gerbeur/src/test/hooks/feed/usePositionAwareSync.test.tsx

import { describe, expect, test } from "vitest";
import { act, renderHook } from "@testing-library/react";
import { type ReactNode, useState } from "react";
import {
  defaultWSValue,
  WSContext,
  type WSContextValue,
} from "../../../contexts/ws/WSContext.ts";
import type { Dump } from "../../../../shared/dump.ts";
import type { Playlist } from "../../../../shared/playlist.ts";
import { useDumpListSync } from "../../../hooks/dump/useDumpListSync.ts";
import { usePositionAwareSync } from "../../../hooks/feed/usePositionAwareSync.ts";
import { useWS } from "../../../hooks/ws/useWS.ts";
import { makeDump, makePlaylist } from "../../fixtures.ts";

/** A WS context whose value a test can push new events into. */
function liveWS() {
  let push: (patch: Partial<WSContextValue>) => void = () => {};
  const base = defaultWSValue;
  function Wrapper({ children }: { children: ReactNode }) {
    const [value, setValue] = useState(base);
    push = (patch) => setValue((v) => ({ ...v, ...patch }));
    return <WSContext.Provider value={value}>{children}</WSContext.Provider>;
  }
  return {
    Wrapper,
    emit: (patch: Partial<WSContextValue>) => act(() => push(patch)),
  };
}

function useList<T>(initial: T[]) {
  const [items, setItems] = useState(initial);
  return { items, setItems };
}

const ids = (xs: { id: string }[]) => xs.map((x) => x.id);

describe("usePositionAwareSync", () => {
  test("a dump that goes private and back returns to its old place", () => {
    const ws = liveWS();
    const initial = ["a", "b", "c"].map((id) => makeDump({ id, userId: "me" }));
    // Wire the pair exactly as UserPublicProfile does.
    const both = renderHook(() => {
      const { items, setItems } = useList(initial);
      const [event, setEvent] = useState<Dump | null>(null);
      usePositionAwareSync(items, setItems, event, (d) => !d.isPrivate);
      useDumpListSync(setItems);
      return { items, setEvent };
    }, { wrapper: ws.Wrapper });

    const b = initial[1];
    act(() => both.result.current.setEvent({ ...b, isPrivate: true }));
    ws.emit({ lastDumpEvent: { ...b, isPrivate: true } });
    expect(ids(both.result.current.items)).toEqual(["a", "c"]);

    act(() => both.result.current.setEvent({ ...b, isPrivate: false }));
    ws.emit({ lastDumpEvent: { ...b, isPrivate: false } });
    expect(ids(both.result.current.items)).toEqual(["a", "b", "c"]);
  });

  test("a dump that goes private for others, as a deletion, comes back where it was", () => {
    const ws = liveWS();
    const initial = ["a", "b", "c"].map((id) => makeDump({ id, userId: "me" }));
    const both = renderHook(() => {
      const { items, setItems } = useList(initial);
      const { lastDumpEvent } = useWS();
      usePositionAwareSync(items, setItems, lastDumpEvent, (d) => !d.isPrivate);
      useDumpListSync(setItems);
      return { items };
    }, { wrapper: ws.Wrapper });
    ws.emit({ deletedDumpIds: new Set(["b"]) });
    expect(ids(both.result.current.items)).toEqual(["a", "c"]);
    ws.emit({ deletedDumpIds: new Set(), lastDumpEvent: initial[1] });
    expect(ids(both.result.current.items)).toEqual(["a", "b", "c"]);
  });

  test("a position is only used once, and clamps to the list end", () => {
    const initial = ["a", "b", "c"].map((id) => makePlaylist({ id }));
    const hook = renderHook(() => {
      const { items, setItems } = useList(initial);
      const [event, setEvent] = useState<Playlist | null>(null);
      usePositionAwareSync(items, setItems, event, (p) => p.isPublic);
      return { items, setItems, setEvent };
    });
    const c = initial[2];
    // It leaves, whatever takes it out, then the list shrinks further.
    act(() => hook.result.current.setItems((prev) => prev.slice(0, 2)));
    act(() => hook.result.current.setItems((prev) => prev.slice(0, 1)));
    act(() => hook.result.current.setEvent({ ...c, isPublic: true }));
    expect(ids(hook.result.current.items)).toEqual(["a", "c"]);
    // Used once: the same event again adds nothing.
    act(() =>
      hook.result.current.setEvent({ ...c, isPublic: true, title: "x" })
    );
    expect(ids(hook.result.current.items)).toEqual(["a", "c"]);
  });
});