pezkuwi-api/packages/api-derive/src/session/info.ts

// Copyright 2017-2026 @pezkuwi/api-derive authors & contributors
// SPDX-License-Identifier: Apache-2.0

import type { Observable } from 'rxjs';
import type { DeriveApi, DeriveSessionInfo } from '../types.js';

import { map } from 'rxjs';

import { objectSpread } from '@pezkuwi/util';

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

/**
 * @name info
 * @description Retrieves all the session and era query and calculates specific values on it as the length of the session and eras.
 * @example
 * ```javascript
 * api.derive.session.info((info) => {
 *   console.log(`Session info ${JSON.stringify(info)}`);
 * });
 * ```
 */
export function info (instanceId: string, api: DeriveApi): () => Observable<DeriveSessionInfo> {
  return memo(instanceId, (): Observable<DeriveSessionInfo> =>
    api.derive.session.indexes().pipe(
      map((indexes) => {
        const sessionLength = api.consts?.babe?.epochDuration || api.registry.createType('u64', 1);
        const sessionsPerEra = api.consts?.staking?.sessionsPerEra || api.registry.createType('SessionIndex', 1);

        return objectSpread({
          eraLength: api.registry.createType('BlockNumber', sessionsPerEra.mul(sessionLength)),
          isEpoch: !!api.query.babe,
          sessionLength,
          sessionsPerEra
        }, indexes);
      })
    )
  );
}