Mercurial > addons > firefox-addons > feed-preview

annotate content_scripts/feed-probe.js @ 31:76e23b361e92

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Allow feed reader addons to subscribe to the currently viewed feed Add a link element to the feed preview that points to the currently viewed feed in order to allow feed reader addons to subscribe to it.
author Guido Berhoerster <guido+feed-preview@berhoerster.name>
date Tue, 22 Jan 2019 14:40:06 +0100
parents da483ce3832d
children ede87e1004f9
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1 /*
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2 * Copyright (C) 2018 Guido Berhoerster <guido+feed-preview@berhoerster.name>
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3 *
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4 * This Source Code Form is subject to the terms of the Mozilla Public
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5 * License, v. 2.0. If a copy of the MPL was not distributed with this
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6 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
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7 */
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8
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9 'use strict';
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10
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11 const TIMEOUT_MAX = 800; // ms
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12
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13 function getFeeds() {
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14 let urlsFeeds = new Map();
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15 let elements = document.querySelectorAll(':-moz-any(link, a)[href]' +
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16 '[rel~=alternate]:-moz-any([type="application/atom+xml"], ' +
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17 '[type="application/rss+xml"])');
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18
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19 for (let element of elements) {
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20 if (element.href === document.URL) {
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21 // do not indicate the availability of a feed if the current
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22 // document is already a feed preview
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23 continue;
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24 }
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25
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26 if (!element.href.match(/^https?:\/\//)) {
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27 continue;
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28 }
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30 urlsFeeds.set(element.href, {
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31 href: element.href,
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32 title: element.title || browser.i18n.getMessage('defaultFeedTitle'),
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33 type: element.type
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34 })
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35 }
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36
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37 return Array.from(urlsFeeds.values());
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38 }
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39
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40 function probeLinkedFeeds() {
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41 if (document.documentElement.nodeName.toUpperCase() !== 'HTML') {
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42 return;
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43 }
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44
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45 let feeds = getFeeds();
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46 if (feeds.length === 0) {
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47 return;
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48 }
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49
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50 // the listener on the background page might not be ready, keep trying to
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51 // send the message with an exponential backoff until TIMEOUT_MAX is
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52 // reached
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53 let timeout = 0;
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54 let sendFeeds = () => {
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55 browser.runtime.sendMessage(feeds).catch(e => {
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56 timeout = (timeout > 0) ? timeout * 2 : 100;
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57 if (timeout > TIMEOUT_MAX) {
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58 console.log(`Error: failed to message the background page: ` +
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59 ` ${e.message}`);
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60 return;
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61 }
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62 setTimeout(sendFeeds, timeout);
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63 });
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64 };
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65 setTimeout(sendFeeds, timeout);
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66 }
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68 probeLinkedFeeds();