discourse/app/mailers/user_notifications.rb

require_dependency 'markdown_linker'
require_dependency 'email/message_builder'
require_dependency 'age_words'

class UserNotifications < ActionMailer::Base
  default charset: 'UTF-8'

  include Email::BuildEmailHelper

  def signup(user, opts={})
    build_email(user.email,
                template: "user_notifications.signup",
                email_token: opts[:email_token])
  end

  def signup_after_approval(user, opts={})
    build_email(user.email,
                template: 'user_notifications.signup_after_approval',
                email_token: opts[:email_token],
                new_user_tips: SiteContent.content_for(:usage_tips))
  end

  def authorize_email(user, opts={})
    build_email(user.email, template: "user_notifications.authorize_email", email_token: opts[:email_token])
  end

  def forgot_password(user, opts={})
    build_email(user.email, template: "user_notifications.forgot_password", email_token: opts[:email_token])
  end

  def digest(user, opts={})
    @user = user
    @base_url = Discourse.base_url

    min_date = opts[:since] || @user.last_emailed_at || @user.last_seen_at || 1.month.ago

    @site_name = SiteSetting.title

    @last_seen_at = I18n.l(@user.last_seen_at || @user.created_at, format: :short)

    # A list of topics to show the user
    @featured_topics = Topic.for_digest(user, min_date).to_a

    # Don't send email unless there is content in it
    if @featured_topics.present?
      @featured_topics, @new_topics = @featured_topics[0..4], @featured_topics[5..-1]
      @markdown_linker = MarkdownLinker.new(Discourse.base_url)

      build_email user.email,
                  from_alias: I18n.t('user_notifications.digest.from', site_name: SiteSetting.title),
                  subject: I18n.t('user_notifications.digest.subject_template',
                  site_name: @site_name,
                  date: I18n.l(Time.now, format: :short))
    end
  end

  def user_invited_to_private_message(user, opts)
    notification_email(user, opts)
  end

  def user_replied(user, opts)
    opts[:allow_reply_by_email] = true
    notification_email(user, opts)
  end

  def user_quoted(user, opts)
    opts[:allow_reply_by_email] = true
    notification_email(user, opts)
  end

  def user_mentioned(user, opts)
    opts[:allow_reply_by_email] = true
    notification_email(user, opts)
  end

  def user_posted(user, opts)
    opts[:allow_reply_by_email] = true
    notification_email(user, opts)
  end

  def user_private_message(user, opts)
    opts[:allow_reply_by_email] = true

    # We use the 'user_posted' event when you are emailed a post in a PM.
    opts[:notification_type] = 'posted'

    notification_email(user, opts)
  end

  protected

  def email_post_markdown(post)
    result = "[email-indent]\n"
    result << "#{post.raw}\n\n"
    result << "#{I18n.t('user_notifications.posted_by', username: post.username, post_date: post.created_at.strftime("%m/%d/%Y"))}\n\n"
    result << "[/email-indent]\n"
    result
  end

  class UserNotificationRenderer < ActionView::Base
    include UserNotificationsHelper
  end

  def notification_email(user, opts)
    return unless @notification = opts[:notification]
    return unless @post = opts[:post]

    username = @notification.data_hash[:display_username]
    notification_type = opts[:notification_type] || Notification.types[@notification.notification_type].to_s

    context = ""
    context_posts = Post.where(topic_id: @post.topic_id)
                        .where("post_number < ?", @post.post_number)
                        .where(user_deleted: false)
                        .order('created_at desc')
                        .limit(SiteSetting.email_posts_context)

    if context_posts.present?
      context << "---\n*#{I18n.t('user_notifications.previous_discussion')}*\n"
      context_posts.each do |cp|
        context << email_post_markdown(cp)
      end
    end

    html = UserNotificationRenderer.new(Rails.configuration.paths["app/views"]).render(
      template: 'email/notification',
      format: :html,
      locals: { context_posts: context_posts, post: @post }
    )

    if @post.topic.private_message?
      opts[:subject_prefix] = "[#{I18n.t('private_message_abbrev')}] "
    end

    email_opts = {
      topic_title: @notification.data_hash[:topic_title],
      message: email_post_markdown(@post),
      url: @post.url,
      post_id: @post.id,
      topic_id: @post.topic_id,
      context: context,
      username: username,
      add_unsubscribe_link: true,
      allow_reply_by_email: opts[:allow_reply_by_email],
      template: "user_notifications.user_#{notification_type}",
      html_override: html,
      style: :notification,
      subject_prefix: opts[:subject_prefix] || ''
    }

    # If we have a display name, change the from address
    if username.present?
      email_opts[:from_alias] = I18n.t(:via, username: username, site_name: SiteSetting.title)
    end

    build_email(user.email, email_opts)
  end

end