src/pipes/utility/bufferToEpoch.js

import { pipe } from "rxjs";
import { map } from "rxjs/operators";

import { groupByChannel } from "../../utils/groupByChannel";

import {
  DATA_PROP as defaultDataProp,
  SAMPLING_RATE as defaultSamplingRate
} from "../../constants";

/**
 * Takes an array or RxJS buffer of EEG Samples and returns an Epoch.
 * @method bufferToEpoch
 * @example eeg$.pipe(bufferTime(1000), bufferToEpoch({ samplingRate: 256 }))
 *
 * @param {Object} options - Data structure options
 * @param {number} [options.samplingRate] Sampling rate
 * @param {string} [options.dataProp='data'] Name of the key associated with eeg data
 *
 * @returns {Observable<Epoch>}
 */
export const bufferToEpoch = ({
  samplingRate = defaultSamplingRate,
  dataProp = defaultDataProp
} = {}) =>
  pipe(
    map(samplesArray => ({
      [dataProp]: groupByChannel(samplesArray, dataProp),
      info: {
        ...(samplesArray[0] && samplesArray[0].info
          ? samplesArray[0].info
          : {}),
        startTime: samplesArray[0].timestamp,
        samplingRate:
          samplesArray[0].info && samplesArray[0].info.samplingRate
            ? samplesArray[0].info.samplingRate
            : samplingRate
      }
    }))
  );