Send Emails using SendGrid SDK for Ruby in Rails using Dynamic SendGrid Email Templates

email_job.rb

# frozen_string_literal: true

require 'sendgrid-ruby'

#### Example Call
# EmailJob.new.perform(
#         @user.id,
#         { name: @user.name },
#         ENV.fetch('EXPORT_TEMPLATE', nil),
#         [
#           {
#             file: @tempfile.path,
#             type: 'application/csv',
#             name: @tempfile.path.split('/').last,
#             content_id: 'export_file'
#           }
#         ]
#       )

# This is the email job that will be sent to the user
class EmailJob
  include SendGrid

  # From Email and Name
  NOREPLY_FROM_EMAIL = 'no-reply@allwallet.app'
  NOREPLY_FROM_NAME = 'All Wallet'

  # include sidekiq to call perform as perform_async
  def perform(user_id, subsitutions, template_id, attachments = nil) # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
    # initialize sendgrid api
    sg = SendGrid::API.new(api_key: ENV.fetch('SENDGRID_API_KEY', nil))
    # we will get to_email from user object saved in db
    user = User.kept.find_by(id: user_id)
    return unless user

    # initialize mail object of sendgrid
    mail = Mail.new
    # fill 'from' data from the constants mentioned above
    mail.from = Email.new(email: NOREPLY_FROM_EMAIL, name: NOREPLY_FROM_NAME)
    # personalization is object for email to data and templates
    personalization = Personalization.new
    # add user data to which email to be sent
    personalization.add_to(Email.new(email: user.email, name: user.name))
    # add substitutions to template created in sendgrid to replace the variable in template like `{{name}}`
    # {
    #   "name": "Sulman Baig"
    # }
    personalization.add_dynamic_template_data(subsitutions)
    mail.add_personalization(personalization)
    mail.template_id = template_id

    # If attachments are sent as arguments
    if attachments.present? && attachments.is_a?(Array) && attachments.size.positive?
      attachments.each do |attachment_input|
        attachment = Attachment.new
        # attachment has to be sent as base64 encoded string
        attachment.content = Base64.strict_encode64(File.read(attachment_input[:file])) # file: path of file saved in local or remote
        attachment.type = attachment_input[:type] # type of file e.g. application/csv
        attachment.filename = attachment_input[:name] # filename
        attachment.disposition = 'attachment'
        attachment.content_id = attachment_input[:content_id] # e.g. export_file
        mail.add_attachment(attachment)
      end
    end

    begin
      # Send Email
      sg.client.mail._('send').post(request_body: mail.to_json)
    rescue StandardError => e
      # TODO: capture exception
    end
  end
end