# frozen_string_literal: true

module LIT
  # @api public
  # @since 0.1.0
  class Serializer
    def initialize(object)
      @object = object
    end

    def serialize
      serialize_object(@object)
    end

    private

    # rubocop:disable Metrics/MethodLength
    def serialize_object(object)
      if object.is_a?(Object::Struct)
        if object.is_a?(Object::EnumVariant)
          serialize_enum_variant(object)
        else
          serialize_struct(object)
        end
      elsif object.is_a?(Module) && object <= Object::EnumVariant
        serialize_enum_variant(object)
      elsif object.is_a?(Object::Array)
        serialize_array(object)
      elsif object.is_a?(Object::Map)
        serialize_map(object)
      elsif object.is_a?(Object::Option::Some) || object == Object::Option::None
        serialize_option(object)
      elsif object.is_a?(String) ||
            object.is_a?(Integer) ||
            object.is_a?(Float) ||
            object == true ||
            object == false ||
            object.nil?
        object
      else
        raise InvalidObjectError, "invalid object: #{object}"
      end
    end
    # rubocop:enable Metrics/MethodLength

    def serialize_struct(struct)
      struct.instance_variables.reduce({}) do |hsh, ivar|
        field_name = ivar.to_s.sub("@", "").to_sym
        hsh.merge(field_name => serialize_object(struct.public_send(field_name)))
      end
    end

    def serialize_enum_variant(variant)
      data =
        if variant.__kind__ == :struct
          serialize_struct(variant)
        else
          nil
        end

      { kind: variant.__name__, data: data }
    end

    def serialize_array(array)
      array.__values__.map { |value| serialize_object(value) }
    end

    def serialize_map(map)
      map.__values__.reduce({}) do |acc, (key, value)|
        acc.merge(serialize_object(key) => serialize_object(value))
      end
    end

    def serialize_option(option)
      if option == Object::Option::None
        nil
      else
        serialize_object(option.__value__)
      end
    end
  end
end