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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 Services = require("Services");
loader.lazyRequireGetter(this, "asyncStorage", "devtools/shared/async-storage");
/**
* 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) {
return new Promise((resolve, reject) => {
const 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")) {
const 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 reject("Empty cache for " + prefName);
}
return resolve(json);
})
.catch(function(e) {
reject(
"JSON not available, CDN error: " +
networkError +
", storage error: " +
e
);
});
}
xhr.onload = () => {
try {
const 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);
});
resolve(json);
} catch (e) {
readFromStorage(e);
}
};
xhr.onerror = e => {
readFromStorage(e);
};
xhr.open("get", Services.prefs.getCharPref(prefName));
xhr.send();
});
};
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