require 'net/smtp'
require 'base64'
require 'kconv'
require 'erb'
#
# This class sends E-mails, generated from message templates.
#
# Author:: FUJIWARA Teruyoshi <tf (at) dsl.gr.jp>
# Copyright:: Copyright (c) 2010 FUJIWARA Teruyoshi
# License:: Distributes under the same terms as Ruby
# Date:: August 23, 2010
# Version:: 1.01
#
# === Usage
# The following is basic usage:
#   mt = MailTemplate.new(:smtp_server => 'smtp.server.com',
#                       :smtp_port => 587,
#                       :mail_from => 'foo@bar.com',
#                       :user => 'foo@bar.com',
#                       :password => 'XXXXXXX',
#                       :auth_type => 'plain')
#   vars = {
#    "mail_to" => "foo@bar.com",
#    "subject" => "subject",
#    "date" => "August 15, 2010"
#   }
#   mt.send("/path/to/template.txt", vars, "recipient@buz.com")
#
# Template should be written in ERB form.
#   From: Foo <foo@bar.com>
#   To: <%= vars["mail_to"] %>
#   Subject: <%= encode_header(vars["subject"]) %>
#   
#   This is a test mail from MailTemplate.rb.
#   This message is sent: <%= vars["date"] %>
#
# You should use 'vars' hash to describe variable element in the template.
class MailTemplate
  # Initiazlize the class. Arguments are specified as hash (such as MailTemplate.new(:smtp_server => "smtphost.com", :smtp_port => 23, :mail_from = "test@test.com"))
  # === Options
  # [:smtp_server] SMTP server (mandatory)
  # [:smtp_port] SMTP port (mandatory)
  # [:mail_from] Sender's mail address (mandatory)
  # [:domain] Sender's domain. If not specified, "localhost.localdomain" is set as default value.
  # [:user] username for SMTP-AUTH
  # [:password] password SMTP-AUTH
  # [:auth_type] type of SMTP-AUTH
  # [:verbose] output verbose logging message.
  # === Return value
  # No value returned, but ArgumentError thrown if any mandatory argument isn't specified.
  def initialize(params)
    if (params[:verbose])
      @verbose = true
    else
      @verbose = false
    end
    
    if (params[:smtp_server])
      @server = params[:smtp_server]
      puts "SMTP server: #{@server}" if @verbose
    else
      raise(ArgumentError, "smtp_server must be specified.")
    end
    
    if (params[:smtp_port])
      @port = params[:smtp_port]
    else
      @port = 23
    end
    puts "SMTP port: #{@port}" if @verbose
    
    if (params[:mail_from])
      @mail_from = params[:mail_from]
      puts "E-mail address (sender): #{@mail_from}" if @verbose
    else
      raise(ArgumentError, "mail_from must be specified.")
    end
    
    if (params[:domain])
      @domain = params[:domain]
    else
      @domain = 'localhost.localdomain'
    end
    puts "Domain (sender): #{@domain}" if @verbose
    
    @user = params[:user]
    @password = params[:password]
    @auth_type = params[:auth_type]
    puts "User/Password/Auth type: #{@user}/#{@password}/#{@auth_type}" if @verbose
  end
  
  # Send an email with message generated from template and 'vars' hash.
  # === Argument
  # [template_file] Pathname of a template file. This template file must be written in ERB form.
  # [vars] A hash used to rewrite the template.
  # [mail_to] An e-mail address of recipient.
  # === Return value
  # No value returned.
  def send(template_file, vars, mail_to)
    mail_string = apply_template(template_file, vars)
    if @verbose
      puts("--------------------------------------------------")
      puts(mail_string)
      puts("--------------------------------------------------")
      print("sending...")
    end
    Net::SMTP.start(@server, @port, @domain, @user, @password, @auth_type) do |smtp|
      smtp.send_message(mail_string, @mail_from, mail_to)
    end
    puts("done.") if @verbose
  end
  
  # Generate message body using ERB.
  # === Arguments
  # [template_file] Pathname of a template file. This template file must be written in ERB form.
  # [vars] A hash used to rewrite the template.
  # === Return value
  # A string is returned. It has a message body genereted from a template.
  def apply_template(template_file, vars)
    f = File.open(template_file)
    template_str = f.read
    f.close
    
    erb = ERB.new(template_str)
    
    return erb.result(binding).tojis
  end
  protected :apply_template
  
  # Mime encode a string for a mail header.
  # === Argument
  # [str] a string to be encoded.
  # === Return value
  # A string encoded in B-encoding.
  def encode_header(str)
    enc = Kconv.tojis(str).split(//,1).pack('m').chomp.gsub("\n", '')
    return "=?ISO-2022-JP?B?#{enc}?="
  end
end