var currentSheet = getPreferredStyleSheet();

function toggleActiveStyleSheet() {
    if (currentSheet == "main") {
        currentSheet = "alternate";
    } else {
        currentSheet = "main";
    }
    var i, a, main;
    for (i = 0; (a = document.getElementsByTagName("link")[i]); i++) {
        if (a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title")) {
            a.disabled = true;
            if (a.getAttribute("title") == currentSheet) a.disabled = false;
        }
    }
}

function getActiveStyleSheet() {
    var i, a;
    for (i = 0; (a = document.getElementsByTagName("link")[i]); i++) {
        if (a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title") && !a.disabled) return a.getAttribute("title");
    }
    return null;
}

function getPreferredStyleSheet() {
    var i, a;
    for (i = 0; (a = document.getElementsByTagName("link")[i]); i++) {
        if (a.getAttribute("rel").indexOf("style") != -1
            && a.getAttribute("rel").indexOf("alt") == -1
            && a.getAttribute("title")
        ) console.log(a.getAttribute("title")); return a.getAttribute("title");
    }
    return null;
}

function createCookie(name, value, days) {
    if (days) {
        var date = new Date();
        date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
        var expires = "; expires=" + date.toGMTString();
    }
    else expires = "";
    document.cookie = name + "=" + value + expires + "; path=/";
}

function readCookie(name) {
    var nameEQ = name + "=";
    var ca = document.cookie.split(';');
    for (var i = 0; i < ca.length; i++) {
        var c = ca[i];
        while (c.charAt(0) == ' ') c = c.substring(1, c.length);
        if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length, c.length);
    }
    return null;
}

window.onload = () => {
    var cookie = readCookie("style");
    var title = cookie ? cookie : getPreferredStyleSheet();
    toggleActiveStyleSheet(title);

    console.log(title);

    if (title == "alternate") {
        // Change slider to go forward
        $("#slider").attr('checked', 'checked');
    }
}

window.onunload = () => {
    var title = getActiveStyleSheet();
    createCookie("style", title, 365);
}

var cookie = readCookie("style");
var title = cookie ? cookie : getPreferredStyleSheet();
toggleActiveStyleSheet(title);