Add snowflake IDs

lib/nulla/application.ex

@@ -7,6 +7,8 @@ defmodule Nulla.Application do
 
   @impl true
   def start(_type, _args) do
+    worker_id = Application.fetch_env!(:nulla, :snowflake)[:worker_id]
+
     children = [
       NullaWeb.Telemetry,
       Nulla.Repo,
@@ -17,7 +19,8 @@ defmodule Nulla.Application do
       # Start a worker by calling: Nulla.Worker.start_link(arg)
       # {Nulla.Worker, arg},
       # Start to serve requests, typically the last entry
-      NullaWeb.Endpoint
+      NullaWeb.Endpoint,
+      {Nulla.Snowflake, worker_id}
     ]
 
     # See https://hexdocs.pm/elixir/Supervisor.html

lib/nulla/models/activity.ex

@@ -2,6 +2,7 @@ defmodule Nulla.Models.Activity do
   use Ecto.Schema
   import Ecto.Changeset
 
+  @primary_key {:id, :integer, autogenerate: false}
   schema "activities" do
     field :type, :string
     field :actor, :string

lib/nulla/models/bookmarks.ex

@@ -5,6 +5,7 @@ defmodule Nulla.Models.Bookmark do
   alias Nulla.Repo
   alias Nulla.Models.Bookmark
 
+  @primary_key {:id, :integer, autogenerate: false}
   schema "bookmarks" do
     field :url, :string
     field :user_id, :id

lib/nulla/models/follow.ex

@@ -2,6 +2,7 @@ defmodule Nulla.Models.Follow do
   use Ecto.Schema
   import Ecto.Changeset
 
+  @primary_key {:id, :integer, autogenerate: false}
   schema "follows" do
     belongs_to :user, Nulla.Models.User
     belongs_to :target, Nulla.Models.User

lib/nulla/models/hashtag.ex

@@ -2,6 +2,7 @@ defmodule Nulla.Models.Hashtag do
   use Ecto.Schema
   import Ecto.Changeset
 
+  @primary_key {:id, :integer, autogenerate: false}
   schema "hashtags" do
     field :tag, :string
     field :usage_count, :integer, default: 0

lib/nulla/models/media_attachment.ex

@@ -2,6 +2,7 @@ defmodule Nulla.Models.MediaAttachment do
   use Ecto.Schema
   import Ecto.Changeset
 
+  @primary_key {:id, :integer, autogenerate: false}
   schema "media_attachments" do
     field :file, :string
     field :mime_type, :string

lib/nulla/models/moderation_log.ex

@@ -2,6 +2,7 @@ defmodule Nulla.Models.ModerationLog do
   use Ecto.Schema
   import Ecto.Changeset
 
+  @primary_key {:id, :integer, autogenerate: false}
   schema "moderation_logs" do
     field :target_type, :string
     field :target_id, :string

lib/nulla/models/note.ex

@@ -5,6 +5,7 @@ defmodule Nulla.Models.Note do
   alias Nulla.Repo
   alias Nulla.Models.Note
 
+  @primary_key {:id, :integer, autogenerate: false}
   schema "notes" do
     field :content, :string
 

lib/nulla/models/notification.ex

@@ -2,6 +2,7 @@ defmodule Nulla.Models.Notification do
   use Ecto.Schema
   import Ecto.Changeset
 
+  @primary_key {:id, :integer, autogenerate: false}
   schema "notifications" do
     field :type, :string
     field :data, :map

lib/nulla/models/session.ex

@@ -2,6 +2,7 @@ defmodule Nulla.Models.Session do
   use Ecto.Schema
   import Ecto.Changeset
 
+  @primary_key {:id, :integer, autogenerate: false}
   schema "sessions" do
     field :token, :string
     field :user_agent, :string

lib/nulla/models/user.ex

@@ -2,8 +2,10 @@ defmodule Nulla.Models.User do
   use Ecto.Schema
   import Ecto.Changeset
   alias Nulla.Repo
+  alias Nulla.Snowflake
   alias Nulla.Models.User
 
+  @primary_key {:id, :integer, autogenerate: false}
   schema "users" do
     field :username, :string
     field :email, :string
@@ -77,6 +79,15 @@ defmodule Nulla.Models.User do
     ])
   end
 
+  def create_user(attrs) do
+    id = Snowflake.next_id()
+
+    %User{}
+    |> User.changeset(attrs)
+    |> Ecto.Changeset.put_change(:id, id)
+    |> Repo.insert()
+  end
+
   def get_user_by_username(username), do: Repo.get_by(User, username: username)
 
   def get_user_by_username!(username), do: Repo.get_by!(User, username: username)

lib/nulla/snowflake.ex

@@ -0,0 +1,62 @@
+defmodule Nulla.Snowflake do
+  use GenServer
+  import Bitwise
+
+  @epoch :calendar.datetime_to_gregorian_seconds({{2020, 1, 1}, {0, 0, 0}}) * 1000
+  @max_sequence 4095
+  @time_shift 22
+  @worker_shift 12
+
+  def start_link(worker_id) when worker_id in 0..1023 do
+    GenServer.start_link(__MODULE__, worker_id, name: __MODULE__)
+  end
+
+  def next_id do
+    GenServer.call(__MODULE__, :next_id)
+  end
+
+  @impl true
+  def init(worker_id) do
+    {:ok, %{last_timestamp: -1, sequence: 0, worker_id: worker_id}}
+  end
+
+  @impl true
+  def handle_call(:next_id, _from, %{worker_id: worker_id} = state) do
+    timestamp = current_time()
+
+    {timestamp, sequence, state} =
+      cond do
+        timestamp < state.last_timestamp ->
+          raise "Clock moved backwards"
+
+        timestamp == state.last_timestamp and state.sequence < @max_sequence ->
+          {timestamp, state.sequence + 1, %{state | sequence: state.sequence + 1}}
+
+        timestamp == state.last_timestamp ->
+          wait_for_next_millisecond(timestamp)
+          new_timestamp = current_time()
+          {new_timestamp, 0, %{state | last_timestamp: new_timestamp, sequence: 0}}
+
+        true ->
+          {timestamp, 0, %{state | last_timestamp: timestamp, sequence: 0}}
+      end
+
+    raw_id =
+      ((timestamp - @epoch) <<< @time_shift)
+      |> bor(worker_id <<< @worker_shift)
+      |> bor(sequence)
+
+    id = Bitwise.band(raw_id, 0x7FFFFFFFFFFFFFFF)
+
+    {:reply, id, %{state | last_timestamp: timestamp, sequence: sequence}}
+  end
+
+  defp current_time do
+    System.system_time(:millisecond)
+  end
+
+  defp wait_for_next_millisecond(last_ts) do
+    :timer.sleep(1)
+    if current_time() <= last_ts, do: wait_for_next_millisecond(last_ts), else: :ok
+  end
+end