71 lines
1.6 KiB
JavaScript
71 lines
1.6 KiB
JavaScript
import { id } from './util.js';
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export function computed(fn, dependencies = [], hash = id) {
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const subscribers = new Set();
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const dependents = new Set();
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let isDirty = true;
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let val;
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let id;
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// Receive dirty flag from parent logic node (dependency). Pass it down.
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function _computedDirtyReporter(_, skipPropagation) {
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if (!isDirty) {
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isDirty = true;
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dependents.forEach(d => d(_, skipPropagation));
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}
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if (subscribers.size && !skipPropagation) {
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accessor();
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}
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}
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const dependentSubscriptions = Array.from(dependencies).map(d => d._d(_computedDirtyReporter));
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// Compute new value, call subscribers if changed.
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const accessor = function _computed() {
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if (isDirty) {
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const newVal = fn.apply(null, dependencies.map(runParam));
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isDirty = false;
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const newId = hash(newVal);
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if (id !== newId) {
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id = newId;
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val = newVal;
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subscribers.forEach(s => s(val));
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}
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}
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return val;
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};
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// Add child nodes to the logic graph (value-based)
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accessor.subscribe = fn => {
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subscribers.add(fn);
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return () => {
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subscribers.delete(fn);
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return subscribers.size;
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};
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};
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// Add child nodes to the logic graph (dirty-based)
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accessor._d = fn => {
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dependents.add(fn);
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return () => dependents.delete(fn);
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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.clear();
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dependents.clear();
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dependentSubscriptions.forEach(runParam);
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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.clear();
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dependents.clear();
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};
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return accessor;
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}
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const runParam = a => (typeof a === 'function' ? a() : a);
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