From 9576ca1b7f68e40d6634ff068f834c3853f275da Mon Sep 17 00:00:00 2001
From: Nils Caspar <ncaspar@me.com>
Date: Sat, 30 May 2015 13:23:55 +0200
Subject: [PATCH] Automatically calculate QR size, fixes #111

---
 .../casino/two_factor_authenticators_helper.rb  | 17 +++++++++++++++--
 ...two_factor_authenticators_controller_spec.rb | 13 +++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/app/helpers/casino/two_factor_authenticators_helper.rb b/app/helpers/casino/two_factor_authenticators_helper.rb
index b4487f8d..db47a8d0 100644
--- a/app/helpers/casino/two_factor_authenticators_helper.rb
+++ b/app/helpers/casino/two_factor_authenticators_helper.rb
@@ -1,3 +1,4 @@
+require 'rqrcode'
 require 'rqrcode_png'
 
 module CASino::TwoFactorAuthenticatorsHelper
@@ -6,7 +7,19 @@ def otp_auth_url(two_factor_authenticator)
   end
 
   def otp_qr_code_data_url(two_factor_authenticator)
-    qr = RQRCode::QRCode.new(otp_auth_url(two_factor_authenticator), size: 5, level: :l)
-    qr.to_img.resize(250,250).to_data_url
+    auth_url = otp_auth_url(two_factor_authenticator)
+    size = otp_qr_code_suggested_size(auth_url)
+    qr = RQRCode::QRCode.new(auth_url, size: size, level: :l)
+    qr.to_img.resize(250, 250).to_data_url
+  end
+
+  def otp_qr_code_suggested_size(data)
+    data_bits = data.length * 8
+    (3..40).each do |size|
+      metadata_bits = 4 + RQRCode::QRUtil.get_length_in_bits(RQRCode::QRMODE[:mode_8bit_byte], size)
+      total_data_bits = metadata_bits + data_bits
+      max_data_bits = RQRCode::QRCode.count_max_data_bits(RQRCode::QRRSBlock.get_rs_blocks(size, 1))
+      return size if total_data_bits < max_data_bits
+    end
   end
 end
diff --git a/spec/controllers/two_factor_authenticators_controller_spec.rb b/spec/controllers/two_factor_authenticators_controller_spec.rb
index d167d61b..6587a882 100644
--- a/spec/controllers/two_factor_authenticators_controller_spec.rb
+++ b/spec/controllers/two_factor_authenticators_controller_spec.rb
@@ -35,6 +35,19 @@
         get :new, request_options
         response.should render_template(:new)
       end
+
+      context 'with a really long service name' do
+        before(:each) do
+          CASino.config.frontend[:sso_name] = 'Na' * 200
+        end
+
+        render_views
+
+        it 'renders the new template' do
+          get :new, request_options
+          response.should render_template(:new)
+        end
+      end
     end
 
     context 'without a ticket-granting ticket' do