Zerotask/rust-jungle

import { readable } from 'svelte/store';
import { browser } from '$app/env';
import type { Lessons } from '$lib/lessonInterfaces';

interface CachedObject {
    expires: number;
    data: Lessons;
}

// 2 hours
const cacheDuration = 7200 * 1000;
const cacheKey = 'lessons';
const endpoint = 'lessons.json';

const getData = async () => {
    const response = await fetch(`${import.meta.env.VITE_APP_URL}/${endpoint}`);
    if (!response.ok) {
        throw new Error('could not fetch lessons.json file.');
    }

    return await response.json();
};

const createStore = () => {
    return readable({ tags: [], stages: {}, lessons: [] }, (set) => {
        if (browser) {
            const lessons: string | null = localStorage.getItem(cacheKey);
            if (lessons) {
                const cachedObject: CachedObject = JSON.parse(lessons);

                // Cache entry is still valid.
                if (cachedObject.expires > Date.now()) {
                    set(cachedObject.data);
                    return;
                }
            }

            getData().then((data: Lessons) => {
                const cacheObject: CachedObject = {
                    expires: Date.now() + cacheDuration,
                    data
                };
                localStorage.setItem(cacheKey, JSON.stringify(cacheObject));
                set(data);
            });
        }
    });
};

const store = createStore();

export default store;