--- /dev/null
+/**
+ * @fileoverview Tracks performance of individual rules.
+ * @author Brandon Mills
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+/* istanbul ignore next */
+/**
+ * Align the string to left
+ * @param {string} str string to evaluate
+ * @param {int} len length of the string
+ * @param {string} ch delimiter character
+ * @returns {string} modified string
+ * @private
+ */
+function alignLeft(str, len, ch) {
+ return str + new Array(len - str.length + 1).join(ch || " ");
+}
+
+/* istanbul ignore next */
+/**
+ * Align the string to right
+ * @param {string} str string to evaluate
+ * @param {int} len length of the string
+ * @param {string} ch delimiter character
+ * @returns {string} modified string
+ * @private
+ */
+function alignRight(str, len, ch) {
+ return new Array(len - str.length + 1).join(ch || " ") + str;
+}
+
+//------------------------------------------------------------------------------
+// Module definition
+//------------------------------------------------------------------------------
+
+const enabled = !!process.env.TIMING;
+
+const HEADERS = ["Rule", "Time (ms)", "Relative"];
+const ALIGN = [alignLeft, alignRight, alignRight];
+
+/* istanbul ignore next */
+/**
+ * display the data
+ * @param {Object} data Data object to be displayed
+ * @returns {void} prints modified string with console.log
+ * @private
+ */
+function display(data) {
+ let total = 0;
+ const rows = Object.keys(data)
+ .map(key => {
+ const time = data[key];
+
+ total += time;
+ return [key, time];
+ })
+ .sort((a, b) => b[1] - a[1])
+ .slice(0, 10);
+
+ rows.forEach(row => {
+ row.push(`${(row[1] * 100 / total).toFixed(1)}%`);
+ row[1] = row[1].toFixed(3);
+ });
+
+ rows.unshift(HEADERS);
+
+ const widths = [];
+
+ rows.forEach(row => {
+ const len = row.length;
+
+ for (let i = 0; i < len; i++) {
+ const n = row[i].length;
+
+ if (!widths[i] || n > widths[i]) {
+ widths[i] = n;
+ }
+ }
+ });
+
+ const table = rows.map(row => (
+ row
+ .map((cell, index) => ALIGN[index](cell, widths[index]))
+ .join(" | ")
+ ));
+
+ table.splice(1, 0, widths.map((width, index) => {
+ const extraAlignment = index !== 0 && index !== widths.length - 1 ? 2 : 1;
+
+ return ALIGN[index](":", width + extraAlignment, "-");
+ }).join("|"));
+
+ console.log(table.join("\n")); // eslint-disable-line no-console
+}
+
+/* istanbul ignore next */
+module.exports = (function() {
+
+ const data = Object.create(null);
+
+ /**
+ * Time the run
+ * @param {*} key key from the data object
+ * @param {Function} fn function to be called
+ * @returns {Function} function to be executed
+ * @private
+ */
+ function time(key, fn) {
+ if (typeof data[key] === "undefined") {
+ data[key] = 0;
+ }
+
+ return function(...args) {
+ let t = process.hrtime();
+
+ fn(...args);
+ t = process.hrtime(t);
+ data[key] += t[0] * 1e3 + t[1] / 1e6;
+ };
+ }
+
+ if (enabled) {
+ process.on("exit", () => {
+ display(data);
+ });
+ }
+
+ return {
+ time,
+ enabled
+ };
+
+}());