refactor($lib): Add callback wrapper around JSZip promise-based interface. Refactor m

Refactor unpack and main exported function to return optional zip, if originally provided, in
addition to the validated project.

BREAKING CHANGE: Change to main api to return originally provided zip (or null if string was
provided) along with validated project, in a 2-element array.

index.js

@@ -14,12 +14,21 @@ var analyze = require('./lib/analyze');
  * @return {Object}
  */
 module.exports = function (input, callback) {
-    async.waterfall([
-        function (cb) {
-            unpack(input, cb);
-        },
-        parse,
-        validate,
-        analyze
-    ], callback);
+    unpack(input, function(err, unpackedProject) {
+        if (err) {
+            return callback(err);
+        }
+        async.waterfall([
+            function (cb) {
+                parse(unpackedProject[0], cb);
+            },
+            validate,
+            analyze
+        ], function(err2, validatedInput) {
+            if (err2) {
+                return callback(err2);
+            }
+            callback(null, [validatedInput, unpackedProject[1]]);
+        });
+    });
 };

lib/unpack.js

@@ -1,4 +1,4 @@
-var JSZip = require('jszip');
+var zip = require('./zip');
 
 /**
  * If input a buffer, transforms buffer into a UTF-8 string.
@@ -12,13 +12,17 @@ var JSZip = require('jszip');
 module.exports = function (input, callback) {
     if (typeof input === 'string') {
         // Pass string to callback
-        return callback(null, input);
+        return callback(null, [input, null]);
     }
 
     // Validate input type
     var typeError = 'Input must be a Buffer or a string.';
     if (!Buffer.isBuffer(input)) {
-        return callback(typeError);
+        try {
+            input = new Buffer(input);
+        } catch (e) {
+            return callback(typeError);
+        }
     }
 
     // Determine format
@@ -34,17 +38,12 @@ module.exports = function (input, callback) {
     if (signature.indexOf('80 75') === 0) isZip = true;
 
     // If not legacy or zip, convert buffer to UTF-8 string and return
-    if (!isZip && !isLegacy) return callback(null, input.toString('utf-8'));
+    if (!isZip && !isLegacy) {
+        return callback(null, [input.toString('utf-8'), null]);
+    }
 
     // Return error if legacy encoding detected
     if (isLegacy) return callback('Parser only supports Scratch 2.X');
 
-    // Handle zip
-    // @todo Handle error
-    JSZip.loadAsync(input).then(function (zip) {
-        zip.file('project.json').async('string')
-            .then(function (project) {
-                callback(null, project);
-            });
-    });
+    zip(input, callback);
 };

lib/zip.js

@@ -0,0 +1,20 @@
+var JSZip = require('jszip');
+
+/**
+ * Unpacks a zip
+ *
+ * @param {String} Input
+ *
+ * @return {Object}
+ */
+module.exports = function (input, callback) {
+    JSZip.loadAsync(input).then(function (zip) {
+        zip.file('project.json').async('string')
+            .then(function (project) {
+                callback(null, [project, zip]);
+            })
+            .catch(function (err) {
+                callback(err);
+            });
+    });
+};