polkadot-js/api

// 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 getHeader
 * @param {( Uint8Array | string )} hash - A block hash as U8 array or string.
 * @returns An array containing the block header and the block author
 * @description Get a specific block header and extend it with the author
 * @example
 * <BR>
 *
 * ```javascript
 * const { author, number } = await api.derive.chain.getHeader('0x123...456');
 *
 * console.log(`block #${number} was authored by ${author}`);
 * ```
 */
export function getHeader (instanceId: string, api: DeriveApi): (blockHash: Uint8Array | string) => Observable<HeaderExtended> {
  return memo(instanceId, (blockHash: Uint8Array | string): Observable<HeaderExtended> =>
    api.rpc.chain.getHeader(blockHash).pipe(
      switchMap((header) =>
        getAuthorDetails(api, header, blockHash)
      ),
      map(([header, validators, author]) =>
        createHeaderExtended((validators || header).registry, header, validators, author)
      )
    )
  );
}