Mercurial > addons > firefox-addons > feed-preview

comparison content_scripts/feed-probe.js @ 0:bc5cc170163c

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Initial revision
author Guido Berhoerster <guido+feed-preview@berhoerster.name>
date Wed, 03 Oct 2018 23:40:57 +0200
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children da483ce3832d
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-1:000000000000 0:bc5cc170163c
1 /*
2 * Copyright (C) 2018 Guido Berhoerster <guido+feed-preview@berhoerster.name>
3 *
4 * This Source Code Form is subject to the terms of the Mozilla Public
5 * License, v. 2.0. If a copy of the MPL was not distributed with this
6 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
7 */
8
9 'use strict';
10
11 const TIMEOUT_MAX = 800; // ms
12
13 function getFeeds() {
14 let urlsFeeds = new Map();
15 let elements = document.querySelectorAll(':-moz-any(link, a)[href]' +
16 '[rel=alternate]:-moz-any([type="application/atom+xml"], ' +
17 '[type="application/rss+xml"])');
18
19 for (let element of elements) {
20 if (!element.href.match(/^https?:\/\//)) {
21 continue;
22 }
23
24 urlsFeeds.set(element.href, {
25 href: element.href,
26 title: element.title || browser.i18n.getMessage('defaultFeedTitle'),
27 type: element.type
28 })
29 }
30
31 return Array.from(urlsFeeds.values());
32 }
33
34 function probeLinkedFeeds() {
35 if (document.documentElement.nodeName.toUpperCase() !== 'HTML') {
36 return;
37 }
38
39 let feeds = getFeeds();
40 if (feeds.length === 0) {
41 return;
42 }
43
44 // the listener on the background page might not be ready, keep trying to
45 // send the message with an exponential backoff until TIMEOUT_MAX is
46 // reached
47 let timeout = 0;
48 let sendFeeds = () => {
49 browser.runtime.sendMessage(feeds).catch(e => {
50 timeout = (timeout > 0) ? timeout * 2 : 100;
51 if (timeout > TIMEOUT_MAX) {
52 console.log(`Error: failed to message the background page: ` +
53 ` ${e.message}`);
54 return;
55 }
56 setTimeout(sendFeeds, timeout);
57 });
58 };
59 setTimeout(sendFeeds, timeout);
60 }
61
62 probeLinkedFeeds();