src/routes/settings/assistants/[assistantId]/avatar/+server.ts

import { collections } from "$lib/server/database";
import { error, type RequestHandler } from "@sveltejs/kit";
import { ObjectId } from "mongodb";

export const GET: RequestHandler = async ({ params }) => {
	const assistant = await collections.assistants.findOne({
		_id: new ObjectId(params.assistantId),
	});

	if (!assistant) {
		throw error(404, "No assistant found");
	}

	if (!assistant.avatar) {
		throw error(404, "No avatar found");
	}

	const fileId = collections.bucket.find({ filename: assistant._id.toString() });

	let mime = "";

	const content = await fileId.next().then(async (file) => {
		mime = file?.metadata?.mime;

		if (!file?._id) {
			throw error(404, "Avatar not found");
		}

		const fileStream = collections.bucket.openDownloadStream(file?._id);

		const fileBuffer = await new Promise<Buffer>((resolve, reject) => {
			const chunks: Uint8Array[] = [];
			fileStream.on("data", (chunk) => chunks.push(chunk));
			fileStream.on("error", reject);
			fileStream.on("end", () => resolve(Buffer.concat(chunks)));
		});

		return fileBuffer;
	});

	return new Response(content, {
		headers: {
			"Content-Type": mime ?? "application/octet-stream",
		},
	});
};