'use strict';

Object.defineProperty(exports, '__esModule', { value: true });

var MILI    = 'milliseconds'
  , SECONDS = 'seconds'
  , MINUTES = 'minutes'
  , HOURS   = 'hours'
  , DAY     = 'day'
  , WEEK    = 'week'
  , MONTH   = 'month'
  , YEAR    = 'year'
  , DECADE  = 'decade'
  , CENTURY = 'century';

var multiplierMilli = {
  'milliseconds': 1,
  'seconds': 1000,
  'minutes': 60 * 1000,
  'hours': 60 * 60 * 1000,
  'day': 24 * 60 * 60 * 1000,
  'week': 7 * 24 * 60 * 60 * 1000 
};

var multiplierMonth = {
  'month': 1,
  'year': 12,
  'decade': 10 * 12,
  'century': 100 * 12
};

function daysOf(year) {
  return [31, daysInFeb(year), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
}

function daysInFeb(year) {
  return (
      year % 4 === 0 
      && year % 100 !== 0
    ) || year % 400 === 0
      ? 29
      : 28
}

function add(d, num, unit) {
  d = new Date(d);

  switch (unit){
    case MILI:
    case SECONDS:
    case MINUTES:
    case HOURS:
    case DAY:
    case WEEK:
      return addMillis(d, num * multiplierMilli[unit])
    case MONTH:
    case YEAR:
    case DECADE:
    case CENTURY:
      return addMonths(d, num * multiplierMonth[unit])
  }

  throw new TypeError('Invalid units: "' + unit + '"')
}

function addMillis(d, num) {
  var nextDate = new Date(+(d) + num);

  return solveDST(d, nextDate)
}

function addMonths(d, num) {
  var year = d.getFullYear()
    , month = d.getMonth()
    , day = d.getDate()
    , totalMonths = year * 12 + month + num
    , nextYear = Math.trunc(totalMonths / 12)
    , nextMonth = totalMonths % 12
    , nextDay = Math.min(day, daysOf(nextYear)[nextMonth]);

  var nextDate = new Date(d);
  nextDate.setFullYear(nextYear);

  // To avoid a bug when sets the Feb month
  // with a date > 28 or date > 29 (leap year)
  nextDate.setDate(1);

  nextDate.setMonth(nextMonth);
  nextDate.setDate(nextDay);

  return nextDate
}

function solveDST(currentDate, nextDate) {
  var currentOffset = currentDate.getTimezoneOffset()
    , nextOffset = nextDate.getTimezoneOffset();

  // if is DST, add the difference in minutes
  // else the difference is zero
  var diffMinutes = (nextOffset - currentOffset);

  return new Date(+(nextDate) + diffMinutes * multiplierMilli['minutes'])
}

function subtract(d, num, unit) {
  return add(d, -num, unit)
}

function startOf(d, unit, firstOfWeek) {
  d = new Date(d);

  switch (unit) {
    case CENTURY:
    case DECADE:
    case YEAR:
        d = month(d, 0);
    case MONTH:
        d = date(d, 1);
    case WEEK:
    case DAY:
        d = hours(d, 0);
    case HOURS:
        d = minutes(d, 0);
    case MINUTES:
        d = seconds(d, 0);
    case SECONDS:
        d = milliseconds(d, 0);
  }

  if (unit === DECADE)
    d = subtract(d, year(d) % 10, 'year');

  if (unit === CENTURY)
    d = subtract(d, year(d) % 100, 'year');

  if (unit === WEEK)
    d = weekday(d, 0, firstOfWeek);

  return d
}

function endOf(d, unit, firstOfWeek){
  d = new Date(d);
  d = startOf(d, unit, firstOfWeek);
  switch (unit) {
    case CENTURY:
    case DECADE:
    case YEAR:
    case MONTH:
    case WEEK:
      d = add(d, 1, unit);
      d = subtract(d, 1, DAY);
      d.setHours(23, 59, 59, 999);
      break;
    case DAY:
      d.setHours(23, 59, 59, 999);
      break;
    case HOURS:
    case MINUTES:
    case SECONDS:
      d = add(d, 1, unit);
      d = subtract(d, 1, MILI);
  }
  return d
}

var eq =  createComparer(function(a, b){ return a === b });
var neq = createComparer(function(a, b){ return a !== b });
var gt =  createComparer(function(a, b){ return a > b });
var gte = createComparer(function(a, b){ return a >= b });
var lt =  createComparer(function(a, b){ return a < b });
var lte = createComparer(function(a, b){ return a <= b });

function min(){
  return new Date(Math.min.apply(Math, arguments))
}

function max(){
  return new Date(Math.max.apply(Math, arguments))
}

function inRange(day, min, max, unit){
  unit = unit || 'day';

  return (!min || gte(day, min, unit))
      && (!max || lte(day, max, unit))
}

var milliseconds = createAccessor('Milliseconds');
var seconds =      createAccessor('Seconds');
var minutes =      createAccessor('Minutes');
var hours =        createAccessor('Hours');
var day =          createAccessor('Day');
var date =         createAccessor('Date');
var month =        createAccessor('Month');
var year =         createAccessor('FullYear');

function decade(d, val) {
  return val === undefined
    ? year(startOf(d, DECADE))
    : add(d, val + 10, YEAR);
}

function century(d, val) {
  return val === undefined
    ? year(startOf(d, CENTURY))
    : add(d, val + 100, YEAR);
}

function weekday(d, val, firstDay) {
    var w = (day(d) + 7 - (firstDay || 0) ) % 7;

    return val === undefined
      ? w
      : add(d, val - w, DAY);
}

function diff(date1, date2, unit, asFloat) {
  var dividend, divisor, result;

  switch (unit) {
    case MILI:
    case SECONDS:
    case MINUTES:
    case HOURS:
    case DAY:
    case WEEK:
      dividend = date2.getTime() - date1.getTime(); break;
    case MONTH:
    case YEAR:
    case DECADE:
    case CENTURY:
      dividend = (year(date2) - year(date1)) * 12 + month(date2) - month(date1); break;
    default:
      throw new TypeError('Invalid units: "' + unit + '"');
  }

  switch (unit) {
    case MILI:
        divisor = 1; break;
    case SECONDS:
        divisor = 1000; break;
    case MINUTES:
        divisor = 1000 * 60; break;
    case HOURS:
        divisor = 1000 * 60 * 60; break;
    case DAY:
        divisor = 1000 * 60 * 60 * 24; break;
    case WEEK:
        divisor = 1000 * 60 * 60 * 24 * 7; break;
    case MONTH:
        divisor = 1; break;
    case YEAR:
        divisor = 12; break;
    case DECADE:
        divisor = 120; break;
    case CENTURY:
        divisor = 1200; break;
    default:
      throw new TypeError('Invalid units: "' + unit + '"');
  }

  result = dividend / divisor;

  return asFloat ? result : Math.round(result);
}

function createAccessor(method){
  var hourLength = (function(method) {  
    switch(method) {
      case 'Milliseconds':
        return 3600000;
      case 'Seconds':
        return 3600;
      case 'Minutes':
        return 60;
      case 'Hours':
        return 1;
      default:
        return null;
    }
  })(method);
  
  return function(d, val){
    if (val === undefined)
      return d['get' + method]()

    var dateOut = new Date(d);
    dateOut['set' + method](val);
    
    if(hourLength && dateOut['get'+method]() != val && (method === 'Hours' || val >=hourLength && (dateOut.getHours()-d.getHours()<Math.floor(val/hourLength))) ){
      //Skip DST hour, if it occurs
      dateOut['set'+method](val+hourLength);
    }
    
    return dateOut
  }
}

function createComparer(operator) {
  return function (a, b, unit) {
    return operator(+startOf(a, unit), +startOf(b, unit))
  };
}

exports.add = add;
exports.century = century;
exports.date = date;
exports.day = day;
exports.decade = decade;
exports.diff = diff;
exports.endOf = endOf;
exports.eq = eq;
exports.gt = gt;
exports.gte = gte;
exports.hours = hours;
exports.inRange = inRange;
exports.lt = lt;
exports.lte = lte;
exports.max = max;
exports.milliseconds = milliseconds;
exports.min = min;
exports.minutes = minutes;
exports.month = month;
exports.neq = neq;
exports.seconds = seconds;
exports.startOf = startOf;
exports.subtract = subtract;
exports.weekday = weekday;
exports.year = year;