add account deletion

app/logical/user_deletion.rb

@@ -0,0 +1,71 @@
+class UserDeletion
+  class ValidationError < Exception ; end
+
+  attr_reader :user, :password
+
+  def initialize(user, password)
+    @user = user
+    @password = password
+  end
+
+  def delete!
+    validate
+    clear_user_settings
+    remove_favorites
+    rename
+    reset_password
+  end
+
+private
+
+  def clear_user_settings
+    user.email = nil
+    user.last_logged_in_at = nil
+    user.last_forum_read_at = nil
+    user.recent_tags = nil
+    user.favorite_tags = nil
+    user.blacklisted_tags = nil
+    user.hide_deleted_posts = false
+    user.time_zone = "Eastern Time (US & Canada)"
+    user.save!
+  end
+
+  def reset_password
+    random = SecureRandom.hex(16)
+    user.password = random
+    user.password_confirmation = random
+    user.old_password = password
+    user.save!
+  end
+
+  def remove_favorites
+    Post.tag_match("fav:#{user.name}").find_each do |post|
+      Favorite.remove(post, user)
+    end
+  end
+
+  def rename
+    name = "user_#{user.id}"
+    n = 0
+    while User.where(:name => name).exists? && (n < 10)
+      name += "~"
+    end
+
+    if n == 10
+      raise ValidationError.new("New name could not be found")
+    end
+
+    user.name = name
+    user.save!
+  end
+
+  def validate
+    if !User.authenticate(user.name, password)
+      raise ValidationError.new("Password is incorrect")
+    end
+
+    if user.level >= User::Levels::ADMIN
+      raise ValidationError.new("Admins cannot delete their account")
+    end
+  end
+end