Lessons 30-33

.iex.exs

@@ -0,0 +1 @@
+alias PhoenixChat.{Repo, User, AnonymousUser, Message}

mix.exs

@@ -21,6 +21,7 @@ defmodule PhoenixChat.Mixfile do
       applications: [
         :comeonin,
         :cowboy,
+        :faker,
         :gettext,
         :logger,
         :phoenix,
@@ -45,6 +46,7 @@ defmodule PhoenixChat.Mixfile do
       {:comeonin, "~> 2.3"},
       {:corsica, "~> 0.4"},
       {:cowboy, "~> 1.0"},
+      {:faker, "~> 0.7"},
       {:gettext, "~> 0.11"},
       {:guardian, "~> 0.10"},
       {:phoenix, "~> 1.2.0"},

mix.lock

@@ -7,6 +7,7 @@
   "db_connection": {:hex, :db_connection, "1.0.0-rc.5", "1d9ab6e01387bdf2de7a16c56866971f7c2f75aea7c69cae2a0346e4b537ae0d", [:mix], [{:connection, "~> 1.0.2", [hex: :connection, optional: false]}, {:poolboy, "~> 1.5", [hex: :poolboy, optional: true]}, {:sbroker, "~> 1.0.0-beta.3", [hex: :sbroker, optional: true]}]},
   "decimal": {:hex, :decimal, "1.1.2", "79a769d4657b2d537b51ef3c02d29ab7141d2b486b516c109642d453ee08e00c", [:mix], []},
   "ecto": {:hex, :ecto, "2.0.5", "7f4c79ac41ffba1a4c032b69d7045489f0069c256de606523c65d9f8188e502d", [:mix], [{:db_connection, "~> 1.0-rc.4", [hex: :db_connection, optional: true]}, {:decimal, "~> 1.1.2 or ~> 1.2", [hex: :decimal, optional: false]}, {:mariaex, "~> 0.7.7", [hex: :mariaex, optional: true]}, {:poison, "~> 1.5 or ~> 2.0", [hex: :poison, optional: true]}, {:poolboy, "~> 1.5", [hex: :poolboy, optional: false]}, {:postgrex, "~> 0.12.0", [hex: :postgrex, optional: true]}, {:sbroker, "~> 1.0-beta", [hex: :sbroker, optional: true]}]},
+  "faker": {:hex, :faker, "0.7.0", "2c42deeac7be717173c78c77fb3edc749fb5d5e460e33d01fe592ae99acc2f0d", [:mix], []},
   "fs": {:hex, :fs, "0.9.2", "ed17036c26c3f70ac49781ed9220a50c36775c6ca2cf8182d123b6566e49ec59", [:rebar], []},
   "gettext": {:hex, :gettext, "0.11.0", "80c1dd42d270482418fa158ec5ba073d2980e3718bacad86f3d4ad71d5667679", [:mix], []},
   "guardian": {:hex, :guardian, "0.12.0", "ab1f0a1ab0cd8f4f9c8cca6e28d61136ca682684cf0f82e55a50e8061be7575a", [:mix], [{:jose, "~> 1.6", [hex: :jose, optional: false]}, {:plug, "~> 1.0", [hex: :plug, optional: false]}, {:poison, ">= 1.3.0", [hex: :poison, optional: false]}, {:uuid, ">=1.1.1", [hex: :uuid, optional: false]}]},

priv/repo/migrations/20160915111446_create_anonymous_users.exs

@@ -0,0 +1,16 @@
+defmodule PhoenixChat.Repo.Migrations.CreateAnonymousUsers do
+  use Ecto.Migration
+
+  def change do
+    # We want to use a `uuid` as primary key so we need to set `primary_key: false`.
+    create table(:anonymous_users, primary_key: false) do
+      # We add the `:id` column manually with a type of `uuid` and set
+      # it as `primary_key`.
+      add :id, :uuid, primary_key: true
+      add :name, :string
+      add :avatar, :string
+
+      timestamps
+    end
+  end
+end

priv/repo/migrations/20160915111609_message_belongs_to_anonymous_user.exs

@@ -0,0 +1,18 @@
+defmodule PhoenixChat.Repo.Migrations.MessageBelongsToAnonymousUser do
+  use Ecto.Migration
+
+  def up do
+    alter table(:messages) do
+      # We need to set `type` as `uuid` so it does not default to `integer`.
+      add :anonymous_user_id, references(:anonymous_users, on_delete: :nilify_all, type: :uuid)
+      remove :from
+    end
+  end
+
+  def down do
+    alter table(:messages) do
+      remove :anonymous_user_id
+      add :from, :string
+    end
+  end
+end

web/channels/admin_channel.ex

@@ -1,33 +1,75 @@
 defmodule PhoenixChat.AdminChannel do
   @moduledoc """
-  The channel used to give the administrator access to all users.
+  The channel used to give the administrator access to all users.
   """
 
   use PhoenixChat.Web, :channel
   require Logger
 
-  alias PhoenixChat.{Presence}
+  alias PhoenixChat.{Presence, Repo, AnonymousUser}
+
+  intercept ~w(lobby_list)
 
   @doc """
   The `admin:active_users` topic is how we identify all users currently using the app.
   """
   def join("admin:active_users", payload, socket) do
     authorize(payload, fn ->
       send(self, :after_join)
-      {:ok, socket}
+      id = socket.assigns[:uuid] || socket.assigns[:user_id]
+      lobby_list = AnonymousUser.recently_active_users
+        |> Repo.all
+      {:ok, %{id: id, lobby_list: lobby_list}, socket}
     end)
   end
 
   @doc """
-  This handles the `:after_join` event and tracks the presence of the socket that has subscribed to the `admin:active_users` topic.
+  This handles the `:after_join` event and tracks the presence of the socket that
+  has subscribed to the `admin:active_users` topic.
   """
-  def handle_info(:after_join, socket) do
+  # We no longer track admin's presence. This will lead to simpler code in the
+  # frontend by not having to filter out admin from the list of users in the Sidebar.
+  def handle_info(:after_join, %{assigns: %{user_id: _user_id}} = socket) do
+    push socket, "presence_state", Presence.list(socket)
+    {:noreply, socket}
+  end
+
+  # We track only the presence of anonymous users and ensure they are stored
+  # in our DB.
+  def handle_info(:after_join, %{assigns: %{uuid: uuid}} = socket) do
+    # We save anonymous user to DB when it hasn't been saved before
+    user = ensure_user_saved!(uuid)
+
+    # Used by the frontend to update their lobby_list (chatrooms displayed
+    # on the sidebar)
+    broadcast! socket, "lobby_list", user
+
     push socket, "presence_state", Presence.list(socket)
     Logger.debug "Presence for socket: #{inspect socket}"
-    id = socket.assigns.user_id || socket.assigns.uuid
-    {:ok, _} = Presence.track(socket, id, %{
+    {:ok, _} = Presence.track(socket, uuid, %{
       online_at: inspect(System.system_time(:seconds))
     })
     {:noreply, socket}
   end
+
+  @doc """
+  Sends the lobby_list only to admins
+  """
+  def handle_out("lobby_list", payload, socket) do
+    assigns = socket.assigns
+    if assigns[:user_id] do
+      push socket, "lobby_list", payload
+    end
+    {:noreply, socket}
+  end
+
+  defp ensure_user_saved!(uuid) do
+    user_exists = Repo.get(AnonymousUser, uuid)
+    if user_exists do
+      user_exists
+    else
+      changeset = AnonymousUser.changeset(%AnonymousUser{}, %{id: uuid})
+      Repo.insert!(changeset)
+    end
+  end
 end

web/channels/room_channel.ex

@@ -9,34 +9,23 @@ defmodule PhoenixChat.RoomChannel do
       messages = room_id
         |> Message.latest_room_messages
         |> Repo.all
-        |> Enum.map(&message_payload/1)
         |> Enum.reverse
       {:ok, %{messages: messages}, socket}
     end)
   end
 
   def handle_in("message", payload, socket) do
     payload = payload
-      |> Map.put("user_id", socket.assigns.user_id)
-      |> Map.put("from", socket.assigns[:uuid])
+      |> Map.put("user_id", socket.assigns[:user_id])
+      |> Map.put("anonymous_user_id", socket.assigns[:uuid])
     changeset = Message.changeset(%Message{}, payload)
 
     case Repo.insert(changeset) do
       {:ok, message} ->
-        payload = message_payload(message)
-        broadcast! socket, "message", payload
+        broadcast! socket, "message", message
         {:reply, :ok, socket}
       {:error, changeset} ->
         {:reply, {:error, %{errors: changeset}}, socket}
     end
   end
-
-  defp message_payload(message) do
-    from = message.user_id || message.from
-    %{body: message.body,
-      timestamp: message.timestamp,
-      room: message.room,
-      from: from,
-      id: message.id}
-  end
 end

web/channels/user_socket.ex

@@ -25,21 +25,23 @@ defmodule PhoenixChat.UserSocket do
   def connect(params, socket) do
     user_id = params["id"]
     user = user_id && Repo.get(User, user_id)
+    # We added this validation. More explanation below at the function def.
+    validate_params!(params)
 
     socket = if user do
-      socket
+        socket
         |> assign(:user_id, user_id)
         |> assign(:username, user.username)
         |> assign(:email, user.email)
       else
+        # No longer add `:user_id` field to socket.assigns
         socket
-          |> assign(:user_id, nil)
-          |> assign(:uuid, params["uuid"])
+        |> assign(:uuid, params["uuid"])
       end
 
     {:ok, socket}
   end
-  
+
   # Socket id's are topics that allow you to identify all sockets for a given user:
   #
   #     def id(socket), do: "users_socket:#{socket.assigns.user_id}"
@@ -51,4 +53,14 @@ defmodule PhoenixChat.UserSocket do
   #
   # Returning `nil` makes this socket anonymous.
   def id(_socket), do: nil
+
+  @empty ["", nil]
+  # We want to raise an error as early as here so our code in channels will not
+  # have to worry about empty values for id or uuid and our frontend won't be
+  # be able to connect to the socket unless they provide an id or uuid.
+  defp validate_params!(%{"id" => id, "uuid" => uuid}) when id in @empty or uuid in @empty do
+    raise "id or uuid must not be empty"
+  end
+
+  defp validate_params!(_), do: nil #noop
 end

web/models/anonymous_user.ex

@@ -0,0 +1,52 @@
+defmodule PhoenixChat.AnonymousUser do
+  use PhoenixChat.Web, :model
+
+  alias PhoenixChat.Message
+
+  # Since we provide the `id` for our AnonymousUser record, we will need to set
+  # the primary key to not autogenerate it.
+  @primary_key {:id, :binary_id, autogenerate: false}
+  # We need to set `@foreign_key_type` below since it defaults to `:integer`.
+  # We are using a UUID as `id` so we need to set type as `:binary_id`.
+  @foreign_key_type :binary_id
+  @derive {Poison.Encoder, only: ~w(id name avatar)a}
+
+  schema "anonymous_users" do
+    field :name
+    field :avatar
+    has_many :messages, Message
+
+    timestamps
+  end
+
+  def changeset(model, params \\ :empty) do
+    model
+    |> cast(params, ~w(id), ~w())
+    |> put_avatar
+    |> put_name
+  end
+
+  @doc """
+  This query returns users with the most recent message sent up to a given limit.
+  """
+  def recently_active_users(limit \\ 20) do
+    from u in __MODULE__,
+      left_join: m in Message, on: m.anonymous_user_id == u.id,
+      limit: ^limit,
+      distinct: u.id,
+      order_by: [desc: u.inserted_at, desc: m.inserted_at]
+  end
+
+  # Set a fake name for our anonymous user every time we create one
+  defp put_name(changeset) do
+    name = (Faker.Color.fancy_name <> " " <> Faker.Company.buzzword()) |> String.downcase
+    changeset
+    |> put_change(:name, name)
+  end
+
+  # Set a fake avatar for our anonymous user every time we create one
+  defp put_avatar(changeset) do
+    changeset
+    |> put_change(:avatar, Faker.Avatar.image_url(25, 25))
+  end
+end

web/models/message.ex

@@ -1,18 +1,33 @@
 defmodule PhoenixChat.Message do
   use PhoenixChat.Web, :model
 
+  alias PhoenixChat.{DateTime}
+
+  # @derive is a module attribute for you to be able to customize how an
+  # Elixir Protocol treats a custom struct.
+  # In this case, we instruct the Poison.Encode protocol to only encode
+  # certain fields and ignore the rest.
+  # More info at:
+  # - https://github.com/devinus/poison#encoding-only-some-attributes
+  #
+  # This replaces the message_payload/1 function in RoomChannel
+  @derive {Poison.Encoder, only: ~w(id body timestamp room user_id anonymous_user_id)a}
+
   schema "messages" do
     field :body, :string
-    field :timestamp, PhoenixChat.DateTime
+    field :timestamp, DateTime
     field :room, :string
-    field :from, :string
+
     belongs_to :user, PhoenixChat.User
+    # Note that we set `:type` below. This is so Ecto is aware the type of the
+    # foreign_key is not an `:integer` but a `:binary_id`.
+    belongs_to :anonymous_user, PhoenixChat.AnonymousUser, type: :binary_id
 
     timestamps
   end
 
   @required_fields ~w(body timestamp room)
-  @optional_fields ~w(user_id from)
+  @optional_fields ~w(anonymous_user_id user_id)
 
   @doc """
   Creates a changeset based on the `model` and `params`.