module Shoulda
  module Matchers
    module Doublespeak
      class Double
        attr_reader :calls

        def initialize(klass, method_name, implementation)
          @klass = klass
          @method_name = method_name
          @implementation = implementation
          @activated = false
          @calls = []
        end

        def to_return(value = nil, &block)
          if block
            implementation.returns(&block)
          else
            implementation.returns(value)
          end
        end

        def activate
          unless @activated
            store_original_method
            replace_method_with_double
            @activated = true
          end
        end

        def deactivate
          if @activated
            restore_original_method
            @activated = false
          end
        end

        def record_call(args, block)
          calls << MethodCall.new(args, block)
        end

        def call_original_method(object, args, block)
          if original_method
            original_method.bind(object).call(*args, &block)
          end
        end

        private

        attr_reader :klass, :method_name, :implementation, :original_method

        def store_original_method
          @original_method = klass.instance_method(method_name)
        end

        def replace_method_with_double
          implementation = @implementation
          double = self

          klass.__send__(:define_method, method_name) do |*args, &block|
            implementation.call(double, self, args, block)
          end
        end

        def restore_original_method
          original_method = @original_method
          klass.__send__(:define_method, method_name) do |*args, &block|
            original_method.bind(self).call(*args, &block)
          end
        end
      end
    end
  end
end