script.js

/**
 * Primary script for the Harker Bell Schedule
 * Hosted at http://harkerdev.github.io/bellschedule
 **/

/**
 * CSS things
 */
addEventListener("scroll", function(event) {
    document.getElementById("header").style.left = scrollX + "px";
});

/**
 * Returns an array of values in the array that aren't in a.
 */
Array.prototype.diff = function(a) {
    return this.filter(function(i) {return a.indexOf(i) < 0;});
};

/**
 * Constants
 */
var days = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"]; //days of the week in string form
var schedules; //array of schedules (each schedule is an array in this array
var mobile = isMobile();

/**
 * Globals
 */
var displayDate; //beginning of time period currently being displayed by the schedule
var updateScheduleID; //ID of interval of updateSchedule
var hasFocus = true; //document.hasFocus() seems to be unreliable; assumes window has focus on page load
var options = {};

var urlParams; //object with GET variables as properties and their respective values as values

var inputStr = "";

var KEY_LEFT = 37;
var KEY_UP = 38;
var KEY_RIGHT = 39;
var KEY_DOWN = 40;
var KEY_A = 65;
var KEY_B = 66;
var KONAMI = "" + KEY_UP + KEY_UP + KEY_DOWN + KEY_DOWN + KEY_LEFT + KEY_RIGHT + KEY_LEFT + KEY_RIGHT + KEY_B + KEY_A;
var isDoge;

var START_DATE = new Date('August 22, 2016'); //The start day of the school year. This should be a weekday.

var START_SCHEDULE = 1; //The schedule on the first day


//On a given day, independent of rotation, after school has a fixed function. This array maps the day (0 for Monday, etc.)
//to the particular function (e.g. Extra Help). This ultimately piggybacks on the replacement system.
var COLLABORATION_REPLACEMENTS = 	[
    "Collaboration -> Office Hours",
    "Collaboration -> Office Hours",
    "Collaboration -> Faculty Meeting",
    "Collaboration -> Office Hours",
    "Collaboration -> After School"
]

var TOTAL_SCHEDULES = 8; //The number of schedules to be cycled

var SCHEDULES = ["A", "B", "C", "D", "A", "B", "C", "D"]

var MILLIS_PER_DAY = 1000 * 60 * 60 * 24;

/**
 * Gets GET variables from URL and sets them as properties of the urlParams object.
 * Then updates the state of the current history entry with the appropriate week.
 */
(function() {
    //decode GET vars in URL
    updateUrlParams();

    //update history state
    window.history.replaceState(getDateFromUrlParams(), document.title, document.location);
}());

/**
 * Event listeners
 */
document.addEventListener("visibilitychange", function(event) {
    if(!document.hidden) { //only slightly redundant; on un-minimize, document gains visibility without focus
	updateSchedule();
	// updateClock();
    }
    updateUpdateInterval();
});

addEventListener("focus", function(event) {
    updateSchedule();
    //updateClock();

    hasFocus = true;
    updateUpdateInterval();
});
addEventListener("blur", function(event) {
    hasFocus = false;
    updateUpdateInterval();
});

/**
 * Event listener for navigating through history.
 * (onload event will not fire when navigating through history items pushed by history.pushState, because the page does not reload)
 */
addEventListener("popstate", function(event) {
    updateUrlParams();
    updateSchedule(event.state);
});

/**
 * Updates urlParams object based on the GET variables in the URL.
 * (variables as properties and values as values)
 */
function updateUrlParams() {
    urlParams = {};

    var match,
	pl = /(?!^)\+/g,  //regex for replacing non-leading + with space
	search = /([^&=]+)=?([^&]*)/g,
	decode = function (s) { return decodeURIComponent(s.replace(pl, " ")); },
	query = location.search.substring(1);

    while (match = search.exec(query))
	urlParams[decode(match[1])] = decode(match[2]);
}

/**
 * Parses schedules, creates schedule for correct week, sets title title on page load.
 */
addEventListener("load", function(event) {
    initViewport();

    initTitle();

    parseRawSchedule();

    //updateSchedule();
    //updateClock();
    download("options.json", createOptions, displayOptionsError);

    isDoge = false;
});

function initViewport() {
    if(mobile) {
	var meta = document.createElement("meta");
	meta.name = "viewport";
	meta.content = 'user-scalable=no, initial-scale=1.0, maximum-scale=1.0';
	document.getElementsByTagName("head")[0].appendChild(meta);
	document.getElementsByTagName("body")[0].class = "mobile";
    }
}

/**
 * Adds appropriate event listeners to items in the schedule title.
 */
function initTitle() {
    document.getElementById("header").addEventListener("click", setTitleTitle);
    document.getElementById("leftArrow").addEventListener("click", goLast);
    document.getElementById("rightArrow").addEventListener("click", goNext);

    document.getElementById("refresh").addEventListener("click", function(){ updateSchedule(null,true) });

    setTitleTitle();
}

/**
 * Parses raw schedule in body of page into schedule array
 * Code is questionable
 */
function parseRawSchedule() {
    var rawSchedules=document.getElementById("schedules").textContent.split("\n"); //get raw schedule text
    schedules = new Array();
    var x=0; //index in schedules
    schedules[0] = new Array(); //create array of special schedule days

    while(rawSchedules.length>0){
	//loop through all lines in raw schedule text
	if(rawSchedules[0].length==0){
	    //if line is empty, move to next index in schedules
	    schedules[++x] = new Array(); //could probably use id as index instead, or just properties
	    rawSchedules.shift();
	} else{
	    //if line has text, save in current location in schedules
	    var str = rawSchedules.shift();
	    if(x==0 && str.indexOf("|")>=0){
		//behavior for blocks of dates with the same schedule
		var start = new Date(str.substring(0,str.indexOf("|")));
		var end = new Date(str.substring(str.indexOf("|")+1,str.indexOf("\t")));
		for(;start<=end;start.setDate(start.getDate()+1)){
		    schedules[0].push(start.getMonth().valueOf()+1+"/"+start.getDate()+"/"+start.getFullYear().toString().substr(-2)+str.substring(str.indexOf("\t")));
		}
	    }
	    else schedules[x].push(str);
	}
    }
}

/**
 * Displays schedule of the week of the given date/time
 */
function setDisplayDate(time, force) {
    var date = (time ? new Date(time) : getDateFromUrlParams()); //variable to keep track of current day in loop

    setDayBeginning(date);

    if(force || !displayDate || (date.valueOf()!=displayDate.valueOf())) {
	var schedule = document.getElementById("schedule"); //get schedule table

	displayDate = new Date(date);

	displayMessage = "Welcome back! Tell a freshman about <a href='http://tiny.cc/bellschedule'>tiny.cc/bellschedule</a>.";

	if(getMonday(date) > getMonday(new Date()))
	    displayMessage += "<br>This is a future date, so the schedule may be incorrect. (In particular, special/alternate schedules may be missing.)"; //display warning if date is in the future

	warn(displayMessage)
	/*warn("<b style='color:#FF8020'>UPDATE FROM STUCO!</b> Find out what Harker Student Council is working on for YOU at <a style='font-weight:bold' href='http://tiny.cc/harkerstuco'>tiny.cc/harkerstuco</a>!"
		  + "<br><b>Submit Honor Council Feedback: </b><a style='font-weight:bold' href=http://bit.ly/harkerfeedback>bit.ly/harkerfeedback</a>"
		  + "<br>Use this link <b>only</b> if you have concerns about possible breaches of academic integrity or wish to report Code of Conduct violations."
		  + "<br><b>Submit StuCo Feedback:</b> Email <a style='font-weight:bold' href=mailto:16GraceG@students.harker.org>16GraceG@students.harker.org</a>"
		  + "<br>Otherwise, direct your suggestions and concerns here."
      	  +"<br><b>Dowload the new iOS app <a href='http://goo.gl/ZDMMRp'>here</a> to get live push notifications.</b>"); //else display message*/

	/*
	  if(date.valueOf()==getMonday(new Date()).valueOf()) document.getElementById("currWeek").style.display = "none"; //hide back to current week button on current week
	  else document.getElementById("currWeek").style.display = "inline"; //else show the button
	*/
	while(schedule.rows.length) schedule.deleteRow(-1); //clear existing weeks (rows); there should only be one, but just in case...

	var week = schedule.insertRow(-1); //create new week (row)

	if(!options.enableDayView) {
	    date = getMonday(date);
	    for(var d=0;d<5;d++) {
		//for each day Monday through Friday (inclusive)
		createDay(week, date);

		date.setDate(date.getDate()+1); //increment day
	    }
	} else createDay(week, date);
    }
}

/**
 * Returns a Date object based on the current urlParams (GET variables in the URL).
 * If any part of the date is not specified, defaults to the current date/month/year.
 * If in week view, uses the Monday of the week instead of the day.
 */
function getDateFromUrlParams() {
    var date = new Date();

    if(urlParams["y"]>0) date.setFullYear("20" + urlParams["y"]);
    if(urlParams["m"]>0) date.setMonth(urlParams["m"]-1);
    if(urlParams["d"]>0) date.setDate(urlParams["d"]);

    if(!options.enableDayView) date = getMonday(date);

    return date;
}

/**
 * Displays the given warning or hides the warning div if no warning text is given.
 */
function warn(text) {
    var warning = document.getElementById("warning")

    if(text) warning.style.display = "block";
    else warning.style.display = "none";

    warning.innerHTML = text;
}

/**
 * Creates the day for the given date and appends it to the given week
 */
function createDay(week, date) {
    var daySchedule = getDayInfo(date); //get schedule for that day

    var col = week.insertCell(-1); //create cell for day
    col.date = date.valueOf(); //store date in cell element

    if(date.getMonth()==9 && date.getDate()==31) //check Halloween
	col.classList.add("halloween");

    var head = document.createElement("div"); //create header div in cell
    head.classList.add("head");
    var headWrapper = document.createElement("div");
    headWrapper.classList.add("headWrapper");
    var scheduleString = ""; //Should we display the schedule id (e.g. A) next to the date
    //Make sure not to display anything if daySchedule is empty
    if (typeof daySchedule.name != 'undefined' || daySchedule.name != null){
    	//Not a weekend, so add
    	scheduleString = "(" + daySchedule.name + ")";
    }
    if (scheduleString === "()") {
    //It's a holiday so delete the extra parenthesis
    scheduleString = "";}
    headWrapper.innerHTML = days[date.getDay()] + "<div class=\"headDate\">" + daySchedule.dateString + " " + scheduleString + "</div>"; //Portion commented out represents schedule id of that day
    head.appendChild(headWrapper);
    col.appendChild(head);

    var prevEnd = "8:00"; //set start of day to 8:00AM
    // for sub periods, passing periods are already handled and do not need to be added in the next iteration

    if(daySchedule.index > 0) { //populates cell with day's schedule (a bit messily)
		for(var i=1;i<schedules[daySchedule.index].length;i++) {

	    	var text = schedules[daySchedule.index][i];
	    	var periodName = makePeriodNameReplacements(text.substring(0,text.indexOf("\t")), daySchedule.replacements);
	    	var periodTime = text.substring(text.indexOf("\t")+1);

	    	var start = periodTime.substring(0,periodTime.indexOf("-"));
	    	var end = periodTime.substring(periodTime.lastIndexOf("-")+1);

	    	// only creates a new passing period before the period if either 1) it's a split lunch period in the new schedule or
	    	// 2) the date is not within the bounds of the new schedule
			if(options.showPassingPeriods) {
	    		var passing = document.createElement("div");
	    		passing.classList.add("period");
	    		createPeriod(passing,"",prevEnd,start,date);
	    		col.appendChild(passing);
			}

	    	prevEnd = end;

	    	var period = document.createElement("div");
	    	period.classList.add("period");

	    	if(periodName.indexOf("|") >= 0) {
				//handle split periods (i.e. lunches)
				var table = document.createElement("table");
				table.classList.add("lunch");
				var row = table.insertRow(-1);

				var period1 = row.insertCell(-1);
				var period2 = row.insertCell(-1);

				var period1Time = periodTime.substring(0,periodTime.indexOf("||"));
				var period2Time = periodTime.substring(periodTime.indexOf("||")+2);

				var period1Name = periodName.substring(0, periodName.indexOf("||"));
				var period2Name = periodName.substring(periodName.indexOf("||")+2);

				//If there are two sets of subperiods (i.e. a|b||c|d) there should be 4 "|"s
				if (findNumberOfOccurences(periodName, "|") == 4) {
					show1Time = true;
					show2Time = true;

					createSubPeriods(
						period1,
						period1Name,
						start,
						period1Time.substring(period1Time.indexOf("-")+1,period1Time.indexOf("|")),
						period1Time.substring(period1Time.indexOf("|")+1,period1Time.lastIndexOf("-")),
						end,
						date,
						show1Time,
						show2Time
		    		);

					createSubPeriods(
						period2,
						period2Name,
						start,
						period2Time.substring(period2Time.indexOf("-")+1,period2Time.indexOf("|")),
						period2Time.substring(period2Time.indexOf("|")+1,period2Time.lastIndexOf("-")),
						end,
						date,
						show1Time,
						show2Time
		    		);
				}
				else {
					//parent, name, start, end, date
					createPeriod(
		    			period1,
		    			period1Name,
		    			start,
		    			end,
		    			date
		   			)

					show1Time = daySchedule.id == 4 || daySchedule.id == "ReCreate";
					show2Time = !(show1Time);
					//parent, name, start1, end1, start2, end2, date, show 1st, show 2nd
					createSubPeriods(
						period2,
						period2Name,
						start,
						period2Time.substring(period2Time.indexOf("-")+1,period2Time.indexOf("|")),
						period2Time.substring(period2Time.indexOf("|")+1,period2Time.lastIndexOf("-")),
						end,
						date,
						show1Time,
						show2Time
			    	);
				}
		    	
 				period.appendChild(table);
			} else {
		    	createPeriod(period,periodName,start,end,date);
		    	//parent, name, start, end, date
		    	//createSubPeriods(
					//lunch2,
					//periodName.substring(periodName.indexOf("||")+2),
					//start,
					//lunch2Time.substring(lunch2Time.indexOf("-")+1,lunch2Time.indexOf("|")),
					//lunch2Time.substring(lunch2Time.indexOf("|")+1,lunch2Time.lastIndexOf("-")),
					//end,
					//date
		    	//);
			}
		    col.appendChild(period);
	    }
	}
}

/**
 * Returns new name for period based on array of replacements.
 * If the current period name is listed in the array of replacements, returns the new, replaced name; otherwise, returns current name.
 * replacements is an array of strings of the form "OldName->NewName"
 */
function makePeriodNameReplacements(periodName, replacements) {
    if(replacements.length > 0) {
	for(var i=0;i<replacements.length;i++) {
	    if(!replacements[i].indexOf(periodName))
		return replacements[i].substring(replacements[i].indexOf("->")+2);
	}
    }
    return periodName;
}

/**
 * Sets the title of the title to a random line from the title titles list
 */
function setTitleTitle() {
    var titles = document.getElementById("titleTitles").textContent.split("\n");
    document.getElementById("title").title=titles[Math.floor(Math.random()*titles.length)];
}

/**
 * Returns the Monday of next week if date is Saturday; else returns the Monday of that week
 */
function getMonday(d) {
    var date = new Date(d);
    if(date.getDay()>=6) date.setDate(date.getDate()+2); //set date to next Monday if today is Saturday
    else date.setDate(date.getDate()-date.getDay()+1); //else set date Monday of this week
    setDayBeginning(date); //set to beginning of day
    return date;
}

/**
 * Sets given date to beginning of the day (12:00 AM).
 */
function setDayBeginning(date) {
    date.setHours(0,0,0,0);
}

/**
 * Takes in a date and a string of form "hh:MM" and turns it into a time on the day of the given date.
 * Assumes hours less than 7 are PM and hours 7 or greater are AM.
 */
function getDateFromString(string, date) {
    var hour = string.substring(0,string.indexOf(":"));
    var min = string.substring(string.indexOf(":")+1);
    if(hour<7) hour = parseInt(hour,10)+12; //assumes hours less than seven are PM and hours 7 or greater are AM
    return new Date(date.getFullYear(),date.getMonth(),date.getDate(),hour,min);
}

/**
 * For given day, returns index of schedule id in schedules, schedule id, and formatted date (mm/dd/yy).
 * Schedule id index is 0 if not found in schedules.
 */
function getDayInfo(day) {
    var dateString = day.getMonth().valueOf()+1 + "/" + day.getDate().valueOf() + "/" + day.getFullYear().toString().substr(-2); //format in mm/dd/YY

    var id;
    var index = 0;
    var replacements = [];

    for(var i=0;i<schedules[0].length;i++) //search for special schedule on day
	if(!schedules[0][i].indexOf(dateString)){
	    //found special schedule
	    if(schedules[0][i].indexOf("[") >= 0) { //check for period replacements
		//cut replacements and space character out of id and save separately
		id = schedules[0][i].substring(schedules[0][i].indexOf("\t")+1,schedules[0][i].indexOf("[")-1)
		replacements = schedules[0][i].substring(schedules[0][i].indexOf("[")+1,schedules[0][i].indexOf("]")).split(",");
	    } else {
		// no replacements to be made
		id = schedules[0][i].substring(schedules[0][i].indexOf("\t")+1);
	    }

	    index = getScheduleIndex(id);
	}

    if(id === undefined) { //no special schedule found
		id = day.getDay();
		if(id==0 || id==6) index = id = 0; //no school on weekends
		else { //default schedule for that day
			id = calculateScheduleRotationID(day);
			index = getScheduleIndex(id);
			//Utilizes the replacement system and the fixed mapping to determine
			//and display the particular after school function on a given day.
			//Note that this is completely independent of the rotation of the
			//schdule.
			replacements = [COLLABORATION_REPLACEMENTS[day.getDay() - 1]];
		}
    }

    var name = "";

    if (id <= TOTAL_SCHEDULES) {
    	name = SCHEDULES[id - 1];
    }

    return { "index": index, "id": id, "dateString": dateString, "replacements": replacements, "name": name };
}

/**
 * Gets the index in the list of schedules of the schedule with the given schedule id (or 0 if no matching schedules were found)
 */
function getScheduleIndex(id) {
    if(id==0) return 0; //schedule id 0 represents no school
    for(var i=1;i<schedules.length;i++) { //find index of schedule id
	if(id==schedules[i][0]) return i; //found specified schedule id
    }
    return 0; //couldn't find specified schedule
}

/**
 * Determines which schedule should be displayed given the four block rotation.
 * This futher factors out weekends and holidays when
 * considering which day to display. Relies on a known starting anchor day with
 * a given schedule and continues the cycle from there.
 */
function calculateScheduleRotationID(date) {
    var daysDifference = (date.getTime() - START_DATE.getTime()) / MILLIS_PER_DAY;
    var weeksDifference = Math.floor(daysDifference / 7);
    //Factor out weekends (2 days per week)
    daysDifference -= weeksDifference * 2;
    //Factor out holidays
    var dateExp = /\d{1,2}\/\d{1,2}\/\d{2}/ //Finds dates of the format M(M)/D(D)/YY
    for (var i = 0; i < schedules[0].length; i++) {
		var entry = schedules[0][i];

		if (entry.search(dateExp) != -1) {
			//Parse entry into date and id
			var dateString = entry.split("\t")[0];
			//Convert the date to format M(M)/D(D)/YYYY because Date defaults to 1900s
			dateString = dateString.substring(0, dateString.length - 2) + "20" + dateString.substring(dateString.length - 2);
			var entryDate = new Date(dateString);
			var entryId = entry.split("\t")[1];
			//If the checked schedule "entry" is a holiday in the future that occurs
			//before the date that is being calculated "date" but after the start of
			//pilot program, don't consider it in the cycle
			if (getScheduleIndex(entryId) == 0 && date > entryDate && entryDate > START_DATE) {
				daysDifference--;
			}
		}
    }

    var id;

    if (daysDifference < 0) //Different formula needed for events before start day
		id = START_SCHEDULE + Math.floor(daysDifference % TOTAL_SCHEDULES) + TOTAL_SCHEDULES;
    else
		id = START_SCHEDULE + Math.floor(daysDifference % TOTAL_SCHEDULES);

	//Even schedules repeat (2 and 6 are the same and 4 and 8 are the same)
	if (id > 4 && id % 2 == 0)
		id = id - 4;

	return id;
}

/**
 * Creates and returns a new period wrapper with the given content and start/end times.
 * Also applies any special properties based on period length (text on single line if too short, block period if longer than regular).
 */
function createPeriod(parent, name, start, end, date, showTime) {
	//Do not show time for very small periods (e.g. class meetings)
	if(typeof(showTime) === "undefined") showTime = true;
    startDate = getDateFromString(start,date);
    endDate = getDateFromString(end,date);

    var periodWrapper = document.createElement("div");
    periodWrapper.classList.add("periodWrapper");
    periodWrapper.periodName = name;
    periodWrapper.start = startDate;
    periodWrapper.end = endDate;
    var length = (endDate-startDate)/60000;
    if (options.color==true)
    {
    if (periodWrapper.periodName == "P1")
    {
    	periodWrapper.classList.add("periodone");
    }
    if (periodWrapper.periodName =="P2")
    {
    	periodWrapper.classList.add("periodtwo");
    }
    if (periodWrapper.periodName =="P3")
    {
    	periodWrapper.classList.add("periodthree");
    }
    if (periodWrapper.periodName == "P4")
    {
    	periodWrapper.classList.add("periodfour");
    }
    if (periodWrapper.periodName == "P5" ||periodWrapper.periodName == "P6")
    {
    	periodWrapper.classList.add("lunchperiod");
    }
    if (periodWrapper.periodName == "Lunch")
    {
    	periodWrapper.classList.add("lunchtime");
    }
    if (periodWrapper.periodName == "P7")
    {
    	periodWrapper.classList.add("periodseven");
    }
    if (periodWrapper.periodName == "P8")
    {
    	periodWrapper.classList.add("periodeight");
    }
    if (periodWrapper.periodName == "School Meeting" || periodWrapper.periodName == "Advisory") 
    {
    	periodWrapper.classList.add("meeting");
    }
    if (periodWrapper.periodName == "Extra Help")
    {
    	periodWrapper.classList.add("extrahelp");
    }
}
    if(length > 0) {
	periodWrapper.style.height = (length-1) + "px"; //minus 1 to account for 1px border

	if(length >= 15) {
	    if(name) periodWrapper.innerHTML = name;
	    //Force long periods (30 minutes and up) to have a time
	    if(showTime) periodWrapper.innerHTML += (length<30 ? " " : "<br />") + start + " – " + end;
	    //if(length>50 && !name.indexOf("P")) //handle block periods (class=long, i.e. bold text)
		//periodWrapper.classList.add("long");
	}

	return parent.appendChild(periodWrapper);
    }
}

/**
 * Creates and appends two new sub-periods and passing period to parent period with given start and end times.
 */
function createSubPeriods(parent, name, start1, end1, start2, end2, date, showFirstTime, showSecondTime) {
	console.log(showSecondTime);
	if (typeof(showFirstTime) === "undefined") showFirstTime = true;
	if (typeof(showSecondTime) === "undefined") showSecondTime = true;

    var p1 = document.createElement("div");
    p1.classList.add("period");
    createPeriod(
	p1,
	name.substring(0,name.indexOf("|")),
	start1,
	end1,
	date,
	showFirstTime);
    parent.appendChild(p1);

    if(options.showPassingPeriods) {
	var lunchPassing = document.createElement("div");
	lunchPassing.classList.add("period");
	createPeriod(lunchPassing,"",end1,start2,date);
	parent.appendChild(lunchPassing);
    }

    var p2 = document.createElement("div");
    p2.classList.add("period");
    //var w2 = document.createElement("div");
    //w2.classList.add("periodWrapper");
    createPeriod(
	p2,
	name.substring(name.indexOf("|")+1),
	start2,
	end2,
	date,
	showSecondTime);
    parent.appendChild(p2);
}

/**
 * Creates and appends just three new sub-periods (passing periods added manually) with given start and end times.
 */
function create3SubPeriods(parent, name1, start1, end1, name2, start2, end2, name3, start3, end3, date) {
    var p1 = document.createElement("div");
    p1.classList.add("period");
    createPeriod(
	p1,
	name1,
	start1,
	end1,
	date);
    parent.appendChild(p1);

    var p2 = document.createElement("div");
    p2.classList.add("period");
    //var w2 = document.createElement("div");
    //w2.classList.add("periodWrapper");
    createPeriod(
	p2,
	name2,
	start2,
	end2,
	date);
    parent.appendChild(p2);

    var p3 = document.createElement("div");
    p3.classList.add("period");
    createPeriod(
	p3,
	name3,
	start3,
	end3,
	date);
    parent.appendChild(p3);
}

/**
 * Navigates schedule to previous date.
 */
function goLast() {
    var date = new Date(displayDate);
    date.setDate(date.getDate() - (options.enableDayView ? 1 : 7));
    updateSchedule(date);

    updateSearch(date);
}

/**
 * Navigates schedule to next date.
 */
function goNext() {
    var date = new Date(displayDate);
    date.setDate(date.getDate() + (options.enableDayView ? 1 : 7));
    updateSchedule(date);

    updateSearch(date);
}

/**
 * Navigates schedule to current date.
 */
function goCurr() {
    var date = new Date();
    updateSchedule(date);

    updateSearch(date);
}

/**
 * Updates GET variables and urlParams to reflect date in week and pushes corresponding history state.
 */
function updateSearch(week, noHistory) {
    var curr = new Date();

    if(!options.enableDayView) curr = getMonday(curr);

    if(week.getDate() != curr.getDate()) {
	urlParams["m"] = week.getMonth()+1;
	urlParams["d"] = week.getDate();
    } else {
	delete urlParams["m"];
	delete urlParams["d"];
    }
    if(week.getYear() != curr.getYear()) urlParams["y"] = week.getFullYear().toString().substr(-2);
    else delete urlParams["y"];

    var search = "?";
    for(var param in urlParams) search += param + "=" + urlParams[param] + "&";
    search = search.slice(0,-1);

    history.pushState(week, document.title, location.protocol + "//" + location.host + location.pathname + search + location.hash);
}

/**
 * Highlights given date/time on the schedule; defaults to now if none is given
 */
function setHighlightedPeriod(time) {
    //set default time argument
    if(!time) time = Date.now();

    //set date based on time (for finding day to highlight)
    var date = new Date(time);
    date.setHours(0,0,0,0);

    //clear previous highlighted day/periods
    //TODO: maybe it would be better to not clear highlights when nothing needs to be changed.
    var prevDay = document.getElementById("today");
    var prevPeriods = [];
    if(prevDay){
	//clear previous highlighted periods
	prevPeriods = Array.prototype.slice.call(prevDay.getElementsByClassName("now")); //get copy of array, not reference to it (needed to check for period changes later)

	for(var i=prevPeriods.length-1;i>=0;i--){
	    var prevPeriod = prevPeriods[i];
	    prevPeriod.classList.remove("now");
	    //remove period length
	    var periodLength = prevPeriod.getElementsByClassName("periodLength")[0];
	    if(periodLength) prevPeriod.removeChild(periodLength);
	}

	//clear previous highlighted day
	//needs to be done after getting prevPeriods, or else prevDay no longer points anywhere
	prevDay.id = "";
    }

    //set new highlighted day/period
    var days = document.getElementById("schedule").rows[0].cells;
    for(var d=0;d<days.length;d++){
	var day = days[d];
	if(date.valueOf() == day.date){ //test if date should be highlighted
	    //set new highlighted day
	    day.id = "today";

	    //set new highlighted periods
		    var periods = day.getElementsByClassName("periodWrapper");
		    for(var p=0;p<periods.length;p++)
		    {
			var period = periods[p];
			if(time-period.start>=0 && time-period.end<0){ //test if period should be highlighted
			    period.classList.add("now");
			    //add period length if it fits
			    if((period.end-period.start)/60000>=40){
				var length = (period.end - time) / 60000;
				period.innerHTML += "<div class=\"periodLength\">" +
				    (length>1 ?
				     Math.round(length) + " min. left</div>" :
				     Math.round(length*60) + " sec. left</div>");
			   
		}
			}
	    		}
	}
    }

    if(options.enablePeriodNotifications) {
	var currPeriods = Array.prototype.slice.call(document.getElementsByClassName("now")); //needs to be an array and not an HTML

	var diff1 = currPeriods.diff(prevPeriods);
	var diff2 = prevPeriods.diff(currPeriods);

	for(var i=0; i<diff1.length; i++) {
	    var name = currPeriods[i].periodName;
	    if(name && !hasFocus) sendNotification(name + " has started.", options.notificationDuration);
	}
	for(var i=0; i<diff2.length; i++) {
	    var name = prevPeriods[i].periodName;
	    if(name && !hasFocus) sendNotification(name + " has ended.", options.notificationDuration);
	}
    }
}

/**
 * Updates schedule to display as it would on the given date/time; defaults to now if none is given.
 * Also updates
 */
function updateSchedule(time,force) {
    setDisplayDate(time,force);
    setHighlightedPeriod();
}
/**
 * Expands the options div and changes the options arrow to point down and to the right.
 */
function expandOptions() {
    document.getElementById("options").classList.add("expanded");
    document.getElementById("optionsArrow").innerHTML = "&#8600;";
}
/**
 * Contracts the options div and changes the options arrow to point up and to the left.
 */
function contractOptions() {
    document.getElementById("options").classList.remove("expanded");
    document.getElementById("optionsArrow").innerHTML = "&#8598;";
}
/**
 * Toggles the options div between extended and contracted and updates options arrow accordingly.
 */
function toggleOptions() {
    if(document.getElementById("options").classList.contains("expanded"))
	contractOptions();
    else expandOptions();

}

/**
 * Initializes automatic option saving and sets options to previously-saved values, if any.
 * If no previous saved value exists, sets current (default) value as saved value.
 */
function initOptions() {
    var opt = document.getElementById("options");
    opt.addEventListener("mouseover", expandOptions);
    opt.addEventListener("mouseout", contractOptions);

    if(mobile) opt.classList.add("mobile");

    document.getElementById("optionsArrow").addEventListener("click", toggleOptions);

    var inputs = opt.getElementsByTagName("input");

    if(localStorage.updateScheduleInterval) {
	//rename key
	localStorage.activeUpdateInterval=localStorage.updateScheduleInterval;
	localStorage.removeItem("updateScheduleInterval");
    }

    for(var i=0; i<inputs.length; i++)
    {
	var input = inputs[i];
	//special cases because localStorage saves values as strings
	if(input.type=="checkbox") {											//booleans
	    input.addEventListener("change", function(event) {
		options[event.target.name] = localStorage[event.target.name] = event.target.checked;
	    });

	    if(localStorage[input.name]) options[input.name] = input.checked = localStorage[input.name]=="true";
	    else options[input.name] = localStorage[input.name] = input.checked;
	}
	else if(input.type=="number") {										//numbers
	    input.addEventListener("change", function(event) {
		options[event.target.name] = parseInt(localStorage[event.target.name] = event.target.value);
	    });

	    if(localStorage[input.name]) options[input.name] = parseInt(input.value = localStorage[input.name]);
	    else options[input.name] = parseInt(localStorage[input.name] = input.value);
	}
	else {																//strings
	    input.addEventListener("change", function(event) {
		options[event.target.name] = localStorage[event.target.name] = event.target.value;
	    });

	    if(localStorage[input.name]) options[input.name] = input.value = localStorage[input.name];
	    else options[input.name] = localStorage[input.name] = input.value;
	}
    }
}

/**
 * Creates options in the options div.
 */
function createOptions(data) {
    // just assume the file has everything for now
    JSON.parse(data).sections.forEach(function(section) {
	if(!section.hasOwnProperty("platforms") ||
	   ((mobile && section.platforms.indexOf("mobile") >= 0) || !mobile)) {
	    createOptionSection(section);
	}
    });

    initOptions();
    attachOptionActions();

    updateSchedule(null, true);
}

/**
 * Displays error about retrieving schedule.
 */
function displayOptionsError(timeout, status) {
    updateSchedule();

    if(timeout) {
	warn("Retrieval of options.json timed out!");
    } else {
	warn("Something went wrong while retrieving options.json!");
    }
}

/**
 * Create and insert options section.
 */
function createOptionSection(section) {
    createOptionSectionTitle(section);
    section.options.forEach(function(option) {
	if(!option.hasOwnProperty("platforms") ||
	   ((mobile && option.platforms.indexOf("mobile") >= 0) || !mobile)) {
	    createOption(option);
	}
    });
}

/**
 * Create and insert options section title.
 */
function createOptionSectionTitle(section) {
    var tr = document.createElement("tr");
    var th = document.createElement("th");
    th.colspan = 2;
    if(section.hasOwnProperty("tooltip")) {
	var span = document.createElement("span");
	span.title = section["tooltip"];
	span.innerHTML = section.name + '<sup class="tooltipIndicator">?</sup>';
	th.appendChild(span);
    } else {
	th.textContent = section.name;
    }
    tr.appendChild(th);
    document.getElementById("optionsContent").appendChild(tr);
}

/**
 * Create and insert option into options.
 */
function createOption(option) {
    var tr = document.createElement("tr");
    var tddesc = document.createElement("td");
    var tdinput = document.createElement("td");
    if(option.hasOwnProperty("tooltip")) {
	var span = document.createElement("span");
	span.title = option.tooltip;
	span.innerHTML = option.description + '<sup class="tooltipIndicator">?</sup>:';
	tddesc.appendChild(span);
    } else {
	tddesc.textContent = option.description + ":";
    }
    var input = document.createElement("input");
    input.name = option.name;
    input.type = option.type;
    var defaultValue = (mobile && option.hasOwnProperty("mobileDefault")) ? option.mobileDefault : option.default; //choose desktop or mobile default value
    if(input.type == "number") {
	input.min = 0; //may as well keep this here until any options can take negative
	input.value = defaultValue;
    } else if(input.type == "checkbox") {
	if(defaultValue) input.checked = "checked";
    }
    tdinput.appendChild(input);
    tr.appendChild(tddesc);
    tr.appendChild(tdinput);
    document.getElementById("optionsContent").appendChild(tr);
}

/**
 * Creates event listeners for option-specific actions on option change and applies option-specific actions on page load.
 */
function attachOptionActions() {
    updateUpdateInterval();
    document.getElementsByName("activeUpdateInterval")[0].addEventListener("change", function(event) {
	updateUpdateInterval();
    });
    document.getElementsByName("showPassingPeriods")[0].addEventListener("change", function(event) {
	updateSchedule(null,true);
    });
    document.getElementsByName("color")[0].addEventListener("change", function(event) {
	updateSchedule(null,true);
    });

    document.getElementsByName("enablePeriodNotifications")[0].addEventListener("change", function(event) {
	if(options.enablePeriodNotifications) {
	    var permission = Notification.permission;
	    if(!("Notification" in window)) {
		alert("This browser does not support desktop notifications.");
	    } else if(permission == "denied") {
		alert("Please allow desktop notifications for this site to enable this feature.");
	    } else if(permission == "default") {
		Notification.requestPermission();
	    }
	}
    });

    document.body.classList.add(options.enableDayView ? "day" : "week");
    document.getElementsByName("enableDayView")[0].addEventListener("change", function(event) {
	updateSchedule(null, true);

	document.body.classList.remove("week");
	document.body.classList.remove("day");
	document.body.classList.add(options.enableDayView ? "day" : "week");

	scrollTo(0,0); //scroll back to top-left corner
    });

    if(!mobile) {
	document.addEventListener("keydown", function(event) {
	    switch (event.keyCode){
	    case 116 : //F5
		if(options.interceptF5){
		    //enabled
		    event.preventDefault();
		    updateSchedule();
		}
		break;
	    case 82 : //R key
		if(options.interceptCtrlR && (event.ctrlKey||event.metaKey)){
		    //enabled and control/cmd (meta)
		    event.preventDefault();
		    updateSchedule();
		}
		break;
	    case 37 : //Left arrow
		goLast();
		break;
	    case 39 : //Right arrow
		goNext();
		break;
	    case 40 : //Down arrow
		goCurr();
		break;
	    }
	    inputStr += event.keyCode;
	    if (inputStr.indexOf(KONAMI) != -1) {
		isDoge = !isDoge;
		setDoge(isDoge);
		inputStr = "";
	    }
	});

	/*setDoge(options.enableDoge);
	  document.getElementsByName("enableDoge")[0].addEventListener("change", function(event) {
	  setDoge(event.target.checked);
	  });*/ // in light of recent complaints, doge mode has been discontinued (1/28/2015)
    }
}

/**
 * Retrieve file data via XMLHttpRequest.
 *
 * cb is for successful retrieval and takes a String as a parameter.
 * errcb is for an error on retrieval and takes:
 *    1. a boolean representing whether or not the error was a timeout.
 *    2. an integer representing the status of the response (this is null on timeout).
 */
function download(url, cb, errcb) {
    var xmlhttp = new XMLHttpRequest();
    xmlhttp.open("GET", url, true);
    xmlhttp.onreadystatechange = function() {
	if(xmlhttp.readyState == 4) {
	    if(xmlhttp.status == 200) {
		cb(xmlhttp.responseText);
	    } else if(errcb) {
		errcb(false, xmlhttp.status);
	    }
	}
    };
    xmlhttp.ontimeout = function() {
	errcb(true, null);
    };
    xmlhttp.send();
}

/**
 * Sets the correct update interval based on the current state (focus and visibility) of the document.
 */
function updateUpdateInterval() {
    if(document.hidden) setUpdateInterval(options.hiddenUpdateInterval); //assume that hidden implies no focus
    else if(hasFocus) setUpdateInterval(options.activeUpdateInterval);
    else setUpdateInterval(options.inactiveUpdateInterval);
}

/**
 * Updates the interval for automatically refreshing the page.
 * seconds is the new interval in seconds.
 */
function setUpdateInterval(seconds) {
    clearInterval(updateScheduleID);
    if(seconds>0)
	updateScheduleID = setInterval(function() {
	    //updateClock();
	    updateSchedule();
	}, seconds * 1000); //convert to milliseconds
    else updateScheduleID = null;
}

/**
 * Creates a desktop notification with the given text for a title and removes it after the given duration in seconds.
 * A duration of 0 or less will disable auto-closing the notification.
 */
function sendNotification(text, duration) {
    if("Notification" in window) { //check that browser supports notifications
	var notification = new Notification(text);
	if(duration > 0)
	    setTimeout(function() {notification.close();}, duration*1000);
    }
}

/**
 * Function to detect whether the page is being displayed on a mobile device.
 * Currently checks if the useragent/vendor matches a regex string for mobile phones.
 */
function isMobile() {
    var a = navigator.userAgent || navigator.vendor || window.opera;
    if(window.innerWidth <= 800 && window.innerHeight <= 600) return true;
    return /(android|bb\d+|meego).+mobile|avantgo|bada\/|blackberry|blazer|compal|elaine|fennec|hiptop|iemobile|ip(hone|od)|iris|kindle|lge |maemo|midp|mmp|mobile.+firefox|netfront|opera m(ob|in)i|palm( os)?|phone|p(ixi|re)\/|plucker|pocket|psp|series(4|6)0|symbian|treo|up\.(browser|link)|vodafone|wap|windows (ce|phone)|xda|xiino/i.test(a) || /1207|6310|6590|3gso|4thp|50[1-6]i|770s|802s|a wa|abac|ac(er|oo|s\-)|ai(ko|rn)|al(av|ca|co)|amoi|an(ex|ny|yw)|aptu|ar(ch|go)|as(te|us)|attw|au(di|\-m|r |s )|avan|be(ck|ll|nq)|bi(lb|rd)|bl(ac|az)|br(e|v)w|bumb|bw\-(n|u)|c55\/|capi|ccwa|cdm\-|cell|chtm|cldc|cmd\-|co(mp|nd)|craw|da(it|ll|ng)|dbte|dc\-s|devi|dica|dmob|do(c|p)o|ds(12|\-d)|el(49|ai)|em(l2|ul)|er(ic|k0)|esl8|ez([4-7]0|os|wa|ze)|fetc|fly(\-|_)|g1 u|g560|gene|gf\-5|g\-mo|go(\.w|od)|gr(ad|un)|haie|hcit|hd\-(m|p|t)|hei\-|hi(pt|ta)|hp( i|ip)|hs\-c|ht(c(\-| |_|a|g|p|s|t)|tp)|hu(aw|tc)|i\-(20|go|ma)|i230|iac( |\-|\/)|ibro|idea|ig01|ikom|im1k|inno|ipaq|iris|ja(t|v)a|jbro|jemu|jigs|kddi|keji|kgt( |\/)|klon|kpt |kwc\-|kyo(c|k)|le(no|xi)|lg( g|\/(k|l|u)|50|54|\-[a-w])|libw|lynx|m1\-w|m3ga|m50\/|ma(te|ui|xo)|mc(01|21|ca)|m\-cr|me(rc|ri)|mi(o8|oa|ts)|mmef|mo(01|02|bi|de|do|t(\-| |o|v)|zz)|mt(50|p1|v )|mwbp|mywa|n10[0-2]|n20[2-3]|n30(0|2)|n50(0|2|5)|n7(0(0|1)|10)|ne((c|m)\-|on|tf|wf|wg|wt)|nok(6|i)|nzph|o2im|op(ti|wv)|oran|owg1|p800|pan(a|d|t)|pdxg|pg(13|\-([1-8]|c))|phil|pire|pl(ay|uc)|pn\-2|po(ck|rt|se)|prox|psio|pt\-g|qa\-a|qc(07|12|21|32|60|\-[2-7]|i\-)|qtek|r380|r600|raks|rim9|ro(ve|zo)|s55\/|sa(ge|ma|mm|ms|ny|va)|sc(01|h\-|oo|p\-)|sdk\/|se(c(\-|0|1)|47|mc|nd|ri)|sgh\-|shar|sie(\-|m)|sk\-0|sl(45|id)|sm(al|ar|b3|it|t5)|so(ft|ny)|sp(01|h\-|v\-|v )|sy(01|mb)|t2(18|50)|t6(00|10|18)|ta(gt|lk)|tcl\-|tdg\-|tel(i|m)|tim\-|t\-mo|to(pl|sh)|ts(70|m\-|m3|m5)|tx\-9|up(\.b|g1|si)|utst|v400|v750|veri|vi(rg|te)|vk(40|5[0-3]|\-v)|vm40|voda|vulc|vx(52|53|60|61|70|80|81|83|85|98)|w3c(\-| )|webc|whit|wi(g |nc|nw)|wmlb|wonu|x700|yas\-|your|zeto|zte\-/i.test(a.substr(0, 4));
}

/**
 * Updates the time on the bell schedule
 */
function updateClock() {
    var now = new Date();
    var h = now.getHours();
    var h12 = h%12;
    var m = now.getMinutes();
    document.getElementById('currentTime').innerHTML = (h12==0 ? 12: h12) + ":" + addLeadingZero(m) + (h>=12 ? " PM" : " AM");
}

/**
 * Adds leading zeroes as necessary to make output (at least) 2 characters long
 * (Assumes that n is an integer.)
 */
function addLeadingZero(n) {
    return (n<10) ? "0"+n : n;
}

/**
 * Checks if two dates are the same, ignoring hours, minutes, and seconds
 */
function isSameDate(d1, d2) {
	return (
    	d1.getFullYear() === d2.getFullYear() &&
    	d2.getMonth() === d2.getMonth() &&
    	d1.getDate() === d2.getDate()
  	);
}

/**
 * Determines how many times the character or character sequence
 * char appears in str. 
 */
function findNumberOfOccurences(str, char) {
	for(var count=-1,index=-2; index != -1; count++,index=str.indexOf(char,index+1) );
	return count;
}