Issue #303 Part 1: Move basilisk files from /browser to /application/basilisk

application/basilisk/components/newtab/PreviewProvider.jsm

@@ -0,0 +1,49 @@
+/* global XPCOMUtils, BackgroundPageThumbs, FileUtils, PageThumbsStorage, Task, MIMEService */
+/* exported PreviewProvider */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["PreviewProvider"];
+
+const {utils: Cu} = Components;
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/Task.jsm");
+Cu.import("resource://gre/modules/PageThumbs.jsm");
+Cu.import("resource://gre/modules/FileUtils.jsm");
+const {OS} = Cu.import("resource://gre/modules/osfile.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "BackgroundPageThumbs",
+  "resource://gre/modules/BackgroundPageThumbs.jsm");
+XPCOMUtils.defineLazyServiceGetter(this, "MIMEService",
+  "@mozilla.org/mime;1", "nsIMIMEService");
+
+let PreviewProvider = {
+  /**
+   * Returns a thumbnail as a data URI for a url, creating it if necessary
+   *
+   * @param {String} url
+   *        a url to obtain a thumbnail for
+   * @return {Promise} A Promise that resolves with a base64 encoded thumbnail
+   */
+  getThumbnail: Task.async(function* PreviewProvider_getThumbnail(url) {
+    try {
+      yield BackgroundPageThumbs.captureIfMissing(url);
+      let imgPath = PageThumbsStorage.getFilePathForURL(url);
+
+      // OS.File object used to easily read off-thread
+      let file = yield OS.File.open(imgPath, {read: true, existing: true});
+
+      // nsIFile object needed for MIMEService
+      let nsFile = FileUtils.File(imgPath);
+
+      let contentType = MIMEService.getTypeFromFile(nsFile);
+      let bytes = yield file.read();
+      let encodedData = btoa(String.fromCharCode.apply(null, bytes));
+      file.close();
+      return `data:${contentType};base64,${encodedData}`;
+    } catch (err) {
+      Cu.reportError(`PreviewProvider_getThumbnail error: ${err}`);
+      throw err;
+    }
+  })
+};