Remove unnecessary redirect from application_controller

schedules/.rubocop.yml

@@ -16,3 +16,6 @@ Metrics/BlockLength:
 
 Style/ClassAndModuleChildren:
   Enabled: false
+
+Style/GuardClause:
+  Enabled: false

schedules/app/controllers/application_controller.rb

 # Configures the application.
 class ApplicationController < ActionController::Base
   protect_from_forgery with: :null_session
-  before_action :set_semester, :set_cookies, :set_cart
 
+  # On each request, set the semester and cart.
+  before_action :set_semester, :set_cart
+
+  # Every page needs to know what semester it should load data from.
+  # set_semester checks both the semester_id query parameter and the user's cookies
+  # to look for a semester id and loads whatever it finds into @semester.
+  #
+  # By default, load the most recent semester.
   def set_semester
     if params.key?(:semester_id)
-      cookies[:semester_id] = params[:semester_id]
       @semester = Semester.find_by_id params[:semester_id]
+      cookies[:semester_id] = @semester.id
     elsif cookies[:semester_id].nil?
-      redirect_to(url_for(params.permit(params.keys).merge(semester_id: Semester.first.id)))
+      @semester = Semester.first
+      cookies[:semester_id] = @semester.id
     else
-      redirect_to(url_for(params.permit(params.keys).merge(semester_id: cookies[:semester_id])))
+      @semester = Semester.find_by_id cookies[:semester_id]
     end
   end
 
+  # The user's cart is stored as a JSON-encoded list of CRNs.
+  # set_cart sets the @cart variable, which is a list of the sections represented by the CRNs.
   def set_cart
+    # set the cart cookie to be empty if it doesn't already exist
+    cookies.permanent[:cart] = "[]" if cookies.permanent[:cart].nil?
+
+    # decode the JSON list into an array
     @cart = JSON.parse(cookies.permanent[:cart])
+
+    # get rid of any invalid CRNs
     @cart = @cart.reject { |crn| CourseSection.find_by_crn(crn).nil? }
-    cookies.permanent[:cart] = @cart.to_json
-  end
 
-  def set_cookies
-    cookies.permanent[:cart] = "[]" if cookies.permanent[:cart].nil?
+    # set the cookie to the JSON-encoded list of valid sections
+    cookies.permanent[:cart] = @cart.to_json
   end
 end