module ActiveModel
  class Serializer
    module Associations #:nodoc:
      class Base #:nodoc:
        def initialize(name, options={}, serializer_options={})
          @name          = name
          @object        = options[:value]

          embed          = options[:embed]
          @embed_ids     = embed == :id || embed == :ids
          @embed_objects = embed == :object || embed == :objects
          @embed_key     = options[:embed_key] || :id
          @embed_in_root = options[:include]

          serializer = options[:serializer]
          @serializer = serializer.is_a?(String) ? serializer.constantize : serializer

          @options = options
          @serializer_options = serializer_options
        end

        attr_reader :object, :root, :name, :embed_ids, :embed_objects, :embed_in_root
        alias embeddable? object
        alias embed_objects? embed_objects
        alias embed_ids? embed_ids
        alias use_id_key? embed_ids?
        alias embed_in_root? embed_in_root

        def key
          if key = options[:key]
            key
          elsif use_id_key?
            id_key
          else
            name
          end
        end

        private

        attr_reader :embed_key, :serializer, :options, :serializer_options

        def find_serializable(object)
          if serializer
            serializer.new(object, serializer_options)
          elsif object.respond_to?(:active_model_serializer) && (ams = object.active_model_serializer)
            ams.new(object, serializer_options)
          else
            object
          end
        end
      end

      class HasMany < Base #:nodoc:
        def root
          options[:root] || name
        end

        def id_key
          "#{name.to_s.singularize}_ids".to_sym
        end

        def serializables
          object.map do |item|
            find_serializable(item)
          end
        end

        def serialize
          object.map do |item|
            find_serializable(item).serializable_hash
          end
        end

        def serialize_ids
          object.map do |item|
            item.read_attribute_for_serialization(embed_key)
          end
        end
      end

      class HasOne < Base #:nodoc:
        def root
          if root = options[:root]
            root
          elsif polymorphic?
            object.class.to_s.pluralize.demodulize.underscore.to_sym
          else
            name.to_s.pluralize.to_sym
          end
        end

        def id_key
          "#{name}_id".to_sym
        end

        def embeddable?
          if polymorphic? && object.nil?
            false
          else
            true
          end
        end

        def serializables
          value = object && find_serializable(object)
          value ? [value] : []
        end

        def serialize
          if object
            if polymorphic?
              {
                :type => polymorphic_key,
                polymorphic_key => find_serializable(object).serializable_hash
              }
            else
              find_serializable(object).serializable_hash
            end
          end
        end

        def serialize_ids
          if object
            id = object.read_attribute_for_serialization(embed_key)
            if polymorphic?
              {
                :type => polymorphic_key,
                :id => id
              }
            else
              id
            end
          end
        end

        private

        def use_id_key?
          embed_ids? && !polymorphic?
        end

        def polymorphic?
          options[:polymorphic]
        end

        def polymorphic_key
          object.class.to_s.demodulize.underscore.to_sym
        end
      end
    end
  end
end