104 lines
3.1 KiB
JavaScript
104 lines
3.1 KiB
JavaScript
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import { noop, safe_not_equal, subscribe, run_all, is_function } from '../internal/index.mjs';
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export { get_store_value as get } from '../internal/index.mjs';
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const subscriber_queue = [];
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/**
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* Creates a `Readable` store that allows reading by subscription.
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* @param value initial value
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* @param {StartStopNotifier}start start and stop notifications for subscriptions
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*/
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function readable(value, start) {
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return {
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subscribe: writable(value, start).subscribe
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};
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}
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/**
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* Create a `Writable` store that allows both updating and reading by subscription.
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* @param {*=}value initial value
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* @param {StartStopNotifier=}start start and stop notifications for subscriptions
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*/
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function writable(value, start = noop) {
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let stop;
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const subscribers = new Set();
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function set(new_value) {
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if (safe_not_equal(value, new_value)) {
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value = new_value;
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if (stop) { // store is ready
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const run_queue = !subscriber_queue.length;
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for (const subscriber of subscribers) {
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subscriber[1]();
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subscriber_queue.push(subscriber, value);
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}
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if (run_queue) {
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for (let i = 0; i < subscriber_queue.length; i += 2) {
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subscriber_queue[i][0](subscriber_queue[i + 1]);
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}
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subscriber_queue.length = 0;
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}
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}
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}
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}
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function update(fn) {
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set(fn(value));
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}
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function subscribe(run, invalidate = noop) {
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const subscriber = [run, invalidate];
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subscribers.add(subscriber);
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if (subscribers.size === 1) {
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stop = start(set) || noop;
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}
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run(value);
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return () => {
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subscribers.delete(subscriber);
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if (subscribers.size === 0) {
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stop();
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stop = null;
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}
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};
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}
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return { set, update, subscribe };
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}
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function derived(stores, fn, initial_value) {
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const single = !Array.isArray(stores);
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const stores_array = single
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? [stores]
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: stores;
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const auto = fn.length < 2;
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return readable(initial_value, (set) => {
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let inited = false;
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const values = [];
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let pending = 0;
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let cleanup = noop;
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const sync = () => {
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if (pending) {
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return;
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}
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cleanup();
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const result = fn(single ? values[0] : values, set);
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if (auto) {
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set(result);
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}
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else {
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cleanup = is_function(result) ? result : noop;
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}
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};
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const unsubscribers = stores_array.map((store, i) => subscribe(store, (value) => {
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values[i] = value;
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pending &= ~(1 << i);
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if (inited) {
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sync();
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}
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}, () => {
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pending |= (1 << i);
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}));
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inited = true;
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sync();
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return function stop() {
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run_all(unsubscribers);
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cleanup();
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};
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});
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}
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export { derived, readable, writable };
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