Allow background downloads

sneat · Apr 16, 2021 · 95461c8 · 95461c8
1 parent d9a69a9
commit 95461c8
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Showing 3 changed files with 218 additions and 130 deletions.
diff --git a/background.js b/background.js
@@ -1,3 +1,134 @@
+class ChromeDownloader {
+  /**
+   * ChromeDownloader manages a maximum concurrent number of download requests (Semaphore)
+   * @param {Number} maxConcurrentRequests
+   */
+  constructor(maxConcurrentRequests = 1) {
+    this.requests = [];
+    this.running = 0;
+    this.max = maxConcurrentRequests;
+    this.callbackComplete = null;
+    this.callbackBeginDownload = null;
+  }
+
+  /**
+   * A callback to trigger when there are no more pending downloads.
+   * @param {Function} func
+   */
+  OnComplete(func) {
+    if (typeof func === 'function') {
+      this.callbackComplete = func;
+    }
+  }
+
+  /**
+   * A callback to trigger when a download starts.
+   * @param func
+   */
+  OnBeginDownload(func) {
+    if (typeof func === 'function') {
+      this.callbackBeginDownload = func;
+    }
+  }
+
+  /**
+   * Request a download.
+   * @see {@link https://developer.chrome.com/docs/extensions/reference/downloads/#method-download} for request details
+   * @param {Object} request
+   * @returns {Promise<Boolean>} Whether the download completed successfully.
+   */
+  Download(request) {
+    return new Promise((resolve, reject) => {
+      this.requests.push({
+        resolve,
+        reject,
+        request,
+      });
+      this.nextDownload();
+    });
+  }
+
+  /**
+   * Triggers the next download to start if it can.
+   */
+  nextDownload() {
+    try {
+      if (!this.requests.length) {
+        if (typeof this.callbackComplete === 'function') {
+          this.callbackComplete();
+        }
+        return;
+      }
+      if (this.running < this.max) {
+        let {resolve, reject, request} = this.requests.shift();
+        this.running++;
+        new Promise(resolve => {
+          if (typeof this.callbackBeginDownload === 'function') {
+            this.callbackBeginDownload();
+          }
+          chrome.downloads.download(request, resolve);
+        }).then(downloadId => {
+          if (chrome.runtime.lastError) {
+            console.error('Patreon Downloader |', request.filename, downloadId, chrome.runtime.lastError.message);
+          } else {
+            console.debug('Patreon Downloader |', `Download started: ${request.filename}`, downloadId);
+          }
+          this.onDownloadComplete(downloadId)
+            .then(success => {
+              if (success) {
+                console.debug('Patreon Downloader |', `Download finished: ${request.filename}`, downloadId);
+              } else {
+                console.debug('Patreon Downloader |', `Download failed: ${request.filename}`, downloadId);
+              }
+              resolve(success);
+            })
+            .catch(err => {
+              console.debug('Patreon Downloader |', `Download failed: ${request.filename}`, downloadId);
+              reject(err);
+            })
+            .finally(() => {
+              this.running--;
+              this.nextDownload();
+            });
+        });
+      }
+    } catch (e) {
+      console.error('huh', e);
+    }
+  }
+
+  /**
+   * Trigger a response when a download finishes successfully or when it is interrupted.
+   * @param {Number} downloadId The downloadId response from chrome.downloads.download
+   * @returns {Promise<Boolean>} Whether the download completed successfully.
+   */
+  onDownloadComplete(downloadId) {
+    return new Promise(resolve => {
+      chrome.downloads.onChanged.addListener(function onChanged({id, state}) {
+        if (id === downloadId && state?.current !== 'in_progress') {
+          chrome.downloads.onChanged.removeListener(onChanged);
+          resolve(state.current === 'complete');
+        }
+      });
+    });
+  }
+}
+
+chrome.runtime.onInstalled.addListener(function () {
+  chrome.declarativeContent.onPageChanged.removeRules(undefined, function () {
+    chrome.declarativeContent.onPageChanged.addRules([
+      {
+        conditions: [
+          new chrome.declarativeContent.PageStateMatcher({
+            pageUrl: {hostEquals: 'www.patreon.com', schemes: ['https'], pathPrefix: '/posts/'},
+          }),
+        ],
+        actions: [new chrome.declarativeContent.ShowPageAction()],
+      },
+    ]);
+  });
+});
+
 chrome.runtime.onMessage.addListener(
   function (message, sender, sendResponse) {
     switch (message.type) {
@@ -6,4 +137,51 @@ chrome.runtime.onMessage.addListener(
         break;
     }
   },
-);
+);
+
+let count = 0;
+let total = 0;
+chrome.extension.onConnect.addListener(function (port) {
+  const throttler = new ChromeDownloader(3);
+  throttler.OnComplete(function () {
+    count = 0;
+    total = 0;
+    try {
+      port.postMessage({type: 'complete'});
+    } catch (e) {
+      console.error('Patreon Downloader | Error OnComplete:', e);
+    }
+  });
+  throttler.OnBeginDownload(function () {
+    count++;
+    try {
+      port.postMessage({type: 'downloadUpdate', count, total});
+    } catch (e) {
+      console.error('Patreon Downloader | Error OnBeginDownload:', e);
+    }
+  });
+  port.onMessage.addListener(function (msg) {
+    if (typeof msg !== 'object') {
+      return;
+    }
+    if (msg.type) {
+      switch (msg.type) {
+        case 'download':
+          if (msg?.requests?.length) {
+            total += msg.requests.length;
+            for (let i = 0; i < msg.requests.length; i++) {
+              throttler.Download(msg.requests[i]);
+            }
+          }
+          break;
+        case 'status':
+          try {
+            port.postMessage({type: 'downloadUpdate', count, total});
+          } catch (e) {
+            console.error('Patreon Downloader | Error OnBeginDownload:', e);
+          }
+          break;
+      }
+    }
+  });
+});