packages/api-derive/src/chain/subscribeNewHeads.ts
// Copyright 2017-2024 @polkadot/api-derive authors & contributors
// SPDX-License-Identifier: Apache-2.0
import type { Observable } from 'rxjs';
import type { HeaderExtended } from '../type/types.js';
import type { DeriveApi } from '../types.js';
import { map, switchMap } from 'rxjs';
import { createHeaderExtended } from '../type/index.js';
import { memo } from '../util/index.js';
import { getAuthorDetails } from './util.js';
/**
* @name subscribeNewHeads
* @returns A header with the current header (including extracted author)
* @description An observable of the current block header and it's author
* @example
* <BR>
*
* ```javascript
* api.derive.chain.subscribeNewHeads((header) => {
* console.log(`block #${header.number} was authored by ${header.author}`);
* });
* ```
*/
export function subscribeNewHeads (instanceId: string, api: DeriveApi): () => Observable<HeaderExtended> {
return memo(instanceId, (): Observable<HeaderExtended> =>
api.rpc.chain.subscribeNewHeads().pipe(
switchMap((header) =>
getAuthorDetails(api, header)
),
map(([header, validators, author]): HeaderExtended => {
header.createdAtHash = header.hash;
return createHeaderExtended(header.registry, header, validators, author);
})
)
);
}