add anonyhash

config/prod.secret.exs

@@ -15,6 +15,7 @@ config :bcrypt_elixir,
   log_rounds: String.to_integer(System.get_env("BCRYPT_ROUNDS") || "12")
 
 config :philomena,
+  anonymous_name_salt: System.get_env("ANONYMOUS_NAME_SALT"),
   password_pepper: System.get_env("PASSWORD_PEPPER"),
   otp_secret_key: System.get_env("OTP_SECRET_KEY"),
   image_url_root: System.get_env("IMAGE_URL_ROOT"),

lib/philomena/attribution.ex

@@ -0,0 +1,17 @@
+defprotocol Philomena.Attribution do
+  @doc """
+    Provides the "parent object" identifier for this object. This is so
+    that anonymous posts under the same topic id can return the same hash
+    for the same user.
+  """
+  @spec object_identifier(struct()) :: String.t()
+  def object_identifier(object)
+
+  @doc """
+    Provides the "best" user identifier for an object. Usually this will be
+    the user_id, but may also be the fingerprint or IP address if other
+    information is unavailable.
+  """
+  @spec best_user_identifier(struct()) :: String.t()
+  def best_user_identifier(object)
+end

lib/philomena/comments/attribution.ex

@@ -0,0 +1,9 @@
+defimpl Philomena.Attribution, for: Philomena.Comments.Comment do
+  def object_identifier(comment) do
+    to_string(comment.image_id || comment.id)
+  end
+
+  def best_user_identifier(comment) do
+    to_string(comment.user_id || comment.fingerprint || comment.ip)
+  end
+end

lib/philomena/images/attribution.ex

@@ -0,0 +1,9 @@
+defimpl Philomena.Attribution, for: Philomena.Images.Image do
+  def object_identifier(image) do
+    to_string(image.id)
+  end
+
+  def best_user_identifier(image) do
+    to_string(image.user_id || image.fingerprint || image.ip)
+  end
+end

lib/philomena/posts/attribution.ex

@@ -0,0 +1,9 @@
+defimpl Philomena.Attribution, for: Philomena.Posts.Post do
+  def object_identifier(post) do
+    to_string(post.topic_id || post.id)
+  end
+
+  def best_user_identifier(post) do
+    to_string(post.user_id || post.fingerprint || post.ip)
+  end
+end

lib/philomena_web/templates/user_attribution/_anon_user.html.slime

@@ -2,4 +2,5 @@
   strong<> = @object.user.name
 - else
   strong<>
-    ' Background Pony
+    | Background Pony #
+    = anonymous_name(@object)

lib/philomena_web/views/user_attribution_view.ex

@@ -1,3 +1,19 @@
 defmodule PhilomenaWeb.UserAttributionView do
+  alias Philomena.Attribution
+  use Bitwise
   use PhilomenaWeb, :view
+
+  def anonymous_name(object) do
+    salt = anonymous_name_salt()
+    id = Attribution.object_identifier(object)
+    user_id = Attribution.best_user_identifier(object)
+
+    (:erlang.crc32(salt <> id <> user_id) &&& 0xffff)
+    |> Integer.to_string(16)
+  end
+
+  defp anonymous_name_salt do
+    Application.get_env(:philomena, :anonymous_name_salt)
+    |> to_string()
+  end
 end