it works

server/routes/download/[file].get.ts

@@ -0,0 +1,32 @@
+import { createReadStream, existsSync, unlink, unlinkSync } from "node:fs"
+import { } from "fs/promises"
+import { join } from "path"
+
+export default defineEventHandler(async (event) => {
+    const session = await getUserSession(event)
+    //const query = await getQuery(event)
+
+    // @ts-ignore
+    const userId = session.secure?.user_id;
+    if (userId == undefined || userId == null)
+        throw createError({ status: 401 })
+
+    const file = await getRouterParam(event, 'file');
+    if (file == undefined)
+        throw createError({ status: 400, message: "No file"})
+    
+    const def_filepath = "/home/suricatingss/Projects/WebStorm/yt2mp3/server/fastapi_server/downloads";
+    const filepath = join(def_filepath, userId.toString(), file.toString())
+    console.log(filepath)
+
+    if (!existsSync(filepath)) 
+        throw createError({ status: 404, message: "Not found"})
+    
+    setHeader(event, 'Content-Disposition', `attachment; filename="${file}"`)
+
+    const file_stream = createReadStream(filepath)
+
+    file_stream.on("close", () =>  unlink(filepath, (err) => { if (err) console.warn(err.message) }))
+
+    return file_stream;
+})