Add a gzip compression task

lib/tools/weightChecker/gzipCompressor.js

@@ -0,0 +1,101 @@
+var debug = require('debug')('ylt:gzipCompressor');
+
+var Q       = require('q');
+var zlib    = require('zlib');
+
+var GzipCompressor = function() {
+
+    function compressFile(entry) {
+        return gzipUncompressedFile(entry)
+
+        .then(gzipOptimizedFile);
+    }
+
+    // Gzip a file if it was not already gziped
+    function gzipUncompressedFile(entry) {
+        var deferred = Q.defer();
+
+        if (isCompressible(entry) && !entry.weightCheck.isCompressed) {
+            debug('Compression missing, trying to gzip file %s', entry.url);
+
+            var uncompressedSize = entry.weightCheck.uncompressedSize;
+
+            zlib.gzip(new Buffer(entry.weightCheck.body, 'utf8'), function(err, buffer) {
+                if (err) {
+                    debug('Could not compress uncompressed file with gzip');
+                    debug(err);
+
+                    deferred.reject(err);
+                } else {
+                    var compressedSize = buffer.length;
+
+                    if (gainIsEnough(uncompressedSize, compressedSize)) {
+                        debug('File correctly gziped, was %d and is now %d bytes', uncompressedSize, compressedSize);
+
+                        entry.weightCheck.afterCompression = compressedSize;
+                        deferred.resolve(entry);
+                    } else {
+                        debug('Gain is not enough, was %d and is now %d bytes', uncompressedSize, compressedSize);
+                    }
+                }
+            });
+        } else {
+            deferred.resolve(entry);
+        }
+
+        return deferred.promise;
+    }
+
+    // Gzip a file after minification or optimization if this step was successful
+    function gzipOptimizedFile(entry) {
+        var deferred = Q.defer();
+
+        if (isCompressible(entry) && !entry.weightCheck.isOptimized && !entry.weightCheck.isMinified) {
+            debug('Trying to gzip file after minification: %s', entry.url);
+
+            var uncompressedSize = entry.weightCheck.optimized || entry.weightCheck.minified;
+
+            zlib.gzip(new Buffer(entry.weightCheck.bodyAfterMinification, 'utf8'), function(err, buffer) {
+                if (err) {
+                    debug('Could not compress minified file with gzip');
+                    debug(err);
+
+                    deferred.reject(err);
+                } else {
+                    var compressedSize = buffer.length;
+
+                    if (gainIsEnough(uncompressedSize, compressedSize)) {
+                        debug('File correctly gziped, was %d and is now %d bytes', uncompressedSize, compressedSize);
+
+                        entry.weightCheck.afterOptimizationAndCompression = compressedSize;
+                        deferred.resolve(entry);
+                    } else {
+                        debug('Gain is not enough, was %d and is now %d bytes', uncompressedSize, compressedSize);
+                    }
+                }
+            });
+        } else {
+            deferred.resolve(entry);
+        }
+
+        return deferred.promise;
+    }
+
+    function isCompressible(entry) {
+        return entry.isJS || entry.isCSS || entry.isHTML || entry.isJSON || entry.isSVG || entry.isTTF || entry.isXML || entry.isFavicon;
+    }
+
+    // The gain is estimated of enough value if it's over 1KB or over 20%,
+    // but it's ignored if is below 100 bytes
+    function gainIsEnough(oldWeight, newWeight) {
+        var gain = oldWeight - newWeight;
+        var ratio = gain / oldWeight;
+        return (gain > 2048 || (ratio > 0.2 && gain > 100));
+    }
+
+    return {
+        compressFile: compressFile
+    };
+};
+
+module.exports = new GzipCompressor();

lib/tools/weightChecker/weightChecker.js

@@ -14,6 +14,7 @@ var request         = require('request');
 
 var imageOptimizer  = require('./imageOptimizer');
 var fileMinifier    = require('./fileMinifier');
+var gzipCompressor  = require('./gzipCompressor');
 
 
 var WeightChecker = function() {
@@ -42,6 +43,8 @@ var WeightChecker = function() {
 
                 .then(fileMinifier.minifyFile)
 
+                .then(gzipCompressor.compress)
+
                 .then(function(newEntry) {
                     callback(null, newEntry);
                 })