/**
 *
 * How it works from the inside?
 *
 * This calendar is used to display certain dates either by specifying range (min and max)
 * or by specifying exact dates that are available.
 *
 * To simplify calculations you need to provide those dates without the needed timezone offset,
 * instead pretend like they are in current timezone. For example, if you need to specify a minimum
 * date of "2015-01-08" for a +12 timezone calendar, when providing this date don't provide a
 * "2015-01-08T00:00:00+12:00" but instead provide a "2015-01-08 00:00:00" as if the timezone you
 * are using is the local one. This simplifies internal calculations while still gives correct
 * results.
 *
 * However, for "Go To Today" functionality to work correctly, you will need to provide a timezone
 * you wish your calendar to work with. This timezone is provided via `options.tz`.
 *
 * Note: at the moment only UTC timezone is supported and is the one used by default.
 *
 */

import frDatepicker from '../../../../public/views/ng/common/frDatepicker.html';

angular.module('fr.datepicker', []).directive('frDatepicker', ['$filter', function ($filter) {
    return {
        restrict: 'A',
        scope: true,
        template: frDatepicker,
        link: function (scope, element, attrs) {
            /**
             * Initialization
             */

            var options = scope.$eval(attrs.options);

            // Expose scope.
            if (options.ctrl) {
                options.ctrl.scope = scope;
            }

            scope.weekly = options.weekly;
            var onChangeHandler = options.onChange || function () {};

            var minDate;
            var maxDate;

            // The day that acts as the day that is chosen when clicking "Go to Today",
            // "Current Week", etc. In other words it's the day that is most relevant in respect
            // to today.
            var currentDay = options.currentDay;

            var years = {};
            var months = {};
            var days = {};

            // Set today as perceived by calendar's timezone.
            var today = new Date();
            today.setHours(0, 0, 0, 0);

            // Setup calendar accordingly to whether it's configured by exact dates or range.
            if (options.dates) {
                setupCalendarByDates();
            } else {
                setupCalendarByRange();
            }

            // Choose Monday as current day for weekly calendar.
            if (scope.weekly) {
                setToMonday(currentDay);
            }

            // This is the actual date that is selected.
            scope.date = options.date || currentDay;

            // This is the currently viewed month. Date may or may not be selected within this month.
            var viewedMonth = new Date(scope.date);

            // Establish how "Go To Today" will look.
            if (scope.weekly) {
                scope.goToText = 'Current Week';
            } else if (options.byDates) {
                scope.goToText = 'Current Game Day';
            } else {
                scope.goToText = 'Go To Today';
            }

            calculateDates();

            /**
             * Private Methods
             */

            function setupCalendarByDates() {
                options.byDates = true;

                // Process each provided date.
                _(options.dates).each(function (date) {
                    // Build dictionary of all years, months and dates.
                    years[(new Date(date.getFullYear(), 0, 1)).getTime()] = true;
                    months[(new Date(date.getFullYear(), date.getMonth(), 1)).getTime()] = true;
                    days[date.getTime()] = true;

                    // Calculate minimum date from provided dates.
                    if (minDate === undefined || minDate.getTime() > date.getTime()) {
                        minDate = date;
                    }

                    // Calculate maximum date from provided dates.
                    if (maxDate === undefined || maxDate.getTime() < date.getTime()) {
                        maxDate = date;
                    }

                    // If no current date specified then we need to establish one by ourselves.
                    if (!options.currentDay) {
                        if (!currentDay) {
                            currentDay = date;
                        } else if (date.getTime() < currentDay.getTime() && today.getTime() <= date.getTime()) {
                            currentDay = date;
                        } else if (date.getTime() > currentDay.getTime() && today.getTime() >= currentDay.getTime()) {
                            currentDay = date;
                        }
                    }
                });
            }

            function setupCalendarByRange() {
                options.byRange = true;

                minDate = options.minDate;
                maxDate = options.maxDate;

                // If no current date specified then we need to establish one by ourselves.
                if (!options.currentDay) {
                    if (today.getTime() < minDate.getTime()) {
                        currentDay = new Date(minDate);
                    } else if (today.getTime() > maxDate.getTime()) {
                        currentDay = new Date(maxDate);
                    } else {
                        currentDay = today;
                    }
                }
            }

            function calculateYears() {
                var year;
                var yearDate;

                scope.selectedYear = viewedMonth.getFullYear();

                // We don't want to overwrite years because it will mess up
                // change detection, plus there is no need to.
                if (scope.years) {
                    return;
                }

                scope.years = [];

                for (year = minDate.getFullYear(); year <= maxDate.getFullYear(); year++) {
                    yearDate = new Date(year, 0, 1);

                    if (options.byDates && !years[yearDate.getTime()]) {
                        continue;
                    }

                    scope.years.push(year);
                }
            }

            function calculateMonths() {
                scope.months = [];

                var date;

                for (var i = 0; i <= 11; i++) {
                    date = new Date(viewedMonth.getFullYear(), i, 1);

                    scope.months.push({
                        date: date,
                        enabled: (options.byDates && months[date.getTime()]) || isDateInRange(date),
                        name: $filter('date')(date, 'MMM'),
                        selected: viewedMonth.getMonth() === i,
                        type: 'month',
                    });
                }
            }

            function calculateWeeks() {
                scope.weeks = [];

                var week;
                var day;

                // Calculate date that calendar's 7 by 6 grid will start from.
                var startingWeekDay = new Date(viewedMonth.getFullYear(), viewedMonth.getMonth(), 1).getDay();
                var daysFromPreviousMonth = ((startingWeekDay === 1) ? 7 : (startingWeekDay === 0) ? 6 : startingWeekDay - 1);

                // Iterate over a 7 by 6 calendar grid.
                for (var i = 1; i <= 6; i++) {
                    week = {
                        type: 'week',
                        enabled: false,
                        selected: false,
                        days: [],
                    };

                    for (var j = 1; j <= 7; j++) {
                        // Set date.
                        let date = new Date(viewedMonth);
                        date.setDate(0 - daysFromPreviousMonth + ((i - 1) * 7 + j));

                        // Get calculated day.
                        day = calculateDay(date);

                        // Enable week if at least one day is enabled.
                        week.enabled = week.enabled || day.enabled;

                        // Select week if at least one day is selected.
                        week.selected = week.selected || day.selected;

                        if (day.date.getDay() === 1) {
                            week.date = day.date;
                        }

                        week.days.push(day);
                    }

                    scope.weeks.push(week);
                }
            }

            function calculateDay(date) {
                return {
                    date: date,
                    enabled: (options.byDates && days[date.getTime()]) || isDateInRange(date),
                    name: date.getDate(),
                    otherMonth: viewedMonth.getMonth() !== date.getMonth(),
                    selected: scope.date.getTime() === date.getTime(),
                    type: 'day',
                };
            }

            function calculateDates() {
                console.time('DatePicker: calculate dates.');

                if (scope.calendarOpened) {
                    calculateYears();
                    calculateMonths();
                    calculateWeeks();
                }

                setSelectedText();
                console.timeEnd('DatePicker: calculate dates.');
            }

            function setYearDate(year) {
                var lastAvailableDate;
                var date;

                for (var i = 0; i < 12; i++) {
                    date = new Date(year, i, 1);

                    if (!(options.byDates && months[date.getTime()]) && !isDateInRange(date)) {
                        continue;
                    }

                    if (lastAvailableDate && viewedMonth.getMonth() < lastAvailableDate.getMonth()) {
                        continue;
                    }

                    lastAvailableDate = date;

                    if (viewedMonth.getMonth() === date.getMonth()) {
                        break;
                    }
                }

                viewedMonth = lastAvailableDate;
            }

            function selectDate(date) {
                scope.date = date;
                viewedMonth = new Date(date);
                viewedMonth.setDate(1);

                calculateDates();
                scope.notifyDateChange();
            }

            function setSelectedText() {
                var startDate = scope.date;
                var endDate;
                var startFormat = 'd';
                var endFormat = 'd MMM, yyyy';

                if (scope.weekly) {
                    endDate = new Date(scope.date);
                    endDate.setDate(endDate.getDate() + 6);

                    if (startDate.getMonth() !== endDate.getMonth()) {
                        startFormat = 'd MMM';
                    }

                    scope.selected = $filter('date')(startDate, startFormat) + ' - ' + $filter('date')(endDate, endFormat);
                } else {
                    scope.selected = $filter('date')(startDate, endFormat);
                }
            }

            function setToMonday(date) {
                var day = date.getDay();
                date.setDate(date.getDate() - day + (day == 0 ? -6 : 1));
            }

            function isDateInRange(date) {
                return options.byRange && date.getTime() >= minDate.getTime() && date.getTime() <= maxDate.getTime();
            }

            scope.notifyDateChange = function () {
                var endDate;

                if (scope.weekly) {
                    endDate = new Date(scope.date);
                    endDate.setDate(endDate.getDate() + 6);
                }

                onChangeHandler(scope.date, endDate);
            };

            /**
             * Interactions.
             */

            scope.clickDate = function (clicked) {
                // Don't process invalid clicks.
                if (clicked.type === 'week' && !scope.weekly || clicked.type === 'day' && scope.weekly || !clicked.enabled) {
                    return;
                }

                // Set viewed month.
                viewedMonth = new Date(clicked.date.getFullYear(), clicked.date.getMonth(), 1);

                // Set viewed date.
                if (clicked.type === 'day' || clicked.type === 'week') {
                    scope.date = new Date(clicked.date);
                    scope.notifyDateChange();
                }

                if (scope.weekly) {
                    setToMonday(scope.date);
                }

                calculateDates();
            };

            scope.clickYear = function (year) {
                setYearDate(year);

                if (scope.weekly) {
                    setToMonday(scope.date);
                }

                calculateDates();
            };

            scope.clickPrev = function () {
                var prevDate = new Date(scope.date);

                while (1) {
                    prevDate.setDate(prevDate.getDate() - 1);

                    // Stop if we hit minimum date.
                    if (prevDate.getTime() < minDate.getTime()) {
                        return;
                    }

                    // If previous condition didn't trigger exit then we are in the range.
                    if (options.byRange) {
                        break;
                    }

                    // Try previous month if this month is not available.
                    if (!months[(new Date(prevDate.getFullYear(), prevDate.getMonth(), 1)).getTime()]) {
                        // Set prevDate to 1st of this month so that
                        // on next iteration it is set to last day of previous month.
                        prevDate.setDate(1);
                        continue;
                    }

                    // Exit the loop if we found available date.
                    if (days[prevDate.getTime()]) {
                        break;
                    }
                }

                // Set day to Monday if we have weekly calendar.
                if (scope.weekly) {
                    setToMonday(prevDate);
                }

                selectDate(prevDate);
            };

            scope.clickNext = function () {
                var nextDate = new Date(scope.date);

                if (scope.weekly) {
                    nextDate.setDate(nextDate.getDate() + 7 - nextDate.getDay());
                }

                while (1) {
                    nextDate.setDate(nextDate.getDate() + 1);

                    // Stop if we hit maximum date.
                    if (nextDate.getTime() > maxDate.getTime()) {
                        return;
                    }

                    // If previous condition didn't trigger exit then we are in the range.
                    if (options.byRange) {
                        break;
                    }

                    // Try next month if this month is not available.
                    if (!months[(new Date(nextDate.getFullYear(), nextDate.getMonth(), 1)).getTime()]) {
                        // Set nextDate to last day of this month so that
                        // on next iteration it is set to first day of next month.
                        nextDate.setMonth(nextDate.getMonth() + 1);
                        nextDate.setDate(0);
                        continue;
                    }

                    // Exit loop if found available date.
                    if (days[nextDate.getTime()]) {
                        break;
                    }
                }

                // Set day to Monday if we have weekly calendar.
                if (scope.weekly) {
                    setToMonday(nextDate);
                }

                selectDate(nextDate);
            };

            scope.clickToday = function () {
                selectDate(currentDay);
            };

            scope.toggleCalendar = function () {
                scope.calendarOpened = !scope.calendarOpened;
                calculateDates();
            };
        },
    };
}]);