// @ts-check

/**
 * @import LoadingCacheValue from "./LoadingCacheValue.mjs"
 * @import { Loader } from "./types.mjs"
 */

import React from "react";

/**
 * React hook to create a memoized {@link Loader loader} from another, that
 * automatically aborts previous loading that started via this hook when new
 * loading starts via this hook, the hook arguments change, or the component
 * unmounts.
 * @param {Loader} load Memoized function that starts the loading.
 * @returns {Loader} Memoized function that starts the loading.
 */
export default function useAutoAbortLoad(load) {
  if (typeof load !== "function")
    throw new TypeError("Argument 1 `load` must be a function.");

  const lastLoadingCacheValueRef = React.useRef(
    /** @type {LoadingCacheValue | undefined} */ (undefined),
  );

  React.useEffect(
    () => () => {
      if (lastLoadingCacheValueRef.current)
        // Abort the last loading as it’s now redundant due to the changed
        // dependencies. Checking if it’s already ended or aborted first is
        // unnecessary.
        lastLoadingCacheValueRef.current.abortController.abort();
    },
    [load],
  );

  return React.useCallback(() => {
    if (lastLoadingCacheValueRef.current)
      // Ensure the last loading is aborted before starting new loading.
      // Checking if it’s already ended or aborted first is unnecessary.
      lastLoadingCacheValueRef.current.abortController.abort();

    const loadingCacheValue = load();

    lastLoadingCacheValueRef.current = loadingCacheValue;

    // After the loading cache value promise resolves, clear the ref (if it
    // still holds the same loading cache value) to allow garbage collection.
    // This might not be worth the bundle size increase.
    loadingCacheValue.promise.then(() => {
      if (lastLoadingCacheValueRef.current === loadingCacheValue)
        lastLoadingCacheValueRef.current = undefined;
    });

    return loadingCacheValue;
  }, [load]);
}