kaiwren/wrest

# frozen_string_literal: true

# Copyright 2009 Sidu Ponnappa

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software distributed under the License
# is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and limitations under the License.

module Wrest
  module Components
    # This is a base implementation of a
    # hash mutator that ensures that the <tt>mutate</tt> method
    # will chain to the next mutator by using a
    # template method.
    module Mutators
      class Base
        attr_reader :next_mutator

        # Registers all subclasses of Mutators::Base in
        # Mutators::REGISTRY making it easy to reference
        # and chain them later.
        #
        # See Mutators#chain for more information.
        def self.inherited(subklass)
          super
          return if Utils.string_blank?(subklass.name)

          key = Utils.string_underscore(Utils.string_demodulize(subklass.name)).to_sym
          Wrest::Components::Mutators.registry[key] = subklass
        end

        def initialize(next_mutator = nil)
          @next_mutator = next_mutator
        end

        # This is a template method which operates on a tuple (well, pair)
        # from a hash map and guarantees mutator chaining.
        #
        # Iterating over any hash using <tt>each</tt> injects
        # each key/value pair from the hash in the
        # form of an array.
        # This method expects of this form as an argument, i.e.
        # an array with the structure [:key, :value]
        #
        # The implementation of the mutation is achieved by
        # overriding the <tt>do_mutate</tt> method in a subclass.
        # Note that failing to do so will result in an exception
        # at runtime.
        def mutate(tuple)
          out_tuple = do_mutate(tuple)
          next_mutator ? next_mutator.mutate(out_tuple) : out_tuple
        end

        protected

        def do_mutate(_tuple)
          raise Wrest::Exceptions::MethodNotOverridden
        end
      end
    end
  end
end