refactor: split Stdlib::Functions into autoloaded adapters

Extract RababaAdapter and SecrystAdapter from the monolithic Functions
module into their own files, autoloaded from the parent namespace.
Simple text-transform functions (title_case, downcase, compose, etc.)
stay inline since they have no heavy dependencies.

- lib/interscript/stdlib.rb: add autoload :Functions entry
- lib/interscript/stdlib/functions.rb: parent namespace file with
  autoload for RababaAdapter and SecrystAdapter
- lib/interscript/stdlib/functions/rababa_adapter.rb: mutex-protected
  diacritizer cache; reverse() works without the gem loaded
- lib/interscript/stdlib/functions/secryst_adapter.rb: per-model
  translator cache

Public API (Interscript::Stdlib::Functions.<name>) is unchanged.
Callers in interpreter.rb and compiler/ruby.rb work without edits.

Zero require_relative added. Zero internal require added.

Author: ronaldtse

lib/interscript/stdlib.rb

@@ -189,88 +189,5 @@ def self.reverse_function
     }
   end
 
-  module Functions
-    def self.title_case(output, word_separator: " ")
-      output = output.gsub(/^(.)/, &:upcase)
-      output = output.gsub(/#{word_separator}(.)/, &:upcase) unless word_separator == ""
-      output
-    end
-
-    def self.downcase(output, word_separator: nil)
-      if word_separator
-        output = output.gsub(/^(.)/, &:downcase)
-        output.gsub(/#{word_separator}(.)/, &:downcase) unless word_separator == ""
-      else
-        output.downcase
-      end
-    end
-
-    def self.compose(output, _: nil)
-      output.unicode_normalize(:nfc)
-    end
-
-    def self.decompose(output, _: nil)
-      output.unicode_normalize(:nfd)
-    end
-
-    def self.separate(output, separator: " ")
-      output.split("").join(separator)
-    end
-
-    def self.unseparate(output, separator: " ")
-      output.split(separator).join("")
-    end
-
-    @secryst_models = {}
-    def self.secryst(output, model:)
-      begin
-        require "secryst"
-      rescue
-        nil
-      end # Try to load secryst, but don't fail hard if not possible.
-      unless defined? Secryst
-        raise Interscript::ExternalUtilError, "Secryst is not loaded. Please read docs/Usage_with_Secryst.adoc"
-      end
-      Interscript.secryst_index_locations.each do |remote|
-        Secryst::Provisioning.add_remote(remote)
-      end
-      @secryst_models[model] ||= Secryst::Translator.new(model_file: model)
-      output.split("\n").map(&:chomp).map do |i|
-        @secryst_models[model].translate(i)
-      end.join("\n")
-    end
-
-    def self.rababa(output, config:)
-      begin
-        require "rababa"
-      rescue
-        nil
-      end # Try to load rababa, but don't fail hard if not possible.
-      unless defined? Rababa
-        raise Interscript::ExternalUtilError, "Rababa is not loaded. Please read docs/Usage_with_Rababa.adoc"
-      end
-
-      config_value = Interscript.rababa_configs[config]
-      model_uri = config_value["model"]
-      rababa_config = config_value["config"]
-      model_path = Interscript.rababa_provision(config, model_uri)
-
-      @rababa_diacritizer ||= Rababa::Diacritizer.new(model_path, rababa_config)
-
-      @rababa_diacritizer.diacritize_text(output)
-    end
-
-    def self.rababa_reverse(output, config:)
-      # require "rababa" rescue nil # Try to load rababa, but don't fail hard if not possible.
-      # unless defined? Rababa
-      #   raise StandardError, "Rababa is not loaded. Please read docs/Usage_with_Rababa.adoc"
-      # end
-
-      # A call to allocate allows us to remove diacritics without initializing the model
-      # Rababa::Diacritizer.allocate.remove_diacritics(output)
-
-      # Unfortunately, this is broken as of now.
-      output.gsub(/[\u064e\u064b\u064f\u064c\u0650\u064d\u0652\u0651]/, "")
-    end
-  end
+  autoload :Functions, "interscript/stdlib/functions"
 end

lib/interscript/stdlib/functions.rb

@@ -0,0 +1,49 @@
+class Interscript::Stdlib
+  module Functions
+    autoload :RababaAdapter, "interscript/stdlib/functions/rababa_adapter"
+    autoload :SecrystAdapter, "interscript/stdlib/functions/secryst_adapter"
+
+    def self.title_case(output, word_separator: " ")
+      output = output.gsub(/^(.)/, &:upcase)
+      output = output.gsub(/#{word_separator}(.)/, &:upcase) unless word_separator == ""
+      output
+    end
+
+    def self.downcase(output, word_separator: nil)
+      if word_separator
+        output = output.gsub(/^(.)/, &:downcase)
+        output.gsub(/#{word_separator}(.)/, &:downcase) unless word_separator == ""
+      else
+        output.downcase
+      end
+    end
+
+    def self.compose(output, _: nil)
+      output.unicode_normalize(:nfc)
+    end
+
+    def self.decompose(output, _: nil)
+      output.unicode_normalize(:nfd)
+    end
+
+    def self.separate(output, separator: " ")
+      output.split("").join(separator)
+    end
+
+    def self.unseparate(output, separator: " ")
+      output.split(separator).join("")
+    end
+
+    def self.secryst(output, model:)
+      SecrystAdapter.call(output, model: model)
+    end
+
+    def self.rababa(output, config:)
+      RababaAdapter.call(output, config: config)
+    end
+
+    def self.rababa_reverse(output, config: nil)
+      RababaAdapter.reverse(output)
+    end
+  end
+end

lib/interscript/stdlib/functions/rababa_adapter.rb

@@ -0,0 +1,56 @@
+class Interscript::Stdlib
+  module Functions
+    class RababaAdapter
+      @rababa_diacritizer = nil
+      @mutex = Mutex.new
+
+      class << self
+        def call(output, config:)
+          diacritizer = diacritizer_for(config)
+          diacritizer.diacritize_text(output)
+        end
+
+        def reverse(output, config: nil)
+          # The legacy rababa reverse path strips harakat directly. It does
+          # not need the model loaded — keep it dependency-free so maps
+          # that only call `rababa_reverse` work without Rababa installed.
+          output.gsub(/[ًٌٍَُِّْ]/, "")
+        end
+
+        def reset_cache
+          @mutex.synchronize { @rababa_diacritizer = nil }
+        end
+
+        private
+
+        def diacritizer_for(config_key)
+          require_rababa!
+          @mutex.synchronize do
+            @rababa_diacritizer ||= build_diacritizer(config_key)
+          end
+        end
+
+        def build_diacritizer(config_key)
+          config_value = Interscript.rababa_configs.fetch(config_key) do
+            raise Interscript::ExternalUtilError,
+              "No rababa config registered under '#{config_key}'"
+          end
+          model_uri = config_value["model"]
+          rababa_config = config_value["config"]
+          model_path = Interscript.rababa_provision(config_key, model_uri)
+          Rababa::Diacritizer.new(model_path, rababa_config)
+        end
+
+        def require_rababa!
+          return if defined?(Rababa)
+          begin
+            require "rababa"
+          rescue LoadError
+            raise Interscript::ExternalUtilError,
+              "Rababa is not loaded. Please read docs/Usage_with_Rababa.adoc"
+          end
+        end
+      end
+    end
+  end
+end

lib/interscript/stdlib/functions/secryst_adapter.rb

@@ -0,0 +1,45 @@
+class Interscript::Stdlib
+  module Functions
+    class SecrystAdapter
+      @translators = {}
+      @mutex = Mutex.new
+
+      class << self
+        def call(output, model:)
+          translator = translator_for(model)
+          output.split("\n").map(&:chomp).map { |line| translator.translate(line) }.join("\n")
+        end
+
+        def reset_cache
+          @mutex.synchronize { @translators.clear }
+        end
+
+        private
+
+        def translator_for(model_key)
+          require_secryst!
+          @mutex.synchronize do
+            @translators[model_key] ||= build_translator(model_key)
+          end
+        end
+
+        def build_translator(model_key)
+          Interscript.secryst_index_locations.each do |remote|
+            Secryst::Provisioning.add_remote(remote)
+          end
+          Secryst::Translator.new(model_file: model_key)
+        end
+
+        def require_secryst!
+          return if defined?(Secryst)
+          begin
+            require "secryst"
+          rescue LoadError
+            raise Interscript::ExternalUtilError,
+              "Secryst is not loaded. Please read docs/Usage_with_Secryst.adoc"
+          end
+        end
+      end
+    end
+  end
+end

spec/stdlib_functions_spec.rb

@@ -0,0 +1,92 @@
+require "interscript"
+
+RSpec.describe Interscript::Stdlib::Functions do
+  it "autoloads the Functions namespace from stdlib.rb" do
+    expect(described_class).to eq(Interscript::Stdlib::Functions)
+  end
+
+  it "lists rababa and secryst as available functions" do
+    expect(Interscript::Stdlib.available_functions).to include(:rababa, :secryst, :rababa_reverse)
+  end
+
+  it "reverse-maps rababa to rababa_reverse" do
+    expect(Interscript::Stdlib.reverse_function[:rababa]).to eq(:rababa_reverse)
+    expect(Interscript::Stdlib.reverse_function[:rababa_reverse]).to eq(:rababa)
+  end
+
+  describe ".title_case" do
+    it "capitalizes the first letter of each word" do
+      expect(described_class.title_case("hello world")).to eq("Hello World")
+    end
+  end
+
+  describe ".downcase" do
+    it "lowercases everything when no separator given" do
+      expect(described_class.downcase("HELLO")).to eq("hello")
+    end
+  end
+
+  describe ".compose / .decompose" do
+    it "round-trips through NFC and NFD" do
+      composed = described_class.compose("café")
+      expect(composed).to eq("café")
+      decomposed = described_class.decompose(composed)
+      expect(decomposed).to eq("café")
+    end
+  end
+
+  describe ".separate / .unseparate" do
+    it "round-trips" do
+      separated = described_class.separate("abc")
+      expect(separated).to eq("a b c")
+      expect(described_class.unseparate(separated)).to eq("abc")
+    end
+  end
+
+  describe ".rababa_reverse" do
+    it "strips harakat without loading the model" do
+      result = described_class.rababa_reverse("كَتَبَ")
+      expect(result).to eq("كتب")
+    end
+
+    it "does not require the config kwarg" do
+      expect { described_class.rababa_reverse("كَتَبَ") }.not_to raise_error
+    end
+  end
+
+  describe ".rababa (without registered config)" do
+    it "raises ExternalUtilError naming the missing config" do
+      expect { described_class.rababa("كتب", config: "default") }.to raise_error(
+        Interscript::ExternalUtilError,
+        /No rababa config registered under 'default'/
+      )
+    end
+  end
+
+  describe ".secryst (without Secryst gem loaded)" do
+    it "raises ExternalUtilError with a helpful message" do
+      expect { described_class.secryst("hello", model: "default") }.to raise_error(
+        Interscript::ExternalUtilError,
+        /Secryst is not loaded/
+      )
+    end
+  end
+end
+
+RSpec.describe Interscript::Stdlib::Functions::RababaAdapter do
+  it "is autoloaded from a separate file" do
+    expect(described_class.name).to eq("Interscript::Stdlib::Functions::RababaAdapter")
+  end
+
+  describe ".reverse" do
+    it "strips harakat without touching the model" do
+      expect(described_class.reverse("كَتَبَ")).to eq("كتب")
+    end
+  end
+end
+
+RSpec.describe Interscript::Stdlib::Functions::SecrystAdapter do
+  it "is autoloaded from a separate file" do
+    expect(described_class.name).to eq("Interscript::Stdlib::Functions::SecrystAdapter")
+  end
+end