require 'active_model_serializers'
require 'fun_with_json_api/active_model_serializers/deserializer_config_builder'

module FunWithJsonApi
  # Converts a json_api document into a rails compatible hash.
  # Acts as an adaptor for ActiveModuleSerializer deserializer classes
  class PreDeserializer
    def self.parse(document, deserializer)
      new(document, deserializer).parse
    end

    attr_reader :document
    attr_reader :deserializer

    def initialize(document, deserializer)
      @document = document.to_h.deep_dup.deep_stringify_keys
      @deserializer = deserializer
    end

    def parse
      ams_deserializer_class.parse(document, ams_deserializer_config) do |invalid_document, reason|
        exception_message = "Invalid payload (#{reason}): #{invalid_document}"
        exception = convert_reason_into_exceptions(exception_message, reason).first ||
                    Exceptions::InvalidDocument.new(exception_message)
        raise exception
      end
    end

    protected

    def convert_reason_into_exceptions(exception_message, reason, values = [])
      if reason.is_a?(String)
        return convert_reason_message_into_error(exception_message, reason, values.join)
      end
      return nil unless reason.is_a?(Hash)
      return nil unless reason.size == 1

      reason.flat_map do |key, value|
        convert_reason_into_exceptions(exception_message, value, (values + ["/#{key}"]))
      end
    end

    def convert_reason_message_into_error(exception_message, reason, source)
      payload = ExceptionPayload.new
      payload.pointer = source.presence
      payload.detail = reason
      Exceptions::InvalidDocument.new(exception_message, payload)
    end

    def ams_deserializer_class
      if defined?(::ActiveModel::Serializer::Adapter::JsonApi::Deserialization)
        ::ActiveModel::Serializer::Adapter::JsonApi::Deserialization
      else
        ::ActiveModelSerializers::Adapter::JsonApi::Deserialization
      end
    end

    def ams_deserializer_config
      @ams_deserializer_config ||=
        FunWithJsonAPi::ActiveModelSerializers::DeserializerConfigBuilder.build(deserializer)
    end
  end
end