const held = new Map<string, Promise<unknown>>();

const fetchPayload = async function fetchPayload(path: string): Promise<unknown> {
    try {
        const response = await fetch(path);
        if (!response.ok) {
            return null;
        }
        const data: unknown = await response.json();
        return data;
    } catch {
        return null;
    }
};

export const loadPayload = async function loadPayload(path: string): Promise<unknown> {
    const pending = held.get(path);
    if (pending !== undefined) {
        return pending;
    }
    const loading = fetchPayload(path).then((payload) => {
        if (payload === null) {
            held.delete(path);
        }
        return payload;
    });
    held.set(path, loading);
    return loading;
};