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<!DOCTYPE html>
<title>Helper IFrame</title>
<script>
'use strict';
// Map of lock_id => function that releases a lock.
const held = new Map();
let next_lock_id = 1;
self.addEventListener('message', e => {
function respond(data) {
parent.postMessage(Object.assign(data, {rqid: e.data.rqid}), '*');
}
switch (e.data.op) {
case 'request':
navigator.locks.request(
e.data.name, {
mode: e.data.mode || 'exclusive',
ifAvailable: e.data.ifAvailable || false
}, lock => {
if (lock === null) {
respond({ack: 'request', failed: true});
return;
}
let lock_id = next_lock_id++;
let release;
const promise = new Promise(r => { release = r; });
held.set(lock_id, release);
respond({ack: 'request', lock_id: lock_id});
return promise
});
break;
case 'release':
held.get(e.data.lock_id)();
held.delete(e.data.lock_id);
respond({ack: 'release', lock_id: e.data.lock_id});
break;
case 'client_id':
navigator.locks.request(e.data.name, async lock => {
const lock_state = await navigator.locks.query();
const held_lock =
lock_state.held.filter(l => l.name === lock.name)[0];
respond({ack: 'client_id', client_id: held_lock.clientId});
});
break;
}
});
</script>