Add Auto calculating semester in LoadCourse service

app/services/load_course.rb

@@ -1,8 +1,8 @@
 class LoadCourse
-  def initialize(user, semester = 1101)
+  def initialize(user, semester = nil)
     Capybara.default_max_wait_time = 1
     Capybara.default_driver = :selenium_chrome_headless
-    @semester = semester
+    @semester ||= calculate_semester(Date.today)
     @user = user
     @user.courses.clear
   end
@@ -26,6 +26,17 @@ def perform
   end
   private
 
+  def calculate_semester(date)
+    roc_year = (date - 1911.years).year
+    semester = 1
+    # 小於 6 月就算第二學期
+    if date.month < 6
+      roc_year -= 1
+      semester = 2
+    end
+    return "#{roc_year}#{semester}"
+  end
+
   def course_urls
     @b = Capybara.current_session
     @b.visit("#{@user.crosslink_url}/timetable/#{@semester}")