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hardened bluesky app fork with microcosm
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type Task<TServerState> = { isOn: boolean resolve: (serverState: TServerState) => void reject: (e: unknown) => void}
type TaskQueue<TServerState> = { activeTask: Task<TServerState> | null queuedTask: Task<TServerState> | null}
function AbortError() { const e = new Error() e.name = 'AbortError' return e}
export function useToggleMutationQueue<TServerState>({ initialState, runMutation, onSuccess,}: { initialState: TServerState runMutation: ( prevState: TServerState, nextIsOn: boolean, ) => Promise<TServerState> onSuccess: (finalState: TServerState) => void}) { // We use the queue as a mutable object. // This is safe becuase it is not used for rendering. const [queue] = useState<TaskQueue<TServerState>>({ activeTask: null, queuedTask: null, })
async function processQueue() { if (queue.activeTask) { // There is another active processQueue call iterating over tasks. // It will handle any newly added tasks, so we should exit early. return } // To avoid relying on the rendered state, capture it once at the start. // From that point on, and until the queue is drained, we'll use the real server state. let confirmedState: TServerState = initialState try { while (queue.queuedTask) { const prevTask = queue.activeTask const nextTask = queue.queuedTask queue.activeTask = nextTask queue.queuedTask = null if (prevTask?.isOn === nextTask.isOn) { // Skip multiple requests to update to the same value in a row. prevTask.reject(new (AbortError as any)()) continue } try { // The state received from the server feeds into the next task. // This lets us queue deletions of not-yet-created resources. confirmedState = await runMutation(confirmedState, nextTask.isOn) nextTask.resolve(confirmedState) } catch (e) { nextTask.reject(e) } } } finally { onSuccess(confirmedState) queue.activeTask = null queue.queuedTask = null } }
function queueToggle(isOn: boolean): Promise<TServerState> { return new Promise((resolve, reject) => { // This is a toggle, so the next queued value can safely replace the queued one. if (queue.queuedTask) { queue.queuedTask.reject(new (AbortError as any)()) } queue.queuedTask = {isOn, resolve, reject} processQueue() }) }
const queueToggleRef = useRef(queueToggle) useEffect(() => { queueToggleRef.current = queueToggle }) const queueToggleStable = useCallback( (isOn: boolean): Promise<TServerState> => { const queueToggleLatest = queueToggleRef.current return queueToggleLatest(isOn) }, [], ) return queueToggleStable}