feat: add per-user session termination for instructors

app/api/instructor/sessions/[id]/route.ts

@@ -0,0 +1,41 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { getServerSession } from 'next-auth';
+import { authOptions } from '@/lib/auth';
+import { sql } from '@/lib/db';
+import { audit } from '@/lib/audit';
+import { recalculateSessionScore } from '@/lib/scoring';
+
+// DELETE /api/instructor/sessions/[id] — force-close a session
+export async function DELETE(
+  _req: NextRequest,
+  { params }: { params: { id: string } }
+) {
+  const session = await getServerSession(authOptions);
+  if (!session?.user?.id || session.user.role !== 'instructor') {
+    return NextResponse.json({ error: 'Forbidden' }, { status: 403 });
+  }
+
+  const sessionId = params.id;
+
+  const rows = await sql`
+    SELECT id, closed_at FROM sessions WHERE id = ${sessionId} LIMIT 1
+  `;
+
+  if (rows.length === 0) {
+    return NextResponse.json({ error: 'Session not found' }, { status: 404 });
+  }
+
+  if (rows[0].closed_at) {
+    return NextResponse.json({ error: 'Session already closed' }, { status: 409 });
+  }
+
+  await sql`
+    UPDATE sessions SET closed_at = now() WHERE id = ${sessionId}
+  `;
+
+  await recalculateSessionScore(sessionId).catch(() => {});
+
+  await audit(session.user.id, 'session.force_closed', 'session', sessionId, {});
+
+  return NextResponse.json({ success: true });
+}

app/instructor/exercises/[id]/submissions/SubmissionsTable.tsx

@@ -2,7 +2,7 @@
 
 import { useState } from 'react';
 import Link from 'next/link';
-import { Flag, ChevronDown, ChevronRight, ShieldCheck, ShieldX, RotateCcw } from 'lucide-react';
+import { Flag, ChevronDown, ChevronRight, ShieldCheck, ShieldX, RotateCcw, XCircle } from 'lucide-react';
 import SearchInput from '@/app/components/SearchInput';
 import Pagination from '@/app/components/Pagination';
 import { toast } from 'sonner';
@@ -16,6 +16,8 @@ export default function SubmissionsTable({ participants }: { participants: Parti
   const [expanded, setExpanded] = useState<Set<string>>(new Set());
   const [overriding, setOverriding] = useState<string | null>(null);
   const [localOverride, setLocalOverride] = useState<Record<string, boolean | null>>({});
+  const [terminating, setTerminating] = useState<string | null>(null);
+  const [localClosed, setLocalClosed] = useState<Set<string>>(new Set());
   const [page, setPage] = useState(1);
 
   async function handleOverride(sessionId: string, value: boolean | null) {
@@ -36,6 +38,21 @@ export default function SubmissionsTable({ participants }: { participants: Parti
     }
   }
 
+  async function handleTerminate(sessionId: string, username: string) {
+    if (!confirm(`Terminate ${username}'s session? This only affects them and cannot be undone.`)) return;
+    setTerminating(sessionId);
+    try {
+      const res = await fetch(`/api/instructor/sessions/${sessionId}`, { method: 'DELETE' });
+      if (!res.ok) throw new Error('Failed');
+      setLocalClosed((prev) => new Set(prev).add(sessionId));
+      toast.success(`${username}'s session terminated`);
+    } catch {
+      toast.error('Failed to terminate session');
+    } finally {
+      setTerminating(null);
+    }
+  }
+
   const filtered = participants.filter((p) => {
     const matchSearch = p.username.toLowerCase().includes(search.toLowerCase());
     const matchFlag = !filterFlagged || p.is_flagged;
@@ -98,6 +115,7 @@ export default function SubmissionsTable({ participants }: { participants: Parti
                   ? localOverride[p.session_id]
                   : p.passed;
                 const isOverridden = p.passed_override !== null || p.session_id in localOverride;
+                const isClosed = localClosed.has(p.session_id) || !!p.closed_at;
 
                 return (
                   <>
@@ -121,6 +139,9 @@ export default function SubmissionsTable({ participants }: { participants: Parti
                         {p.final_count === p.total_questions && (
                           <span className="badge badge-green" style={{ marginLeft: 6, fontSize: 10 }}>Done</span>
                         )}
+                        {isClosed && p.final_count < p.total_questions && (
+                          <span className="badge badge-gray" style={{ marginLeft: 6, fontSize: 10 }}>Closed</span>
+                        )}
                       </td>
                       <td>
                         {p.is_flagged
@@ -175,6 +196,17 @@ export default function SubmissionsTable({ participants }: { participants: Parti
                               <RotateCcw size={11} />
                             </button>
                           )}
+                          {!isClosed && (
+                            <button
+                              className="btn btn-sm btn-danger"
+                              disabled={terminating === p.session_id}
+                              onClick={() => handleTerminate(p.session_id, p.username)}
+                              title="Terminate session"
+                              style={{ fontSize: 11 }}
+                            >
+                              <XCircle size={11} /> End
+                            </button>
+                          )}
                         </div>
                       </td>
                     </tr>

app/instructor/exercises/[id]/submissions/page.tsx

@@ -15,6 +15,7 @@ export interface ParticipantRow {
   score: number | null;
   passed: boolean | null;
   passed_override: boolean | null;
+  closed_at: string | null;
   total_questions: number;
   answered: number;
   final_count: number;
@@ -47,6 +48,7 @@ export default async function SubmissionListPage({ params }: Props) {
       s.score,
       s.passed,
       s.passed_override,
+      s.closed_at,
       e.question_count                                            AS total_questions,
       COUNT(sub.id)::int                                          AS answered,
       COUNT(sub.id) FILTER (WHERE sub.is_final = true)::int       AS final_count,
@@ -67,7 +69,7 @@ export default async function SubmissionListPage({ params }: Props) {
     JOIN exercises e ON e.id = s.exercise_id
     LEFT JOIN submissions sub ON sub.session_id = s.id
     WHERE s.exercise_id = ${exerciseId}
-    GROUP BY s.id, u.username, s.score, s.passed, s.passed_override, e.question_count
+    GROUP BY s.id, u.username, s.score, s.passed, s.passed_override, s.closed_at, e.question_count
     ORDER BY u.username
   `;
 
@@ -77,6 +79,7 @@ export default async function SubmissionListPage({ params }: Props) {
     score: r.score != null ? Number(r.score) : null,
     passed: r.passed != null ? (r.passed as boolean) : null,
     passed_override: r.passed_override != null ? (r.passed_override as boolean) : null,
+    closed_at: r.closed_at as string | null,
     total_questions: r.total_questions as number,
     answered: r.answered as number,
     final_count: r.final_count as number,