72 lines
1.6 KiB
JavaScript
72 lines
1.6 KiB
JavaScript
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import * as I from 'immutable';
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import immutablediff from 'immutablediff';
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export class StateSynchronizer {
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constructor(statefuls) {
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this._state = I.Map();
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this._statefuls = statefuls;
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this.updateState();
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}
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acceptStateChange(change) {
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for (const key in change) {
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const stateful = this._statefuls[key];
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if (!stateful) {
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continue;
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}
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stateful.acceptStateChange(change[key]);
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}
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}
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diff() {
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const state = this.state();
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if (this.previousState === state) {
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return StateSynchronizer.noChange;
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}
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// Take a pure JS diff.
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const steps = immutablediff(this.previousState, state).toJS();
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let diff = {};
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for (const {op, path, value} of steps) {
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if ('replace' === op || 'add' === op) {
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if ('/' === path) {
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diff = value;
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}
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else {
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const parts = path.split('/');
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parts.shift();
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let walk = diff;
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for (let i = 0; i < parts.length; ++i) {
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const part = parts[i];
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walk[part] = walk[part] || {};
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if (i === parts.length - 1) {
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walk[part] = value;
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}
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else {
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walk = walk[part];
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}
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}
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}
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}
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}
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// Side-effect.
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this.previousState = this.state();
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return diff;
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}
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state() {
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this.updateState();
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return this._state;
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}
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updateState() {
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for (const key in this._statefuls) {
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const stateful = this._statefuls[key];
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this._state = this._state.set(key, stateful.state());
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}
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}
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}
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StateSynchronizer.noChange = {};
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