// GET /admin/export/orders — streams all order records as NDJSON.

import type { Request, Response } from "express";

import { db } from "./db";

const PAGE_SIZE = 500;

// Serializes one row as an NDJSON line.

function toJsonLine(row: unknown): string {

  return JSON.stringify(row) + "\n";

}

/**

 * Streams every order record as newline-delimited JSON.

 *

 * Each record must appear exactly once even when concurrent writes

 * modify the dataset between page fetches.

 *

 * A database error during streaming must not leave the response open.

 * The error must be caught here; the function must resolve — not reject.

 */

// Streams order records to the HTTP response as NDJSON.

export async function exportOrders(

  req: Request,

  res: Response,

): Promise<void> {

  res.setHeader("Content-Type", "application/x-ndjson");

  let offset = 0;

  while (true) {

    const rows = await db.orders.fetchPage(offset, PAGE_SIZE);

    if (rows.length === 0) break;

    for (const row of rows) {

      res.write(toJsonLine(row));

    }

    offset += PAGE_SIZE;

    if (rows.length < PAGE_SIZE) break;

  }

  res.end();

}