 .../app/controllers/assignmentController.js   |  98 +++++++++++++++-
 server/app/controllers/authController.js      |  37 +++---
 server/app/middleware/documentUpload.js       |  19 ++++
 server/app/models/Assignment.js               |   8 ++
 server/app/models/Submission.js               |   2 +
 server/app/routes/assignments.js              |   7 +-
 11 files changed, 389 insertions(+), 69 deletions(-)
 create mode 100644 server/app/middleware/documentUpload.js

diff --git a/client/src/components/CourseView/AssignmentCard.jsx b/client/src/components/CourseView/AssignmentCard.jsx
index 76e47b3..74597d7 100644
--- a/client/src/components/CourseView/AssignmentCard.jsx
+++ b/client/src/components/CourseView/AssignmentCard.jsx
@@ -12,6 +12,7 @@ function AssignmentCard({
   mySubmission,
   submissions,
   submissionText,
+  submissionFile,
   isLocked,
   lockedByTitle,
   lockedByOrder,
@@ -179,6 +180,28 @@ function AssignmentCard({
           </div>
         )}
 
+        {/* Assignment attachments (visible to all) */}
+        {assignment.attachments?.length > 0 && (
+          <div className="mt-4 pt-4 border-t border-[var(--border)]/10">
+            <p className="text-[11px] font-bold text-[var(--muted)] uppercase tracking-[0.12em] mb-2">
+              📎 Attachments
+            </p>
+            <div className="flex flex-wrap gap-2">
+              {assignment.attachments.map((att) => (
+                <a
+                  key={att.id}
+                  href={att.url}
+                  target="_blank"
+                  rel="noopener noreferrer"
+                  className="flex items-center gap-2 px-3.5 py-2 bg-[var(--accent)]/8 hover:bg-[var(--accent)]/15 text-[var(--accent)] rounded-xl text-xs font-bold border border-[var(--accent)]/12 transition-all duration-300"
+                >
+                  {att.name.endsWith(".pdf") ? "📄" : "📝"} {att.name}
+                </a>
+              ))}
+            </div>
+          </div>
+        )}
+
         {/* Student: submission form */}
         {!isTeacher && !hasSubmission && !isLocked && (
           <div className="mt-5 pt-5 border-t border-[var(--border)]">
@@ -189,17 +212,41 @@ function AssignmentCard({
               className="w-full px-4 py-3.5 bg-[var(--surface-elevated)] border border-[var(--border)] rounded-2xl text-sm outline-none
                          resize-y focus:border-[var(--accent)] focus:ring-2 focus:ring-[var(--accent)]/12
                          transition-all duration-300 text-[var(--text)] placeholder:text-[var(--muted)] min-h-[100px] font-medium"
-              placeholder="Write your answer here..."
+              placeholder="Write your answer here... (optional if uploading a file)"
               value={submissionText || ""}
-              onChange={(e) => onSubmit(assignment.id, e.target.value, true)}
+              onChange={(e) => onSubmit(assignment.id, e.target.value, "text")}
             />
+            {/* File upload */}
+            <div className="mt-3">
+              <label className="flex items-center gap-3 px-4 py-3 bg-[var(--surface-elevated)] border border-[var(--border)] rounded-2xl cursor-pointer hover:border-[var(--accent)]/40 transition-all duration-300">
+                <span className="text-lg">📎</span>
+                <span className="text-sm text-[var(--muted)] flex-1 truncate">
+                  {submissionFile ? submissionFile.name : "Attach PDF or DOCX (optional)"}
+                </span>
+                <input
+                  type="file"
+                  accept=".pdf,.doc,.docx"
+                  className="hidden"
+                  onChange={(e) => onSubmit(assignment.id, e.target.files[0] || null, "file")}
+                />
+              </label>
+              {submissionFile && (
+                <button
+                  type="button"
+                  onClick={() => onSubmit(assignment.id, null, "file")}
+                  className="mt-1 ml-1 text-[11px] text-red-400 hover:text-red-300 cursor-pointer"
+                >
+                  Remove file
+                </button>
+              )}
+            </div>
             <div className="flex justify-end mt-3">
               <button
-                onClick={() => onSubmit(assignment.id, submissionText, false)}
-                disabled={!submissionText?.trim()}
+                onClick={() => onSubmit(assignment.id, null, "submit")}
+                disabled={!submissionText?.trim() && !submissionFile}
                 className="px-6 py-2.5 sc-btn-glow disabled:opacity-35 rounded-xl text-xs font-bold cursor-pointer disabled:cursor-not-allowed transition-all active:scale-95"
               >
-                Submit Answer →
+                Submit →
               </button>
             </div>
           </div>
@@ -212,9 +259,21 @@ function AssignmentCard({
               Your Submission
             </p>
             <div className="glass rounded-2xl px-5 py-4 border border-[var(--border)]/12">
-              <p className="text-sm text-[var(--text)] leading-relaxed">
-                {mySubmission.content}
-              </p>
+              {mySubmission.content && (
+                <p className="text-sm text-[var(--text)] leading-relaxed">
+                  {mySubmission.content}
+                </p>
+              )}
+              {mySubmission.fileUrl && (
+                <a
+                  href={mySubmission.fileUrl}
+                  target="_blank"
+                  rel="noopener noreferrer"
+                  className="inline-flex items-center gap-2 mt-2 px-3.5 py-2 bg-[var(--accent)]/8 hover:bg-[var(--accent)]/15 text-[var(--accent)] rounded-xl text-xs font-bold border border-[var(--accent)]/12 transition-all duration-300"
+                >
+                  📎 {mySubmission.fileName || "Download file"}
+                </a>
+              )}
               {mySubmission.feedback && (
                 <div className="mt-4 pt-4 border-t border-[var(--border)]/12">
                   <p className="text-[11px] font-bold text-[var(--accent)] uppercase tracking-[0.12em] mb-1.5 flex items-center gap-1.5">
@@ -286,14 +345,28 @@ function AssignmentCard({
                           </button>
                         </div>
                       </div>
-                      <p className="text-[13px] text-[var(--text)] leading-relaxed pl-[42px]">
-                        {s.content}
-                      </p>
-                      {s.feedback && (
-                        <p className="text-[11px] text-[var(--muted)] mt-1.5 pl-[42px] italic">
-                          "{s.feedback}"
-                        </p>
-                      )}
+                      <div className="pl-[42px]">
+                        {s.content && (
+                          <p className="text-[13px] text-[var(--text)] leading-relaxed">
+                            {s.content}
+                          </p>
+                        )}
+                        {s.fileUrl && (
+                          <a
+                            href={s.fileUrl}
+                            target="_blank"
+                            rel="noopener noreferrer"
+                            className="inline-flex items-center gap-2 mt-1.5 px-3 py-1.5 bg-[var(--accent)]/8 hover:bg-[var(--accent)]/15 text-[var(--accent)] rounded-xl text-[11px] font-bold border border-[var(--accent)]/12 transition-all duration-300"
+                          >
+                            📎 {s.fileName || "View file"}
+                          </a>
+                        )}
+                        {s.feedback && (
+                          <p className="text-[11px] text-[var(--muted)] mt-1.5 italic">
+                            "{s.feedback}"
+                          </p>
+                        )}
+                      </div>
                     </div>
                   );
                 })}
diff --git a/client/src/components/CourseView/AssignmentModal.jsx b/client/src/components/CourseView/AssignmentModal.jsx
index aab3162..3bcedfa 100644
--- a/client/src/components/CourseView/AssignmentModal.jsx
+++ b/client/src/components/CourseView/AssignmentModal.jsx
@@ -10,6 +10,11 @@ function AssignmentModal({
 }) {
   if (!isOpen) return null;
 
+  const handleFileChange = (e) => {
+    const file = e.target.files[0] || null;
+    onChange({ ...form, attachmentFile: file });
+  };
+
   return modalOverlay(
     onClose,
     <>
@@ -68,6 +73,35 @@ function AssignmentModal({
             />
           </div>
         </div>
+
+        {/* Optional document attachment */}
+        <div>
+          <label className="block text-[11px] font-bold text-[var(--text)] uppercase tracking-wider mb-2 ml-1 opacity-80">
+            Attach Document <span className="normal-case font-normal opacity-60">(PDF or DOCX, optional)</span>
+          </label>
+          <label className="flex items-center gap-3 px-4 py-3 bg-[var(--surface-elevated)] border border-[var(--border)] rounded-2xl cursor-pointer hover:border-[var(--accent)]/40 transition-all duration-300">
+            <span className="text-xl">📎</span>
+            <span className="text-sm text-[var(--muted)] flex-1 truncate">
+              {form.attachmentFile ? form.attachmentFile.name : "Click to choose file…"}
+            </span>
+            <input
+              type="file"
+              accept=".pdf,.doc,.docx,application/pdf,application/msword,application/vnd.openxmlformats-officedocument.wordprocessingml.document"
+              className="hidden"
+              onChange={handleFileChange}
+            />
+          </label>
+          {form.attachmentFile && (
+            <button
+              type="button"
+              onClick={() => onChange({ ...form, attachmentFile: null })}
+              className="mt-1.5 ml-1 text-[11px] text-red-400 hover:text-red-300 cursor-pointer"
+            >
+              Remove file
+            </button>
+          )}
+        </div>
+
         <div className="flex justify-end gap-3 pt-6 mt-2 border-t border-[var(--border)]/30">
           <button
             type="button"
diff --git a/client/src/components/CourseView/AssignmentsTab.jsx b/client/src/components/CourseView/AssignmentsTab.jsx
index 5fc8720..eddd970 100644
--- a/client/src/components/CourseView/AssignmentsTab.jsx
+++ b/client/src/components/CourseView/AssignmentsTab.jsx
@@ -6,6 +6,7 @@ function AssignmentsTab({
   mySubmissions,
   expandedSubs,
   submissionText,
+  submissionFile,
   onSubmit,
   onToggleSubs,
   onDelete,
@@ -119,12 +120,11 @@ function AssignmentsTab({
                   mySubmission={mySubmissions[a.id]}
                   submissions={expandedSubs[a.id]}
                   submissionText={submissionText[a.id]}
+                  submissionFile={submissionFile?.[a.id]}
                   isLocked={!!lockInfo}
                   lockedByTitle={lockInfo?.byTitle}
                   lockedByOrder={lockInfo?.byOrder}
-                  onSubmit={(aid, text, isUpdate) =>
-                    isUpdate ? onSubmit(aid, text) : onSubmit(aid, text, false)
-                  }
+                  onSubmit={onSubmit}
                   onToggleSubs={onToggleSubs}
                   onDelete={onDelete}
                   onGrade={onGrade}
diff --git a/client/src/components/CourseView/QuizzesTab.jsx b/client/src/components/CourseView/QuizzesTab.jsx
index a6ea18a..d6e1ec7 100644
--- a/client/src/components/CourseView/QuizzesTab.jsx
+++ b/client/src/components/CourseView/QuizzesTab.jsx
@@ -1,6 +1,6 @@
 import { useNavigate } from "react-router-dom";
 
-function QuizzesTab({ quizzes, isTeacher, onDelete, onAddClick }) {
+function QuizzesTab({ quizzes, isTeacher, myQuizResults = {}, onDelete, onAddClick }) {
   const navigate = useNavigate();
 
   return (
@@ -120,26 +120,55 @@ function QuizzesTab({ quizzes, isTeacher, onDelete, onAddClick }) {
                         })}
                       </span>
                     )}
+                    {/* Score pill — shown after student completes quiz */}
+                    {!isTeacher && myQuizResults[q.id] && (() => {
+                      const r = myQuizResults[q.id];
+                      const pct = r.percentage ?? 0;
+                      const colorCls = pct >= 70
+                        ? "bg-emerald-500/12 text-emerald-400 border-emerald-500/20"
+                        : pct >= 40
+                          ? "bg-amber-500/12 text-amber-400 border-amber-500/20"
+                          : "bg-red-500/12 text-red-400 border-red-500/20";
+                      return (
+                        <span className={`flex items-center gap-1.5 px-3 py-1.5 rounded-xl text-[11px] font-black border ${colorCls}`}>
+                          🏆 {r.score}/{r.totalPoints} pts · {pct}%
+                        </span>
+                      );
+                    })()}
                   </div>
 
                   {/* Actions */}
-                  <div className="flex gap-2.5">
-                    {!isTeacher && (
-                      <button
-                        onClick={() => navigate(`/quiz/${q.id}`)}
-                        className="flex items-center gap-2 px-5 py-2.5 sc-btn-glow rounded-xl text-xs font-bold cursor-pointer active:scale-95"
-                      >
-                        Take Quiz
-                        <svg
-                          width="12"
-                          height="12"
-                          viewBox="0 0 16 16"
-                          fill="currentColor"
+                  <div className="flex items-center gap-2.5">
+                    {!isTeacher && (() => {
+                      const taken = !!myQuizResults[q.id];
+                      return (
+                        <button
+                          onClick={() => !taken && navigate(`/quiz/${q.id}`)}
+                          disabled={taken}
+                          className={`flex items-center gap-2 px-5 py-2.5 rounded-xl text-xs font-bold transition-all active:scale-95
+                            ${taken
+                              ? "bg-emerald-500/10 text-emerald-400 border border-emerald-500/20 cursor-not-allowed opacity-80"
+                              : "sc-btn-glow cursor-pointer"
+                            }`}
                         >
-                          <path d="M8.22 2.97a.75.75 0 011.06 0l4.25 4.25a.75.75 0 010 1.06l-4.25 4.25a.75.75 0 01-1.06-1.06l2.97-2.97H3.75a.75.75 0 010-1.5h7.44L8.22 4.03a.75.75 0 010-1.06z" />
-                        </svg>
-                      </button>
-                    )}
+                          {taken ? (
+                            <>
+                              <svg width="12" height="12" viewBox="0 0 16 16" fill="currentColor">
+                                <path d="M13.78 4.22a.75.75 0 010 1.06l-7.25 7.25a.75.75 0 01-1.06 0L2.22 9.28a.75.75 0 011.06-1.06L6 10.94l6.72-6.72a.75.75 0 011.06 0z" />
+                              </svg>
+                              Quiz Taken
+                            </>
+                          ) : (
+                            <>
+                              Take Quiz
+                              <svg width="12" height="12" viewBox="0 0 16 16" fill="currentColor">
+                                <path d="M8.22 2.97a.75.75 0 011.06 0l4.25 4.25a.75.75 0 010 1.06l-4.25 4.25a.75.75 0 01-1.06-1.06l2.97-2.97H3.75a.75.75 0 010-1.5h7.44L8.22 4.03a.75.75 0 010-1.06z" />
+                              </svg>
+                            </>
+                          )}
+                        </button>
+                      );
+                    })()}
                     {isTeacher && (
                       <>
                         <button
diff --git a/client/src/pages/CourseView.jsx b/client/src/pages/CourseView.jsx
index 9524089..a16d345 100644
--- a/client/src/pages/CourseView.jsx
+++ b/client/src/pages/CourseView.jsx
@@ -66,6 +66,8 @@ function CourseView() {
   const [expandedSubs, setExpandedSubs] = useState({});
   const expandedSubsRef = useRef({});
   const [submissionText, setSubmissionText] = useState({});
+  const [submissionFile, setSubmissionFile] = useState({});
+  const [myQuizResults, setMyQuizResults] = useState({});
   const [gradeForm, setGradeForm] = useState({ score: "", feedback: "" });
   const [gradingSubId, setGradingSubId] = useState(null);
   const [matForm, setMatForm] = useState({
@@ -81,6 +83,7 @@ function CourseView() {
     description: "",
     dueDate: "",
     maxScore: 100,
+    attachmentFile: null,
   });
   const [quizForm, setQuizForm] = useState({
     title: "",
@@ -279,6 +282,17 @@ function CourseView() {
     });
   }, [assignments, isTeacher, user.id]);
 
+  useEffect(() => {
+    if (isTeacher || quizzes.length === 0) return;
+    quizzes.forEach((q) => {
+      apiFetch(`/api/quizzes/${q.id}/my-result?studentId=${user.id}`)
+        .then((r) => r.json())
+        .then((d) => {
+          if (!d.error) setMyQuizResults((p) => ({ ...p, [q.id]: d }));
+        });
+    });
+  }, [quizzes, isTeacher, user.id]);
+
   // Material actions
   const saveMaterial = async (e) => {
     e.preventDefault();
@@ -353,15 +367,32 @@ function CourseView() {
     const res = await apiFetch(`/api/courses/${id}/assignments`, {
       method: "POST",
       headers: { "Content-Type": "application/json" },
-      body: JSON.stringify({ ...assForm, teacherId: user.id }),
+      body: JSON.stringify({
+        title: assForm.title,
+        description: assForm.description,
+        dueDate: assForm.dueDate,
+        maxScore: assForm.maxScore,
+        teacherId: user.id,
+      }),
     });
     if (res.ok) {
-      const data = await res.json();
+      let data = await res.json();
+      // Upload attachment if provided
+      if (assForm.attachmentFile) {
+        const fd = new FormData();
+        fd.append("file", assForm.attachmentFile);
+        fd.append("teacherId", user.id);
+        const attRes = await apiFetch(`/api/assignments/${data.id}/attachments`, {
+          method: "POST",
+          body: fd,
+        });
+        if (attRes.ok) data = await attRes.json();
+      }
       setAssignments((p) =>
         p.some((a) => String(a.id) === String(data.id)) ? p : [data, ...p],
       );
       setModal(null);
-      setAssForm({ title: "", description: "", dueDate: "", maxScore: 100 });
+      setAssForm({ title: "", description: "", dueDate: "", maxScore: 100, attachmentFile: null });
     }
     setSaving(false);
   };
@@ -380,18 +411,34 @@ function CourseView() {
     });
   };
 
-  const submitAssignment = async (aid, content, isUpdate = false) => {
-    if (!isUpdate) {
-      if (!content?.trim()) return;
-      const res = await apiFetch(`/api/assignments/${aid}/submit`, {
-        method: "POST",
-        headers: { "Content-Type": "application/json" },
-        body: JSON.stringify({ studentId: user.id, content }),
-      });
-      const data = await res.json();
-      if (!data.error) setMySubmissions((p) => ({ ...p, [aid]: data }));
-    } else {
-      setSubmissionText((p) => ({ ...p, [aid]: content }));
+  const submitAssignment = async (aid, value, action = "submit") => {
+    if (action === "text") {
+      setSubmissionText((p) => ({ ...p, [aid]: value }));
+      return;
+    }
+    if (action === "file") {
+      setSubmissionFile((p) => ({ ...p, [aid]: value }));
+      return;
+    }
+    // action === "submit"
+    const text = submissionText[aid] || "";
+    const file = submissionFile[aid] || null;
+    if (!text.trim() && !file) return;
+
+    const formData = new FormData();
+    formData.append("studentId", user.id);
+    if (text.trim()) formData.append("content", text);
+    if (file) formData.append("file", file);
+
+    const res = await apiFetch(`/api/assignments/${aid}/submit`, {
+      method: "POST",
+      body: formData,
+    });
+    const data = await res.json();
+    if (!data.error) {
+      setMySubmissions((p) => ({ ...p, [aid]: data }));
+      setSubmissionText((p) => ({ ...p, [aid]: "" }));
+      setSubmissionFile((p) => ({ ...p, [aid]: null }));
     }
   };
 
@@ -794,6 +841,7 @@ ${
                     mySubmissions={mySubmissions}
                     expandedSubs={expandedSubs}
                     submissionText={submissionText}
+                    submissionFile={submissionFile}
                     onSubmit={submitAssignment}
                     onToggleSubs={toggleSubs}
                     onDelete={deleteAssignment}
@@ -811,6 +859,7 @@ ${
                   <QuizzesTab
                     quizzes={quizzes}
                     isTeacher={isTeacher}
+                    myQuizResults={myQuizResults}
                     onDelete={deleteQuiz}
                     onAddClick={() => setModal("quiz")}
                   />
diff --git a/server/app/controllers/assignmentController.js b/server/app/controllers/assignmentController.js
index 9f40482..6a16aa8 100644
--- a/server/app/controllers/assignmentController.js
+++ b/server/app/controllers/assignmentController.js
@@ -3,6 +3,7 @@ import Submission from "../models/Submission.js";
 import Course from "../models/Course.js";
 import { emitToCourse, emitToUser } from "../services/socketService.js";
 import { pushNotification } from "../services/notificationService.js";
+import { uploadToCloudinary } from "../utils/cloudinary.js";
 
 // ─── POST /api/courses/:courseId/assignments ──────────────────────────────────
 export async function createAssignment(req, res) {
@@ -137,6 +138,76 @@ export async function deleteAssignment(req, res) {
   }
 }
 
+// ─── POST /api/assignments/:id/attachments ────────────────────────────────────
+export async function addAttachment(req, res) {
+  try {
+    const { id } = req.params;
+    const { teacherId } = req.body;
+
+    if (!req.file) return res.status(400).json({ error: "No file provided." });
+
+    const assignment = await Assignment.findById(id);
+    if (!assignment) return res.status(404).json({ error: "Assignment not found." });
+    if (assignment.createdBy.toString() !== teacherId)
+      return res.status(403).json({ error: "Only the assignment creator can add attachments." });
+
+    const result = await uploadToCloudinary(req.file.buffer, {
+      resource_type: "raw",
+      folder: "smartclass/assignment-attachments",
+      public_id: `${id}_${Date.now()}`,
+      use_filename: true,
+    });
+
+    const attachment = {
+      url: result.secure_url,
+      name: req.file.originalname,
+      publicId: result.public_id,
+      type: "raw",
+    };
+    assignment.attachments.push(attachment);
+    await assignment.save();
+
+    const formatted = formatAssignment(assignment);
+    emitToCourse(assignment.course.toString(), "assignment:updated", formatted);
+    res.status(201).json(formatted);
+  } catch (err) {
+    console.error("addAttachment error:", err);
+    res.status(500).json({ error: "Failed to upload attachment." });
+  }
+}
+
+// ─── DELETE /api/assignments/:id/attachments/:attachmentId ───────────────────
+export async function deleteAttachment(req, res) {
+  try {
+    const { id, attachmentId } = req.params;
+    const { teacherId } = req.body;
+
+    const assignment = await Assignment.findById(id);
+    if (!assignment) return res.status(404).json({ error: "Assignment not found." });
+    if (assignment.createdBy.toString() !== teacherId)
+      return res.status(403).json({ error: "Only the assignment creator can remove attachments." });
+
+    const att = assignment.attachments.id(attachmentId);
+    if (!att) return res.status(404).json({ error: "Attachment not found." });
+
+    // Delete from Cloudinary
+    try {
+      const { default: cloudinary } = await import("../utils/cloudinary.js");
+      await cloudinary.uploader.destroy(att.publicId, { resource_type: "raw" });
+    } catch (_) {}
+
+    assignment.attachments.pull(attachmentId);
+    await assignment.save();
+
+    const formatted = formatAssignment(assignment);
+    emitToCourse(assignment.course.toString(), "assignment:updated", formatted);
+    res.json(formatted);
+  } catch (err) {
+    console.error("deleteAttachment error:", err);
+    res.status(500).json({ error: "Failed to delete attachment." });
+  }
+}
+
 // ─── POST /api/assignments/:id/submit ────────────────────────────────────────
 export async function submitAssignment(req, res) {
   try {
@@ -187,11 +258,29 @@ export async function submitAssignment(req, res) {
     const now = new Date();
     const isLate = assignment.dueDate && now > assignment.dueDate;
 
+    // Handle optional file upload
+    let uploadedFileUrl = fileUrl || "";
+    let uploadedFileName = "";
+    let uploadedFilePublicId = "";
+    if (req.file) {
+      const result = await uploadToCloudinary(req.file.buffer, {
+        resource_type: "raw",
+        folder: "smartclass/submissions",
+        public_id: `${id}_${studentId}_${Date.now()}`,
+        use_filename: true,
+      });
+      uploadedFileUrl = result.secure_url;
+      uploadedFileName = req.file.originalname;
+      uploadedFilePublicId = result.public_id;
+    }
+
     const submission = await Submission.findOneAndUpdate(
       { assignment: id, student: studentId },
       {
         content: content || "",
-        fileUrl: fileUrl || "",
+        fileUrl: uploadedFileUrl,
+        fileName: uploadedFileName,
+        filePublicId: uploadedFilePublicId,
         status: isLate ? "late" : "submitted",
         submittedAt: now,
         score: null,
@@ -312,6 +401,12 @@ function formatAssignment(a) {
     order: a.order,
     course: a.course,
     createdBy: a.createdBy ? { id: a.createdBy._id || a.createdBy, name: a.createdBy.name } : null,
+    attachments: (a.attachments || []).map((att) => ({
+      id: att._id,
+      url: att.url,
+      name: att.name,
+      publicId: att.publicId,
+    })),
     createdAt: a.createdAt,
   };
 }
@@ -325,6 +420,7 @@ function formatSubmission(s) {
       : null,
     content: s.content,
     fileUrl: s.fileUrl,
+    fileName: s.fileName,
     status: s.status,
     score: s.score,
     feedback: s.feedback,
diff --git a/server/app/controllers/authController.js b/server/app/controllers/authController.js
index 86ad525..0f4c11e 100644
--- a/server/app/controllers/authController.js
+++ b/server/app/controllers/authController.js
@@ -84,24 +84,29 @@ export async function register(req, res) {
   if (!name || !email || !password)
     return res.status(400).json({ error: "Name, email and password are required." });
 
-  const existing = await User.findOne({ email });
-  if (existing?.isVerified)
-    return res.status(409).json({ error: "Email already registered. Please sign in." });
-
-  // Create or update pending user
-  let user = existing || new User({ name, email, password, role: role || "student" });
-  if (existing) {
-    user.name = name;
-    user.password = password;
-    user.role = role || "student";
-  }
-  await user.save();
+  try {
+    const existing = await User.findOne({ email });
+    if (existing?.isVerified)
+      return res.status(409).json({ error: "Email already registered. Please sign in." });
+
+    // Create or update pending user
+    let user = existing || new User({ name, email, password, role: role || "student" });
+    if (existing) {
+      user.name = name;
+      user.password = password;
+      user.role = role || "student";
+    }
+    await user.save();
 
-  const otp = generateOtp();
-  saveOtp(email, otp);
-  await sendOtpEmail(email, otp);
+    const otp = generateOtp();
+    saveOtp(email, otp);
+    await sendOtpEmail(email, otp);
 
-  res.json({ message: "OTP sent to your email.", email });
+    res.json({ message: "OTP sent to your email.", email });
+  } catch (err) {
+    console.error("Register error:", err.message);
+    res.status(500).json({ error: err.message });
+  }
 }
 
 // POST /api/auth/verify-otp
diff --git a/server/app/middleware/documentUpload.js b/server/app/middleware/documentUpload.js
new file mode 100644
index 0000000..59bd806
--- /dev/null
+++ b/server/app/middleware/documentUpload.js
@@ -0,0 +1,19 @@
+import multer from "multer";
+
+function fileFilter(_req, file, cb) {
+  const allowed = [
+    "application/pdf",
+    "application/vnd.openxmlformats-officedocument.wordprocessingml.document", // .docx
+    "application/msword", // .doc
+  ];
+  if (allowed.includes(file.mimetype)) return cb(null, true);
+  cb(new Error("Only PDF and Word documents (.pdf, .doc, .docx) are allowed."));
+}
+
+const documentUpload = multer({
+  storage: multer.memoryStorage(),
+  fileFilter,
+  limits: { fileSize: 20 * 1024 * 1024 }, // 20 MB
+});
+
+export default documentUpload;
diff --git a/server/app/models/Assignment.js b/server/app/models/Assignment.js
index eda07ff..5adc9de 100644
--- a/server/app/models/Assignment.js
+++ b/server/app/models/Assignment.js
@@ -9,6 +9,14 @@ const assignmentSchema = new mongoose.Schema(
     order: { type: Number, default: 0 }, // sequential order within a course (1-based)
     course: { type: mongoose.Schema.Types.ObjectId, ref: "Course", required: true },
     createdBy: { type: mongoose.Schema.Types.ObjectId, ref: "User", required: true },
+    attachments: [
+      {
+        url: { type: String, required: true },
+        name: { type: String, required: true },
+        publicId: { type: String, required: true },
+        type: { type: String, default: "raw" },
+      },
+    ],
   },
   { timestamps: true }
 );
diff --git a/server/app/models/Submission.js b/server/app/models/Submission.js
index 7a92d72..27f1288 100644
--- a/server/app/models/Submission.js
+++ b/server/app/models/Submission.js
@@ -6,6 +6,8 @@ const submissionSchema = new mongoose.Schema(
     student: { type: mongoose.Schema.Types.ObjectId, ref: "User", required: true },
     content: { type: String, trim: true, default: "" },
     fileUrl: { type: String, trim: true, default: "" },
+    fileName: { type: String, trim: true, default: "" },
+    filePublicId: { type: String, trim: true, default: "" },
     status: {
       type: String,
       enum: ["submitted", "late", "graded"],
diff --git a/server/app/routes/assignments.js b/server/app/routes/assignments.js
index 4840fb5..5c7d152 100644
--- a/server/app/routes/assignments.js
+++ b/server/app/routes/assignments.js
@@ -9,7 +9,10 @@ import {
   getSubmissions,
   getMySubmission,
   gradeSubmission,
+  addAttachment,
+  deleteAttachment,
 } from "../controllers/assignmentController.js";
+import documentUpload from "../middleware/documentUpload.js";
 
 // Course-scoped assignment routes (mergeParams inherits :courseId)
 export const courseAssignmentRouter = Router({ mergeParams: true });
@@ -21,9 +24,11 @@ const router = Router();
 router.get("/:id", getAssignment);
 router.patch("/:id", updateAssignment);
 router.delete("/:id", deleteAssignment);
-router.post("/:id/submit", submitAssignment);
+router.post("/:id/submit", documentUpload.single("file"), submitAssignment);
 router.get("/:id/submissions", getSubmissions);
 router.get("/:id/my-submission", getMySubmission);
 router.patch("/submissions/:submissionId/grade", gradeSubmission);
+router.post("/:id/attachments", documentUpload.single("file"), addAttachment);
+router.delete("/:id/attachments/:attachmentId", deleteAttachment);
 
 export default router;