Automatically delete old accounts after 14 days. TODO: Tests

app/controllers/api/abstract_controller.rb

@@ -213,6 +213,7 @@ module Api
     # Devices have a `last_saw_api` field to assist users with debugging.
     # We update this column every time an FBOS device talks to the API.
     def mark_as_seen(bot = (current_user && current_user.device))
+      current_user && current_user.reset_inactivity_tracking!
       when_farmbot_os do
         if bot
           v = fbos_version

app/jobs/inactive_account_job.rb

@@ -0,0 +1,55 @@
+# Recurring task that deletes inactive accounts.
+class InactiveAccountJob < ApplicationJob
+  queue_as :default
+  LIMIT = 1000
+  INACTIVE_WITH_DEVICE = 11.months + 15.days
+  INACTIVE_NO_DEVICE = 2.months + 15.days
+
+  def perform
+    notify_old_accounts
+    delete_old_accounts
+  end
+
+  private
+
+  def notify_old_accounts
+    all_inactive
+      .where(inactivity_warning_sent_at: nil)
+      .map(&:send_inactivity_warning)
+  end
+
+  def delete_old_accounts
+    all_inactive
+      .where
+      .not(inactivity_warning_sent_at: nil)
+      .where("inactivity_warning_sent_at < ?", 14.days.ago)
+      .map(&:deactivate_account)
+  end
+
+  # Returns a Map. Key is the number of warnings sent, value is a User object
+  # (not a device, but device is preloaded)
+  def all_inactive
+    return @all_inactive if @all_inactive
+    users = User.includes(:device)
+
+    # They signed up for an account, but never configured a device.
+    no_device = users
+      .where("devices.fbos_version" => nil)
+      .references(:devices)
+
+    # They signed up for an account and once had a working device.
+    ok_device = users
+      .where
+      .not("devices.fbos_version" => nil)
+      .references(:devices)
+
+    inactive_3mo = no_device
+      .where("last_sign_in_at < ?", INACTIVE_NO_DEVICE.ago)
+    inactive_11mo = ok_device
+      .where("last_sign_in_at < ?", INACTIVE_WITH_DEVICE.ago)
+    @all_inactive = inactive_11mo
+      .or(inactive_3mo)
+      .order("RANDOM()")
+      .limit(LIMIT)
+  end
+end

app/mailers/inactivity_mailer.rb

@@ -0,0 +1,11 @@
+class InactivityMailer < ApplicationMailer
+  attr_reader :user
+
+  SUBJECT = "Your FarmBot Account Will Be Deleted Due to Inactivity"
+  ORDER = { 1 => "First", 2 => "Second", 3 => "Final" }
+
+  def send_warning(user)
+    @user = user
+    mail to: user.email, subject: SUBJECT
+  end
+end

app/models/user.rb

@@ -54,4 +54,26 @@ class User < ApplicationRecord
       .current
       .raw_amqp_send(msg.to_json, Api::RmqUtilsController::PUBLIC_BROADCAST)
   end
+
+  # The web app deletes account that go inactive for long periods.
+  # It is called when the user logs in to the app.
+  def reset_inactivity_tracking!
+    update!(inactivity_warning_sent_at: nil)
+  end
+
+  def send_inactivity_warning
+    User.transaction do
+      update!(inactivity_warning_sent_at: Time.now)
+      InactivityMailer.send_warning(self).deliver_later
+    end
+  end
+
+  def deactivate_account
+    User.transaction do
+      raise "HALTING ERRONEOUS DELETION" if last_sign_in_at > 3.months.ago
+      # Prevent double deletion / race conditions.
+      u.update!(last_sign_in_at: Time.now, inactivity_warning_sent_at: nil)
+      u.delay.destroy!
+    end
+  end
 end

app/views/inactivity_mailer/send_warning.html.erb

@@ -0,0 +1,3 @@
+You have not logged in <%= time_ago_in_words(user.last_sign_in_at) %>. Your account will be automatically deleted after 14 days of inactivity.
+
+To halt the deletion process, please log in to your account.

db/migrate/20191119204916_add_inactivity_fields_to_users.rb

@@ -0,0 +1,5 @@
+class AddInactivityFieldsToUsers < ActiveRecord::Migration[6.0]
+  def change
+    add_column :users, :inactivity_warning_sent_at, :datetime
+  end
+end

db/structure.sql

@@ -1648,7 +1648,8 @@ CREATE TABLE public.users (
     confirmation_token character varying,
     agreed_to_terms_at timestamp without time zone,
     confirmation_sent_at timestamp without time zone,
-    unconfirmed_email character varying
+    unconfirmed_email character varying,
+    inactivity_warning_sent_at timestamp without time zone
 );
 
 
@@ -3366,6 +3367,7 @@ INSERT INTO "schema_migrations" (version) VALUES
 ('20190924190539'),
 ('20190930202839'),
 ('20191002125625'),
-('20191107170431');
+('20191107170431'),
+('20191119204916');