module Virtus

  # Attribute placeholder used when type constant is passed as a string or symbol
  #
  # @private
  class PendingAttribute
    attr_reader :type, :options, :name

    # @api private
    def initialize(type, options)
      @type, @options = type.to_s, options
      @name = options[:name]
    end

    # @api private
    def finalize
      Attribute::Builder.call(determine_type, options).finalize
    end

    # @api private
    def finalized?
      false
    end

    # @api private
    def determine_type
      if type.include?('::')
        # TODO: wrap it up in Virtus.constantize and use feature-detection to
        #       pick up either Inflecto or ActiveSupport, whateve is available
        if defined?(Inflecto)
          Inflecto.constantize(type)
        else
          raise NotImplementedError, 'Virtus needs inflecto gem to constantize namespaced constant names'
        end
      else
        Object.const_get(type)
      end
    end

  end # PendingAttribute

  # Extracts the actual type primitive from input type
  #
  # @private
  class TypeDefinition
    attr_reader :type, :primitive

    # @api private
    def initialize(type)
      @type = type
      initialize_primitive
    end

    # @api private
    def pending?
      @pending
    end

    private

    # @api private
    def initialize_primitive
      @primitive =
        if type.instance_of?(String) || type.instance_of?(Symbol)
          if !type.to_s.include?('::') && Object.const_defined?(type)
            Object.const_get(type)
          elsif not Attribute::Builder.determine_type(type)
            @pending = true
            type
          else
            type
          end
        elsif not type.is_a?(Class)
          type.class
        else
          type
        end
    end
  end

  class Attribute

    # Builder is used to set up an attribute instance based on input type and options
    #
    # @private
    class Builder
      attr_reader :attribute, :options, :type_definition, :klass, :type

      # @api private
      def self.call(type, options = {})
        type_definition = TypeDefinition.new(type)

        if type_definition.pending?
          PendingAttribute.new(type, options)
        else
          new(type_definition, options).attribute
        end
      end

      # @api private
      def self.determine_type(klass, default = nil)
        type = Attribute.determine_type(klass)

        if klass.is_a?(Class)
          type ||=
            if klass < Axiom::Types::Type
              determine_type(klass.primitive)
            elsif EmbeddedValue.handles?(klass)
              EmbeddedValue
            elsif klass < Enumerable
              Collection
            end
        end

        type || default
      end

      # @api private
      def initialize(type_definition, options)
        @type_definition = type_definition

        initialize_class
        initialize_type
        initialize_options(options)
        initialize_default_value
        initialize_coercer
        initialize_attribute
      end

      private

      # @api private
      def initialize_class
        @klass = self.class.determine_type(type_definition.primitive, Attribute)
      end

      # @api private
      def initialize_type
        @type = klass.build_type(type_definition)
      end

      # @api private
      def initialize_options(options)
        @options = klass.options.merge(:coerce => Virtus.coerce).update(options)
        klass.merge_options!(type, @options)
        determine_visibility
      end

      # @api private
      def initialize_default_value
        options.update(:default_value => DefaultValue.build(options[:default]))
      end

      # @api private
      def initialize_coercer
        options.update(:coercer => determine_coercer)
      end

      # @api private
      def initialize_attribute
        @attribute = klass.new(type, options)

        @attribute.extend(Accessor)    if options[:name]
        @attribute.extend(Coercible)   if options[:coerce]
        @attribute.extend(Strict)      if options[:strict]
        @attribute.extend(LazyDefault) if options[:lazy]

        @attribute.finalize if options[:finalize]
      end

      # @api private
      def determine_coercer
        options.fetch(:coercer) { klass.build_coercer(type, options) }
      end

      # @api private
      def determine_visibility
        default_accessor  = options.fetch(:accessor)
        reader_visibility = options.fetch(:reader, default_accessor)
        writer_visibility = options.fetch(:writer, default_accessor)
        options.update(:reader => reader_visibility, :writer => writer_visibility)
      end

    end # class Builder

  end # class Attribute
end # module Virtus