import assert from "node:assert/strict";
import { test } from "node:test";
import { readBatches } from "../src/read-batches.js";

test("caps concurrent reads, keeps result order and includes the final partial batch", async () => {
  let active = 0;
  let peak = 0;
  const input = Array.from({ length: 23 }, (_, index) => index);
  const output = await readBatches(input, async (batch) => {
    peak = Math.max(peak, ++active);
    await new Promise((resolve) => setTimeout(resolve, batch[0] % 2 ? 1 : 5));
    active--;
    return batch;
  }, 5, 3);
  assert.equal(peak, 3);
  assert.deepEqual(output, input);
});

test("does not query empty input or return incomplete results after failure", async () => {
  assert.deepEqual(await readBatches([], () => { throw new Error("should not run"); }), []);
  await assert.rejects(readBatches([1, 2], async () => { throw new Error("DB unavailable"); }), /DB unavailable/);
});