una/sw.js.php

<?php
/**
 * Copyright (c) UNA, Inc - https://una.io
 * MIT License - https://opensource.org/licenses/MIT
 *
 * @defgroup    UnaCore UNA Core
 * @{
 */

define('BX_SERVICE_WORKER', true);

require_once('./inc/header.inc.php');

$aAssets = BxDolPreloader::getInstance()->getSystemAssets(BxDolTemplate::getInstance());

header("Content-Type: text/javascript");
?>

// Core assets
let coreAssets = <?php echo json_encode($aAssets); ?>;

// On install, cache core assets
self.addEventListener('install', function (event) {
    // Cache core assets
    event.waitUntil(caches.open('app').then(function (cache) {
        for (let asset of coreAssets) {
            cache.add(new Request(asset));
        }
        return cache;
    }));
});

// Listen for request events
self.addEventListener('fetch', function (event) {

    // Get the request
    let request = event.request;

    // Bug fix
    // https://stackoverflow.com/a/49719964
    if (event.request.cache === 'only-if-cached' && event.request.mode !== 'same-origin') return;

    // HTML files
    // Network-first
    if (request.headers.get('Accept').includes('text/html')) {
        event.respondWith(
            fetch(request).then(function (response) {
                // Create a copy of the response and save it to the cache
                let copy = response.clone();
                event.waitUntil(caches.open('app').then(function (cache) {
                    return cache.put(request, copy);
                }));

                // Return the response
                return response;
            }).catch(function (error) {
                // If there's no item in cache, respond with a fallback
                return caches.match(request).then(function (response) {
                    return response || caches.match('/offline.html');
                });
            })
        );
    }

    // CSS & JavaScript
    // Offline-first
    if (request.headers.get('Accept').includes('text/css') || request.headers.get('Accept').includes('text/javascript')) {
        event.respondWith(
            caches.match(request).then(function (response) {
                return response || fetch(request).then(function (response) {
                    // Return the response
                    return response;
                });
            })
        );
        return;
    }

    // Images
    // Offline-first
    if (request.headers.get('Accept').includes('image')) {
        event.respondWith(
            caches.match(request).then(function (response) {
                return response || fetch(request).then(function (response) {
                    // Save a copy of it in cache
                    let copy = response.clone();
                    event.waitUntil(caches.open('app').then(function (cache) {
                        return cache.put(request, copy);
                    }));

                    // Return the response
                    return response;
                });
            })
        );
    }
});