Add configuration and database core

app/csv_export.py

@@ -1 +1,40 @@
 """CSV export helpers."""
+
+from __future__ import annotations
+
+import csv
+from io import StringIO
+
+from app.db import connect
+
+
+async def export_session_csv(db_path: str, sid: str) -> str:
+    out = StringIO()
+    writer = csv.writer(out)
+    writer.writerow(["sid", "student_id", "name", "question_idx", "answer", "elapsed_ms", "score", "status"])
+    async with connect(db_path) as db:
+        cursor = await db.execute(
+            """
+            SELECT p.sid, p.student_id, p.name, s.question_idx, s.answer, s.elapsed_ms, s.score, s.status
+            FROM participants p
+            LEFT JOIN submissions s ON s.sid = p.sid AND s.student_id = p.student_id
+            WHERE p.sid = ?
+            ORDER BY p.student_id, s.question_idx
+            """,
+            (sid,),
+        )
+        rows = await cursor.fetchall()
+    for row in rows:
+        writer.writerow(
+            [
+                row["sid"],
+                row["student_id"],
+                row["name"],
+                "" if row["question_idx"] is None else row["question_idx"],
+                row["answer"] or "",
+                "" if row["elapsed_ms"] is None else row["elapsed_ms"],
+                "" if row["score"] is None else row["score"],
+                row["status"] or "",
+            ]
+        )
+    return out.getvalue()