/**
 * // USAGE
 * var humanizer = new HumanizeDuration();
 *
 * humanizer.humanize(10080,      'minutes'     ); // Returns: '1 week'
 * humanizer.humanize(21344,      'minutes'     ); // Returns: '2 weeks, 19 hours, 44 minutes'
 * humanizer.humanize(2101080000, 'milliseconds'); // Returns: '3 weeks, 3 days, 7 hours, 38 minutes'
 * humanizer.humanize(59,         'days'        ); // Returns: '8 weeks, 3 days'
 * humanizer.humanize(211777,     'seconds'     ); // Returns: '2 days, 10 hours, 49 minutes, 37 seconds'
 * humanizer.humanize(10080,      'hours'       ); // Returns: '60 weeks'
 *
 * humanizer.humanize(10080,  'minutes', '-week');                   // Returns: ''
 * humanizer.humanize(10080,  'minutes', '-week +day +millisecond'); // Returns: '0 days, 0 milliseconds'
 * humanizer.humanize(211777, 'seconds', '-hour +week');             // Returns: '0 week, 2 days, 49 minutes, 37 seconds'
 *
 */

'use strict';

var MILLISECOND  = 'millisecond';
var MILLISECONDS = 'milliseconds';
var SECOND       = 'second';
var SECONDS      = 'seconds';
var MINUTE       = 'minute';
var MINUTES      = 'minutes';
var HOUR         = 'hour';
var HOURS        = 'hours';
var DAY          = 'day';
var DAYS         = 'days';
var WEEK         = 'week';
var WEEKS        = 'weeks';

var _      = require('lodash');
var moment = require('moment');

var getValue = function(duration, unit){
  switch(unit){
    case 'w':
    case 'week':
    case 'weeks':
      return Math.floor(duration.as(unit));

    case 'd':
    case 'day':
    case 'days':
      return Math.floor(duration.as(unit) % 7);

    default:
      return duration.get(unit);
  }
};

var shouldInclude = function(duration, fields, unit){
  var value = getValue(duration, unit);
  return _.includes(fields, '+' + unit) || (!_.includes(fields, '-' + unit) && value !== 0);
};

var valueString = function(duration, labels, unit){
  var value = getValue(duration, unit);
  return value + ' ' + labels[value === 1 ? 'single' : 'plural'][unit];
};

function HumanizeDuration(labels){

  this.labels = _.merge({
    single: {
      millisecond : MILLISECOND,
      second      : SECOND,
      minute      : MINUTE,
      hour        : HOUR,
      day         : DAY,
      week        : WEEK
    },

    plural: {
      millisecond : MILLISECONDS,
      second      : SECONDS,
      minute      : MINUTES,
      hour        : HOURS,
      day         : DAYS,
      week        : WEEKS
    }
  }, labels);

}

HumanizeDuration.prototype.humanize = function(value, unit, fields){

  fields = _.isEmpty(fields) ? [] : (_.isArray(fields) ? fields : fields.split(' '));

  var duration = moment.duration(value, unit);

  var strings = [];

  if (shouldInclude(duration, fields, 'week'       )){ strings.push(valueString(duration, this.labels, 'week'       )); }
  if (shouldInclude(duration, fields, 'day'        )){ strings.push(valueString(duration, this.labels, 'day'        )); }
  if (shouldInclude(duration, fields, 'hour'       )){ strings.push(valueString(duration, this.labels, 'hour'       )); }
  if (shouldInclude(duration, fields, 'minute'     )){ strings.push(valueString(duration, this.labels, 'minute'     )); }
  if (shouldInclude(duration, fields, 'second'     )){ strings.push(valueString(duration, this.labels, 'second'     )); }
  if (shouldInclude(duration, fields, 'millisecond')){ strings.push(valueString(duration, this.labels, 'millisecond')); }

  return strings.join(', ');

};

module.exports = HumanizeDuration;