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.has_password? ? "user_notifications.forgot_password" : "user_notifications.set_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]

      # Sort the new topics by score
      @new_topics.sort! {|a, b| (b.score || 0) - (a.score || 0) } if @new_topics.present?

      @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

  def mailing_list_notify(user, post)
    send_notification_email(
      title: post.topic.title,
      post: post,
      from_alias: post.user.username,
      allow_reply_by_email: true,
      notification_type: "posted",
      user: user
    )
  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 self.get_context_posts(post, topic_user)

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

    if topic_user && topic_user.last_emailed_post_number
      context_posts = context_posts.where("post_number > ?", topic_user.last_emailed_post_number)
    end

    context_posts
  end

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

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

    return if SiteSetting.enable_mailing_list_mode &&
      user.mailing_list_mode &&
       ["replied", "mentioned", "quoted", "posted"].include?(notification_type)

    title = @notification.data_hash[:topic_title]
    allow_reply_by_email = opts[:allow_reply_by_email]

    send_notification_email(
      title: title,
      post: @post,
      from_alias: username,
      allow_reply_by_email: allow_reply_by_email,
      notification_type: notification_type,
      user: user
    )

  end

  def send_notification_email(opts)
    post = opts[:post]
    title = opts[:title]
    allow_reply_by_email = opts[:allow_reply_by_email]
    from_alias = opts[:from_alias]
    notification_type = opts[:notification_type]
    user = opts[:user]

    context = ""
    tu = TopicUser.get(post.topic_id, user)
    context_posts = self.class.get_context_posts(post, tu)

    # make .present? cheaper
    context_posts = context_posts.to_a

    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 }
    )

    template = "user_notifications.user_#{notification_type}"
    if post.topic.private_message?
      template << "_pm"
    end

    email_opts = {
      topic_title: title,
      message: email_post_markdown(post),
      url: post.url,
      post_id: post.id,
      topic_id: post.topic_id,
      context: context,
      username: from_alias,
      add_unsubscribe_link: true,
      allow_reply_by_email: allow_reply_by_email,
      template: template,
      html_override: html,
      style: :notification
    }

    # If we have a display name, change the from address
    if from_alias.present?
      email_opts[:from_alias] = from_alias
    end

    TopicUser.change(user.id, post.topic_id, last_emailed_post_number: post.post_number)

    build_email(user.email, email_opts)
  end
end