SendGrid integration; Transactional EMail template via Ruby : Send data to tr-email

base.rb

# /email/base.rb
class Email::Base
  # This class is mostly responsible for Sending email via SendGrid or Other Provier in future
  # Code in here are Common to all its successors

  RootURL = 'http://dashboard.thepact.com'
  VarPrefix = '{{'
  VarSuffix = '}}'
  attr_reader :client, :from, :template, :subject, :recipients

  def initialize(options)
    @subject = ' '
    @from = "[email protected]"
    @client = SendGrid::Client.new do |c|
      c.api_key = ENV['SENDGRID_API']
    end
    @recipients = parse_recipients(options[:to])
    @template = SendGrid::Template.new(parse_template_id)
  end

  def send
    mail_defaults = {
        from: from,
        html: html,
        text: text,
        subject: subject
    }
    mailer = SendGrid::TemplateMailer.new(client, template, recipients)
    mailer.mail(mail_defaults)
  end

  protected

  # Parses all the recipients from the Array
  # @param tos [Array] collection of emails
  #   can of format [" Shiva Bhusal <[email protected]>", "[email protected]"]
  # @return [Array] collection of SendGrid::Recipient
  def parse_recipients(tos)
    collection = []
    tos = [tos].flatten
    tos.map do |to|
      recipient = SendGrid::Recipient.new(to)
      add_contents(recipient)
      collection << recipient
    end
    collection
  end

  # Adds contents in wrapped Data into SMTP Header
  #  to be sent to SendGrid / Email sender
  # @param recipient [SendGrid::Recipient]
  # @return [SendGrid::Recipient] Modified; substitution added
  def add_contents(recipient)
    wrapped_data.map do |key, value|
      recipient.add_substitution(key, value)
    end
    recipient
  end

  # Wraps data with appropriate prefix and suffix
  # @return [Hash] Modified value of Data hash
  def wrapped_data
    sample = data.merge(default_data)

    result = sample.map do |key, value|
      {(VarPrefix + key.to_s + VarSuffix) => value}
    end

    result.reduce(:merge)
  end

  # Data to be send to SendGrid to embed in template
  # @note The data identifier shall have format
  #       %var_name%
  # @note The Prefix and Suffix are auto added when SMTP request sent
  #       VarPrefix = 'sg_'
  #       VarSuffix = '_sg'
  # @return [Hash]
  # Example:
  #   {
  #    name: @pact.child.name
  #    }
  #
  def data
    {

    }
  end

  # HTML Contents to be substituted inplace of %body%
  # @return [String]
  #   It can be String containing HTML Markups of any kind (Permitted only)
  # @note it cannot be empty
  #
  def html
    ' '
  end

  # Text Contents to be substituted inplace of  %body%
  # @return [String]
  # @note it cannot be empty
  #
  def text
    ' '
  end

  # The root URL relative to which assets URL to be fixed
  # For example
  # - if asset_url = '/images/facebook.png'
  #   then it has to be reference with resp to root_url
  def root_url
    RootURL
  end

  # Default data always to be passed to the transactional templates
  # @note these data are subject to change so thay are extracted out here
  #
  # Like
  #   - title logo
  #   - social icons
  #   - email's assets URL
  def default_data
    {
        'root_url' => RootURL,
        'asset_url' => "#{RootURL}/sendgrid",
        'signin_url' => "#{RootURL}/signin",
        'signup_url' => "#{RootURL}/signup",
        'dashboard_url' => "#{RootURL}/signin",

        'faq_url' => "#{RootURL}/signin",
        'resources_url' => "#{RootURL}/signin",
        'help_desk_url' => "#{RootURL}/signin",

        'src_facebook_icon' => "#{RootURL}/sendgrid/images/facebook_icon.png",
        'src_twitter_icon' => "#{RootURL}/sendgrid/images/twitter_icon.png",
        'src_pinterest_icon' => "#{RootURL}/sendgrid/images/pinterest_icon.png",
        'src_logo_icon' => "#{RootURL}/sendgrid/images/logo.png",

        'this_year' => Date.current.year.to_s,
        'support_email' => "[email protected]",

        'href_facebook' => "https://facebook.com/thepact",
        'href_twitter' => "https://twitter.com/thepact",
        'href_pinterest' => "https://pinterest.com/thepact",
    }
  end

  def parse_template_id
    conf = YAML.load(File.read Rails.root.join('config', 'email_templates.yml'))
    
    this_class_name_with_namespaces = self.class.ancestors.first.to_s

    conf[this_class_name_with_namespaces]
  end
end

pact_order.rb

# in orders_signup/confirmation/pact_order.rb
class OrdersSignup::Confirmation::PactOrder < Email::Base
  # Responsible solely for sending Pact Order Confirmation Email
  # Send email with order information with login info / write to marketing email list
  # @note @path is its property, it may not be present in its other siblings
  #

  attr_reader :pact

  def initialize(options)
    @pact = options[:pact]
    super
  end

  def data
    {
        parent_first_name: subscriber.parent.first_name,
        child_first_name: pact.child.first_name,
        order_number: 123,
        subscription_type: 'month',
        billing_date: billing_date,
        number_of_pacts_subscribed: subscriptions.count,
        order_details_markup: order_details_markup,
        parent_email: subscriber.email
    }
  end

  private

  def subscriptions
    Stripe::Customer.retrieve(subscriber.stripe_id).subscriptions
  end

  def subscriber
    pact.parent
  end

  def billing_date
    Date.today.day.ordinalize
  end

  def order_details_markup
    plans = ''
    charge = 0
    subscriptions.each do |subscription|
      plans += <<-EOS
                  <li style="text-align: left">Plan Name: #{subscription.plan.name} : Plan amount USD $#{subscription.plan.amount/100.0}</li>
      EOS
      charge += subscription.plan.amount
    end
    total = "<p style=\"text-align: left\"><strong>Total Amount $#{charge/100.0}</strong></p>"

    plans + total
  end

end