braille_table.js revision cedac228d2dd51db4b79ea1e72c7f249408ee061 
1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5/**
6 * @fileoverview Holds information about a braille table.
7 */
8
9goog.provide('cvox.BrailleTable');
10
11
12/**
13 * @typedef {{
14 *   locale:string,
15 *   dots:string,
16 *   id:string,
17 *   grade:(string|undefined),
18 *   fileName:string
19 * }}
20 */
21cvox.BrailleTable.Table;
22
23
24/**
25 * @const {string}
26 */
27cvox.BrailleTable.TABLE_PATH = 'chromevox/background/braille/tables.json';
28
29
30/**
31 * Retrieves a list of all available braille tables.
32 * @param {function(!Array.<cvox.BrailleTable.Table>)} callback
33 */
34cvox.BrailleTable.getAll = function(callback) {
35  var url = chrome.extension.getURL(cvox.BrailleTable.TABLE_PATH);
36  if (!url) {
37    throw 'Invalid path: ' + cvox.BrailleTable.TABLE_PATH;
38  }
39
40  var xhr = new XMLHttpRequest();
41  xhr.open('GET', url, true);
42  xhr.onreadystatechange = function() {
43    if (xhr.readyState == 4) {
44      if (xhr.status == 200) {
45        callback(/** @type {!Array.<cvox.BrailleTable.Table>} */ (
46            JSON.parse(xhr.responseText)));
47      }
48    }
49  };
50  xhr.send();
51};
52
53
54/**
55 * Finds a table in a list of tables by id.
56 * @param {!Array.<cvox.BrailleTable.Table>} tables tables to search in.
57 * @param {string} id id of table to find.
58 * @return {cvox.BrailleTable.Table}
59 */
60cvox.BrailleTable.forId = function(tables, id) {
61  return tables.filter(function(table) { return table.id === id })[0] || null;
62};
63
64
65/**
66 * Returns an uncontracted braille table corresponding to another, possibly
67 * contracted, table.  If {@code table} is the lowest-grade table for its
68 * locale and dot count, {@code table} itself is returned.
69 * @param {!Array.<cvox.BrailleTable.Table>} tables tables to search in.
70 * @param {!cvox.BrailleTable.Table} table Table to match.
71 * @return {!cvox.BrailleTable.Table} Corresponding uncontracted table,
72 *     or {@code table} if it is uncontracted.
73 */
74cvox.BrailleTable.getUncontracted = function(tables, table) {
75  function mostUncontractedOf(current, candidate) {
76    // An 8 dot table for the same language is prefered over a 6 dot table
77    // even if the locales differ by region.
78    if (current.dots === '6' &&
79        candidate.dots === '8' &&
80        current.locale.lastIndexOf(candidate.locale, 0) == 0) {
81      return candidate;
82    }
83    if (current.locale === candidate.locale &&
84        current.dots === candidate.dots &&
85        goog.isDef(current.grade) &&
86        goog.isDef(candidate.grade) &&
87        candidate.grade < current.grade) {
88      return candidate;
89    }
90    return current;
91  }
92  return tables.reduce(mostUncontractedOf, table);
93};
94