99 lines
3.5 KiB
JavaScript
99 lines
3.5 KiB
JavaScript
function createOutboxCoordinator({
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storage,
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locks = globalThis.navigator?.locks,
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channelFactory = typeof globalThis.BroadcastChannel === 'function' ?
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() => new globalThis.BroadcastChannel('stackchain-outbox-v1') : null,
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addStorageListener = globalThis.addEventListener?.bind(globalThis),
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removeStorageListener = globalThis.removeEventListener?.bind(globalThis),
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tabId = globalThis.crypto?.randomUUID?.() || String(Date.now()) + '-' + Math.random().toString(16).slice(2),
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now = () => Date.now(),
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leaseMs = 15000,
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} = {}) {
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const changeKey = 'stackchain.outbox-change.v1';
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const subscribers = new Set();
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const channel = channelFactory ? channelFactory() : null;
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let sequence = 0;
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function validChange(value) {
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return value && ['issue', 'authored', 'today', 'later'].includes(value.queue) ? value : null;
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}
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function publish(change) {
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subscribers.forEach(listener => listener(change));
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}
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if (channel) {
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channel.onmessage = event => {
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const change = validChange(event?.data);
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if (change && change.tabId !== tabId) publish(change);
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};
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}
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const onStorage = event => {
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if (event?.key !== changeKey || !event.newValue) return;
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try {
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const change = validChange(JSON.parse(event.newValue));
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if (change && change.tabId !== tabId) publish(change);
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} catch (_error) { /* Ignore malformed cross-tab signals. */ }
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};
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if (addStorageListener) addStorageListener('storage', onStorage);
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function notify(queue) {
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const change = { queue, tabId, changedAt: Number(now()), sequence: ++sequence };
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if (!validChange(change)) return;
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try { storage?.setItem(changeKey, JSON.stringify(change)); } catch (_error) { /* Broadcast may still work. */ }
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try { channel?.postMessage(change); } catch (_error) { /* Storage events remain available. */ }
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}
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function skipped() {
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return { confirmed: [], remaining: [], blocked: 0, lease_skipped: true };
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}
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async function withFallbackLease(queue, work) {
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const key = 'stackchain.outbox-lease.' + queue + '.v1';
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const token = tabId + ':' + (++sequence);
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const timestamp = Number(now());
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try {
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const current = JSON.parse(storage?.getItem(key) || 'null');
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if (current?.token && Number(current.expiresAt) > timestamp) return skipped();
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storage?.setItem(key, JSON.stringify({ token, expiresAt: timestamp + leaseMs }));
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const claimed = JSON.parse(storage?.getItem(key) || 'null');
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if (claimed?.token !== token) return skipped();
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} catch (_error) {
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return work();
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}
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try {
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return await work();
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} finally {
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try {
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const current = JSON.parse(storage?.getItem(key) || 'null');
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if (current?.token === token) storage?.removeItem(key);
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} catch (_error) { /* An expired lease will be reclaimed. */ }
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}
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}
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async function runExclusive(queue, work) {
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if (locks?.request) {
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return locks.request('stackchain-outbox-' + queue + '-v1', { mode: 'exclusive', ifAvailable: true },
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lock => lock ? work() : skipped());
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}
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return withFallbackLease(queue, work);
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}
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function subscribe(listener) {
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if (typeof listener !== 'function') return () => {};
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subscribers.add(listener);
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return () => subscribers.delete(listener);
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}
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function close() {
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subscribers.clear();
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try { channel?.close(); } catch (_error) { /* No-op. */ }
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if (removeStorageListener) removeStorageListener('storage', onStorage);
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}
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return { runExclusive, notify, subscribe, close };
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}
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if (typeof module !== 'undefined' && module.exports) module.exports = createOutboxCoordinator;
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