/**
 * A new UI for picking dates
 * 
 * @constructor
 * @dependencies jQuery 1.7
 * 
 * @param {HTMLElement} input The input you want to make a date picker
 * @param {Object} options Overide the config defaults if you want to.
 */
function DatePicker(input, options) {

    this.date = new Date();
    this.input  = input;
    this.config = {
        spacer: '/',
        order: ['month', 'day', 'year'],
        year: {
            start: 2004,
            end: 2012,
            rangeChange: 0,
            infinite: true
        },
        selected: {
            year: '',
            month: '',
            day: ''
        },
        months: {
            '0': 'Jan',
            '1': 'Feb',
            '2': 'Mar',
            '3': 'Apr',
            '4': 'May',
            '5': 'Jun',
            '6': 'Jul',
            '7': 'Aug',
            '8': 'Sep',
            '9': 'Oct',
            '10': 'Nov',
            '11': 'Dec'
        },
        position: 'default',
        where: 'top',
        currentDay : this.date.getDate(),
        currentMonth : this.date.getMonth(),
        currentYear  : this.date.getFullYear()
    }
    this.uniqueClass = 'dp_input_' + Math.floor(Math.random()*11);
    this.wrapper     = undefined;
    
    $.extend({}, this.config, options);
}

/**
 * @return {boolean}
 */
DatePicker.prototype.init = function() {
    if ( this.input.size() == 0 ) return false;
    
    this.hideInput();
    
    this.wrapper = $(this.buildTagBox());
    this.wrapper.insertAfter(this.input);
    
    // Next: positioning
    
    this.bind.focusTagBoxInput(this);
    this.bind.pickYear(this);
    this.bind.pickMonth(this);
    this.bind.pickDay(this);
    this.bind.updateYear(this);
    this.bind.updateMonth(this);
    this.bind.updateDay(this);
    this.bind.backspaceTagBoxInput(this);
    this.bind.blurTagBoxInput(this);
    this.bind.yearFuture(this);
    this.bind.yearPast(this);
    this.bind.forceFocusOnInput(this);
    
    return true;
}

/**
 * Prepends the years, months or days into wrapper.
 * 
 * @return {undefined}
 */
DatePicker.prototype.insertDateChoice = function(content) {
    this.wrapper.find('.dp_choice').remove();
    this.wrapper.prepend(content);
}

/**
 *
 */
DatePicker.prototype.showCorrectDateChoice = function() {
    var that    = this,
        year    = that.wrapper.find('.dp_tag.dp_tag_year'),
        month   = that.wrapper.find('.dp_tag.dp_tag_month'),
        day     = that.wrapper.find('.dp_tag.dp_tag_day'),
        choice;
    
    // Nothing choosen yet
    if ( year.size() == 0 ) {
        choice = $(that.build.yearRange(that, {start: that.config.year.start, 
                                                 end: that.config.year.end}));
            
        that.insertDateChoice(choice);
        return;
    }
    
    // Year is already choosen
    if ( year.size() > 0 && month.size() == 0 ) {
        choice = $(that.build.months(that));
        that.insertDateChoice(choice);
        return;
    }
    
    // Year and Month is already choosen
    if ( year.size() > 0 && month.size() > 0 && day.size() == 0 ) {
        choice = $(that.build.days(that));
        that.insertDateChoice(choice);
        return;
    }
    
    // Year, Month and day is already choosen
//    if ( year.size() > 0 && month.size() > 0 && day.size() > 0 ) {
//        choice = $(that.build.days(that));
//        that.insertDateChoice(choice);
//        return;
//    }
    
}

/**
 * Methods that build markup.
 * 
 * @return {string}
 */
DatePicker.prototype.build = {
    /**
     * Build the list of years to choose from.
     * 
     * @param {!DatePicker} dpObj
     * @param {Object} range
     * @return {string}
     */
    yearRange: function(dpObj, range) {
        var that  = dpObj,
            div   = ['<div class="dp_years dp_choice">'],
            start = range.start,
            end   = range.end;
            
        if ( that.config.year.infinite ) {
            div.push('<span class="dp_pastYears dp_yearNav">∧</span>');
        }
        
        div.push('<ol>');
        

        // Build year list
        for ( var i=start; i<(end + 1); i++ ) {
            if(i == that.config.currentYear){
                div.push('<li class="dp_year dp_current">' + i + '</li>');
            }
            else {
                div.push('<li class="dp_year">' + i + '</li>');
            }
        }
        
        div.push('</ol>');
        
        if ( that.config.year.infinite ) {
            div.push('<span class="dp_futureYears dp_yearNav">∨</span>');
        }
        
        div.push('</div>');

        return div.join('');
    },
    /**
     * Build the months to pick from.
     * 
     * @param {!DatePicker} dpObj
     * @return {string}
     */
    months: function(dpObj) {
        var that   = dpObj,
            months = that.config.months,
            div    = ['<div class="dp_months dp_choice">'];

        div.push('<ol>');
        
        for ( var month in months ) {
            if ( months.hasOwnProperty(month) ) {
                if(month == that.config.currentMonth && that.config.selected.year == that.config.currentYear) {
                    div.push('<li class="dp_month dp_current" data-month="' + month + '">' + months[month] + '</li>');
                }
                else {
                    div.push('<li class="dp_month" data-month="' + month + '">' + months[month] + '</li>');
                }
            }
        }
        
        div.push('</ol>');

        div.push('</div>');

        return div.join('');
    },
    days: function(dpObj) {
        var that               = dpObj,
            days_in_each_month = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31],
            year               = that.config.selected.year,
            month              = that.config.selected.month,
            howManyDays        = days_in_each_month[month];
            
        // February Leap Year Check
        if ( month == 1 ) {
            if ( (year % 4 == 0 && year % 100 != 0) || year % 400 == 0 ) {
                howManyDays = 29;
            }
        }
                
        var date = new Date(year, month, 1),
            day  = date.getDay(),
            days = ['<div class="dp_choice dp_days">', '<table>', '<tr>'];
        
        // Prepend Days of Week Headers
        days.push('<th>S</th>');
        days.push('<th>M</th>');
        days.push('<th>T</th>');
        days.push('<th>W</th>');
        days.push('<th>T</th>');
        days.push('<th>F</th>');
        days.push('<th>S</th>');
        
        days.push('</tr>');
        days.push('<tr>');
        
        // Prepend empty days
        for ( var p=0; p<day; p++ ) {
            days.push('<td class="dp_day dp_empty_day"></td>');
        }
        
        // Build days
        for ( var i=1; i<=howManyDays; i++ ) {
            if(i == that.config.currentDay 
                && that.config.selected.year == that.config.currentYear
                && that.config.selected.month == that.config.currentMonth) {
               days.push('<td class="dp_day dp_day_' + day + ' dp_current">' + i + '</td>');
            }
            else {
                days.push('<td class="dp_day dp_day_' + day + ' ">' + i + '</td>');
            }
            
            if ( 6 == day ) {
                day = 0;
                days.push('</tr>');
                days.push('<tr>');
            } else {
                day++;
            }
        }
        
        // Append empty days
        if ( 0 != day ) {
            var daysLeft = 7-day;
            
            for ( var d=0; d<daysLeft; d++) {
                days.push('<td class="dp_day dp_empty_day"></td>');
            }
        }
        
        days.push('</tr>');
        days.push('</table>');
        days.push('</div>');
        
        return days.join('');
    }
};

/**
 * 
 */
DatePicker.prototype.bind = {
    /**
     * What happens when you focus the dynamic input?
     * 
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    focusTagBoxInput: function(dpObj) {
        var that = dpObj;

        that.wrapper.on('focus', 'input', function() {
            if ( that.wrapper.find('.dp_choice').size() == 0 ) {
                that.showCorrectDateChoice();
            }
        });
    },
    /**
     * Forces the input to be focused
     * 
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    forceFocusOnInput: function(dpObj) {
        var that = dpObj;
        
        that.wrapper.on('click', '.dp_tagBox', function() {
            that.wrapper.find('input').focus();
        });
    },
    /**
     * What happens when you blur the dynamic input?
     * 
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    blurTagBoxInput: function(dpObj) {
        var that = dpObj;
        
        that.wrapper.on('blur', 'input', function() {
            //that.wrapper.find('.dp_choice').remove();
        });
    },
    /**
     * What happens once you pick a year?
     * 
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    pickYear: function(dpObj) {
        var that = dpObj;

        that.wrapper.on('click', '.dp_year', function() {
            var year = $(this).text();
            
            that.insertTag('year', year, year);
            that.config.selected.year = year;

            // Build the months after picking a year
            var months = $(that.build.months(that));
            that.insertDateChoice(months);
            
            // Remove dependant tags
            that.wrapper.find('.dp_tag_month, .dp_tag_day').remove();
            
            that.updateHiddenInput();
        });
    },
    /**
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    pickMonth: function(dpObj) {
        var that = dpObj;
        
        that.wrapper.on('click', '.dp_month', function() {
            var month    = $(this).text(),
                monthVal = $(this).data('month') + 1;
            
            that.insertTag('month', month, monthVal);
            that.config.selected.month = $(this).data('month');
            
            // Build the days after picking a month
            var days = $(that.build.days(that));
            that.insertDateChoice(days);
            
            // Remove dependant tags
            that.wrapper.find('.dp_tag_day').remove();
            
            that.updateHiddenInput();
        });
    },
    /**
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    pickDay: function(dpObj) {
        var that = dpObj;
        
        that.wrapper.on('click', '.dp_day', function() {
            var day = $(this).text();
            
            that.insertTag('day', day, day);
            that.config.selected.day = day;
            
            that.updateHiddenInput();
            that.wrapper.find('.dp_choice').remove();
        });
    },
    /**
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    updateYear: function(dpObj) {
        var that = dpObj;
        
        that.wrapper.on('click', '.dp_tag_year', function() {
            var yearConfig = that.config.year,
                rangeChange =  yearConfig.rangeChange,
                newStart  = yearConfig.start + rangeChange,
                newEnd    = yearConfig.end + rangeChange,
                years = $(that.build.yearRange(that, {start: newStart, end: newEnd}));
                
            that.insertDateChoice(years);
        });
    },
    /**
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    updateMonth: function(dpObj) {
        var that = dpObj;
        
        that.wrapper.on('click', '.dp_tag_month', function() {
            // Build the days
            var months = $(that.build.months(that));
            that.insertDateChoice(months);
        });
    },
    /**
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    updateDay: function(dpObj) {
        var that = dpObj;
        
        that.wrapper.on('click', '.dp_tag_day', function() {
            // Build the days
            var days = $(that.build.days(that));
            that.insertDateChoice(days);
        });
    },
    /**
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    backspaceTagBoxInput: function(dpObj) {
        var that = dpObj;
        
        that.wrapper.on('keyup', 'input', function(e) {
            var key = e.keyCode,
                backspace = 8;
            
            if ( key == backspace ) {
                that.wrapper.find('.dp_tag:first').remove();
                that.showCorrectDateChoice();
                that.updateHiddenInput();
            }
        });
    },
    /**
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    yearFuture: function(dpObj) {
        var that       = dpObj,
            yearConfig = that.config.year;
            
        that.wrapper.on('click', '.dp_futureYears', function(e) {
            e.preventDefault();
            
            yearConfig.rangeChange = yearConfig.rangeChange + 9;
            
            var newStart = yearConfig.start + yearConfig.rangeChange,
                newEnd   = yearConfig.end + yearConfig.rangeChange,
                years    = $(that.build.yearRange(that, {start: newStart, end: newEnd}));
        
            that.insertDateChoice(years);    
        });
    },
    /**
     * @param {!DatePicker} dpObj
     * @return {undefined}
     */
    yearPast: function(dpObj) {
        var that       = dpObj,
            yearConfig = that.config.year;
            
        that.wrapper.on('click', '.dp_pastYears', function(e) {
            e.preventDefault();
            
            yearConfig.rangeChange = yearConfig.rangeChange - 9;
            
            var newStart = yearConfig.start + yearConfig.rangeChange,
                newEnd   = yearConfig.end + yearConfig.rangeChange,
                years    = $(that.build.yearRange(that, {start: newStart, end: newEnd}));
        
            that.insertDateChoice(years);    
        });
    }
}

/**
 * @return {undefined}
 */
DatePicker.prototype.updateHiddenInput = function() {
    var that  = this,
        tag   = that.wrapper.find('.dp_tag'),
        value = '',
        order = that.config.order;
    
    that.input.val('');
    
    for ( var i=0; i<order.length; i++ ) {
        if ( i < 2 ) {
            value += $('.dp_tag_' + order[i]).data('valuesubmitted') + that.config.spacer;
        } else {
            value += $('.dp_tag_' + order[i]).data('valuesubmitted');
        }
        
    }
    
    that.input.val(value);
}

/**
 * @param {string} type The type of tag it is. (year, month, day)
 * @param {string} valueDisplayed The value of the tag.
 * @param {string|number} valueSubmitted The value of the tag submitted.
 * @return {undefined}
 */
DatePicker.prototype.insertTag = function(type, valueDisplayed, valueSubmitted) {
    var that   = this,
        tagBox = that.wrapper.find('.dp_tagBox'),
        tag    = tagBox.find('.dp_tag.dp_tag_' + type);

    if ( tag.size() > 0 ) {
        tag.text(valueDisplayed);
    } else {
        tagBox.prepend('<span class="dp_tag dp_tag_' + type + '" data-valuesubmitted="' + valueSubmitted + '">' + valueDisplayed + '</span>');
    }
}

/**
 * @return {undefined}
 */
DatePicker.prototype.buildTagBox = function() {
    var classes = 'dp_wrapper ' + this.uniqueClass,
        config  = this.config;
    
    if ( 'absolute' == config.position ) {
        classes += (' ' + config.position + ' ' + config.where);
    }
    
    var div = '<div class="' + classes + '"><div class="dp_tagBox"><input type="text"></div></div>';
    
    return div;
}

/**
 * @return {undefined}
 */
DatePicker.prototype.hideInput = function() {
    this.input.hide();
}

var datePicker = new DatePicker($('#datePicker'));
datePicker.init();