/**
 * Add methods to dynamically insert and remove css styles.
 *
 * @author Jan-Hendrik Willms <tleilax+studip@gmail.com>
 * @copyright Stud.IP Core Group 2014
 * @license GPL2 or any later version
 * @since Stud.IP 3.1
 */
// "Private" stylesheet rules are applied to, generated from a dynamically
// inserted style tag in the document's header
var sheet = null;

/**
 * Dynamically add a ruleset for a given selector to the current site
 *
 * @param {string} selector - CSS selector to add rules for
 * @param {object} css - Actual css rules as hash object
 * @param {array} vendors - Optional array of vendor prefixes to apply
 */
function addRule(selector, css, vendors) {
    vendors = vendors || [];
    vendors.push('');

    var style, propText;
    if (sheet === null) {
        style = document.createElement('style');
        sheet = document.head.appendChild(style).sheet;
    }

    propText = Object.keys(css)
        .map(function(p) {
            var result = [],
                i;
            for (i = 0; i < vendors.length; i += 1) {
                result.push(vendors[i] + p + ':' + css[p]);
            }
            return result.join(';');
        })
        .join(';');

    sheet.insertRule(selector + '{' + propText + '}', sheet.cssRules.length);
}

/**
 * Removes a currently added, dynamic ruleset.
 *
 * @param {string} selector - CSS selector to remove rules for
 */
function removeRule(selector) {
    var i;
    if (sheet !== null) {
        for (i = sheet.cssRules.length - 1; i >= 0; i -= 1) {
            if (sheet.cssRules[i].selectorText === selector) {
                sheet.deleteRule(i);
            }
        }
    }
}

// Expose functions to global STUDIP object, namespaced under CSS
const CSS = {
    addRule,
    removeRule
};

export default CSS;