grafana/public/app/plugins/datasource/loki/components/LokiExploreQueryEditor.tsx

// Libraries
import React, { memo } from 'react';
import _ from 'lodash';

// Types
import { ExploreQueryFieldProps } from '@grafana/data';
import { LokiDatasource } from '../datasource';
import { LokiQuery, LokiOptions } from '../types';
import { LokiQueryField } from './LokiQueryField';
import LokiExploreExtraField from './LokiExploreExtraField';

type Props = ExploreQueryFieldProps<LokiDatasource, LokiQuery, LokiOptions>;

export function LokiExploreQueryEditor(props: Props) {
  const { range, query, data, datasource, history, onChange, onRunQuery } = props;

  function onChangeQueryLimit(value: string) {
    const { query, onChange } = props;
    const nextQuery = { ...query, maxLines: preprocessMaxLines(value) };
    onChange(nextQuery);
  }

  function preprocessMaxLines(value: string): number {
    if (value.length === 0) {
      // empty input - falls back to dataSource.maxLines limit
      return NaN;
    } else if (value.length > 0 && (isNaN(+value) || +value < 0)) {
      // input with at least 1 character and that is either incorrect (value in the input field is not a number) or negative
      // falls back to the limit of 0 lines
      return 0;
    } else {
      // default case - correct input
      return +value;
    }
  }

  function onMaxLinesChange(e: React.SyntheticEvent<HTMLInputElement>) {
    if (query.maxLines !== preprocessMaxLines(e.currentTarget.value)) {
      onChangeQueryLimit(e.currentTarget.value);
    }
  }

  function onReturnKeyDown(e: React.KeyboardEvent<HTMLInputElement>) {
    if (e.key === 'Enter') {
      onRunQuery();
    }
  }

  return (
    <LokiQueryField
      datasource={datasource}
      query={query}
      onChange={onChange}
      onBlur={() => {}}
      onRunQuery={onRunQuery}
      history={history}
      data={data}
      range={range}
      ExtraFieldElement={
        <LokiExploreExtraField
          label={'Line limit'}
          onChangeFunc={onMaxLinesChange}
          onKeyDownFunc={onReturnKeyDown}
          value={query?.maxLines?.toString() || ''}
          type={'number'}
          min={0}
        />
      }
    />
  );
}

export default memo(LokiExploreQueryEditor);