irc-sep-28.rb

require 'net/smtp'
require 'minitest/autorun'
require 'time'
require 'date'
require 'securerandom'
require 'socket'
# require 'minitest/stub_any_instance'
 
class SendEmail
  def self.build(host, port)
    new.tap do |instance|
      instance.smtp = Net::SMTP.new(host, port)
    end
  end

  attr_accessor :smtp

  def call(from, to, subject, body)
    message = build_message(from, to, subject, body)

    # Connect and send message.
    smtp.start(
      Socket.gethostname,
      ENV.fetch('SMTP_USER', nil),
      ENV.fetch('SMTP_PASSWORD', nil),
      :plain
    ) do |ssmtp|
      ssmtp.send_message(message, from, to)
    end
  end

  def build_message(from, to, subject, body)
    hostname = Socket.gethostname
    message = <<~MAIL
      From: #{from}
      To: #{Array(to).join(', ')}
      Subject: #{subject}
      Date: #{Time.new.rfc2822}
      Message-Id: <#{SecureRandom.uuid}@#{hostname}>

      #{body}
    MAIL
  end
end

class SMTPTest < Minitest::Test
  class MockSMTP
    Delivery = Struct.new(:from, :to, :message)

    attr_accessor :deliveries

    def initialize
      @deliveries = []
    end

    def start(*)
      yield self
    end

    def send_message(message, from, to)
      @deliveries.push Delivery.new(from, to, message)
    end
  end

  def test_send_email
    send_email = SendEmail.new
    send_email.smtp = smtp = MockSMTP.new

    mail = send_email.call("from", "to", "subject", "body")

    assert smtp.deliveries.first.from == "from"
  end
end

__END__

module SMTP
  class << self
    def send_email(to, subject, body)
      # Connection setup.
      smtp = Net::SMTP.new(ENV.fetch('SMTP_HOST'), ENV.fetch('SMTP_PORT', 25))
 
      # Message setup.
      from = ENV.fetch('SMTP_FROM')
      hostname = Socket.gethostname
      message = <<~MAIL
        From: #{from}
        To: #{to.instance_of?(Array) ? to.join(', ') : to}
        Subject: #{subject}
        Date: #{Time.new.rfc2822}
        Message-Id: <#{SecureRandom.uuid}@#{hostname}>
 
        #{body}
      MAIL
 
      # Connect and send message.
      smtp.start(
        hostname,
        ENV.fetch('SMTP_USER', nil),
        ENV.fetch('SMTP_PASSWORD', nil),
        :plain
      ) do |ssmtp|
        ssmtp.send_message(message, from, to)
      end
    end
  end
end

class SMTPTest < Minitest::Test
  def test_send_email
    Net::SMTP.stub_any_instance(
      :start,
      lambda do |*|
        def send_message(msgstr, from_addr, *to_addrs)
          { msgstr: msgstr, from_addr: from_addr, to_addrs: to_addrs }
        end
        yield(self)
      end
    ) do
      mail = SMTP.send_email('to', 'subject', 'body')
      assert_equal('from', mail[:from_addr])
    end
  end
end