/*
	Calendar.js - A simple JavaScript calendar generator
	2022 by mercury0x0d, Creative Commons Attribution 4.0 International License

	Revision history:
	2022-08-05 - Added CalendarDayPart(), and also corrected a typo
	2022-07-22 - Initial version
*/





function CalendarCreate(year, month, day, element)
{
	/*
		Generates a calendar inside the DIV specified by element for the month, day, and year specified
		Adapted from https://w3schoolweb.com/how-to-create-a-calendar-in-html-and-css with the following changes:
			- Dependency upon JQuery removed
			- JavaScript changed to dynamically add the calendar details to make it easier to dynamically spawn calendars
			- Now properly accounts for leap years
			- Physically shrunken so as to not take up so much dang space

		Input:
			year		The year of the base date upon which the calendar will be generated
			month		The month (0 to 11) of the base date upon which the calendar will be generated
			day			The day of the base date upon which the calendar will be generated
			element		A DIV element inside which the calendar will be built

		Output:
			n/a
	*/


	var newDIV, newUL, newLI;
	var startDay = new Date(year, month, 1).getDay();

	var dayNames = ["SUN", "MON", "TUE", "WED", "THU", "FRI", "SAT"];
	var monthNames = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
	var monthDaysCount = ["31", "28", "31", "30", "31", "30", "31", "31", "30", "31", "30", "31"];

	var prevMonth = monthDaysCount[month - 1];


	// adjust for yeap year
	if (CalendarYearIsLeap(year)) monthDaysCount[1]++;

	// adjust for the January/December crossover
	if (month == 11)
	{
		prevMonth = monthDaysCount[0];
	} else if (month == 0) {
		prevMonth = monthDaysCount[11];
	}

	var totalDays = monthDaysCount[month];
	var counter = 0;
	var precounter = prevMonth - (startDay - 1);
	var rightbox = 6;
	var flag = true;


	// create a DIV for the month name at the top of the calendar and set the name to it
	newDIV = document.createElement("div");
	newDIV.classList.add("CalendarHeaderMonth");
	newDIV.innerText = monthNames[month].toUpperCase() + " " + year;
	element.appendChild(newDIV);


	// create a DIV for the header showing the days of the week and set the week names to it
	newDIV = document.createElement("div");
	newDIV.classList.add("CalendarHeaderDay");
	newUL = document.createElement("ul");
	newUL.classList.add("CalendarUL");
	for (var i = 0; i < dayNames.length; i++)
	{
		newLI = document.createElement("li");
		newLI.innerHTML = dayNames[i];
		newUL.appendChild(newLI);
	}
	newDIV.appendChild(newUL);
	element.appendChild(newDIV);


	// create a DIV for the header showing the days of the week and set the week names to it
	newDIV = document.createElement("div");
	newDIV.classList.add("CalendarDateSquares");
	newUL = document.createElement("ul");
	newUL.classList.add("CalendarUL");
	newDIV.appendChild(newUL);
	element.appendChild(newDIV);


	// populate that calendar!
	for (var i = 0; i < 42; i++)
	{
		if (i >= startDay)
		{
			counter++;
			if (counter > totalDays)
			{
				counter = 1;
				flag = false;
			}
			if (flag == true)
			{
				// we're on one of the days of the current month - create a new LI and set it accordingly
				newLI = document.createElement("li");
				newLI.innerHTML = counter;

				// since we're in the current month, check to see if we're on the current day and change the background color if so
				if (counter == day)
				{
					newLI.style.color = "#FFFFFF";
					newLI.style.backgroundColor = "#02548B";
				}
			} else {
				// we're on one of the days of the next month - create a new LI and set it accordingly
				newLI = document.createElement("li");
				newLI.style.backgroundColor = "#555";
				newLI.innerHTML = counter;
			}
		} else {
			// we're on one of the days of the previous month - create a new LI and set it accordingly
			newLI = document.createElement("li");
			newLI.style.backgroundColor = "#555";
			newLI.innerHTML = precounter;
			precounter++;
		}

		if (i == rightbox)
		{
			newLI.classList.add("CalendarDateSquareRight");
			rightbox = rightbox + 7;
		}

		if (i > 34)
		{
			newLI.classList.add("CalendarDateSquareBottom");
		}

		// set a couple things that would conflict if we relied upon the CSS, then tack this onto the parent
		newLI.style.width = 39;
		newLI.style.lineHeight = "30px";
		newDIV.firstElementChild.appendChild(newLI);
	}
}




function CalendarDayIsWeekday(year, month, day)
{
	/*
		Determines if the day specified is a weekday

		Input:
			month	The month of the date
			day		The day of the date
			year	The year of the date

		Output:
			Boolean
				true - The day is a weekday
				false - The day is not a weekday
	*/


	var day = new Date(year, month, day).getDay();
	return day != 0 && day != 6;
}





function CalendarDayPart(dateObject)
{
	/*
		Returns the part (morning, afternoon, evening) of the day specified
		Adapted from https://www.encodedna.com/javascript/say-good-morning-afternoon-evening-using-javascript.htm

		Input:
			dateObject		The date object whose hour will be evaluated

		Output:
			String
				morning		The hour of the date object provided was less than 12
				afternoon	The hour of the date object provided was between 12 and 17 (noon and 5:59 PM)
				evening		The hour of the date object provided was between 18 and 23 (6:00 PM and 11:59 PM)
	*/


	var hour = dateObject.getHours();
	var part;

	if (hour < 12) part = 'morning';
	else if (hour >= 12 && hour <= 17) part = 'afternoon';
	else if (hour >= 18 && hour <= 23) part = 'evening';

	return part;
}





function CalendarDaysInMonth(month, year)
{
	/*
		Returns the number of days in the month specified of the year specified

		Input:
			month	The month of the date
			year	The year of the date

		Output:
			Number of days in the month given
	*/


	return new Date(year, month + 1, 0).getDate();
}





function CalendarMonthWeekdaysCount(month, year)
{
	/*
		Returns the number of weekdays in the month specified of the year specified

		Input:
			month	The month of the date
			year	The year of the date

		Output:
			Number of weekdays in the month given
	*/


	var days = CalendarDaysInMonth(month, year);
	
	var weekdays = 0;
	for (var i = 0; i < days; i++)
	{
		if (CalendarDayIsWeekday(year, month, i+1)) weekdays++;
	}

	return weekdays;
}





function CalendarWeekdaysToDate(month, day, year)
{
	/*
		Returns the number of weekdays between now and the date specified

		Input:
			month	The month of the date
			day		The day of the date
			year	The year of the date

		Output:
			Number of weekdays between now and the date specified
	*/


	var weekdays = 0;

	for (var i = 0; i < day; i++)
	{
		if (CalendarDayIsWeekday(year, month, i+1)) weekdays++;
	}

	return weekdays;
}





function CalendarYearIsLeap(year)
{
	/*
		Determines if the given date is a leap year
		From code found at https://stackoverflow.com/questions/16353211/check-if-year-is-leap-year-in-javascript

		Input:
			year	The year to be tested

		Output:
			Boolean
				true - The year is a leap year
				false - The year is not a leap year
	*/


	return ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0);
}