sflow/src/pageStream.spec.ts

sflow is a powerful and highly-extensible library designed for processing and manipulating streams of data effortlessly. Inspired by the functional programming paradigm, it provides a rich set of utilities for transforming streams, including chunking, fil

import { expectTypeOf } from "expect-type";
import Keyv from "keyv";
import { KeyvCachedWith } from "keyv-cached-with";
import DIE from "phpdie";
import sflow, { nil, pageFlow, pageStream } from "./index";

it("works with number", async () => {
  expect(
    await sflow(
      pageStream(0, (page: number) => {
        expectTypeOf(page).toBeNumber();
        const data = [1, 2, 3, 4, 5][page];
        if (!data) return {};
        return { data, next: page + 1 };
      }),
    ).toArray(),
  ).toEqual([1, 2, 3, 4, 5]);
});

it("works with cache with wrapper", async () => {
  const cache1d = KeyvCachedWith(new Keyv<unknown>({ ttl: 86400e3 }));
  expect(
    await sflow(
      pageStream(0, (page: number) => {
        expectTypeOf(page).toBeNumber();
        return cache1d((page) => {
          const data = [1, 2, 3, 4][page] as number | undefined;
          // expectTypeOf(page).toBeNumber(); // fail
          return { data, next: (!!data && page + 1) || null };
        }, page);
      }),
    )
      .map((e) => e)
      .filter()
      .map((e) => e)
      .toArray(),
  ).toEqual([1, 2, 3, 4]);
});
it("works with cache without wrapper", async () => {
  const cache1d = KeyvCachedWith(new Keyv<unknown>({ ttl: 86400e3 }));
  expect(
    await sflow(
      pageStream(
        0,
        cache1d((page: number) => {
          const data = [1, 2, 3, 4][page] as number | undefined;
          // expectTypeOf(page).toBeNumber(); // fail
          return { data, next: (!!data && page + 1) || null };
        }),
      ),
    )
      .map((e) => e)
      .filter()
      .map((e) => e)
      .toArray(),
  ).toEqual([1, 2, 3, 4]);
});

it("works with cacheTails", async () => {
  const store = new Keyv<number[]>({ ttl: 86400e3 });
  // cache full content
  expect(
    await pageFlow(0, (page: number) => {
      const data = [5, 4, 3, 2, 1][page] as number | undefined;
      return { data, next: (!!data && page + 1) || null };
    })
      .filter()
      .cacheTail(store, "page")
      .toArray(),
  ).toEqual([5, 4, 3, 2, 1]);

  // emit only page head, but got full cached content
  expect(
    await pageFlow(0, (page: number) => {
      const data = [6, 5][page] as number | undefined;
      return { data, next: (!!data && page + 1) || null };
    })
      .filter()
      .cacheTail(store, "page")
      .toArray(),
  ).toEqual([6, 5, 4, 3, 2, 1]);
});

it("works with signal polling", async () => {
  const st = +new Date();
  let id = 0;
  const fetcher = async () => {
    const now = +new Date();
    if (st + 1000 < now) DIE("no data");
    if (id === 3) return "END"; // done
    return "signal" + id++;
  };

  expect(
    await sflow(
      pageStream(0, async (page: number) => {
        const data = await fetcher().catch(nil);
        if ("END" === data) return { data: null };
        return { data, next: page };
      }),
    )
      .filter()
      .map((e) => e)
      .toArray(),
  ).toEqual(["signal0", "signal1", "signal2"]);
});