refactor: implement self-registration pattern for language support

app/domain/contributions/entities/file_contributions.rb

@@ -9,17 +9,6 @@ module Entity
     class FileContributions
       include Mixins::ContributionsCalculator
 
-      WANTED_LANGUAGES = [
-        Value::CodeLanguage::Ruby,
-        Value::CodeLanguage::Python,
-        Value::CodeLanguage::Javascript,
-        Value::CodeLanguage::Css,
-        Value::CodeLanguage::Html,
-        Value::CodeLanguage::Slim,
-        Value::CodeLanguage::Erb,
-        Value::CodeLanguage::Markdown
-      ].freeze
-
       attr_reader :file_path, :lines
 
       def initialize(file_path:, lines:)
@@ -36,7 +25,7 @@ def total_credits
       end
 
       def credit_share
-        return Value::CreditShare.new if not_wanted
+        return Value::CreditShare.new if unwanted?
 
         @credit_share ||=
           lines.each_with_object(Value::CreditShare.new) do |line, credit|
@@ -50,13 +39,8 @@ def contributors
 
       private
 
-      def not_wanted
-        !wanted
-      end
-
-      def wanted
-        WANTED_LANGUAGES.include?(language)
-      end
+      def unwanted? = language.unwanted?
+      def wanted? = language.wanted?
     end
   end
 end

app/domain/contributions/values/code_language.rb

@@ -7,9 +7,28 @@ module CodeLanguage
       WHITESPACE = '[ \t]'
       LINE_END = '$'
 
+      # Registry for language classes
+      @registry = {}
+
+      def self.register(extension, language_class)
+        @registry[extension] = language_class
+      end
+
+      def self.extension_language(file_extension)
+        @registry.fetch(file_extension) { Unknown }
+      end
+
+      def self.wanted_extensions
+        @registry.keys.freeze
+      end
+
       module LanguageMethods
         attr_reader :code
 
+        def self.included(base)
+          base.extend(ClassMethods)
+        end
+
         def setup(code)
           @code = code
         end
@@ -21,55 +40,97 @@ def name
         def useless?
           code.match?(self.class.const_get(:USELESS))
         end
+
+        # Delegate to class methods
+        def wanted? = self.class.wanted?
+        def unwanted? = self.class.unwanted?
+
+        module ClassMethods
+          def extension(ext = nil)
+            if ext
+              @extension = ext
+              CodeLanguage.register(ext, self)
+            end
+            @extension
+          end
+
+          # Single source of truth for wanted/unwanted at class level
+          def wanted? = true
+          def unwanted? = !wanted?
+        end
       end
 
       class Ruby
         include LanguageMethods
+
+        extension 'rb'
+
         def initialize(code) = setup(code)
         COMMENT = '[#\/]'
         USELESS = /^#{WHITESPACE}*(#{COMMENT}|#{LINE_END})/
       end
 
       class Python
         include LanguageMethods
+
+        extension 'py'
+
         def initialize(code) = setup(code)
         COMMENT = '[#\/]'
         USELESS = /^#{WHITESPACE}*(#{COMMENT}|#{LINE_END})/
       end
 
       class Javascript
         include LanguageMethods
+
+        extension 'js'
+
         def initialize(code) = setup(code)
         COMMENT = '//'
         USELESS = /^#{WHITESPACE}*(#{COMMENT}|#{LINE_END})/
       end
 
       class Html
         include LanguageMethods
+
+        extension 'html'
+
         def initialize(code) = setup(code)
         USELESS = /^#{WHITESPACE}*#{LINE_END}/
       end
 
       class Erb
         include LanguageMethods
+
+        extension 'erb'
+
         def initialize(code) = setup(code)
         USELESS = /^#{WHITESPACE}*#{LINE_END}/
       end
 
       class Slim
         include LanguageMethods
+
+        extension 'slim'
+
         def initialize(code) = setup(code)
         USELESS = /^#{WHITESPACE}*#{LINE_END}/
       end
 
       class Css
         include LanguageMethods
+
+        extension 'css'
+
         def initialize(code) = setup(code)
         USELESS = /^#{WHITESPACE}*#{LINE_END}/
       end
 
       class Markdown
         include LanguageMethods
+
+        extension 'md'
+
         def initialize(code) = setup(code)
         USELESS = /^#{WHITESPACE}*#{LINE_END}/
       end
@@ -78,25 +139,14 @@ class Unknown
         include LanguageMethods
 
         def initialize(code) = setup(code)
+        # Override: all lines are useless
         def useless? = true
         def self.lang_name = 'not recognized'
+        # Override: class is not wanted
+        def self.wanted? = false
       end
 
-      LANGUAGE_EXTENSION = {
-        'rb'   => Ruby,
-        'py'   => Python,
-        'js'   => Javascript,
-        'css'  => Css,
-        'html' => Html,
-        'erb'  => Erb,
-        'slim' => Slim,
-        'md'   => Markdown
-      }.freeze
       UNKNOWN_LANGUAGE = CodeLanguage::Unknown.freeze
-
-      def self.extension_language(file_extension)
-        LANGUAGE_EXTENSION[file_extension] || UNKNOWN_LANGUAGE
-      end
     end
   end
 end

app/domain/contributions/values/file_path.rb

@@ -17,13 +17,19 @@ def initialize(filepath)
       end
 
       def extension
-        @extension ||= filename.match(/\.([a-zA-Z0-9]+$)/).captures.first
+        @extension ||= filename.match(/\.([a-zA-Z0-9]+$)/)&.captures&.first
       end
 
       def language
+        return CodeLanguage::Unknown unless extension
+
         CodeLanguage.extension_language(extension)
       end
 
+      def wanted?
+        language.wanted?
+      end
+
       def folder_after(root)
         raise(ArgumentError, 'Path mismatch') unless
           self.start_with?(root) || root.empty?

app/infrastructure/git/repositories/local_repo.rb

@@ -13,8 +13,6 @@ module Errors
     class LocalGitRepo
       ONLY_FOLDERS = '**/'
       FILES_AND_FOLDERS = '**/*'
-      TEXT_FILES = %w[rb py js css html slim md erb].join('|')
-      CODE_FILENAME_MATCH = /\.(#{TEXT_FILES})$/
 
       attr_reader :git_repo_path
 
@@ -33,7 +31,7 @@ def files
 
         @files ||= in_repo do
           Dir.glob(FILES_AND_FOLDERS).select do |path|
-            File.file?(path) && (path =~ CODE_FILENAME_MATCH)
+            File.file?(path) && Value::FilePath.new(path).wanted?
           end
         end
       end