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Compute offset to correct browser time for accurate expiration countdown

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This commit is contained in:
Ben Holt
2021-03-11 17:04:43 -05:00
parent 250b118c50
commit 8edebbfd85
1 changed files with 18 additions and 1 deletions
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19
src/courseware/data/api.js
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@@ -118,6 +118,7 @@ function normalizeTabUrls(id, tabs) {
function normalizeMetadata(metadata) {
return {
timeOffsetMillis: metadata.timeOffsetMillis, // This should move to a global time correction reference
accessExpiration: camelCaseObject(metadata.access_expiration),
canShowUpgradeSock: metadata.can_show_upgrade_sock,
contentTypeGatingEnabled: metadata.content_type_gating_enabled,
@@ -156,7 +157,23 @@ function normalizeMetadata(metadata) {
export async function getCourseMetadata(courseId) {
let url = `${getConfig().LMS_BASE_URL}/api/courseware/course/${courseId}`;
url = appendBrowserTimezoneToUrl(url);
const { data } = await getAuthenticatedHttpClient().get(url);
const requestTime = Date.now();
const { data, headers } = await getAuthenticatedHttpClient().get(url);
const responseTime = Date.now();
// Time offset computation should move down into the HttpClient wrapper to maintain a global time correction reference
// Requires 'Access-Control-Expose-Headers: Date' on the server response per https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#access-control-expose-headers
const headerDate = headers.date;
let timeOffsetMillis = 0;
if (headerDate !== undefined) {
const headerTime = Date.parse(headerDate);
const roundTripMillis = requestTime - responseTime;
const localTime = responseTime - (roundTripMillis / 2); // Roughly compensate for transit time
timeOffsetMillis = headerTime - localTime;
}
data.timeOffsetMillis = timeOffsetMillis; // This should move to a global time correction reference
return normalizeMetadata(data);
}