46 lines
1.8 KiB
JavaScript
Executable File
46 lines
1.8 KiB
JavaScript
Executable File
/* ============================================================================
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* async-guard — tiny concurrency helper shared by the frontend.
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*
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* Keeps long-running native operations (offline-cache download/delete, playlist
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* mutations) from being triggered twice at once for the same target, so the UI
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* stays responsive and on-device state can't be corrupted by rapid clicks.
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*
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* Framework-free and dependency-free on purpose:
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* • Loads as a plain <script> under CSP `script-src 'self'` (browser global
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* `window.AsyncGuard`).
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* • `require`-able by `node --test` (CommonJS `module.exports`).
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* ========================================================================== */
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(function (root) {
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'use strict';
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/**
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* Run `fn` exclusively for `key`: if an operation for `key` is already
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* in-flight (tracked in `set`), this call is a no-op and resolves to
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* `undefined`. Otherwise `key` is added to `set`, `fn` runs, and `key` is
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* removed once it settles — on success AND on failure — so a failed
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* operation can be retried.
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*
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* @param {Set<string>} set in-flight key registry (caller owns it)
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* @param {string} key identifies the target being operated on
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* @param {() => (any|Promise<any>)} fn the work to run exclusively
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* @returns {Promise<any>} fn's resolved value, or undefined if skipped
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*/
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async function runExclusive(set, key, fn) {
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if (set.has(key)) return undefined;
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set.add(key);
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try {
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return await fn();
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} finally {
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set.delete(key);
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}
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}
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const AsyncGuard = { runExclusive };
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if (typeof module !== 'undefined' && module.exports) {
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module.exports = AsyncGuard;
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} else {
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root.AsyncGuard = AsyncGuard;
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}
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})(typeof globalThis !== 'undefined' ? globalThis : this);
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