/**
 * Wrap an async function to cache its result.
 *
 * On first call of the wrapped function, the result will be stored and further
 * calls will directly return this cached value (always inside a promise).
 *
 * A `.noCache` method is provided to force getting a fresh value.
 *
 * Each cache value is scoped to the array of arguments that yielded it
 * (comparison done using its JSON representation).
 *
 * @param fun Function to wrap.
 * @return Wrapped function.
 */
const makeCached = fun =>
{
    const cachedResults = new Map();

    const noCache = async (...args) =>
    {
        const result = await fun(...args);
        cachedResults.set(JSON.stringify(args), result);
        return result;
    };

    const withCache = async (...args) =>
    {
        const key = JSON.stringify(args);

        if (cachedResults.has(key))
        {
            return cachedResults.get(key);
        }
        else
        {
            const result = await fun(...args);
            cachedResults.set(key, result);
            return result;
        }
    };

    withCache.noCache = noCache;
    return withCache;
};

exports.makeCached = makeCached;