66 lines
1.6 KiB
JavaScript
66 lines
1.6 KiB
JavaScript
import { id, registerFire, registerSubscriptions, call } from './util.js';
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export const hashableStream = hash => (fn, dependencies = []) => {
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let subscribers = [];
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let isDirty = true;
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let val;
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let oldId;
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let currentProcess;
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// Compute new value, call subscribers if changed.
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const accessor = function _stream() {
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if (!isDirty) {
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return Promise.resolve(val);
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}
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if (!currentProcess) {
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currentProcess = Promise.all(dependencies.map(call))
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.then(params => fn.apply(null, params))
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.then(res => {
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const newId = hash(res);
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isDirty = false;
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if (oldId !== newId) {
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oldId = newId;
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val = res;
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accessor.fire(val);
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}
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return val;
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})
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.finally(_ => {
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isDirty = false;
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currentProcess = null;
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});
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}
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return currentProcess;
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};
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// Add child nodes to the logic graph (value-based)
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accessor.subscribe = registerSubscriptions(subscribers);
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accessor.fire = registerFire(subscribers);
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// Receive dirty flag from parent logic node (dependency). Pass it down.
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accessor.setDirty = function setDirty() {
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if (!isDirty) {
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isDirty = true;
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subscribers.forEach(s => s.setDirty && s.setDirty());
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}
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return subscribers.length && accessor;
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};
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// Remove this node from the logic graph completely
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accessor.detach = () => {
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subscribers = [];
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dependentSubscriptions.forEach(call);
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};
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// Remove child nodes from the logic graph
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accessor.unsubscribeAll = () => {
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subscribers = [];
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};
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const dependentSubscriptions = dependencies.map(d => d.subscribe(accessor.setDirty));
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return accessor;
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};
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export const stream = hashableStream(id);
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