(function($) {
  $.fn.continuousCalendar = function(options) {
    var defaults = {
      weeksBefore: 26,
      weeksAfter: 26,
      startField: this.find('input.startDate'),
      endField: this.find('input.endDate'),
      isPopup: false,
      selectToday: false,
      locale: DATE_LOCALE_EN,
      callback: function() {
      },
      onChange: function() {
      }
    };
    var params = $.extend(defaults, options);
    
    var Status = {
      CREATE:'create',
      MOVE:'move',
      NONE:'none'
    };

    params.locale.init();
    var rangeLengthLabel = $('<span>');
    var startDate = fieldDate(params.startField);
    var endDate = fieldDate(params.endField);

    if (params.selectToday) {
      var today = Date.NOW;
      var formattedToday = formatDate(today);
      startDate = today;
      endDate = today;
      setStartField(formattedToday);
      setEndField(formattedToday);
    }

    var firstWeekdayOfGivenDate = (startDate || Date.NOW).getFirstDateOfWeek(params.locale.firstWeekday);
    var container = this;
    var dateCells = null;
    var dateCellDates = null;
    var moveStartDate = null;
    var mouseDownDate = null;
    var averageCellHeight;
    var yearTitle;
    var selection;
    var calendarRange;
    var status = Status.NONE;
    var calendar;

    createCalendar();
    container.trigger('calendarChange');

    function createCalendar() {
      if (startDate && endDate) {
        selection = new DateRange(startDate, endDate);
      } else {
        selection = DateRange.emptyRange();
      }
      container.data('calendarRange', selection);
      var rangeStart = 'firstDate' in params ? Date.parseDate(params.firstDate, params.locale.shortDateFormat) : firstWeekdayOfGivenDate.plusDays(-(params.weeksBefore * 7));
      var rangeEnd = 'lastDate' in params ? Date.parseDate(params.lastDate, params.locale.shortDateFormat) : firstWeekdayOfGivenDate.plusDays(params.weeksAfter * 7 + 6);
      calendarRange = new DateRange(rangeStart, rangeEnd);

      var headerTable = $('<table>').addClass('calendarHeader').append(headerRow());
      var bodyTable = $('<table>').addClass('calendarBody').append(calendarBody());
      var scrollContent = $('<div>').addClass('calendarScrollContent').append(bodyTable);
      calendar = getCalendarContainerOrCreateOne();
      calendar.append(headerTable).append(scrollContent);
      if (params.isPopup) {
        calendar.addClass('popup');
        var icon = $('<a href="#" class="calendarIcon"><span>calendar</span></a>').click(toggleCalendar);
        container.append(icon);
      }

      if (container.find('.startDateLabel').isEmpty()) {
        addDateLabels(container);
      }

      dateCells = container.find('.date');
      dateCellDates = dateCells.map(function() {
        return this.date;
      });
      if (isRange()) {
        initRangeCalendarEvents(container, bodyTable);
      } else {
        initSingleDateCalendarEvents();
      }
      averageCellHeight = parseInt(bodyTable.height() / bodyTable.find('tr').size());
      yearTitle = headerTable.find('th.month');
      setScrollBehaviors(scrollContent);
      if (params.isPopup) calendar.hide();
      params.callback.call(container, selection);
    }

    function getCalendarContainerOrCreateOne() {
      var existingContainer = container.find('.continuousCalendar');
      if (existingContainer.exists()) {
        return existingContainer;
      } else {
        var newContainer = $('<div>').addClass('continuousCalendar');
        container.append(newContainer);
        return newContainer;
      }
    }

    function addDateLabels(container) {
      var dateLabelContainer = $('<div class="label">');
      dateLabelContainer.append('<span class="startDateLabel"></span>');
      if (isRange()) {
        dateLabelContainer.append('<span class="separator"> - </span>').append('<span class="endDateLabel"></span>');
      }
      container.append(dateLabelContainer);
    }

    function initRangeCalendarEvents(container, bodyTable) {
      var daysContainer = $('<em>');
      rangeLengthLabel.text(Date.daysLabel(selection.days()));
      daysContainer.append(rangeLengthLabel);
      container.find('.continuousCalendar').append(daysContainer);
      bodyTable.addClass('range');
      bodyTable.mousedown(mouseDown).mouseover(mouseMove).mouseup(mouseUp);
      disableTextSelection(bodyTable.get(0));
      setRangeLabels();
    }

    function setScrollBehaviors(scrollContent) {
      scrollContent.scroll(function() {
        setYearLabel(this);
      });

      var selected = scrollContent.find('.today, .selected').get(0);
      if (selected) {
        scrollContent.scrollTop(selected.offsetTop - (scrollContent.height() - selected.offsetHeight) / 2);
      }
    }

    function setYearLabel(scrollContent) {
      var table = $(scrollContent).find('table').get(0);
      var rowNumber = parseInt(scrollContent.scrollTop / averageCellHeight);
      var date = table.rows[rowNumber].cells[2].date;
      yearTitle.text(date.getFullYear());
    }

    function headerRow() {
      var tr = $('<tr>').append(yearCell());
      var thead = $('<thead>').append(tr);
      tr.append('<th class="week"></th>');
      $(Date.dayNames).each(function(index) {
        var weekDay = $('<th>').append(Date.dayNames[(index + params.locale.firstWeekday) % 7].substr(0, 2)).addClass('weekDay');
        tr.append(weekDay);
      });
      if (params.isPopup) {
        var close = $('<th><a href="#"><span>close</span></a>');
        close.find('a').click(toggleCalendar);
        tr.append(close);
      }
      return thead;

      function yearCell() {
        return $('<th>').addClass('month').append(firstWeekdayOfGivenDate.getFullYear());
      }
    }

    function toggleCalendar() {
      calendar.toggle();
      return false;
    }

    function calendarBody() {
      var tbody = $('<tbody>');
      var firstWeekDay = calendarRange.start.getFirstDateOfWeek(params.locale.firstWeekday);
      while (firstWeekDay.compareTo(calendarRange.end) <= 0) {
        tbody.append(calendarRow(firstWeekDay.clone()));
        firstWeekDay = firstWeekDay.plusDays(7);
      }
      return tbody;
    }

    function calendarRow(firstDayOfWeek) {
      var tr = $('<tr>').append(monthCell(firstDayOfWeek)).append(weekCell(firstDayOfWeek));
      for (var i = 0; i < 7; i++) {
        var date = firstDayOfWeek.plusDays(i);
        var dateCell = $('<td>').addClass(dateStyles(date)).append(date.getDate());
        dateCell.get(0).date = date;
        if (date.isToday()) dateCell.addClass('today');
        if (isRange()) {
          dateCell.toggleClass('selected', selection.hasDate(date))
          .toggleClass('rangeStart', date.equalsOnlyDate(selection.start))
          .toggleClass('rangeEnd', date.equalsOnlyDate(selection.end));
        } else {
          dateCell.toggleClass('selected', date.equalsOnlyDate(startDate));
        }
        tr.append(dateCell);
      }
      return tr;
    }

    function monthCell(firstDayOfWeek) {
      var th = $('<th>').addClass('month').addClass(backgroundBy(firstDayOfWeek));
      if (firstDayOfWeek.getDate() <= 7) {
        th.append(Date.monthNames[firstDayOfWeek.getMonth()]).addClass('monthName');
      } else if (firstDayOfWeek.getDate() <= 7 * 2 && firstDayOfWeek.getMonth() == 0) {
        th.append(firstDayOfWeek.getFullYear());
      }
      return th;
    }

    function weekCell(firstDayOfWeek) {
      return $('<th>').addClass('week').addClass(backgroundBy(firstDayOfWeek)).append(firstDayOfWeek.getWeekInYear('ISO'));
    }

    function dateStyles(date) {return 'date ' + backgroundBy(date) + disabledOrNot(date) + todayStyle(date);}
    function backgroundBy(date) {return date.isOddMonth() ? ' odd' : '';}
    function disabledOrNot(date) {return calendarRange.hasDate(date) ? '' : ' disabled';}
    function todayStyle(date) {return date.isToday() ? ' today' : '';}

    function initSingleDateCalendarEvents() {
      dateCells.click(function() {
        dateCells.removeClass('selected');
        var dateCell = $(this);
        dateCell.addClass('selected');
        var formattedDate = date(dateCell).dateFormat(params.locale.shortDateFormat);
        params.startField.val(formattedDate);
        setDateLabel(formattedDate);
        if (params.isPopup) {
          toggleCalendar.call(this);
        }
        params.onChange.call(formattedDate, dateCell);
      });
      setDateLabel(params.startField.val());
    }

    function mouseDown(event) {
      var elem = event.target;
      if (isDateCell(elem) && isEnabled(elem)) {
        status = Status.CREATE;
        mouseDownDate = elem.date;
        if (mouseDownDate.equalsOnlyDate(selection.end)) {
          mouseDownDate = selection.start;
        } else if (mouseDownDate.equalsOnlyDate(selection.start)) {
          mouseDownDate = selection.end;
        } else if (selection.hasDate(mouseDownDate)) {
          status = Status.MOVE;
          moveStartDate = mouseDownDate;
        } else if (event.shiftKey) {
          status = Status.NONE;
          selection.expandTo(mouseDownDate);
        } else {
          selection = new DateRange(mouseDownDate, mouseDownDate);
        }
      } else if (isWeekCell(elem)) {
        status = Status.NONE;
        var dayInWeek = date($(elem).siblings('.date'));
        selection = new DateRange(dayInWeek, dayInWeek.plusDays(6));
      } else if (isMonthCell(elem)) {
        status = Status.NONE;
        var dayInMonth = date($(elem).siblings('.date'));
        selection = new DateRange(dayInMonth.firstDateOfMonth(), dayInMonth.lastDateOfMonth());
      }
    }

    function mouseMove(event) {
      if(status == Status.NONE)
        return;
      var date = event.target.date;
      if (isEnabled(event.target)) {
        switch (status) {
          case Status.MOVE:
            var deltaDays = moveStartDate.distanceInDays(date);
            moveStartDate = date;
            selection.shiftDays(deltaDays);
            selection = selection.and(calendarRange);
            break;
          case Status.CREATE:
            selection = new DateRange(mouseDownDate, date);
            break;
        }
        drawSelection();
      }
    }

    function mouseUp() {
      status = Status.NONE;
      drawSelection();
      afterSelection();
    }

    function drawSelection() {
      drawSelectionBetweenDates(selection.start, selection.end);
      rangeLengthLabel.text(Date.daysLabel(selection.days()));
    }

    function drawSelectionBetweenDates(start, end) {
      dateCells.each(function(i, elem) {
        var date = dateCellDates[i];
        var styleClass = [dateStyles(date)];
        if (date.equalsOnlyDate(end)) {
          styleClass.push('selected rangeEnd');
        } else if (date.equalsOnlyDate(start)) {
          styleClass.push('selected rangeStart');
        } else if (date.isBetweenDates(start, end)) {
          styleClass.push('selected');
        }
        elem.className = styleClass.join(' ');
      });
    }

    function afterSelection() {
      var formattedStart = formatDate(selection.start);
      var formattedEnd = formatDate(selection.end);
      container.data('calendarRange', selection);
      setStartField(formattedStart);
      setEndField(formattedEnd);
      setRangeLabels();
      params.callback.call(container, selection);
      container.trigger('calendarChange');
    }

    function setRangeLabels() {
      if (selection.start && selection.end) {
        var format = params.locale.weekDateFormat;
        container.find('span.startDateLabel').text(selection.start.dateFormat(format));
        container.find('span.endDateLabel').text(selection.end.dateFormat(format));
      }
    }

    function fieldDate(field) {
      if (field.length > 0 && field.val().length > 0)
        return Date.parseDate(field.val(), params.locale.shortDateFormat);
      else
        return null;
    }

    function disableTextSelection(elem) {
      if ($.browser.mozilla) {//Firefox
        $(elem).css('MozUserSelect', 'none');
      } else if ($.browser.msie) {//IE
        $(elem).bind('selectstart', function() {
          return false;
        });
      } else {//Opera, etc.
        $(elem).mousedown(function() {
          return false;
        });
      }
    }

    function isDateCell(elem) {return $(elem).hasClass('date');}
    function isWeekCell(elem) {return $(elem).hasClass('week');}
    function isMonthCell(elem) {return $(elem).hasClass('month');}
    function isEnabled(elem) {return !$(elem).hasClass('disabled');}
    function date(elem) {return elem.get(0).date;}
    function setStartField(value) {params.startField.val(value);}
    function setEndField(value) {params.endField.val(value);}
    function formatDate(date) {return date.dateFormat(params.locale.shortDateFormat);}
    function setDateLabel(val) {container.find('span.startDateLabel').text(val);}
    function isRange() {return params.endField && params.endField.length > 0;}
  };
  $.fn.calendarRange = function() {
    return $(this).data('calendarRange');
  };
})(jQuery);

$.fn.exists = function() {
  return this.length > 0;
};

$.fn.isEmpty = function() {
  return this.length == 0;
};

function DateRange(date1, date2) {
  var hasTimes = false;
  if (!date1 || !date2) {
    throw('two dates must be specified, date1=' + date1 + ', date2=' + date2);
  }
  this.start = date1.compareTo(date2) > 0 ? date2 : date1;
  this.end = date1.compareTo(date2) > 0 ? date1 : date2;
  var days;
  var hours;
  var minutes;

  this.hours = function() {return hours;};
  this.minutes = function() {return minutes;};
  this.hasDate = function(date) {return date.isBetweenDates(this.start, this.end);};
  this.isValid = function() {return this.end.getTime() - this.start.getTime() >= 0;};

  this.days = function() {
    if (hasTimes) {
      return days;
    } else {
      return Math.round(this.start.distanceInDays(this.end) + 1);
    }
  };
  
  this.shiftDays = function(days) {
    this.start = this.start.plusDays(days);
    this.end = this.end.plusDays(days);
  };

  this.expandTo = function(date) {
    if (date.compareTo(this.start) < 0) {
      this.start = date;
    } else if (date.compareTo(this.end) > 0) {
      this.end = date;
    }
  };

  this.and = function(that) {
    var latestStart = this.start.compareTo(that.start) > 0 ? this.start : that.start;
    var earliestEnd = this.end.compareTo(that.end) > 0 ? that.end : this.end;
    if (latestStart.compareTo(earliestEnd) < 0) {
      return new DateRange(latestStart, earliestEnd);
    } else {
      return DateRange.emptyRange();
    }
  };

  this.setTimes = function(startTimeStr, endTimeStr) {
    this.start = dateWithTime(this.start, startTimeStr);
    this.end = dateWithTime(this.end, endTimeStr);
    hasTimes = true;
    setDaysHoursAndMinutes.call(this);
  };

  function setDaysHoursAndMinutes() {
    if (hasTimes) {
      var ms = parseInt((this.end.getTime() - this.start.getTime()));
      days = parseInt(ms / Date.DAY);
      ms = ms - (days * Date.DAY);
      hours = parseInt(ms / Date.HOUR);
      ms = ms - (hours * Date.HOUR);
      minutes = parseInt(ms / Date.MINUTE);
    }
  }

  function dateWithTime(dateWithoutTime, timeStr) {
    var parsedTime = parseTime(timeStr);
    var date = dateWithoutTime.clone();
    date.setHours(parsedTime.get(0));
    date.setMinutes(parsedTime.get(1));
    date.setMilliseconds(0);
    return date;
  }

  function parseTime(timeStr) {
    return $(timeStr.split(':')).map(function() {
      return parseInt(this);
    });
  }

  this.toString = function(locale) {
    if (hasTimes) {
      var minutes = this.minutes() > 0 ? ',' + (this.minutes() / 6) : '';
      return  Date.daysLabel(this.days())  + ' ' + Date.hoursLabel(this.hours() + minutes);
    } else {
      return this.start.dateFormat(locale.shortDateFormat) + ' - ' + this.end.dateFormat(locale.shortDateFormat);
    }
  };
}

DateRange.emptyRange = function() {
  function NullDateRange() {
    this.start = null;
    this.end = null;
    this.days = function() {return 0;};
    this.shiftDays = function() {};
    this.hasDate = function() {return false;};
  }

  return new NullDateRange();
};
DateRange.parse = function(dateStr1, dateStr2, dateFormat) {
  return new DateRange(Date.parseDate(dateStr1, dateFormat), Date.parseDate(dateStr2, dateFormat));
};