storage: add response-content-* parameters to signed url

lib/storage/file.js

@@ -1019,12 +1019,22 @@ File.prototype.getSignedPolicy = function(options, callback) {
  *     link will expire.
  * @param {string=} options.extensionHeaders - If these headers are used, the
  *     server will check to make sure that the client provides matching values.
+ * @param {string=} options.promptSaveAs - If you provide this value the SaveAs 
+ *     prompt will be displayed when accessing the signed url and the file name 
+ *     will be set to the provided value. If options.responseDisposition is set 
+ *     this option is ignored.
+ * @param {string=} options.responseDisposition - If you provide this value, 
+ *     the response-content-disposition parameter (http://goo.gl/yMWxQV) of the 
+ *     signed url is set accordingly.
+ * @param {string=} options.responseType - If you provide this value, the 
+ *     response-content-type parameter of the signed url is set accordingly.
  * @param {function=} callback - The callback function.
  *
  * @example
  * file.getSignedUrl({
  *   action: 'read',
- *   expires: Math.round(Date.now() / 1000) + (60 * 60 * 24 * 14) // 2 weeks.
+ *   expires: Math.round(Date.now() / 1000) + (60 * 60 * 24 * 14), // 2 weeks.
+ *   promptSaveAs: 'filename.ext'
  * }, function(err, url) {});
  */
 File.prototype.getSignedUrl = function(options, callback) {
@@ -1060,11 +1070,38 @@ File.prototype.getSignedUrl = function(options, callback) {
     ].join('\n'));
     var signature = sign.sign(credentials.private_key, 'base64');
 
+    var responseContentType = '';
+    if (util.is(options.responseType, 'string')) {
+      responseContentType = 
+        '&response-content-type=' + 
+        encodeURIComponent(options.responseType);
+    }
+
+    var responseContentDisposition = '';
+    if (util.is(options.promptSaveAs, 'string')) {
+      responseContentDisposition =
+        '&response-content-disposition=attachment; filename="' + 
+        encodeURIComponent(options.promptSaveAs) + '"';
+    }
+    if (util.is(options.responseDisposition, 'string')) {
+      if (responseContentDisposition !== '') {
+        console.warn([
+          'getSignedUrl: the promptSaveAs option is ignored',
+          'when responseDisposition is provided.'
+        ].join(' '));
+      }
+      responseContentDisposition = 
+        '&response-content-disposition=' + 
+        encodeURIComponent(options.responseDisposition);
+    }
+
     callback(null, [
       'https://storage.googleapis.com' + options.resource,
       '?GoogleAccessId=' + credentials.client_email,
       '&Expires=' + options.expires,
-      '&Signature=' + encodeURIComponent(signature)
+      '&Signature=' + encodeURIComponent(signature),
+      responseContentType,
+      responseContentDisposition
     ].join(''));
   });
 };

test/storage/file.js

@@ -1350,6 +1350,66 @@ describe('File', function() {
       });
     });
 
+    it('should add response-content-type parameter', function(done) {
+      var type = 'application/json';
+      directoryFile.getSignedUrl({
+        action: 'read',
+        expires: Math.round(Date.now() / 1000) + 5,
+        responseType: type
+      }, function(err, signedUrl) {
+        assert(signedUrl.indexOf(encodeURIComponent(type)) > -1);
+        done();
+      });
+    });
+
+    describe('promptSaveAs', function() {
+      it('should add response-content-disposition', function(done) {
+        var disposition = 'attachment; filename="fname.ext"';
+        directoryFile.getSignedUrl({
+          action: 'read',
+          expires: Math.round(Date.now() / 1000) + 5,
+          promptSaveAs: 'fname.ext'
+        }, function(err, signedUrl) {
+          assert(signedUrl.indexOf(disposition) > -1);
+          done();
+        });
+      });
+    });
+
+    describe('responseDisposition', function() {
+      it('should add response-content-disposition', function(done) {
+        var disposition = 'attachment; filename="fname.ext"';
+        directoryFile.getSignedUrl({
+          action: 'read',
+          expires: Math.round(Date.now() / 1000) + 5,
+          responseDisposition: disposition
+        }, function(err, signedUrl) {
+          assert(signedUrl.indexOf(encodeURIComponent(disposition)) > -1);
+          done();
+        });
+      });
+
+      it('should warn and ignore promptSaveAs if set', function(done) {
+        var disposition = 'attachment; filename="fname.ext"';
+        var saveAs = 'fname2.ext';
+        var oldWarn = console.warn;
+        console.warn = function(message) {
+          assert(message.indexOf('promptSaveAs') > -1);
+          console.warn = oldWarn;
+        };
+        directoryFile.getSignedUrl({
+          action: 'read',
+          expires: Math.round(Date.now() / 1000) + 5,
+          promptSaveAs: saveAs,
+          responseDisposition: disposition
+        }, function(err, signedUrl) {
+          assert(signedUrl.indexOf(encodeURIComponent(disposition)) > -1);
+          assert(signedUrl.indexOf(encodeURIComponent(saveAs)) === -1);
+          done();
+        });
+      });
+    });
+
     describe('expires', function() {
       var nowInSeconds = Math.floor(Date.now() / 1000);