Add option "--timing" to mesure gitbook performances

lib/utils/timing.js

@@ -0,0 +1,89 @@
+var Immutable = require('immutable');
+var is = require('is');
+
+var timers = {};
+var startDate = Date.now();
+
+/**
+    Mesure an operation
+
+    @parqm {String} type
+    @param {Promise} p
+    @return {Promise}
+*/
+function measure(type, p) {
+    timers[type] = timers[type] || {
+        type: type,
+        count: 0,
+        total: 0,
+        min: undefined,
+        max: 0
+    };
+
+    var start = Date.now();
+
+    return p
+    .fin(function() {
+        var end = Date.now();
+        var duration = (end - start);
+
+        timers[type].count ++;
+        timers[type].total += duration;
+
+        if (is.undefined(timers[type].min)) {
+            timers[type].min = duration;
+        } else {
+            timers[type].min = Math.min(timers[type].min, duration);
+        }
+
+        timers[type].max = Math.max(timers[type].max, duration);
+    });
+}
+
+/**
+    Return a milliseconds number as a second string
+
+    @param {Number} ms
+    @return {String}
+*/
+function time(ms) {
+    if (ms < 1000) {
+        return (ms.toFixed(0)) + 'ms';
+    }
+
+    return (ms/1000).toFixed(2) + 's';
+}
+
+/**
+    Dump all timers to a logger
+
+    @param {Logger} logger
+*/
+function dump(logger) {
+    var prefix = '    > ';
+    var measured = 0;
+    var totalDuration = Date.now() - startDate;
+
+    Immutable.Map(timers)
+        .valueSeq()
+        .sortBy(function(timer) {
+            measured += timer.total;
+            return timer.total;
+        })
+        .forEach(function(timer) {
+            logger.debug.ln('Timer "' + timer.type + '" (' + timer.count + ' times) :');
+            logger.debug.ln(prefix + 'Total: ' + time(timer.total));
+            logger.debug.ln(prefix + 'Average: ' + time(timer.total / timer.count));
+            logger.debug.ln(prefix + 'Min: ' + time(timer.min));
+            logger.debug.ln(prefix + 'Max: ' + time(timer.max));
+            logger.debug.ln('---------------------------');
+        });
+
+
+    logger.debug.ln(time(totalDuration - measured) + ' spent in non-mesured sections');
+}
+
+module.exports = {
+    measure: measure,
+    dump: dump
+};