'use strict'

var extend = require('xtend/mutable')

module.exports = PostgresInterval

function PostgresInterval (raw) {
  if (!(this instanceof PostgresInterval)) {
    return new PostgresInterval(raw)
  }
  extend(this, parse(raw))
}
var properties = ['seconds', 'minutes', 'hours', 'days', 'months', 'years']
PostgresInterval.prototype.toPostgres = function () {
  return properties
    .filter(this.hasOwnProperty, this)
    .map(function (property) {
      return this[property] + ' ' + property
    }, this)
    .join(' ')
}

var NUMBER = '([+-]?\\d+)'
var YEAR = NUMBER + '\\s+years?'
var MONTH = NUMBER + '\\s+mons?'
var DAY = NUMBER + '\\s+days?'
var TIME = '([+-])?(\\d\\d):(\\d\\d):(\\d\\d):?(\\d\\d\\d)?'
var INTERVAL = new RegExp([YEAR, MONTH, DAY, TIME].map(function (regexString) {
  return '(' + regexString + ')?'
})
.join('\\s*'))

// Positions of values in regex match
var positions = {
  years: 2,
  months: 4,
  days: 6,
  hours: 9,
  minutes: 10,
  seconds: 11,
  milliseconds: 12
}
// We can use negative time
var negatives = ['hours', 'minutes', 'seconds']

function parse (interval) {
  if (!interval) return {}
  var matches = INTERVAL.exec(interval)
  var isNegative = matches[8] === '-'
  return Object.keys(positions)
    .reduce(function (parsed, property) {
      var position = positions[property]
      var value = matches[position]
      // no empty string
      if (!value) return parsed
      value = parseInt(value, 10)
      // no zeros
      if (!value) return parsed
      if (isNegative && ~negatives.indexOf(property)) {
        value *= -1
      }
      parsed[property] = value
      return parsed
    }, {})
}
