@koopjs/featureserver/src/helpers/fields/statistics-fields.js

*An open source implementation of the GeoServices specification*

const { isDate } = require('../data-type-utils');
const { getEsriTypeFromDefinition } = require('./esri-type-utils');
const { ESRI_FIELD_TYPE_DATE } = require('./constants');
const {
  StatisticField,
  StatisticDateField,
  FieldFromFieldDefinition,
  FieldFromKeyValue,
} = require('./field-classes');

class StatisticsFields {
  static normalizeOptions(inputOptions = {}) {
    const {
      statistics,
      metadata: { fields } = {},
      groupByFieldsForStatistics = [],
      attributeSample,
      ...options
    } = inputOptions;

    return {
      statisticsSample: Array.isArray(statistics) ? statistics[0] : statistics,
      fieldDefinitions: options.fieldDefinitions || options.fields || fields,
      groupByFieldsForStatistics: getGroupByFields(groupByFieldsForStatistics),
      ...options,
    };
  }

  static create(inputOptions) {
    const options = StatisticsFields.normalizeOptions(inputOptions);
    return new StatisticsFields(options);
  }

  constructor(options = {}) {
    const {
      statisticsSample,
      groupByFieldsForStatistics = [],
      fieldDefinitions = [],
      outStatistics,
    } = options;
    const dateFieldRegexs = getDateFieldRegexs(fieldDefinitions, outStatistics);

    this.fields = Object.entries(statisticsSample).map(([key, value]) => {
      if (groupByFieldsForStatistics.includes(key)) {
        const fieldDefinition = fieldDefinitions.find(({ name }) => name === key);

        if (fieldDefinition) {
          return new FieldFromFieldDefinition(fieldDefinition);
        }

        return new FieldFromKeyValue(key, value);
      }

      if (isDateField(dateFieldRegexs, key, value)) {
        return new StatisticDateField(key);
      }

      return new StatisticField(key);
    });

    return this.fields;
  }
}

function getGroupByFields(inputVal) {
  if (Array.isArray(inputVal)) {
    return inputVal;
  }

  return inputVal.split(',').map((str) => str.trim());
}

function isDateField(regexs, fieldName, value) {
  return (
    regexs.some((regex) => {
      return regex.test(fieldName);
    }) || isDate(value)
  );
}

function getDateFieldRegexs(fieldDefinitions = [], outStatistics = []) {
  const dateFields = fieldDefinitions
    .filter(({ type }) => {
      return getEsriTypeFromDefinition(type) === ESRI_FIELD_TYPE_DATE;
    })
    .map(({ name }) => name);

  return outStatistics
    .filter(({ onStatisticField }) => dateFields.includes(onStatisticField))
    .map((statistic) => {
      const { onStatisticField, outStatisticFieldName } = statistic;

      const name = outStatisticFieldName || onStatisticField;
      const spaceEscapedName = name.replace(/\s/g, '_');
      return new RegExp(`${spaceEscapedName}$`);
    });
}

module.exports = StatisticsFields;