RocketChat/Rocket.Chat

self.addEventListener('install', function(event) {
    event.waitUntil(self.skipWaiting()); // Activate worker immediately
});

self.addEventListener('activate', function(event) {
    event.waitUntil(self.clients.claim()); // Become available to all pages
});

function base64Decode(string) {
    string = atob(string);
    const length = string.length,
        buf = new ArrayBuffer(length),
        bufView = new Uint8Array(buf);
    for (var i = 0; i < string.length; i++) {
        bufView[i] = string.charCodeAt(i);
    }
    return buf;
}

function base64DecodeString(string) {
    return atob(string);
}

const decrypt = async (key, iv, file) => {
    const ivArray = base64Decode(iv);
    const cryptoKey = await crypto.subtle.importKey('jwk', key, { name: 'AES-CTR' }, true, ['encrypt', 'decrypt']);
    const result = await crypto.subtle.decrypt({ name: 'AES-CTR', counter: ivArray, length: 64 }, cryptoKey, file);

    return result;
};

const getUrlParams = (url) => {
    const urlObj = new URL(url, location.origin);

    const k = base64DecodeString(urlObj.searchParams.get('key'));

    urlObj.searchParams.delete('key');

    const { key, iv, name, type } = JSON.parse(k);

    const newUrl = urlObj.href.replace('/file-decrypt/', '/');

    return { key, iv, url: newUrl, name, type };
};

self.addEventListener('fetch', (event) => {
    if (!event.request.url.includes('/file-decrypt/')) {
        return;
    }

    try {
        const { url, key, iv, name, type } = getUrlParams(event.request.url);

        const requestToFetch = new Request(url, {
            ...event.request,
            mode: 'cors',
        });

        event.respondWith(
            caches.match(requestToFetch).then((response) => {
                if (response) {
                    return response;
                }

                return fetch(requestToFetch)
                    .then(async (res) => {
                        const file = await res.arrayBuffer();

                        if (res.status !== 200 || file.byteLength === 0) {
                            console.error('Failed to fetch file', { req: requestToFetch, res });
                            return res;
                        }

                        const result = await decrypt(key, iv, file);

                        const newHeaders = new Headers(res.headers);
                        newHeaders.set('Content-Disposition', 'inline; filename="'+name+'"');
                        newHeaders.set('Content-Type', type);

                        const response = new Response(result, {
                            status: res.status,
                            statusText: res.statusText,
                            headers: newHeaders,
                        });

                        await caches.open('v1').then((cache) => {
                            cache.put(requestToFetch, response.clone());
                        });

                        return response;
                    })
                    .catch((error) => {
                        console.error('Fetching failed:', error);

                        throw error;
                    });
            }),
        );
    } catch (error) {
        console.error(error);
        throw error;
    }
});

self.addEventListener('message', async (event) => {
    if (event.data.type !== 'attachment-download') {
        return;
    }

    const requestToFetch = new Request(event.data.url);

    const { url, key, iv } = getUrlParams(event.data.url);
    const res = (await caches.match(requestToFetch)) ?? (await fetch(url));

    const file = await res.arrayBuffer();
    const result = await decrypt(key, iv, file);
    event.source
        .postMessage({
            id: event.data.id,
            type: 'attachment-download-result',
            result,
        });
        // .catch((error) => {
        //     console.error('Posting message failed:', error);
        //     event.source.postMessage({
        //         id: event.data.id,
        //         type: 'attachment-download-result',
        //         error,
        //     });
        // });
});