make script levels redirect to 2017 versions again

dashboard/app/controllers/script_levels_controller.rb

@@ -1,10 +1,12 @@
 require 'cdo/script_config'
 require 'dynamic_config/dcdo'
 require 'dynamic_config/gatekeeper'
+require 'cdo/script_constants'
 
 class ScriptLevelsController < ApplicationController
   check_authorization
   include LevelsHelper
+  include ScriptConstants
 
   # Default s-maxage to use for script level pages which are configured as
   # publicly cacheable.  Used if the DCDO.public_proxy_max_age is not defined.
@@ -67,7 +69,7 @@ def next
   def show
     @current_user = current_user && User.includes(:teachers).where(id: current_user.id).first
     authorize! :read, ScriptLevel
-    @script = Script.get_from_cache(params[:script_id])
+    @script = Script.get_from_cache(params[:script_id], version_year: DEFAULT_VERSION_YEAR)
 
     # Redirect to the same script level within @script.redirect_to.
     # There are too many variations of the script level path to use

dashboard/app/models/script.rb

@@ -354,7 +354,7 @@ def cached
     self.class.get_from_cache(id)
   end
 
-  def self.get_without_cache(id_or_name)
+  def self.get_without_cache(id_or_name, version_year: nil)
     # Also serve any script by its new_name, if it has one.
     script = id_or_name && Script.find_by(new_name: id_or_name)
     return script if script
@@ -369,36 +369,51 @@ def self.get_without_cache(id_or_name)
     unless is_id
       # We didn't find a script matching id_or_name. Next, look for a script
       # in the id_or_name script family to redirect to, e.g. csp1 --> csp1-2017.
-      script_with_redirect = Script.get_script_family_redirect(id_or_name)
+      script_with_redirect = Script.get_script_family_redirect(id_or_name, version_year: version_year)
       return script_with_redirect if script_with_redirect
     end
 
-    raise ActiveRecord::RecordNotFound.new("Couldn't find Script with id|name=#{id_or_name}")
+    raise ActiveRecord::RecordNotFound.new("Couldn't find Script with id|name|family_name=#{id_or_name}")
   end
 
-  def self.get_from_cache(id_or_name)
-    return get_without_cache(id_or_name) unless should_cache?
-
-    script_cache.fetch(id_or_name.to_s) do
+  # Returns the script with the specified id, or a script with the specified
+  # name, or a redirect to the latest version of the script within the specified
+  # family. Also populates the script cache so that future responses will be cached.
+  # For example:
+  #   get_from_cache('11') --> script_cache['11'] = <Script id=11, name=...>
+  #   get_from_cache('frozen') --> script_cache['frozen'] = <Script name="frozen", id=...>
+  #   get_from_cache('csp1') --> script_cache['csp1'] = <Script redirect_to="csp1-2018">
+  #   get_from_cache('csp1', version_year: '2017') --> script_cache['csp1/2017'] = <Script redirect_to="csp1-2017">
+  #
+  # @param id_or_name [String|Integer] script id, script name, or script family name.
+  # @param version_year [String] If specified, when looking for a script to redirect
+  #   to within a script family, redirect to this version rather than the latest.
+  def self.get_from_cache(id_or_name, version_year: nil)
+    return get_without_cache(id_or_name, version_year: version_year) unless should_cache?
+    cache_key_suffix = version_year ? "/#{version_year}" : ''
+    cache_key = "#{id_or_name}#{cache_key_suffix}"
+    script_cache.fetch(cache_key) do
       # Populate cache on miss.
-      script_cache[id_or_name.to_s] = get_without_cache(id_or_name)
+      script_cache[cache_key] = get_without_cache(id_or_name, version_year: version_year)
     end
   end
 
   # Given a script family name, return a dummy Script with redirect_to field
-  # pointing toward the latest stable script in that family.
+  # pointing toward the latest stable script in that family, or to a specific
+  # version_year if one is specified.
   # @param family_name [String] The name of the script family to search in.
+  # @param version_year [String] Version year to return. Optional.
   # @return [Script|nil] A dummy script object, not persisted to the database,
   #   with only the redirect_to field set.
-  def self.get_script_family_redirect(family_name)
-    script_name =
+  def self.get_script_family_redirect(family_name, version_year: nil)
+    scripts =
       Script.
         where(family_name: family_name).
         all.
         select(&:is_stable).
-        sort_by(&:version_year).
-        last.
-        try(:name)
+        sort_by(&:version_year)
+    scripts.select! {|s| s.version_year == version_year} if version_year
+    script_name = scripts.last.try(:name)
     script_name ? Script.new(redirect_to: script_name) : nil
   end