var util = require('./util'),
    moment = require('moment');

    /**
 * @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
 */
TimeStep = function(start, end, minimumStep) {
    // 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);
};

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


/**
 * 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";
        return;
    }

    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());
    }
};


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

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

/**
 * 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() {
    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);
        // Note: this is no bug. Major label is equal for both minute and hour scale
        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;
    }

    switch (this.scale) {
        case TimeStep.SCALE.MILLISECOND:  return moment(date).format('SSS');
        case TimeStep.SCALE.SECOND:       return moment(date).format('s');
        case TimeStep.SCALE.MINUTE:       return moment(date).format('HH:mm');
        case TimeStep.SCALE.HOUR:         return moment(date).format('HH:mm');
        case TimeStep.SCALE.WEEKDAY:      return moment(date).format('ddd D');
        case TimeStep.SCALE.DAY:          return moment(date).format('D');
        case TimeStep.SCALE.MONTH:        return moment(date).format('MMM');
        case TimeStep.SCALE.YEAR:         return moment(date).format('YYYY');
        default:                          return '';
    }
};


/**
 * Returns formatted text for the major axislabel, 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;
    }

    //noinspection FallthroughInSwitchStatementJS
    switch (this.scale) {
        case TimeStep.SCALE.MILLISECOND:return moment(date).format('HH:mm:ss');
        case TimeStep.SCALE.SECOND:     return moment(date).format('D MMMM HH:mm');
        case TimeStep.SCALE.MINUTE:
        case TimeStep.SCALE.HOUR:       return moment(date).format('ddd D MMMM');
        case TimeStep.SCALE.WEEKDAY:
        case TimeStep.SCALE.DAY:        return moment(date).format('MMMM YYYY');
        case TimeStep.SCALE.MONTH:      return moment(date).format('YYYY');
        case TimeStep.SCALE.YEAR:       return '';
        default:                        return '';
    }
};

// exports
module.exports = exports = TimeStep;