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/* 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";
const {CC} = require("chrome");
const defer = require("devtools/shared/defer");
const promise = require("promise");
const Services = require("Services");
loader.lazyRequireGetter(this, "asyncStorage", "devtools/shared/async-storage");
const XMLHttpRequest = CC("@mozilla.org/xmlextras/xmlhttprequest;1");
/**
* Downloads and caches a JSON file from an URL given by a pref.
*
* @param {String} prefName
* The preference for the target URL
*
* @return {Promise}
* - Resolved with the JSON object in case of successful request
* or cache hit
* - Rejected with an error message in case of failure
*/
exports.getJSON = function (prefName) {
let deferred = defer();
let xhr = new XMLHttpRequest();
// We used to store cached data in preferences, but now we use asyncStorage
// Migration step: if it still exists, move this now useless preference in its
// new location and clear it
if (Services.prefs.prefHasUserValue(prefName + "_cache")) {
let json = Services.prefs.getCharPref(prefName + "_cache");
asyncStorage.setItem(prefName + "_cache", json).catch(function (e) {
// Could not move the cache, let's log the error but continue
console.error(e);
});
Services.prefs.clearUserPref(prefName + "_cache");
}
function readFromStorage(networkError) {
asyncStorage.getItem(prefName + "_cache").then(function (json) {
if (!json) {
return promise.reject("Empty cache for " + prefName);
}
return deferred.resolve(json);
}).catch(function (e) {
deferred.reject("JSON not available, CDN error: " + networkError +
", storage error: " + e);
});
}
xhr.onload = () => {
try {
let json = JSON.parse(xhr.responseText);
asyncStorage.setItem(prefName + "_cache", json).catch(function (e) {
// Could not update cache, let's log the error but continue
console.error(e);
});
deferred.resolve(json);
} catch (e) {
readFromStorage(e);
}
};
xhr.onerror = (e) => {
readFromStorage(e);
};
xhr.open("get", Services.prefs.getCharPref(prefName));
xhr.send();
return deferred.promise;
};
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