Chunk streaming -- progressive download with Range request support for large media files
BlobCache -- in-memory cache for assembled chunks with LRU eviction
Widget HTML serving -- intercepts GetResource requests and serves from ContentStore
Version-aware activation -- prevents re-activation of same SW version to preserve in-flight streams
XLF-driven media resolution -- parses layout XLF to determine exactly which media each layout needs
Adaptive chunk sizing -- adjusts chunk size and concurrency based on device RAM (4GB/8GB+ tiers)
Unclaimed media -- media files not claimed by any layout are enqueued for download

Architecture

Browser fetch()                   Service Worker                    Proxy ContentStore
     |                                 |                                   |
     +-- GET /media/video.mp4 ------> RequestHandler.handleMedia()         |
     |                                 +- Check BlobCache (in-memory) ---> [hit: return blob]
     |                                 +- Miss: stream from chunks         |
     |                                 |  +- GET /store/media/video.mp4 ---+
     |                                 |  +- Assemble chunks, cache blob   |
     |                                 +- Return Response with Range support
     |
     +-- GET /widgets/1/2/3 --------> RequestHandler.handleWidget()        |
     |                                 +- GET /store/widget/1/2/3 ---------+
     |                                 +- Return HTML response             |
     |
     +-- postMessage(download) ------> MessageHandler.handleMessage()      |
                                       +- Parse XLF for media IDs          |
                                       +- Enqueue downloads                |
                                       +- Report progress                  |

Installation

npm install @xiboplayer/sw

Exports

Export	Description
`RequestHandler`	Fetch event handler: media streaming, widget serving, Range support
`MessageHandler`	PostMessage handler: download orchestration, progress reporting
`extractMediaIdsFromXlf`	Parse XLF XML to extract all required media file IDs
`calculateChunkConfig`	Adaptive chunk/concurrency config based on device RAM

Usage

// In sw-pwa.js (Service Worker entry point)
import { RequestHandler, MessageHandler } from '@xiboplayer/sw';

const requestHandler = new RequestHandler();
const messageHandler = new MessageHandler();

self.addEventListener('fetch', (event) => {
  const response = requestHandler.handle(event.request);
  if (response) event.respondWith(response);
});

self.addEventListener('message', (event) => {
  messageHandler.handle(event);
});

XLF media extraction

import { extractMediaIdsFromXlf } from '@xiboplayer/sw';

const mediaIds = extractMediaIdsFromXlf(xlfXmlString);
// Returns: Set<string> of media file IDs needed by this layout
// Includes: fileId from media tags, data widget IDs (no fileId), background images

Adaptive chunk config

import { calculateChunkConfig } from '@xiboplayer/sw';

const config = calculateChunkConfig();
// 4GB RAM: { chunkSize: 25MB, concurrency: 4 }
// 8GB+ RAM: { chunkSize: 50MB, concurrency: 6 }