import { getMessageById } from "$lib/api/message";
import { isErrorResponse, type Message } from "$lib/types";
import { get, writable, type Writable } from "svelte/store";

const messagesCache: Writable<Map<number, Message>> = writable(new Map<number, Message>());

const runningCaches = new Set();

export function addMessageToCache(message: Message) {
    messagesCache.update((messages) => messages.set(message.id, message));
}

export async function getCachedMessage(messageId: number): Promise<Message | null> {
    const cached = get(messagesCache).get(messageId);

    if (cached)
        return cached;

    if (runningCaches.has(messageId))
        return await new Promise((resolve) => {
            messagesCache.subscribe((users) => {

                const user = users.get(messageId);
                if (user) {
                    runningCaches.delete(messageId);
                    resolve(user);
                }
            });
        });

    runningCaches.add(messageId);

    const response = await getMessageById(messageId);
    if (isErrorResponse(response))
        return null;

    const message = response as Message;

    addMessageToCache(message);

    return message;
}