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144 lines
4.5 KiB
TypeScript
144 lines
4.5 KiB
TypeScript
const fastDeepEqual = require('fast-deep-equal');
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const events = require('events');
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export class EventManager {
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private emitter_: any;
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private appStatePrevious_: any;
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private appStateWatchedProps_: string[];
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private appStateListeners_: any;
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public constructor() {
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this.reset();
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}
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public reset() {
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this.emitter_ = new events.EventEmitter();
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this.appStatePrevious_ = {};
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this.appStateWatchedProps_ = [];
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this.appStateListeners_ = {};
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}
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// eslint-disable-next-line @typescript-eslint/ban-types -- Old code before rule was applied
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public on(eventName: string, callback: Function) {
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return this.emitter_.on(eventName, callback);
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}
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public emit(eventName: string, object: any = null) {
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return this.emitter_.emit(eventName, object);
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}
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// eslint-disable-next-line @typescript-eslint/ban-types -- Old code before rule was applied
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public removeListener(eventName: string, callback: Function) {
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return this.emitter_.removeListener(eventName, callback);
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}
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// eslint-disable-next-line @typescript-eslint/ban-types -- Old code before rule was applied
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public off(eventName: string, callback: Function) {
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return this.removeListener(eventName, callback);
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}
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// eslint-disable-next-line @typescript-eslint/ban-types -- Old code before rule was applied
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public filterOn(filterName: string, callback: Function) {
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return this.emitter_.on(`filter:${filterName}`, callback);
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}
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// eslint-disable-next-line @typescript-eslint/ban-types -- Old code before rule was applied
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public filterOff(filterName: string, callback: Function) {
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return this.removeListener(`filter:${filterName}`, callback);
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}
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public async filterEmit(filterName: string, object: any) {
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let output = object;
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const listeners = this.emitter_.listeners(`filter:${filterName}`);
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for (const listener of listeners) {
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// When we pass the object to the plugin, it is always going to be
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// modified since it is serialized/unserialized. So we need to use a
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// deep equality check to see if it's been changed. Normally the
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// filter objects should be relatively small so there shouldn't be
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// much of a performance hit.
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const newOutput = await listener(output);
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// Plugin didn't return anything - so we leave the object as it is.
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if (newOutput === undefined) continue;
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if (!fastDeepEqual(newOutput, output)) {
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output = newOutput;
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}
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}
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return output;
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}
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// eslint-disable-next-line @typescript-eslint/ban-types -- Old code before rule was applied
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public appStateOn(propName: string, callback: Function) {
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if (!this.appStateListeners_[propName]) {
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this.appStateListeners_[propName] = [];
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this.appStateWatchedProps_.push(propName);
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}
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this.appStateListeners_[propName].push(callback);
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}
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// eslint-disable-next-line @typescript-eslint/ban-types -- Old code before rule was applied
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public appStateOff(propName: string, callback: Function) {
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if (!this.appStateListeners_[propName]) {
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throw new Error('EventManager: Trying to unregister a state prop watch for a non-watched prop (1)');
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}
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const idx = this.appStateListeners_[propName].indexOf(callback);
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if (idx < 0) throw new Error('EventManager: Trying to unregister a state prop watch for a non-watched prop (2)');
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this.appStateListeners_[propName].splice(idx, 1);
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}
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private stateValue_(state: any, propName: string) {
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const parts = propName.split('.');
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let s = state;
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for (const p of parts) {
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if (!(p in s)) throw new Error(`Invalid state property path: ${propName}`);
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s = s[p];
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}
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return s;
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}
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// This function works by keeping a copy of the watched props and, whenever this function
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// is called, comparing the previous and new values and emitting events if they have changed.
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// The appStateEmit function should be called from a middleware.
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public appStateEmit(state: any) {
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if (!this.appStateWatchedProps_.length) return;
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for (const propName of this.appStateWatchedProps_) {
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let emit = false;
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const stateValue = this.stateValue_(state, propName);
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if (!(propName in this.appStatePrevious_) || this.appStatePrevious_[propName] !== stateValue) {
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this.appStatePrevious_[propName] = stateValue;
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emit = true;
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}
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if (emit) {
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const listeners = this.appStateListeners_[propName];
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if (!listeners || !listeners.length) continue;
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const eventValue = Object.freeze(stateValue);
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for (const listener of listeners) {
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listener({ value: eventValue });
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}
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}
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}
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}
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public once(eventName: string, callback: any) {
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return this.emitter_.once(eventName, callback);
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}
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}
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const eventManager = new EventManager();
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export default eventManager;
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