class SassC::FunctionsHandler

def arguments_from_native_list(native_argument_list)
  native_argument_list_length = Native.list_get_length(native_argument_list)
  (0...native_argument_list_length).map do |i|
    native_value = Native.list_get_value(native_argument_list, i)
    Script::ValueConversion.from_native(native_value, @options)
  end.compact
end

def error(message)
  $stderr.puts "[SassC::FunctionsHandler] #{message}"
  Native.make_error(message)
end

def initialize(options)
  @options = options
end

def setup(native_options, functions: Script::Functions)
  @callbacks = {}
  @function_names = {}
  list = Native.make_function_list(Script.custom_functions(functions: functions).count)
  # use an anonymous class wrapper to avoid mutations in a threaded environment
  functions_wrapper = Class.new do
    attr_accessor :options
    include functions
  end.new
  functions_wrapper.options = @options
  Script.custom_functions(functions: functions).each_with_index do |custom_function, i|
    @callbacks[custom_function] = FFI::Function.new(:pointer, [:pointer, :pointer]) do |native_argument_list, cookie|
      begin
        function_arguments = arguments_from_native_list(native_argument_list)
        result = functions_wrapper.send(custom_function, *function_arguments)
        to_native_value(result)
      rescue StandardError => exception
        # This rescues any exceptions that occur either in value conversion
        # or during the execution of a custom function.
        error(exception.message)
      end
    end
    @function_names[custom_function] = Script.formatted_function_name(custom_function, functions: functions)
    callback = Native.make_function(
      @function_names[custom_function],
      @callbacks[custom_function],
      nil
    )
    Native::function_set_list_entry(list, i, callback)
  end
  Native::option_set_c_functions(native_options, list)
end

def to_native_value(sass_value)
  # if the custom function returns nil, we provide a "default" return
  # value of an empty string
  sass_value ||= SassC::Script::Value::String.new("")
  sass_value.options = @options
  Script::ValueConversion.to_native(sass_value)
end