49 lines
1.7 KiB
TypeScript
49 lines
1.7 KiB
TypeScript
// Copyright 2017-2019 @polkadot/api-derive authors & contributors
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// This software may be modified and distributed under the terms
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// of the Apache-2.0 license. See the LICENSE file for details.
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import { Observable, combineLatest, of } from 'rxjs';
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import { filter, map, switchMap } from 'rxjs/operators';
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import { ApiInterface$Rx } from '@plugnet/api/types';
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import { AccountId, Header, HeaderExtended } from '@plugnet/types';
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import { drr } from '../util/drr';
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export type HeaderAndValidators = [Header, Array<AccountId>];
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/**
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* @description Subscribe to block headers and extend it with the author
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* @example
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* <BR>
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*
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* ```javascript
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* api.derive.chain.subscribeNewHead(({ author, blockNumber }) => {
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* console.log(`block #${blockNumber} was authored by ${author}`);
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* });
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* ```
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*/
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export function subscribeNewHead (api: ApiInterface$Rx) {
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return (): Observable<HeaderExtended> =>
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(api.rpc.chain.subscribeNewHead() as Observable<Header>)
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.pipe(
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filter((header: Header) =>
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header && !!header.blockNumber
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),
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switchMap((header: Header): Observable<HeaderAndValidators> =>
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(combineLatest(
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of(header),
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// theoretically we could combine at the first call with session.validators(), however
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// we make 100% sure we actually get the validators at a specific block so when these
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// change at an era boundary, we have the previous values to ensure our indexes are correct
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api.query.session
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? api.query.session.validators.at(header.hash)
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: of([])
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) as Observable<HeaderAndValidators>)
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),
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map(([header, validators]) =>
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new HeaderExtended(header, validators)
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),
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drr()
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);
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}
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