feat: add service worker server as an alternative to renderMedia (#2098)

* feat: add service worker server as an alternative to renderMedia

* code QL

* thanks gh auto merge

Co-authored-by: Diego Rodríguez Baquero <github@diegorbaquero.com>

1 files changed, 68 insertions, 1 deletions

diff --git a/index.js b/index.js
index 8866665..ec516a0 100644
--- a/index.js
+++ b/index.js
@@ -1,5 +1,6 @@
 /*! webtorrent. MIT License. WebTorrent LLC <https://webtorrent.io/opensource> */
-/* global FileList */
+/* global FileList, ServiceWorker */
+/* eslint-env browser */
 
 const { EventEmitter } = require('events')
 const concat = require('simple-concat')
@@ -81,6 +82,10 @@ class WebTorrent extends EventEmitter {
     this._downloadLimit = Math.max((typeof opts.downloadLimit === 'number') ? opts.downloadLimit : -1, -1)
     this._uploadLimit = Math.max((typeof opts.uploadLimit === 'number') ? opts.uploadLimit : -1, -1)
 
+    this.serviceWorker = null
+    this.workerKeepAliveInterval = null
+    this.workerPortCount = 0
+
     if (opts.secure === true) {
       require('./lib/peer').enableSecure()
     }
@@ -157,6 +162,68 @@ class WebTorrent extends EventEmitter {
     }
   }
 
+  /**
+   * Accepts an existing service worker registration [navigator.serviceWorker.controller]
+   * which must be activated, "creates" a file server for streamed file rendering to use.
+   *
+   * @param  {ServiceWorker} controller
+   * @param {function=} cb
+   * @return {null}
+   */
+  loadWorker (controller, cb = () => {}) {
+    if (!(controller instanceof ServiceWorker)) throw new Error('Invalid worker registration')
+    if (controller.state !== 'activated') throw new Error('Worker isn\'t activated')
+    const keepAliveTime = 20000
+
+    this.serviceWorker = controller
+
+    navigator.serviceWorker.addEventListener('message', event => {
+      const { data } = event
+      if (!data.type || !data.type === 'webtorrent' || !data.url) return null
+      let [infoHash, ...filePath] = data.url.slice(data.url.indexOf(data.scope + 'webtorrent/') + 11 + data.scope.length).split('/')
+      filePath = decodeURI(filePath.join('/'))
+      if (!infoHash || !filePath) return null
+
+      const [port] = event.ports
+
+      const file = this.get(infoHash) && this.get(infoHash).files.find(file => file.path === filePath)
+      if (!file) return null
+
+      const [response, stream, raw] = file._serve(data)
+      const asyncIterator = stream && stream[Symbol.asyncIterator]()
+
+      const cleanup = () => {
+        port.onmessage = null
+        if (stream) stream.destroy()
+        if (raw) raw.destroy()
+        this.workerPortCount--
+        if (!this.workerPortCount) {
+          clearInterval(this.workerKeepAliveInterval)
+          this.workerKeepAliveInterval = null
+        }
+      }
+
+      port.onmessage = async msg => {
+        if (msg.data) {
+          let chunk
+          try {
+            chunk = (await asyncIterator.next()).value
+          } catch (e) {
+            // chunk is yet to be downloaded or it somehow failed, should this be logged?
+          }
+          port.postMessage(chunk)
+          if (!chunk) cleanup()
+          if (!this.workerKeepAliveInterval) this.workerKeepAliveInterval = setInterval(() => fetch(`${this.serviceWorker.scriptURL.substr(0, this.serviceWorker.scriptURL.lastIndexOf('/') + 1).slice(window.location.origin.length)}webtorrent/keepalive/`), keepAliveTime)
+        } else {
+          cleanup()
+        }
+      }
+      this.workerPortCount++
+      port.postMessage(response)
+    })
+    cb(this.serviceWorker)
+  }
+
   get downloadSpeed () { return this._downloadSpeed() }
 
   get uploadSpeed () { return this._uploadSpeed() }