packages/rpc-core/src/util/memo.ts
// Copyright 2017-2024 @polkadot/api-derive authors & contributors
// SPDX-License-Identifier: Apache-2.0
import type { Observer, TeardownLogic } from 'rxjs';
import type { Memoized } from '@polkadot/util/types';
import { Observable } from 'rxjs';
import { memoize } from '@polkadot/util';
import { drr } from './drr.js';
type ObsFn <T> = (...params: unknown[]) => Observable<T>;
// Wraps a derive, doing 2 things to optimize calls -
// 1. creates a memo of the inner fn -> Observable, removing when unsubscribed
// 2. wraps the observable in a drr() (which includes an unsub delay)
/** @internal */
// eslint-disable-next-line @typescript-eslint/ban-types
export function memo <T> (instanceId: string, inner: Function): Memoized<ObsFn<T>> {
const options = { getInstanceId: () => instanceId };
const cached = memoize(
(...params: unknown[]): Observable<T> =>
new Observable((observer: Observer<T>): TeardownLogic => {
const subscription = (inner as ObsFn<T>)(...params).subscribe(observer);
return (): void => {
cached.unmemoize(...params);
subscription.unsubscribe();
};
}).pipe(drr()),
options
);
return cached;
}