Email merge script in ruby

emailmerge.rb

#!/usr/bin/env ruby
# Encoding: utf-8
#
# This takes a csv file of values, and a txt file as a template
# and sends out a pile of customized emails.
#

require 'csv'
require 'mail'

class EmailMerge
  def initialize(data_file, template_file)
    @data = parse_data(data_file)
    @subject, @body = parse_template(template_file)
    @from = "[email protected]"
    @to_field = "email"
  end

  def from=(email)
    @from = email
  end

  def to_field=(field_name)
    @to_field = field_name
  end

  def to(data)
    data[@to_field]
  end

  def recipients
    @data.map{|data| data[@to_field] }
  end

  def preview(n=1)
    @data[0..n-1].each do |data|
      puts "-"*80
      puts "Subject: "+ render(@subject, data)
      puts "-"*80
      puts render(@body, data)
      puts "-"*80
    end
  end

  def render(template, data)
    text = template.dup
    text.gsub(/{{(.+?)}}/) do |match|
      var = match.gsub(/{{/,'').gsub(/}}/,'')
      data[var]
    end
  end

  def deliver_all!(opts={})
    @data.each do |data|
      mail(data, opts)
    end
  end

  def deliver_n!(n=1, opts={})
    @data[0..n-1].each do |data|
      mail(data, opts)
    end
  end

  # you can override :from, :to, :subject, :body, with opts
  def mail(data, opts={})
    mail = Mail.new
    mail.delivery_method :sendmail
    mail.charset = 'UTF-8'
    mail.content_transfer_encoding = "8bit"
    mail.content_type = 'text/html'
    mail.from    = opts[:from]     || @from
    mail.to      = opts[:to]       || data[@to_field]
    mail.subject = opts[:subject]  || self.render(@subject, data)
    mail.body    = opts[:body]     || self.render(@body, data)

    ok = mail.deliver!
    p [ok, mail]
  end

  private

  def parse_template(template_file)
    text = File.readlines(template_file)
    [
      text.shift.gsub(/Subject:\s+/i,'').strip,
      text.join.strip
    ]
  end

  # reads file, returns array of hashes based on the header
  def parse_data(data_file)
    data = []
    headers = nil
    CSV.open(data_file).each do |row|
      if headers.nil?
        headers = row
      else
        data << Hash[*headers.zip(row).flatten]
      end
    end
    data
  end
end


if $0 == __FILE__
  base_dir = "data/campaign_20140314"
  data_file = "#{base_dir}/data.csv"
  template_file = "#{base_dir}/template.html"

  em = EmailMerge.new(data_file, template_file)
  em.from = "[email protected]"
  em.to_field = "email"

  testing = true
  if testing
    em.preview 1 # show a few
    puts em.recipients # show were they'd go if we ran it for real
    em.deliver_n!(n=1, to: '[email protected]') # test deliver a few
  end
  
  # DO IT FOR REAL, CAREFUL! TEST FIRST
  #em.deliver_all!(to: '[email protected]')
  #em.deliver_all!
end