function setCookie(label_name, value) {
    /**
     * Create a cookie for ten years?
     */
    var today = new Date();
    var expires = new Date();

    expires.setTime(today.getTime() + (10*365*24*60*60*1000));
    document.cookie = label_name + "=" + value + ";expires=" + expires.toGMTString();
}

function getCookie(label_name) {
    /**
     * Retrieve the value of a cookie due to it's label_name.
     */
    var regex = new RegExp("(?:; )?" + label_name + "=([^;]*);?");

    if (regex.test(document.cookie))
        return (RegExp["$1"]);
    else
        return null;
}

function labels_tab_to_str(labels) {
    /**
     * Transform tab of labels to string.
     * ex : [{'id_label': 1, 'label_name': "Learn C++", 'father_id': 6}]
     * = 1, Learn C++, 6|...
     */
    var result = "";
    var inter = []
    for (var i = 0; labels[i]; i++)
        inter.push([labels[i]['id'], labels[i]['label_name'], labels[i]['father_id']]);
    result = inter.join('|');
    return (result);
}

function str_to_labels_tab(str) {
    /**
     * Transform string to 2D tab.
     * Ex : "42, test, 5|56, salut, 3" =>
     * [[42, 'test', 5], [56, 'salut', 3]]
     */
    var result = [];
    var split = str.split('|');
    for (var i = 0; split[i]; i++) {
        var inter = split[i].split(',')
        if (inter.length == 2)
            result.push({'id': inter[0], 'label_name': inter[1]});
        else
            result.push({'id': inter[0], 'label_name': inter[1], 'father_id': inter[2]});
    }
    return (result);
}

function save_session() {
    /**
     * Save mandatory_labels and unselect_tab in Cookies.
     */
    setCookie("cookies_mandatory_labels", labels_tab_to_str(hierarchy.mandatory_labels));
    setCookie("cookies_forbiden_labels", labels_tab_to_str(hierarchy.forbiden_labels));
}

function setup_session() {
    /**
     * Return 0 no cookies are found return 0.
     * Else return 1 if old_tab cookie are found => the initialization of tutos
     * and labels is done from the labels contained in old_tab.
     * need to be initialise (return 0).
     */
    var success = 0;
    if (getCookie('cookies_mandatory_labels') != null && getCookie('cookies_mandatory_labels').length != 0)
        hierarchy.mandatory_labels = str_to_labels_tab(getCookie('cookies_mandatory_labels'));
    if (getCookie('cookies_forbiden_labels') != null && getCookie('cookies_forbiden_labels').length != 0)
        hierarchy.forbiden_labels = str_to_labels_tab(getCookie('cookies_forbiden_labels'));

    if (getCookie('cookies_mandatory_labels') != null && getCookie('cookies_mandatory_labels').length != 0) {
        update_elements_and_labels();
        success = 1;
    } else if (getCookie('cookies_forbiden_labels') != null && getCookie('cookies_forbiden_labels').length != 0) {
        update_elements_and_labels();
        success = 1;
    }
    return (success);
}