Drop forum subscriptions.

Few people used forum subscriptions (only around 100), and even fewer
people were subscribed to active threads. Most subscriptions were for
old threads that will never be bumped again. The implementation also had
a few problems:

* Unsubscribe links in emails didn't work (they unset the user's
  receive_email_notifications flag, but forum subscriptions didn't
  respect this flag).
* Some users had invalid email addresses, which caused notifications to
  bounce. There was no mechanism for preventing bounces.
* The implementation wasn't scalable. It involved a daily linear scan
  over _all_ forum subscriptions looking for any topics that had been updated.

app/controllers/forum_topics_controller.rb

@@ -4,8 +4,8 @@ class ForumTopicsController < ApplicationController
   before_action :member_only, :except => [:index, :show]
   before_action :moderator_only, :only => [:new_merge, :create_merge]
   before_action :normalize_search, :only => :index
-  before_action :load_topic, :only => [:edit, :show, :update, :destroy, :undelete, :new_merge, :create_merge, :subscribe, :unsubscribe]
+  before_action :load_topic, :only => [:edit, :show, :update, :destroy, :undelete, :new_merge, :create_merge]
-  before_action :check_min_level, :only => [:show, :edit, :update, :new_merge, :create_merge, :destroy, :undelete, :subscribe, :unsubscribe]
+  before_action :check_min_level, :only => [:show, :edit, :update, :new_merge, :create_merge, :destroy, :undelete]
   skip_before_action :api_check
 
   def new
@@ -88,20 +88,6 @@ class ForumTopicsController < ApplicationController
     redirect_to forum_topic_path(@merged_topic)
   end
 
-  def subscribe
-    subscription = ForumSubscription.where(:forum_topic_id => @forum_topic.id, :user_id => CurrentUser.user.id).first
-    unless subscription
-      ForumSubscription.create(:forum_topic_id => @forum_topic.id, :user_id => CurrentUser.user.id, :last_read_at => @forum_topic.updated_at)
-    end
-    respond_with(@forum_topic)
-  end
-
-  def unsubscribe
-    subscription = ForumSubscription.where(:forum_topic_id => @forum_topic.id, :user_id => CurrentUser.user.id).first
-    subscription&.destroy
-    respond_with(@forum_topic)
-  end
-
   private
 
   def normalize_search

app/logical/danbooru_maintenance.rb

@@ -9,7 +9,6 @@ module DanbooruMaintenance
     safely { Upload.prune! }
     safely { Delayed::Job.where('created_at < ?', 45.days.ago).delete_all }
     safely { PostDisapproval.prune! }
-    safely { ForumSubscription.process_all! }
     safely { PostDisapproval.dmail_messages! }
     safely { regenerate_post_counts! }
     safely { SuperVoter.init! }

app/mailers/user_mailer.rb

@@ -7,11 +7,4 @@ class UserMailer < ActionMailer::Base
     @dmail = dmail
     mail(:to => "#{dmail.to.name} <#{dmail.to.email}>", :subject => "#{Danbooru.config.app_name} - Message received from #{dmail.from.name}")
   end
-
-  def forum_notice(user, forum_topic, forum_posts)
-    @user = user
-    @forum_topic = forum_topic
-    @forum_posts = forum_posts
-    mail(:to => "#{user.name} <#{user.email}>", :subject => "#{Danbooru.config.app_name} forum topic #{forum_topic.title} updated")
-  end
 end

app/models/forum_subscription.rb

@@ -1,24 +0,0 @@
-class ForumSubscription < ApplicationRecord
-  belongs_to :user
-  belongs_to :forum_topic
-
-  def self.prune!
-    where("last_read_at < ?", 3.months.ago).delete_all
-  end
-
-  def self.process_all!
-    ForumSubscription.find_each do |subscription|
-      forum_topic = subscription.forum_topic
-      if forum_topic.updated_at > subscription.last_read_at
-        CurrentUser.scoped(subscription.user, "127.0.0.1") do
-          forum_posts = forum_topic.posts.where("created_at > ?", subscription.last_read_at).order("id desc")
-          begin
-            UserMailer.forum_notice(subscription.user, forum_topic, forum_posts).deliver_now
-          rescue Net::SMTPSyntaxError
-          end
-          subscription.update_attribute(:last_read_at, forum_topic.updated_at)
-        end
-      end
-    end
-  end
-end

app/models/forum_topic.rb

@@ -16,7 +16,6 @@ class ForumTopic < ApplicationRecord
   has_many :posts, -> {order("forum_posts.id asc")}, :class_name => "ForumPost", :foreign_key => "topic_id", :dependent => :destroy
   has_many :moderation_reports, through: :posts
   has_one :original_post, -> {order("forum_posts.id asc")}, class_name: "ForumPost", foreign_key: "topic_id", inverse_of: :topic
-  has_many :subscriptions, :class_name => "ForumSubscription"
   before_validation :initialize_is_deleted, :on => :create
   validates_presence_of :title
   validates_associated :original_post
@@ -126,16 +125,9 @@ class ForumTopic < ApplicationRecord
     end
   end
 
-  module SubscriptionMethods
-    def user_subscription(user)
-      subscriptions.where(:user_id => user.id).first
-    end
-  end
-
   extend SearchMethods
   include CategoryMethods
   include VisitMethods
-  include SubscriptionMethods
 
   def editable_by?(user)
     (creator_id == user.id || user.is_moderator?) && visible?(user)

app/views/forum_topics/_secondary_links.html.erb

@@ -18,11 +18,6 @@
   <% if CurrentUser.is_member? && @forum_topic && !@forum_topic.new_record? %>
     <li>|</li>
     <%= subnav_link_to "Reply", new_forum_post_path(:topic_id => @forum_topic.id) %>
-    <% if @forum_topic.user_subscription(CurrentUser.user) %>
-      <%= subnav_link_to "Unsubscribe", unsubscribe_forum_topic_path(@forum_topic), :method => :post %>
-    <% else %>
-      <%= subnav_link_to "Subscribe", subscribe_forum_topic_path(@forum_topic), :method => :post, :data => {:confirm => "Are you sure you want to receive email notifications for this forum topic?"} %>
-    <% end %>
     <% if !@forum_topic.new_record? && @forum_topic.editable_by?(CurrentUser.user) %>
       <%= subnav_link_to "Edit", edit_forum_topic_path(@forum_topic), "data-shortcut": "e" %>
       <% if CurrentUser.is_moderator? %>

app/views/user_mailer/forum_notice.html.erb

@@ -1,13 +0,0 @@
-<p>"<%= @forum_topic.title %>" was updated:</p>
-
-<% @forum_posts.each do |forum_post| %>
-  <p>
-    <strong><%= forum_post.creator.name %> said:</strong>
-  </p>
-  <%= format_text(forum_post.body, base_url: root_url) %>
-  <br>
-  <hr>
-  <br>
-<% end %>
-
-<p><%= link_to "View topic", forum_topic_url(@forum_topic, :page => @forum_topic.last_page, :host => Danbooru.config.hostname, :only_path => false) %> | <%= link_to "Unsubscribe", maintenance_user_email_notification_url(:user_id => @user.id, :sig => email_sig(@user), :host => Danbooru.config.hostname, :only_path => false) %></p>

config/routes.rb

@@ -142,8 +142,6 @@ Rails.application.routes.draw do
       post :undelete
       get :new_merge
       post :create_merge
-      post :subscribe
-      post :unsubscribe
     end
     collection do
       post :mark_all_as_read

db/migrate/20200119193110_drop_forum_subscriptions.rb

@@ -0,0 +1,7 @@
+require_relative "20140725003232_create_forum_subscriptions"
+
+class DropForumSubscriptions < ActiveRecord::Migration[6.0]
+  def change
+    revert CreateForumSubscriptions
+  end
+end

db/structure.sql

@@ -2014,38 +2014,6 @@ CREATE SEQUENCE public.forum_posts_id_seq
 ALTER SEQUENCE public.forum_posts_id_seq OWNED BY public.forum_posts.id;
 
 
---
--- Name: forum_subscriptions; Type: TABLE; Schema: public; Owner: -
---
-
-CREATE TABLE public.forum_subscriptions (
-    id integer NOT NULL,
-    user_id integer,
-    forum_topic_id integer,
-    last_read_at timestamp without time zone,
-    delete_key character varying
-);
-
-
---
--- Name: forum_subscriptions_id_seq; Type: SEQUENCE; Schema: public; Owner: -
---
-
-CREATE SEQUENCE public.forum_subscriptions_id_seq
-    START WITH 1
-    INCREMENT BY 1
-    NO MINVALUE
-    NO MAXVALUE
-    CACHE 1;
-
-
---
--- Name: forum_subscriptions_id_seq; Type: SEQUENCE OWNED BY; Schema: public; Owner: -
---
-
-ALTER SEQUENCE public.forum_subscriptions_id_seq OWNED BY public.forum_subscriptions.id;
-
-
 --
 -- Name: forum_topic_visits; Type: TABLE; Schema: public; Owner: -
 --
@@ -4040,13 +4008,6 @@ ALTER TABLE ONLY public.forum_post_votes ALTER COLUMN id SET DEFAULT nextval('pu
 ALTER TABLE ONLY public.forum_posts ALTER COLUMN id SET DEFAULT nextval('public.forum_posts_id_seq'::regclass);
 
 
---
--- Name: forum_subscriptions id; Type: DEFAULT; Schema: public; Owner: -
---
-
-ALTER TABLE ONLY public.forum_subscriptions ALTER COLUMN id SET DEFAULT nextval('public.forum_subscriptions_id_seq'::regclass);
-
-
 --
 -- Name: forum_topic_visits id; Type: DEFAULT; Schema: public; Owner: -
 --
@@ -4394,14 +4355,6 @@ ALTER TABLE ONLY public.forum_posts
     ADD CONSTRAINT forum_posts_pkey PRIMARY KEY (id);
 
 
---
--- Name: forum_subscriptions forum_subscriptions_pkey; Type: CONSTRAINT; Schema: public; Owner: -
---
-
-ALTER TABLE ONLY public.forum_subscriptions
-    ADD CONSTRAINT forum_subscriptions_pkey PRIMARY KEY (id);
-
-
 --
 -- Name: forum_topic_visits forum_topic_visits_pkey; Type: CONSTRAINT; Schema: public; Owner: -
 --
@@ -6425,20 +6378,6 @@ CREATE INDEX index_forum_posts_on_topic_id ON public.forum_posts USING btree (to
 CREATE INDEX index_forum_posts_on_updated_at ON public.forum_posts USING btree (updated_at);
 
 
---
--- Name: index_forum_subscriptions_on_forum_topic_id; Type: INDEX; Schema: public; Owner: -
---
-
-CREATE INDEX index_forum_subscriptions_on_forum_topic_id ON public.forum_subscriptions USING btree (forum_topic_id);
-
-
---
--- Name: index_forum_subscriptions_on_user_id; Type: INDEX; Schema: public; Owner: -
---
-
-CREATE INDEX index_forum_subscriptions_on_user_id ON public.forum_subscriptions USING btree (user_id);
-
-
 --
 -- Name: index_forum_topic_visits_on_forum_topic_id; Type: INDEX; Schema: public; Owner: -
 --
@@ -7426,6 +7365,7 @@ INSERT INTO "schema_migrations" (version) VALUES
 ('20200115010442'),
 ('20200117220602'),
 ('20200118015014'),
-('20200119184442');
+('20200119184442'),
+('20200119193110');
 
 

test/factories/forum_subscription.rb

@@ -1,3 +0,0 @@
-FactoryBot.define do
-  factory(:forum_subscription)
-end

test/mailers/previews/user_mailer_preview.rb

@@ -3,12 +3,4 @@ class UserMailerPreview < ActionMailer::Preview
     dmail = User.admins.first.dmails.first
     UserMailer.dmail_notice(dmail)
   end
-
-  def forum_notice
-    topic = ForumTopic.first
-    posts = topic.posts
-    user = topic.creator
-
-    UserMailer.forum_notice(user, topic, posts)
-  end
 end