# frozen_string_literal: true

module Truemail
  module Validate
    class Smtp
      class Request
        require 'net/smtp'

        SMTP_PORT = 25
        CONNECTION_TIMEOUT_ERROR = 'connection timed out'
        RESPONSE_TIMEOUT_ERROR = 'server response timeout'
        CONNECTION_DROPPED = 'server dropped connection after response'

        attr_reader :configuration, :host, :email, :response

        def initialize(configuration:, host:, email:, attempts: nil)
          @configuration = Truemail::Validate::Smtp::Request::Configuration.new(configuration)
          @response = Truemail::Validate::Smtp::Response.new
          @host = host
          @email = email
          @attempts = attempts
        end

        def check_port
          Timeout.timeout(configuration.connection_timeout) do
            return response.port_opened = !TCPSocket.new(host, Truemail::Validate::Smtp::Request::SMTP_PORT).close
          end
        rescue => error
          retry if attempts_exist? && error.is_a?(Timeout::Error)
          response.port_opened = false
        end

        def run
          session.start do |smtp_request|
            response.connection = true
            smtp_handshakes(smtp_request, response)
          end
        rescue => error
          retry if attempts_exist?
          assign_error(attribute: :connection, message: compose_from(error))
        end

        private

        class Configuration
          REQUEST_PARAMS = %i[connection_timeout response_timeout verifier_domain verifier_email].freeze

          def initialize(configuration)
            REQUEST_PARAMS.each do |attribute|
              self.class.class_eval { attr_reader attribute }
              instance_variable_set(:"@#{attribute}", configuration.public_send(attribute))
            end
          end
        end

        attr_reader :attempts

        def attempts_exist?
          return false unless attempts
          (@attempts -= 1).positive?
        end

        def session
          Net::SMTP.new(host, Truemail::Validate::Smtp::Request::SMTP_PORT).tap do |settings|
            settings.open_timeout = configuration.connection_timeout
            settings.read_timeout = configuration.response_timeout
          end
        end

        def compose_from(error)
          case error.class.name
          when 'Net::OpenTimeout' then Truemail::Validate::Smtp::Request::CONNECTION_TIMEOUT_ERROR
          when 'Net::ReadTimeout' then Truemail::Validate::Smtp::Request::RESPONSE_TIMEOUT_ERROR
          when 'EOFError' then Truemail::Validate::Smtp::Request::CONNECTION_DROPPED
          else error.message
          end
        end

        def assign_error(attribute:, message:)
          response.errors[attribute] = message
          response.public_send(:"#{attribute}=", false)
        end

        def session_data
          {
            helo: configuration.verifier_domain,
            mailfrom: configuration.verifier_email,
            rcptto: email
          }
        end

        def smtp_resolver(smtp_request, method, value)
          smtp_request.public_send(method, value)
        rescue => error
          assign_error(attribute: method, message: compose_from(error))
        end

        def smtp_handshakes(smtp_request, smtp_response)
          session_data.all? do |method, value|
            smtp_response.public_send(:"#{method}=", smtp_resolver(smtp_request, method, value))
          end
        end
      end
    end
  end
end