polkadot-js/api

// Copyright 2017-2024 @polkadot/api-derive authors & contributors
// SPDX-License-Identifier: Apache-2.0

import type { Observable } from 'rxjs';
import type { QueryableStorage } from '@polkadot/api-base/types';
import type { Compact, Vec } from '@polkadot/types';
import type { AccountId, BlockNumber, Header } from '@polkadot/types/interfaces';
import type { SpCoreSr25519Public } from '@polkadot/types/lookup';
import type { Codec, IOption } from '@polkadot/types/types';
import type { DeriveApi } from '../types.js';

import { combineLatest, map, mergeMap, of, switchMap } from 'rxjs';

import { memo, unwrapBlockNumber } from '../util/index.js';

export type BlockNumberDerive = (instanceId: string, api: DeriveApi) => () => Observable<BlockNumber>;

type OptionMapping = IOption<{ account: AccountId } & Codec>;
type OptionNimbus = IOption<{ nimbus: SpCoreSr25519Public } & Codec>;

export function createBlockNumberDerive <T extends { number: Compact<BlockNumber> | BlockNumber }> (fn: (api: DeriveApi) => Observable<T>): BlockNumberDerive {
  return (instanceId: string, api: DeriveApi) =>
    memo(instanceId, () =>
      fn(api).pipe(
        map(unwrapBlockNumber)
      )
    );
}

/** @internal */
function getAuthorDetailsWithAt (header: Header, queryAt: QueryableStorage<'rxjs'>): Observable<[Header, Vec<AccountId> | null, AccountId | null]> {
  const validators = queryAt.session?.validators
    ? queryAt.session.validators()
    : of(null);

  // nimbus consensus stores the session key of the block author in header logs
  const { logs: [log] } = header.digest;
  const loggedAuthor = (log && (
    (log.isConsensus && log.asConsensus[0].isNimbus && log.asConsensus[1]) ||
    (log.isPreRuntime && log.asPreRuntime[0].isNimbus && log.asPreRuntime[1])
  ));

  if (loggedAuthor) {
    // use the author mapping pallet, if available (ie: moonbeam, moonriver), to map session (nimbus) key to author (collator/validator) key
    if (queryAt['authorMapping']?.['mappingWithDeposit']) {
      return combineLatest([
        of(header),
        validators,
        queryAt['authorMapping']['mappingWithDeposit']<OptionMapping>(loggedAuthor).pipe(
          map((o) =>
            o.unwrapOr({ account: null }).account
          )
        )
      ]);
    }

    // fall back to session and parachain staking pallets, if available (ie: manta, calamari), to map session (nimbus) key to author (collator) key
    if (queryAt['parachainStaking']?.['selectedCandidates'] && queryAt.session?.nextKeys) {
      const loggedHex = loggedAuthor.toHex();

      return combineLatest([
        of(header),
        validators,
        queryAt['parachainStaking']['selectedCandidates']<Vec<AccountId>>().pipe(
          mergeMap((selectedCandidates) =>
            combineLatest([
              of(selectedCandidates),
              queryAt.session.nextKeys.multi<OptionNimbus>(selectedCandidates).pipe(
                map((nextKeys) =>
                  nextKeys.findIndex((o) =>
                    o.unwrapOrDefault().nimbus.toHex() === loggedHex
                  )
                )
              )
            ])
          ),
          map(([selectedCandidates, index]) =>
            index === -1
              ? null
              : selectedCandidates[index]
          )
        )
      ]);
    }
  }

  // normal operation, non-mapping
  return combineLatest([
    of(header),
    validators,
    of(null)
  ]);
}

export function getAuthorDetails (api: DeriveApi, header: Header, blockHash?: Uint8Array | string): Observable<[Header, Vec<AccountId> | null, AccountId | null]> {
  // For on-chain state, we need to retrieve it as per the start
  // of the block being constructed, i.e. session validators would
  // be at the point of the block construction, not when all operations
  // has been supplied.
  //
  // However for the first block (no parentHash available), we would
  // just use the as-is
  return api.queryAt(
    header.parentHash.isEmpty
      ? blockHash || header.hash
      : header.parentHash
  ).pipe(
    switchMap((queryAt) =>
      getAuthorDetailsWithAt(header, queryAt)
    )
  );
}