User: implement cursor pagination for this nextjs server action "use server";

import { Difficulty, LANGUAGE_MAP, SortBy } from "@/const/language-map";
import { db } from "@/db";
import { videos } from "@/db-stuff/migrations/schema";
import { and, gt, inArray, isNotNull } from "drizzle-orm";
import { getDifficultyDrizzleValues } from "./get-difficulty-drizzle-values";
import { getOrderDrizzleValues } from "./get-order-drizzle-values";
import { getDifficultyFromScore } from "./get-difficulty-from-score";

export const searchVideos = async (
  language: string,
  sortBy: SortBy,
  difficulty: Difficulty
) => {
  // @ts-ignore
  const languageCodes: string[] = LANGUAGE_MAP[language];
  const difficultyScores = getDifficultyDrizzleValues(difficulty);
  const orderBy = getOrderDrizzleValues(sortBy);

  if (!languageCodes.length) return [];
  const result = await db
    .select()
    .from(videos)
    .where(
      and(
        inArray(videos.language, languageCodes),
        isNotNull(videos.score),
        isNotNull(videos.duration),
        gt(videos.duration, 120),
        ...difficultyScores
      )
    )
    .orderBy(orderBy);

  return result.map((v) => ({
    title: v.title,
    id: v.id,
    duration: v.duration!,
    difficulty: getDifficultyFromScore(v.score),
  }));
};
Assistant: To implement cursor pagination in your Next.js server action for the `searchVideos` function, you'll need to adjust how you query the database and handle the results. Cursor pagination is typically more efficient than offset pagination, especially for large datasets, as it allows you to query directly from a position in the data instead of calculating offsets.

Here's how you can implement cursor pagination:

1. **Modify the Function to Accept a Cursor**:
   Add parameters for the cursor (e.g., `after`) and the `limit` of items you want to fetch per request.

```javascript
export const searchVideos = async (
  language: string,
  sortBy: SortBy,
  difficulty: Difficulty,
  after?: string, // Cursor for pagination
  limit = 10 // Number of items per page
) => {
  // Existing logic...
};
```

2. **Adjust the Query to Use the Cursor**:
   Modify the query to use the cursor (`after`) if provided. You typically compare the cursor with a column of increasing value (e.g., an `id` or `createdAt` timestamp).

```javascript
const result = await db
  .select()
  .from(videos)
  .where(
    and(
      inArray(videos.language, languageCodes),
      isNotNull(videos.score),
      isNotNull(videos.duration),
      gt(videos.duration, 120),
      ...difficultyScores,
      after ? gt(videos.id, after) : true // Use cursor for pagination
    )
  )
  .orderBy(orderBy)
  .limit(limit); // Limit the number of results
```

3. **Modify the Return to Include a New Cursor**:
   Include the new cursor in the return value, typically the `id` of the last item in the current page.

```javascript
const resultsMapped = result.map((v) => ({
  title: v.title,
  id: v.id,
  duration: v.duration!,
  difficulty: getDifficultyFromScore(v.score),
}));

const lastItem = result[result.length - 1];
const newCursor = lastItem ? lastItem.id : null; // Set new cursor to the last item's id

return {
  videos: resultsMapped,
  cursor: newCursor, // Return new cursor
};
```

4. **Handle the Pagination on the Client Side**:
   On the client side, manage the `cursor` to request subsequent pages.

Here's a basic example of how you might call the server action and handle pagination:

```javascript
const fetchVideos = async (language, sortBy, difficulty, cursor) => {
  const response = await searchVideos(language, sortBy, difficulty, cursor);
  // Handle new videos and store/update cursor for next fetch
  // Example: Update state with new videos and cursor
  setVideos((prev) => [...prev, ...response.videos]);
  setCursor(response.cursor);
};
```

This approach assumes you are using column values like `id` for the cursor. Ensure you adapt your schema or add suitable indexes if needed for efficiency, especially with large datasets. Adjust the code as required for your specific database operations and column choices.
User: Will it work even if my id is a random string?
Assistant: