feat: add batch/topic/question DB queries

backend/db/queries.py

@@ -79,3 +79,89 @@ async def delete_old_refresh_tokens(user_id: str) -> None:
         await conn.execute(
             "DELETE FROM refresh_tokens WHERE user_id = $1", user_id
         )
+
+
+async def create_batch(name: str, instructor_id: str) -> asyncpg.Record:
+    async with get_pool().acquire() as conn:
+        return await conn.fetchrow(
+            """
+            INSERT INTO batches (name, instructor_id)
+            VALUES ($1, $2)
+            RETURNING *
+            """,
+            name, instructor_id,
+        )
+
+
+async def get_batch_by_instructor_id(instructor_id: str) -> Optional[asyncpg.Record]:
+    async with get_pool().acquire() as conn:
+        return await conn.fetchrow(
+            "SELECT * FROM batches WHERE instructor_id = $1", instructor_id
+        )
+
+
+async def get_batch_by_id(batch_id: str) -> Optional[asyncpg.Record]:
+    async with get_pool().acquire() as conn:
+        return await conn.fetchrow(
+            "SELECT * FROM batches WHERE id = $1", batch_id
+        )
+
+
+async def create_topic(batch_id: str, name: str, order_index: int) -> asyncpg.Record:
+    async with get_pool().acquire() as conn:
+        return await conn.fetchrow(
+            """
+            INSERT INTO topics (batch_id, name, order_index)
+            VALUES ($1, $2, $3)
+            RETURNING *
+            """,
+            batch_id, name, order_index,
+        )
+
+
+async def get_topics_by_batch_id(batch_id: str) -> list[asyncpg.Record]:
+    async with get_pool().acquire() as conn:
+        return await conn.fetch(
+            "SELECT * FROM topics WHERE batch_id = $1 ORDER BY order_index ASC",
+            batch_id,
+        )
+
+
+async def get_topic_by_id(topic_id: str) -> Optional[asyncpg.Record]:
+    async with get_pool().acquire() as conn:
+        return await conn.fetchrow(
+            "SELECT * FROM topics WHERE id = $1", topic_id
+        )
+
+
+async def set_topic_unlock(topic_id: str, is_unlocked: bool) -> asyncpg.Record:
+    async with get_pool().acquire() as conn:
+        return await conn.fetchrow(
+            """
+            UPDATE topics SET is_unlocked = $1
+            WHERE id = $2
+            RETURNING *
+            """,
+            is_unlocked, topic_id,
+        )
+
+
+async def create_questions_bulk(topic_id: str, rows: list[dict]) -> int:
+    async with get_pool().acquire() as conn:
+        await conn.executemany(
+            """
+            INSERT INTO questions (topic_id, question_text, difficulty)
+            VALUES ($1, $2, $3)
+            """,
+            [(topic_id, r["question_text"], r["difficulty"]) for r in rows],
+        )
+        return len(rows)
+
+
+async def get_question_count_by_topic(topic_id: str) -> int:
+    async with get_pool().acquire() as conn:
+        result = await conn.fetchrow(
+            "SELECT COUNT(*) AS count FROM questions WHERE topic_id = $1",
+            topic_id,
+        )
+        return result["count"]