blob: 4574b31f29710de1772adab2c075391334550099 [file] [log] [blame]
/**
* @license
* Copyright 2021 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
import {BehaviorSubject, Observable, Subscription} from 'rxjs';
import {deepEqual} from '../../utils/deep-util';
import {Finalizable} from '../../types/types';
/**
* A Model stores a value <T> and controls changes to that value via `subject$`
* while allowing others to subscribe to value updates via the `state$`
* Observable.
*
* Typically a given Model subclass will provide:
* 1. An initial value. If there is no good default to start with, then
* include `undefined` in the type `T`.
* 2. "reducers": functions for users to request changes to the value
* 3. "selectors": convenient sub-Observables that only contain updates for a
* nested property from the value
*
* Any new subscriber will immediately receive the current value.
*/
export abstract class Model<T> implements Finalizable {
/**
* rxjs does not like `next()` being called on a subject during processing of
* another `next()` call. So make sure that state updates complete before
* starting another one.
*/
private stateUpdateInProgress = false;
private subject$: BehaviorSubject<T>;
public state$: Observable<T>;
protected subscriptions: Subscription[] = [];
constructor(initialState: T) {
this.subject$ = new BehaviorSubject(initialState);
this.state$ = this.subject$.asObservable();
}
getState() {
return this.subject$.getValue();
}
setState(state: T) {
if (this.stateUpdateInProgress) {
setTimeout(() => this.setState(state));
return;
}
if (deepEqual(state, this.getState())) return;
try {
this.stateUpdateInProgress = true;
this.subject$.next(state);
} finally {
this.stateUpdateInProgress = false;
}
}
updateState(state: Partial<T>) {
if (this.stateUpdateInProgress) {
setTimeout(() => this.updateState(state));
return;
}
this.setState({...this.getState(), ...state});
}
finalize() {
this.subject$.complete();
for (const s of this.subscriptions) {
s.unsubscribe();
}
this.subscriptions = [];
}
}