index.js

'use strict'

// ====================================================================

var forEach = require('lodash/forEach')
var moment = require('moment')

// ====================================================================

var EOL = '\n'

function encode (val, attr) {
  var type = (attr && attr.type) || 'string'

  if (type === 'numeric') {
    return +val
  }
  if (type === 'date') {
    val = moment.utc(val).format(attr.format)
  }
  return JSON.stringify(val)
}

function isDefined (val) {
  return val != null
}

// ====================================================================

exports.format = exports.stringify = function format (relation) {
  var arff = []

  var name = relation.relation
  if (isDefined(name)) {
    arff.push('@RELATION ', name, EOL, EOL)
  }

  var attributes = relation.attributes
  forEach(attributes, function (attr) {
    arff.push('@ATTRIBUTE ', attr.name, ' ')

    var type = attr.type
    if (type === 'date') {
      arff.push('date')

      if (attr.format) {
        arff.push(' ', encode(attr.format))
      }
    } else if (type === 'enum') {
      arff.push('{')

      forEach(attr.values, function (value) {
        arff.push(encode(value), ',')
      })

      // Replace trailing comma with closing bracket.
      arff[arff.length - 1] = '}'
    } else {
      arff.push(type)
    }

    arff.push(EOL)
  })
  arff.push(EOL)

  arff.push('@DATA', EOL)
  forEach(relation.data, function (datum) {
    forEach(attributes, function (attr) {
      var value = datum[attr.name]

      arff.push(isDefined(value) ? encode(value, attr) : '?', ',')
    })

    // Replace trailing comma with a EOL.
    arff[arff.length - 1] = EOL
  })

  return arff.join('')
}

exports.parse = require('./parser').parse