Mercurial > addons > firefox-addons > feed-preview

comparison js/background.js @ 6:5d7c13e998e9

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Create feed previews using a stream filter Instead of replacing the feed document with an XHTML preview from a content script after it has already been rendered, create an XHTML preview using a stream filter before it is passed into the rendering engine and use an XSL style sheet to convert it to HTML. This has two advantages, firstly it results in an HTMLDocument with the full HTML DOM available and secondly it avoids rendering the document twice. Refactor the feed preview creation and split parsing and rendering into seperate modules.
author Guido Berhoerster <guido+feed-preview@berhoerster.name>
date Thu, 08 Nov 2018 16:30:34 +0100
parents background.js@bc5cc170163c
children ff5e5e3eba32
comparison
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5:341a0f4b7ce0 6:5d7c13e998e9
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 import * as feedParser from './feed-parser.js';
12 import {renderFeedPreview} from './feed-preview.js';
13
14 const FEED_MAGIC = [
15 '<rss',
16 '<feed',
17 ...Object.values(feedParser.XMLNS)
18 ];
19 var tabsFeeds = new Map();
20 var fetchingFeedPreview = fetch('web_resources/feed-preview.xhtml')
21 .then(response => response.text());
22
23 function parseContentType(header) {
24 let contentType = {
25 mediaType: '',
26 charset: 'utf-8'
27 };
28 let parts = header.toLowerCase().split(';');
29 contentType.mediaType = parts.shift().trim();
30 for (let parameter of parts) {
31 let [, name, value, ] = parameter.trim().split(/([^=]+)="?([^"]*)"?/);
32 if (name.toLowerCase() === 'charset') {
33 contentType.charset = value.toLowerCase();
34 break;
35 }
36 }
37
38 return contentType;
39 }
40
41 async function handleFeed(inputText, url) {
42 // fast-path: eliminate XML documents which cannot be Atom nor RSS feeds
43 let inputTextStart = inputText.substring(0, 512);
44 if (!FEED_MAGIC.some(element => inputTextStart.includes(element))) {
45 return inputText;
46 }
47
48 let feed;
49 try {
50 feed = (new feedParser.FeedParser).parseFromString(inputText, url);
51 } catch (e) {
52 if (e instanceof feedParser.ParserError ||
53 e instanceof feedParser.UnsupportedFeedTypeError) {
54 // let the browser deal with non-well formed XML or XML documents
55 // which are not supported Atom or RSS feeds
56 return inputText;
57 }
58 throw e;
59 }
60 console.log(`parsed feed ${url}:\n`, feed);
61
62 // render the preview document
63 let feedPreviewDocument = new DOMParser()
64 .parseFromString(await fetchingFeedPreview, 'text/html');
65 renderFeedPreview(feedPreviewDocument, feed);
66
67 return new XMLSerializer().serializeToString(feedPreviewDocument);
68 }
69
70 browser.webRequest.onHeadersReceived.addListener(details => {
71 if (details.statusCode !== 200) {
72 return {};
73 }
74
75 let contentTypeIndex = details.responseHeaders.findIndex(header =>
76 header.name.toLowerCase() === 'content-type' &&
77 typeof header.value !== 'undefined');
78 if (contentTypeIndex < 0) {
79 // no Content-Type header found
80 return {};
81 }
82 let headerValue = details.responseHeaders[contentTypeIndex].value
83 let contentType = parseContentType(headerValue);
84 // until content handlers become available to webextensions
85 // (https://bugzilla.mozilla.org/show_bug.cgi?id=1457500) intercept all
86 // responses and change the content type from application/atom+xml or
87 // application/rss+xml to application/xml which will then be probed for
88 // Atom or RSS content
89 switch (contentType.mediaType) {
90 case 'application/atom+xml':
91 case 'application/rss+xml':
92 case 'application/rdf+xml':
93 case 'application/xml':
94 break;
95 default:
96 // non-XML media type
97 return {};
98 }
99 console.log(`response is an XML document\n`,
100 `media type: ${contentType.mediaType}\n`,
101 `charset: ${contentType.charset}`);
102
103 let decoder;
104 try {
105 decoder = new TextDecoder(contentType.charset);
106 } catch (e) {
107 if (e instanceof RangeError) {
108 // unsupported charset
109 return {};
110 } else {
111 throw e;
112 }
113 }
114 let encoder = new TextEncoder();
115 let inputText = '';
116 let filter = browser.webRequest.filterResponseData(details.requestId);
117 filter.addEventListener('data', ev => {
118 inputText += decoder.decode(ev.data, {stream: true});
119 });
120 filter.addEventListener('stop', async ev => {
121 let result = await handleFeed(inputText, details.url);
122 filter.write(encoder.encode(result));
123 filter.close();
124 });
125
126 details.responseHeaders[contentTypeIndex] = {
127 name: 'Content-Type',
128 value: `application/xml;charset=${contentType.charset}`
129 };
130
131 return {responseHeaders: details.responseHeaders};
132 },
133 {urls: ['http://*/*', 'https://*/*'], types: ['main_frame']},
134 ['blocking', 'responseHeaders']);
135
136 browser.runtime.onMessage.addListener((request, sender, sendResponse) => {
137 let tab = sender.tab;
138 if (typeof tab !== 'undefined') {
139 // content script sending feeds
140 tabsFeeds.set(tab.id, request);
141 browser.pageAction.show(tab.id);
142 } else {
143 // popup querying feeds
144 sendResponse(tabsFeeds.get(request));
145 }
146 });
147
148 browser.tabs.onUpdated.addListener((id, changeInfo, tab) => {
149 if (typeof changeInfo.url === 'undefined') {
150 // filter out updates which do not change the URL
151 return;
152 }
153
154 // hide the page action when the URL changes since it is no longer valid,
155 // it will be shown again if the content script detects a feed
156 browser.pageAction.hide(tab.id);
157 });
158
159 browser.tabs.onRemoved.addListener((tabId, removeInfo) => {
160 tabsFeeds.delete(tabId);
161 });