bitvid/sw.min.js

(() => {
  "use strict";

  const SW_VERSION = "bitvid-sw-2026-07-02";
  const SW_METADATA = Object.freeze({
    version: SW_VERSION,
    runtimePathPrefix: "/webtorrent/",
  });

  // Cross-origin image cache (thumbnails / avatars / banners). These are the
  // images bitvid does NOT control headers for (external hosts, user CDNs), so
  // without this they can re-download on every visit. Strategy:
  // stale-while-revalidate — serve the cached copy instantly, refresh it in the
  // background — so revisits are instant AND a changed image self-heals on the
  // next view. Same-origin assets are left alone (they ride the host's HTTP
  // cache + the dist cache-purge pipeline). Bump the version to discard.
  const IMAGE_CACHE = "bitvid-images-v1";
  const IMAGE_CACHE_MAX_ENTRIES = 300;

  function isCacheableImageRequest(request) {
    if (!request || request.method !== "GET") {
      return false;
    }
    if (request.destination !== "image") {
      return false;
    }
    const url = request.url || "";
    if (!/^https?:/.test(url)) {
      return false;
    }
    // Same-origin images (app assets) keep the normal HTTP-cache path.
    try {
      return new URL(url).origin !== self.location.origin;
    } catch (error) {
      return false;
    }
  }

  async function trimImageCache(cache) {
    try {
      const keys = await cache.keys();
      if (keys.length <= IMAGE_CACHE_MAX_ENTRIES) {
        return;
      }
      // Cache keys() preserves insertion order; drop the oldest overflow.
      const excess = keys.length - IMAGE_CACHE_MAX_ENTRIES;
      await Promise.all(keys.slice(0, excess).map((key) => cache.delete(key)));
    } catch (error) {
      // Trimming is best-effort.
    }
  }

  async function putImageInCache(cache, request, response) {
    try {
      await cache.put(request, response);
      await trimImageCache(cache);
    } catch (error) {
      // Quota pressure (opaque responses are padded heavily for quota
      // accounting) or storage failure: drop the whole image cache and keep
      // going — the page still got its network response.
      try {
        await caches.delete(IMAGE_CACHE);
      } catch (cleanupError) {
        // fail open
      }
    }
  }

  async function handleImageRequest(event) {
    const request = event.request;
    const cache = await caches.open(IMAGE_CACHE);
    const cached = await cache.match(request, { ignoreVary: true });

    const refresh = fetch(request)
      .then((response) => {
        // Cache good responses; opaque (cross-origin no-cors) counts as good —
        // its status is unreadable, and these are exactly the images we target.
        if (response && (response.ok || response.type === "opaque")) {
          event.waitUntil(putImageInCache(cache, request, response.clone()));
        }
        return response;
      })
      .catch((error) => {
        if (cached) {
          return cached;
        }
        throw error;
      });

    if (cached) {
      // Keep the background refresh alive after we respond.
      event.waitUntil(refresh.catch(() => {}));
      return cached;
    }
    return refresh;
  }

  let cancelled = false;

  function broadcastLifecycle(eventType, details = {}) {
    return clients
      .matchAll({ type: "window", includeUncontrolled: true })
      .then((windowClients) => {
        windowClients.forEach((client) => {
          client.postMessage({
            type: "BITVID_SW_LIFECYCLE",
            eventType,
            metadata: SW_METADATA,
            ...details,
          });
        });
      });
  }

  // Handle messages from clients
  self.addEventListener("message", (event) => {
    if (event.data && event.data.type === "SKIP_WAITING") {
      self.skipWaiting();
    }
    if (event.data && event.data.type === "CLEAR_CACHES") {
      caches
        .keys()
        .then((cacheNames) =>
          Promise.all(cacheNames.map((cacheName) => caches.delete(cacheName)))
        );
    }
    if (event.data && event.data.type === "ENSURE_CLIENTS_CLAIM") {
      event.waitUntil(clients.claim());
    }
  });

  // Immediately install and skip waiting
  self.addEventListener("install", (event) => {
    event.waitUntil(Promise.all([self.skipWaiting(), broadcastLifecycle("install")]));
  });

  // Claim clients on activation and clear caches. The CURRENT image cache is
  // preserved (it is versioned; stale versions and everything else are wiped) so
  // an SW update doesn't throw away every cached thumbnail/avatar.
  self.addEventListener("activate", (event) => {
    event.waitUntil(
      Promise.all([
        clients.claim(),
        self.skipWaiting(),
        broadcastLifecycle("activate", {
          scope: self.registration?.scope || null,
        }),
        caches
          .keys()
          .then((cacheNames) =>
            Promise.all(
              cacheNames
                .filter((cacheName) => cacheName !== IMAGE_CACHE)
                .map((cacheName) => caches.delete(cacheName))
            )
          ),
      ])
    );
  });

  // Handle fetch events
  self.addEventListener("fetch", (event) => {
    const requestURL = event.request.url;

    // Cross-origin images: serve from the image cache (stale-while-revalidate).
    // Fail open — any handler error falls back to a plain network fetch so a
    // caching bug can never break image loading.
    if (isCacheableImageRequest(event.request)) {
      event.respondWith(
        handleImageRequest(event).catch(() => fetch(event.request))
      );
      return;
    }

    // Only handle WebTorrent streaming requests
    if (!requestURL.includes("/webtorrent/")) {
      return;
    }

    // Create a promise to handle the request
    const responsePromise = (async () => {
      // 1) Keepalive check
      if (requestURL.includes("/webtorrent/keepalive/")) {
        return new Response();
      }

      // 2) Cancel check
      if (requestURL.includes("/webtorrent/cancel/")) {
        return new Response(
          new ReadableStream({
            cancel() {
              cancelled = true;
            },
          })
        );
      }

      // 3) Streaming requests
      // We define an async function and immediately invoke it with `event`
      return (async function ({ request }) {
        const { url, method, headers, destination } = request;

        // 3a) Find open window clients
        const windowClients = await clients.matchAll({
          type: "window",
          includeUncontrolled: true,
        });

        // 3b) We send a message to each client with a MessageChannel
        const [clientResponse, port] = await new Promise((resolve) => {
          for (const client of windowClients) {
            const channel = new MessageChannel();
            channel.port1.onmessage = ({ data }) => {
              resolve([data, channel.port1]);
            };
            client.postMessage(
              {
                url,
                method,
                headers: Object.fromEntries(headers.entries()),
                scope: self.registration.scope,
                destination,
                type: "webtorrent",
              },
              [channel.port2]
            );
          }
        });

        // 3c) Setup a small helper to close the port
        let timeoutId = null;
        const closeChannel = () => {
          port.postMessage(false);
          clearTimeout(timeoutId);
          port.onmessage = null;
        };

        // 3d) Build a Headers object that prevents caching
        const responseHeaders = new Headers(clientResponse.headers);
        responseHeaders.set(
          "Cache-Control",
          "no-cache, no-store, must-revalidate, max-age=0"
        );
        responseHeaders.set("Pragma", "no-cache");
        responseHeaders.set("Expires", "0");
        responseHeaders.set("X-Bitvid-SW-Version", SW_VERSION);

        // 3e) If the response is not a streaming request, return it directly
        if (clientResponse.body !== "STREAM") {
          closeChannel();
          return new Response(clientResponse.body, {
            status: clientResponse.status,
            statusText: clientResponse.statusText,
            headers: responseHeaders,
          });
        }

        // 3f) Otherwise, create a streaming response
        return new Response(
          new ReadableStream({
            pull(controller) {
              return new Promise((resolvePull) => {
                port.onmessage = ({ data }) => {
                  if (data) {
                    controller.enqueue(data);
                  } else {
                    closeChannel();
                    controller.close();
                  }
                  resolvePull();
                };

                // If not cancelled, auto‐close after 5s of no data
                // *** Increase the timeout to avoid frequent CPU wake-ups ***
                if (!cancelled && destination !== "document") {
                  clearTimeout(timeoutId);
                  timeoutId = setTimeout(() => {
                    closeChannel();
                    resolvePull();
                  }, 30000); // 30 seconds
                }

                // Request next chunk from client
                port.postMessage(true);
              });
            },
            cancel() {
              closeChannel();
            },
          }),
          {
            status: clientResponse.status,
            statusText: clientResponse.statusText,
            headers: responseHeaders,
          }
        );
      })(event);
    })();

    // respondWith the promise if it exists
    event.respondWith(responsePromise);
  });
})();