var moment = require('../module/moment');
var DateUtil = require('./DateUtil');

/**
 * @constructor  TimeStep
 * The class TimeStep is an iterator for dates. You provide a start date and an
 * end date. The class itself determines the best scale (step size) based on the
 * provided start Date, end Date, and minimumStep.
 *
 * If minimumStep is provided, the step size is chosen as close as possible
 * to the minimumStep but larger than minimumStep. If minimumStep is not
 * provided, the scale is set to 1 DAY.
 * The minimumStep should correspond with the onscreen size of about 6 characters
 *
 * Alternatively, you can set a scale by hand.
 * After creation, you can initialize the class by executing first(). Then you
 * can iterate from the start date to the end date via next(). You can check if
 * the end date is reached with the function hasNext(). After each step, you can
 * retrieve the current date via getCurrent().
 * The TimeStep has scales ranging from milliseconds, seconds, minutes, hours,
 * days, to years.
 *
 * Version: 1.2
 *
 * @param {Date} [start]         The start date, for example new Date(2010, 9, 21)
 *                               or new Date(2010, 9, 21, 23, 45, 00)
 * @param {Date} [end]           The end date
 * @param {Number} [minimumStep] Optional. Minimum step size in milliseconds
 */
function TimeStep(start, end, minimumStep, hiddenDates) {
  // variables
  this.current = new Date();
  this._start = new Date();
  this._end = new Date();

  this.autoScale  = true;
  this.scale = TimeStep.SCALE.DAY;
  this.step = 1;

  // initialize the range
  this.setRange(start, end, minimumStep);

  // hidden Dates options
  this.switchedDay = false;
  this.switchedMonth = false;
  this.switchedYear = false;
  this.hiddenDates = hiddenDates;
  if (hiddenDates === undefined) {
    this.hiddenDates = [];
  }
}

// enum scale
TimeStep.SCALE = {
  MILLISECOND: 1,
  SECOND: 2,
  MINUTE: 3,
  HOUR: 4,
  DAY: 5,
  WEEKDAY: 6,
  MONTH: 7,
  YEAR: 8
};

// array with lower case scale names
TimeStep.SCALE_INDEX = {};
Object.keys(TimeStep.SCALE).forEach(function (key) {
  var index = TimeStep.SCALE[key];
  TimeStep.SCALE_INDEX[index] = key.toLowerCase();
});

// Time formatting
TimeStep.FORMAT = {
  minorLabels: {
    'millisecond':'SSS',
    'second':     's',
    'minute':     'HH:mm',
    'hour':       'HH:mm',
    'weekday':    'ddd D',
    'day':        'D',
    'month':      'MMM',
    'year':       'YYYY'
  },
  majorLabels: {
    'millisecond':'HH:mm:ss',
    'second':     'D MMMM HH:mm',
    'minute':     'ddd D MMMM',
    'hour':       'ddd D MMMM',
    'weekday':    'MMMM YYYY',
    'day':        'MMMM YYYY',
    'month':      'YYYY',
    'year':       ''
  }
};

/**
 * Set a new range
 * If minimumStep is provided, the step size is chosen as close as possible
 * to the minimumStep but larger than minimumStep. If minimumStep is not
 * provided, the scale is set to 1 DAY.
 * The minimumStep should correspond with the onscreen size of about 6 characters
 * @param {Date} [start]      The start date and time.
 * @param {Date} [end]        The end date and time.
 * @param {int} [minimumStep] Optional. Minimum step size in milliseconds
 */
TimeStep.prototype.setRange = function(start, end, minimumStep) {
  if (!(start instanceof Date) || !(end instanceof Date)) {
    throw  "No legal start or end date in method setRange";
  }

  this._start = (start != undefined) ? new Date(start.valueOf()) : new Date();
  this._end = (end != undefined) ? new Date(end.valueOf()) : new Date();

  if (this.autoScale) {
    this.setMinimumStep(minimumStep);
  }
};

/**
 * Set the range iterator to the start date.
 */
TimeStep.prototype.first = function() {
  this.current = new Date(this._start.valueOf());
  this.roundToMinor();
};

/**
 * Round the current date to the first minor date value
 * This must be executed once when the current date is set to start Date
 */
TimeStep.prototype.roundToMinor = function() {
  // round to floor
  // IMPORTANT: we have no breaks in this switch! (this is no bug)
  //noinspection FallthroughInSwitchStatementJS
  switch (this.scale) {
    case TimeStep.SCALE.YEAR:
      this.current.setFullYear(this.step * Math.floor(this.current.getFullYear() / this.step));
      this.current.setMonth(0);
    case TimeStep.SCALE.MONTH:        this.current.setDate(1);
    case TimeStep.SCALE.DAY:          // intentional fall through
    case TimeStep.SCALE.WEEKDAY:      this.current.setHours(0);
    case TimeStep.SCALE.HOUR:         this.current.setMinutes(0);
    case TimeStep.SCALE.MINUTE:       this.current.setSeconds(0);
    case TimeStep.SCALE.SECOND:       this.current.setMilliseconds(0);
    //case TimeStep.SCALE.MILLISECOND: // nothing to do for milliseconds
  }

  if (this.step != 1) {
    // round down to the first minor value that is a multiple of the current step size
    switch (this.scale) {
      case TimeStep.SCALE.MILLISECOND:  this.current.setMilliseconds(this.current.getMilliseconds() - this.current.getMilliseconds() % this.step);  break;
      case TimeStep.SCALE.SECOND:       this.current.setSeconds(this.current.getSeconds() - this.current.getSeconds() % this.step); break;
      case TimeStep.SCALE.MINUTE:       this.current.setMinutes(this.current.getMinutes() - this.current.getMinutes() % this.step); break;
      case TimeStep.SCALE.HOUR:         this.current.setHours(this.current.getHours() - this.current.getHours() % this.step); break;
      case TimeStep.SCALE.WEEKDAY:      // intentional fall through
      case TimeStep.SCALE.DAY:          this.current.setDate((this.current.getDate()-1) - (this.current.getDate()-1) % this.step + 1); break;
      case TimeStep.SCALE.MONTH:        this.current.setMonth(this.current.getMonth() - this.current.getMonth() % this.step);  break;
      case TimeStep.SCALE.YEAR:         this.current.setFullYear(this.current.getFullYear() - this.current.getFullYear() % this.step); break;
      default: break;
    }
  }
};

/**
 * Check if the there is a next step
 * @return {boolean}  true if the current date has not passed the end date
 */
TimeStep.prototype.hasNext = function () {
  return (this.current.valueOf() <= this._end.valueOf());
};

/**
 * Do the next step
 */
TimeStep.prototype.next = function() {
  var prev = this.current.valueOf();

  // Two cases, needed to prevent issues with switching daylight savings
  // (end of March and end of October)
  if (this.current.getMonth() < 6)   {
    switch (this.scale) {
      case TimeStep.SCALE.MILLISECOND:

        this.current = new Date(this.current.valueOf() + this.step); break;
      case TimeStep.SCALE.SECOND:       this.current = new Date(this.current.valueOf() + this.step * 1000); break;
      case TimeStep.SCALE.MINUTE:       this.current = new Date(this.current.valueOf() + this.step * 1000 * 60); break;
      case TimeStep.SCALE.HOUR:
        this.current = new Date(this.current.valueOf() + this.step * 1000 * 60 * 60);
        // in case of skipping an hour for daylight savings, adjust the hour again (else you get: 0h 5h 9h ... instead of 0h 4h 8h ...)
        var h = this.current.getHours();
        this.current.setHours(h - (h % this.step));
        break;
      case TimeStep.SCALE.WEEKDAY:      // intentional fall through
      case TimeStep.SCALE.DAY:          this.current.setDate(this.current.getDate() + this.step); break;
      case TimeStep.SCALE.MONTH:        this.current.setMonth(this.current.getMonth() + this.step); break;
      case TimeStep.SCALE.YEAR:         this.current.setFullYear(this.current.getFullYear() + this.step); break;
      default:                      break;
    }
  }
  else {
    switch (this.scale) {
      case TimeStep.SCALE.MILLISECOND:  this.current = new Date(this.current.valueOf() + this.step); break;
      case TimeStep.SCALE.SECOND:       this.current.setSeconds(this.current.getSeconds() + this.step); break;
      case TimeStep.SCALE.MINUTE:       this.current.setMinutes(this.current.getMinutes() + this.step); break;
      case TimeStep.SCALE.HOUR:         this.current.setHours(this.current.getHours() + this.step); break;
      case TimeStep.SCALE.WEEKDAY:      // intentional fall through
      case TimeStep.SCALE.DAY:          this.current.setDate(this.current.getDate() + this.step); break;
      case TimeStep.SCALE.MONTH:        this.current.setMonth(this.current.getMonth() + this.step); break;
      case TimeStep.SCALE.YEAR:         this.current.setFullYear(this.current.getFullYear() + this.step); break;
      default:                      break;
    }
  }

  if (this.step != 1) {
    // round down to the correct major value
    switch (this.scale) {
      case TimeStep.SCALE.MILLISECOND:  if(this.current.getMilliseconds() < this.step) this.current.setMilliseconds(0);  break;
      case TimeStep.SCALE.SECOND:       if(this.current.getSeconds() < this.step) this.current.setSeconds(0);  break;
      case TimeStep.SCALE.MINUTE:       if(this.current.getMinutes() < this.step) this.current.setMinutes(0);  break;
      case TimeStep.SCALE.HOUR:         if(this.current.getHours() < this.step) this.current.setHours(0);  break;
      case TimeStep.SCALE.WEEKDAY:      // intentional fall through
      case TimeStep.SCALE.DAY:          if(this.current.getDate() < this.step+1) this.current.setDate(1); break;
      case TimeStep.SCALE.MONTH:        if(this.current.getMonth() < this.step) this.current.setMonth(0);  break;
      case TimeStep.SCALE.YEAR:         break; // nothing to do for year
      default:                break;
    }
  }

  // safety mechanism: if current time is still unchanged, move to the end
  if (this.current.valueOf() == prev) {
    this.current = new Date(this._end.valueOf());
  }

  DateUtil.stepOverHiddenDates(this, prev);
};


/**
 * Get the current datetime
 * @return {Date}  current The current date
 */
TimeStep.prototype.getCurrent = function() {
  return this.current;
};

/**
 * Set a custom scale. Autoscaling will be disabled.
 * For example setScale(SCALE.MINUTES, 5) will result
 * in minor steps of 5 minutes, and major steps of an hour.
 *
 * @param {TimeStep.SCALE} newScale
 *                               A scale. Choose from SCALE.MILLISECOND,
 *                               SCALE.SECOND, SCALE.MINUTE, SCALE.HOUR,
 *                               SCALE.WEEKDAY, SCALE.DAY, SCALE.MONTH,
 *                               SCALE.YEAR.
 * @param {Number}     newStep   A step size, by default 1. Choose for
 *                               example 1, 2, 5, or 10.
 */
TimeStep.prototype.setScale = function(newScale, newStep) {
  this.scale = newScale;

  if (newStep > 0) {
    this.step = newStep;
  }

  this.autoScale = false;
};

/**
 * Enable or disable autoscaling
 * @param {boolean} enable  If true, autoascaling is set true
 */
TimeStep.prototype.setAutoScale = function (enable) {
  this.autoScale = enable;
};


/**
 * Automatically determine the scale that bests fits the provided minimum step
 * @param {Number} [minimumStep]  The minimum step size in milliseconds
 */
TimeStep.prototype.setMinimumStep = function(minimumStep) {
  if (minimumStep == undefined) {
    return;
  }

  //var b = asc + ds;

  var stepYear       = (1000 * 60 * 60 * 24 * 30 * 12);
  var stepMonth      = (1000 * 60 * 60 * 24 * 30);
  var stepDay        = (1000 * 60 * 60 * 24);
  var stepHour       = (1000 * 60 * 60);
  var stepMinute     = (1000 * 60);
  var stepSecond     = (1000);
  var stepMillisecond= (1);

  // find the smallest step that is larger than the provided minimumStep
  if (stepYear*1000 > minimumStep)        {this.scale = TimeStep.SCALE.YEAR;        this.step = 1000;}
  if (stepYear*500 > minimumStep)         {this.scale = TimeStep.SCALE.YEAR;        this.step = 500;}
  if (stepYear*100 > minimumStep)         {this.scale = TimeStep.SCALE.YEAR;        this.step = 100;}
  if (stepYear*50 > minimumStep)          {this.scale = TimeStep.SCALE.YEAR;        this.step = 50;}
  if (stepYear*10 > minimumStep)          {this.scale = TimeStep.SCALE.YEAR;        this.step = 10;}
  if (stepYear*5 > minimumStep)           {this.scale = TimeStep.SCALE.YEAR;        this.step = 5;}
  if (stepYear > minimumStep)             {this.scale = TimeStep.SCALE.YEAR;        this.step = 1;}
  if (stepMonth*3 > minimumStep)          {this.scale = TimeStep.SCALE.MONTH;       this.step = 3;}
  if (stepMonth > minimumStep)            {this.scale = TimeStep.SCALE.MONTH;       this.step = 1;}
  if (stepDay*5 > minimumStep)            {this.scale = TimeStep.SCALE.DAY;         this.step = 5;}
  if (stepDay*2 > minimumStep)            {this.scale = TimeStep.SCALE.DAY;         this.step = 2;}
  if (stepDay > minimumStep)              {this.scale = TimeStep.SCALE.DAY;         this.step = 1;}
  if (stepDay/2 > minimumStep)            {this.scale = TimeStep.SCALE.WEEKDAY;     this.step = 1;}
  if (stepHour*4 > minimumStep)           {this.scale = TimeStep.SCALE.HOUR;        this.step = 4;}
  if (stepHour > minimumStep)             {this.scale = TimeStep.SCALE.HOUR;        this.step = 1;}
  if (stepMinute*15 > minimumStep)        {this.scale = TimeStep.SCALE.MINUTE;      this.step = 15;}
  if (stepMinute*10 > minimumStep)        {this.scale = TimeStep.SCALE.MINUTE;      this.step = 10;}
  if (stepMinute*5 > minimumStep)         {this.scale = TimeStep.SCALE.MINUTE;      this.step = 5;}
  if (stepMinute > minimumStep)           {this.scale = TimeStep.SCALE.MINUTE;      this.step = 1;}
  if (stepSecond*15 > minimumStep)        {this.scale = TimeStep.SCALE.SECOND;      this.step = 15;}
  if (stepSecond*10 > minimumStep)        {this.scale = TimeStep.SCALE.SECOND;      this.step = 10;}
  if (stepSecond*5 > minimumStep)         {this.scale = TimeStep.SCALE.SECOND;      this.step = 5;}
  if (stepSecond > minimumStep)           {this.scale = TimeStep.SCALE.SECOND;      this.step = 1;}
  if (stepMillisecond*200 > minimumStep)  {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 200;}
  if (stepMillisecond*100 > minimumStep)  {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 100;}
  if (stepMillisecond*50 > minimumStep)   {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 50;}
  if (stepMillisecond*10 > minimumStep)   {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 10;}
  if (stepMillisecond*5 > minimumStep)    {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 5;}
  if (stepMillisecond > minimumStep)      {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 1;}
};

/**
 * Snap a date to a rounded value.
 * The snap intervals are dependent on the current scale and step.
 * @param {Date} date   the date to be snapped.
 * @return {Date} snappedDate
 */
TimeStep.prototype.snap = function(date) {
  var clone = new Date(date.valueOf());

  if (this.scale == TimeStep.SCALE.YEAR) {
    var year = clone.getFullYear() + Math.round(clone.getMonth() / 12);
    clone.setFullYear(Math.round(year / this.step) * this.step);
    clone.setMonth(0);
    clone.setDate(0);
    clone.setHours(0);
    clone.setMinutes(0);
    clone.setSeconds(0);
    clone.setMilliseconds(0);
  }
  else if (this.scale == TimeStep.SCALE.MONTH) {
    if (clone.getDate() > 15) {
      clone.setDate(1);
      clone.setMonth(clone.getMonth() + 1);
      // important: first set Date to 1, after that change the month.
    }
    else {
      clone.setDate(1);
    }

    clone.setHours(0);
    clone.setMinutes(0);
    clone.setSeconds(0);
    clone.setMilliseconds(0);
  }
  else if (this.scale == TimeStep.SCALE.DAY) {
    //noinspection FallthroughInSwitchStatementJS
    switch (this.step) {
      case 5:
      case 2:
        clone.setHours(Math.round(clone.getHours() / 24) * 24); break;
      default:
        clone.setHours(Math.round(clone.getHours() / 12) * 12); break;
    }
    clone.setMinutes(0);
    clone.setSeconds(0);
    clone.setMilliseconds(0);
  }
  else if (this.scale == TimeStep.SCALE.WEEKDAY) {
    //noinspection FallthroughInSwitchStatementJS
    switch (this.step) {
      case 5:
      case 2:
        clone.setHours(Math.round(clone.getHours() / 12) * 12); break;
      default:
        clone.setHours(Math.round(clone.getHours() / 6) * 6); break;
    }
    clone.setMinutes(0);
    clone.setSeconds(0);
    clone.setMilliseconds(0);
  }
  else if (this.scale == TimeStep.SCALE.HOUR) {
    switch (this.step) {
      case 4:
        clone.setMinutes(Math.round(clone.getMinutes() / 60) * 60); break;
      default:
        clone.setMinutes(Math.round(clone.getMinutes() / 30) * 30); break;
    }
    clone.setSeconds(0);
    clone.setMilliseconds(0);
  } else if (this.scale == TimeStep.SCALE.MINUTE) {
    //noinspection FallthroughInSwitchStatementJS
    switch (this.step) {
      case 15:
      case 10:
        clone.setMinutes(Math.round(clone.getMinutes() / 5) * 5);
        clone.setSeconds(0);
        break;
      case 5:
        clone.setSeconds(Math.round(clone.getSeconds() / 60) * 60); break;
      default:
        clone.setSeconds(Math.round(clone.getSeconds() / 30) * 30); break;
    }
    clone.setMilliseconds(0);
  }
  else if (this.scale == TimeStep.SCALE.SECOND) {
    //noinspection FallthroughInSwitchStatementJS
    switch (this.step) {
      case 15:
      case 10:
        clone.setSeconds(Math.round(clone.getSeconds() / 5) * 5);
        clone.setMilliseconds(0);
        break;
      case 5:
        clone.setMilliseconds(Math.round(clone.getMilliseconds() / 1000) * 1000); break;
      default:
        clone.setMilliseconds(Math.round(clone.getMilliseconds() / 500) * 500); break;
    }
  }
  else if (this.scale == TimeStep.SCALE.MILLISECOND) {
    var step = this.step > 5 ? this.step / 2 : 1;
    clone.setMilliseconds(Math.round(clone.getMilliseconds() / step) * step);
  }
  
  return clone;
};

/**
 * Check if the current value is a major value (for example when the step
 * is DAY, a major value is each first day of the MONTH)
 * @return {boolean} true if current date is major, else false.
 */
TimeStep.prototype.isMajor = function() {
  if (this.switchedYear == true) {
    this.switchedYear = false;
    switch (this.scale) {
      case TimeStep.SCALE.YEAR:
      case TimeStep.SCALE.MONTH:
      case TimeStep.SCALE.WEEKDAY:
      case TimeStep.SCALE.DAY:
      case TimeStep.SCALE.HOUR:
      case TimeStep.SCALE.MINUTE:
      case TimeStep.SCALE.SECOND:
      case TimeStep.SCALE.MILLISECOND:
        return true;
      default:
        return false;
    }
  }
  else if (this.switchedMonth == true) {
    this.switchedMonth = false;
    switch (this.scale) {
      case TimeStep.SCALE.WEEKDAY:
      case TimeStep.SCALE.DAY:
      case TimeStep.SCALE.HOUR:
      case TimeStep.SCALE.MINUTE:
      case TimeStep.SCALE.SECOND:
      case TimeStep.SCALE.MILLISECOND:
        return true;
      default:
        return false;
    }
  }
  else if (this.switchedDay == true) {
    this.switchedDay = false;
    switch (this.scale) {
      case TimeStep.SCALE.MILLISECOND:
      case TimeStep.SCALE.SECOND:
      case TimeStep.SCALE.MINUTE:
      case TimeStep.SCALE.HOUR:
        return true;
      default:
        return false;
    }
  }

  switch (this.scale) {
    case TimeStep.SCALE.MILLISECOND:
      return (this.current.getMilliseconds() == 0);
    case TimeStep.SCALE.SECOND:
      return (this.current.getSeconds() == 0);
    case TimeStep.SCALE.MINUTE:
      return (this.current.getHours() == 0) && (this.current.getMinutes() == 0);
    case TimeStep.SCALE.HOUR:
      return (this.current.getHours() == 0);
    case TimeStep.SCALE.WEEKDAY: // intentional fall through
    case TimeStep.SCALE.DAY:
      return (this.current.getDate() == 1);
    case TimeStep.SCALE.MONTH:
      return (this.current.getMonth() == 0);
    case TimeStep.SCALE.YEAR:
      return false;
    default:
      return false;
  }
};


/**
 * Returns formatted text for the minor axislabel, depending on the current
 * date and the scale. For example when scale is MINUTE, the current time is
 * formatted as "hh:mm".
 * @param {Date} [date] custom date. if not provided, current date is taken
 */
TimeStep.prototype.getLabelMinor = function(date) {
  if (date == undefined) {
    date = this.current;
  }

  var scaleName = TimeStep.SCALE_INDEX[this.scale];
  var format = TimeStep.FORMAT.minorLabels[scaleName];
  return (format && format.length > 0) ? moment(date).format(format) : '';
};

/**
 * Returns formatted text for the major axis label, depending on the current
 * date and the scale. For example when scale is MINUTE, the major scale is
 * hours, and the hour will be formatted as "hh".
 * @param {Date} [date] custom date. if not provided, current date is taken
 */
TimeStep.prototype.getLabelMajor = function(date) {
  if (date == undefined) {
    date = this.current;
  }

  var scaleName = TimeStep.SCALE_INDEX[this.scale];
  var format = TimeStep.FORMAT.majorLabels[scaleName];
  return (format && format.length > 0) ? moment(date).format(format) : '';
};

module.exports = TimeStep;