winnow/lib/normalize-query-options/classification.js

Apply sql-like filters to GeoJSON

function normalizeClassification ({ classification, classificationDef } = {}) {
  if (classification) return classification // TODO: ? normalize standard classification
  else if (classificationDef) return normalizeGeoservicesClassBreaks(classificationDef)
  else return undefined
}

function normalizeGeoservicesClassBreaks (classificationDef) {
  const {
    type,
    classificationField,
    classificationMethod,
    standardDeviationInterval,
    breakCount,
    normalizationType,
    normalizationField,
    uniqueValueFields
  } = classificationDef

  if (type === 'classBreaksDef') {
    return {
      type: 'classes',
      field: classificationField,
      method: normalizeClassificationMethod(classificationMethod),
      stddev_intv: standardDeviationInterval || undefined,
      breakCount: breakCount,
      normType: normalizeTranformationMethod(normalizationType),
      normField: normalizationField
    }
  }

  if (type === 'uniqueValueDef') {
    return {
      type: 'unique',
      fields: uniqueValueFields
    }
  }

  throw new Error(`Input classification type invalid: ${type}`)
}

function normalizeClassificationMethod (method) {
  switch (method) {
    case 'esriClassifyEqualInterval': return 'equalInterval'
    case 'esriClassifyNaturalBreaks': return 'naturalBreaks'
    case 'esriClassifyQuantile': return 'quantile'
    case 'esriClassifyGeometricalInterval': return 'geomInterval'
    case 'esriClassifyStandardDeviation': return 'stddev'
    default: return method
  }
}

function normalizeTranformationMethod (method) {
  switch (method) {
    case 'esriNormalizeByField': return 'field'
    case 'esriNormalizeByLog': return 'log'
    case 'esriNormalizeByPercentOfTotal': return 'percent'
    default: return method
  }
}

module.exports = normalizeClassification