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kvStoreMaintenance.js
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kvStoreMaintenance.js
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/**
* Module for maintenance of items in kvStore. During idle time, it checks the
* expiry times of items and removes those that expired a specified "leeway"
* time ago.
*
* This module provides an API at mw.centralNotice.kvStoreMaintenance.
*/
( function () {
var kvStoreMaintenance,
now = Date.now() / 1000,
// Regex to find kvStore localStorage keys. Must correspond with PREFIX
// in ext.centralNotice.kvStore.
PREFIX_REGEX = /^CentralNoticeKV/,
// Must coordinate with PREFIX_IN_COOKIES and SEPARATOR_IN_COOKIES in
// ext.centralNotice.kvStore.
PREFIX_AND_SEPARATOR_IN_COOKIES = 'CN!',
// Time past expiry before actually removing items: 1 day (in seconds).
// (This should prevent race conditions among browser tabs.)
LEEWAY_FOR_REMOVAL = 86400,
// Minimum amount of time (in milliseconds) for an iteration involving localStorage access.
MIN_WORK_TIME = 3;
/**
* @return {jQuery.Promise} List of key strings
*/
function getKeys() {
return $.Deferred( function ( d ) {
mw.requestIdleCallback( function ( deadline ) {
var key,
keys = [],
index = localStorage.length;
// We don't expect to have more keys than we can handle in a single iteration.
// But just in case, ensure we don't stall for too long.
while ( index-- > 0 && deadline.timeRemaining() > MIN_WORK_TIME ) {
key = localStorage.key( index );
// Operate only on our own localStorage items.
// Also recheck key existence as it may race with other tabs.
if ( key !== null && PREFIX_REGEX.test( key ) ) {
keys.push( key );
}
}
d.resolve( keys );
} );
} ).promise();
}
/**
* @param queue
* @return {jQuery.Promise}
*/
function processKeys( queue ) {
return $.Deferred( function ( d ) {
mw.requestIdleCallback( function iterate( deadline ) {
var key, rawValue, value;
while ( queue[ 0 ] !== undefined && deadline.timeRemaining() > MIN_WORK_TIME ) {
key = queue.shift();
try {
rawValue = localStorage.getItem( key );
if ( rawValue ) {
value = JSON.parse( rawValue );
if ( !value.expiry || ( value.expiry + LEEWAY_FOR_REMOVAL ) < now ) {
localStorage.removeItem( key );
}
}
} catch ( e ) {
localStorage.removeItem( key );
mw.log.warn( 'CentralNotice kvStoreMaintenance error for key ' + key, e );
}
}
if ( queue[ 0 ] !== undefined ) {
// Time's up, continue later
mw.requestIdleCallback( iterate );
} else {
d.resolve();
}
} );
} ).promise();
}
function purgeFallbackCookies() {
var cookies = document.cookie.split( ';' ),
i, matches,
r = new RegExp( '^' + PREFIX_AND_SEPARATOR_IN_COOKIES + '[^=]*(?==)' );
for ( i = 0; i < cookies.length; i++ ) {
matches = cookies[ i ].trim().match( r );
if ( matches ) {
document.cookie = matches[ 0 ] +
'=; expires=Thu, 01 Jan 1970 00:00:00 GMT; path=/';
}
}
}
/**
* Public API
*/
kvStoreMaintenance = {
/**
* Start the removal of expired KVStore items. Also check for fallback
* cookies and remove them if LocalStorage is available.
*
* @return {jQuery.Promise}
*/
doMaintenance: function () {
try {
if ( !window.localStorage || !localStorage.length ) {
return $.Deferred().resolve();
}
} catch ( e ) {
return $.Deferred().resolve();
}
// Fallback cookies? LocalStorage seems to work, so purge them.
if ( document.cookie.indexOf( PREFIX_AND_SEPARATOR_IN_COOKIES ) !== -1 ) {
purgeFallbackCookies();
}
return getKeys().then( processKeys );
}
};
module.exports = kvStoreMaintenance;
}() );

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