1 files changed, 94 insertions, 0 deletions
diff --git a/toolkit/components/reader/Readerable.js b/toolkit/components/reader/Readerable.js
new file mode 100644
index 0000000000..828b4f507c
--- /dev/null
+++ b/toolkit/components/reader/Readerable.js
@@ -0,0 +1,94 @@
+// -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+// This file and Readability-readerable.js are merged together into
+// Readerable.sys.mjs.
+
+/* exported Readerable */
+/* import-globals-from readability/Readability-readerable.js */
+
+const { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
+
+var Readerable = {
+  get isEnabledForParseOnLoad() {
+    return this.isEnabled;
+  },
+
+  /**
+   * Decides whether or not a document is reader-able without parsing the whole thing.
+   *
+   * @param doc A document to parse.
+   * @return boolean Whether or not we should show the reader mode button.
+   */
+  isProbablyReaderable(doc) {
+    // Only care about 'real' HTML documents:
+    if (
+      doc.mozSyntheticDocument ||
+      !doc.defaultView.HTMLDocument.isInstance(doc)
+    ) {
+      return false;
+    }
+
+    let uri = Services.io.newURI(doc.location.href);
+    if (!this.shouldCheckUri(uri)) {
+      return false;
+    }
+
+    return isProbablyReaderable(doc, this._isNodeVisible);
+  },
+
+  _isNodeVisible(node) {
+    return node.clientHeight > 0 && node.clientWidth > 0;
+  },
+
+  _blockedHosts: [
+    "amazon.com",
+    "github.com",
+    "mail.google.com",
+    "pinterest.com",
+    "reddit.com",
+    "twitter.com",
+    "youtube.com",
+    "app.slack.com",
+  ],
+
+  shouldCheckUri(uri, isBaseUri = false) {
+    if (!["http", "https", "file", "moz-nullprincipal"].includes(uri.scheme)) {
+      return false;
+    }
+
+    if (!isBaseUri && uri.scheme.startsWith("http")) {
+      // Sadly, some high-profile pages have false positives, so bail early for those:
+      let { host } = uri;
+      if (this._blockedHosts.some(blockedHost => host.endsWith(blockedHost))) {
+        // Allow github on non-project pages
+        if (
+          host == "github.com" &&
+          !uri.filePath.includes("/projects") &&
+          !uri.filePath.includes("/issues")
+        ) {
+          return true;
+        }
+        return false;
+      }
+
+      if (uri.filePath == "/") {
+        return false;
+      }
+    }
+
+    return true;
+  },
+};
+
+XPCOMUtils.defineLazyPreferenceGetter(
+  Readerable,
+  "isEnabled",
+  "reader.parse-on-load.enabled",
+  true
+);