discourse/lib/email.rb

# frozen_string_literal: true

require 'mail'

module Email
  def self.is_valid?(email)
    return false unless String === email
    !!(EmailValidator.email_regex =~ email)
  end

  def self.downcase(email)
    return email unless Email.is_valid?(email)
    email.downcase
  end

  def self.obfuscate(email)
    return email if !Email.is_valid?(email)

    first, _, last = email.rpartition('@')

    # Obfuscate each last part, except tld
    last = last.split('.')
    tld = last.pop
    last.map! { |part| obfuscate_part(part) }
    last << tld

    "#{obfuscate_part(first)}@#{last.join('.')}"
  end

  def self.cleanup_alias(name)
    name ? name.gsub(/[:<>,"]/, '') : name
  end

  def self.extract_parts(raw)
    mail = Mail.new(raw)
    text = nil
    html = nil

    if mail.multipart?
      text = mail.text_part
      html = mail.html_part
    elsif mail.content_type.to_s["text/html"]
      html = mail
    else
      text = mail
    end

    [text&.decoded, html&.decoded]
  end

  def self.site_title
    SiteSetting.email_site_title.presence || SiteSetting.title
  end

  # https://tools.ietf.org/html/rfc850#section-2.1.7
  def self.message_id_rfc_format(message_id)
    message_id.present? && !is_message_id_rfc?(message_id) ? "<#{message_id}>" : message_id
  end

  def self.message_id_clean(message_id)
    message_id.present? && is_message_id_rfc?(message_id) ? message_id.gsub(/^<|>$/, "") : message_id
  end

  private

  def self.is_message_id_rfc?(message_id)
    message_id.start_with?('<') && message_id.include?('@') && message_id.end_with?('>')
  end

  def self.obfuscate_part(part)
    if part.size < 3
      "*" * part.size
    elsif part.size < 5
      part[0] + "*" * (part.size - 1)
    else
      part[0] + "*" * (part.size - 2) + part[-1]
    end
  end
end