import * as T from "../../Task/_core";
import type { EIO, IO } from "../../Task/model";
import type { XPromise } from "../model";
import { Done } from "../state";

/**
 * Completes the promise with the specified effect. If the promise has
 * already been completed, the method will produce false.
 *
 * Note that since the promise is completed with a task, the effect will
 * be evaluated each time the value of the promise is retrieved through
 * combinators such as `wait`, potentially producing different results if
 * the effect produces different results on subsequent evaluations. In this
 * case te meaning of the "exactly once" guarantee of `Promise` is that the
 * promise can be completed with exactly one effect. For a version that
 * completes the promise with the result of a task see
 * `Promise.complete`.
 */
export const completeWith = <E, A>(io: EIO<E, A>) => (promise: XPromise<E, A>): IO<boolean> =>
   T.total(() => {
      const state = promise.state.get;

      switch (state._tag) {
         case "Done": {
            return false;
         }
         case "Pending": {
            promise.state.set(new Done(io));
            state.joiners.forEach((f) => {
               f(io);
            });
            return true;
         }
      }
   });