(function () {

    if (typeof self === 'undefined' || !self.Prism || !self.document) {
        return;
    }

    /**
     * Class name for <pre> which is activating the plugin
     * @type {String}
     */
    var PLUGIN_CLASS = 'line-numbers';

    /**
     * Resizes line numbers spans according to height of line of code
     * @param  {Element} element <pre> element
     */
    var _resizeElement = function (element) {
        var codeStyles = getStyles(element);
        var whiteSpace = codeStyles['white-space'];

        if (whiteSpace === 'pre-wrap' || whiteSpace === 'pre-line') {
            var codeElement = element.querySelector('code');
            var lineNumbersWrapper = element.querySelector('.line-numbers-rows');
            var lineNumberSizer = element.querySelector('.line-numbers-sizer');
            var codeLines = element.textContent.split('\n');

            if (!lineNumberSizer) {
                lineNumberSizer = document.createElement('span');
                lineNumberSizer.className = 'line-numbers-sizer';

                codeElement.appendChild(lineNumberSizer);
            }

            lineNumberSizer.style.display = 'block';

            codeLines.forEach(function (line, lineNumber) {
                lineNumberSizer.textContent = line || '\n';
                var lineSize = lineNumberSizer.getBoundingClientRect().height;
                lineNumbersWrapper.children[lineNumber].style.height = lineSize + 'px';
            });

            lineNumberSizer.textContent = '';
            lineNumberSizer.style.display = 'none';
        }
    };

    /**
     * Returns style declarations for the element
     * @param {Element} element
     */
    var getStyles = function (element) {
        if (!element) {
            return null;
        }

        return window.getComputedStyle ? getComputedStyle(element) : (element.currentStyle || null);
    };

    window.addEventListener('resize', function () {
        Array.prototype.forEach.call(document.querySelectorAll('pre.' + PLUGIN_CLASS), _resizeElement);
    });

    Prism.hooks.add('complete', function (env) {
        if (!env.code) {
            return;
        }

        // works only for <code> wrapped inside <pre> (not inline)
        var pre = env.element.parentNode;
        // Original regex check for class, leaving it here
        // for its redundancy check
        var clsReg = /\s*\bline-numbers\b\s*/;
        // New regex check for opt-out class
        var clsRegB = /\s*\bno-line-numbers\b\s*/;

        if (env.element.querySelector(".line-numbers-rows")) {
            // Abort if line numbers already exists
            return;
        }

        // Added to facilitate opting out
        if (clsRegB.test(pre.className)) {
            // Respect the opt-out
            return;
        }

        if (clsReg.test(env.element.className)) {
            // Remove the class "line-numbers" from the <code>
            env.element.className = env.element.className.replace(clsReg, ' ');
        }
        if (!clsReg.test(pre.className)) {
            // Add the class "line-numbers" to the <pre>
            pre.className += ' line-numbers';
        }

        var match = env.code.match(/\n(?!$)/g);
        var linesNum = match ? match.length + 1 : 1;
        var lineNumbersWrapper;

        var lines = new Array(linesNum + 1);
        lines = lines.join('<span></span>');

        lineNumbersWrapper = document.createElement('span');
        lineNumbersWrapper.setAttribute('aria-hidden', 'true');
        lineNumbersWrapper.className = 'line-numbers-rows';
        lineNumbersWrapper.innerHTML = lines;

        if (pre.hasAttribute('data-start')) {
            pre.style.counterReset = 'linenumber ' + (parseInt(pre.getAttribute('data-start'), 10) - 1);
        }

        env.element.appendChild(lineNumbersWrapper);

        _resizeElement(pre);
    });

}());