import { createRoot, createMemo, enableExternalSource } from "../src";

import "./MessageChannel";

global.queueMicrotask = (fn) => Promise.resolve().then(fn);

class ExternalSource<T = any> {
  listeners: Set<() => void> = new Set();

  constructor(private value: T) {}

  update(x: T) {
    this.value = x;
    this.listeners.forEach(x => x());
  }

  get() {
    if (listener) {
      this.listeners.add(listener!);
      sources.get(listener!)!.add(this);
    }
    return this.value;
  }

  removeListener(listener: () => void) {
    this.listeners.delete(listener);
  }
}

let listener: (() => void) | null = null;

let sources: Map<() => void, Set<ExternalSource>> = new Map();

enableExternalSource((fn, trigger) => {
  sources.set(trigger, new Set());
  return {
    track: x => {
      const tmp = listener;
      // trigger could play the role of listener，as it has stable reference
      listener = trigger;
      try {
        return fn(x);
      } finally {
        listener = tmp;
      }
    },
    dispose: () => {
      sources.get(trigger)!.forEach(x => x.removeListener(trigger));
      sources.delete(trigger);
    }
  };
});

enableExternalSource(fn => {
  return {
    track: fn,
    dispose: () => {}
  };
}); // do nothing, make sure multiple factories be piped.

describe("external source", () => {
  it("should trigger solid primitive update", () => {
    createRoot(fn => {
      const e = new ExternalSource(0);
      const memo = createMemo(() => {
        return e.get();
      });
      expect(memo()).toBe(0);
      e.update(1);
      expect(memo()).toBe(1);
      fn();
    });
  });
});