ActivityPub helpers and object route

config/config.exs

@@ -25,6 +25,10 @@ config :logger, :console,
 # Use Jason for JSON parsing in Phoenix
 config :phoenix, :json_library, Jason
 
+config :mime, :types, %{
+  "application/activity+json" => ["activity+json"]
+}
+
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
 import_config "#{Mix.env()}.exs"

config/dev.exs

@@ -16,6 +16,7 @@ config :clacks, Clacks.Repo,
 # watchers to your application. For example, we use it
 # with webpack to recompile .js and .css sources.
 config :clacks, ClacksWeb.Endpoint,
+  url: [scheme: "http", port: 4000],
   http: [port: 4000],
   debug_errors: true,
   code_reloader: true,

config/prod.exs

@@ -10,7 +10,7 @@ use Mix.Config
 # which you should run after static files are built and
 # before starting your production server.
 config :clacks, ClacksWeb.Endpoint,
-  url: [host: "example.com", port: 80],
+  url: [scheme: "http", host: "example.com", port: 80],
   cache_static_manifest: "priv/static/cache_manifest.json"
 
 # Do not print debug messages in production

lib/clacks/activity.ex

@@ -1,6 +1,5 @@
 defmodule Clacks.Activity do
   use Ecto.Schema
-
   import Ecto.Changeset
 
   @type t() :: %__MODULE__{}

lib/clacks/activitypub.ex

@@ -0,0 +1,85 @@
+defmodule Clacks.ActivityPub do
+  @context ["https://www.w3.org/ns/activitystreams"]
+  @public "https://www.w3.org/ns/activitystreams#Public"
+
+  @spec note(
+          actor :: String.t(),
+          html :: String.t(),
+          context :: String.t(),
+          id :: String.t() | nil,
+          published :: DateTime.t(),
+          to :: [String.t()],
+          cc :: [String.t()]
+        ) :: map()
+  def note(
+        actor,
+        html,
+        context,
+        id \\ nil,
+        published \\ DateTime.utc_now(),
+        to \\ [@public],
+        cc \\ []
+      ) do
+    id = id || object_id(Ecto.UUID.generate())
+
+    %{
+      "@context" => @context,
+      "id" => id,
+      "url" => id,
+      "type" => "Note",
+      "actor" => actor,
+      "attributedTo" => actor,
+      "to" => to,
+      "cc" => cc,
+      "content" => html,
+      "conversation" => context,
+      "context" => context,
+      "published" => published |> DateTime.to_iso8601()
+    }
+  end
+
+  @spec create(
+          object :: map(),
+          id :: String.t() | nil,
+          actor :: String.t() | nil,
+          to :: [String.t()] | nil,
+          cc :: [String.t()] | nil
+        ) :: map()
+  def create(object, id \\ nil, actor \\ nil, to \\ nil, cc \\ nil) do
+    %{
+      "@context" => @context,
+      "id" => id || activity_id(Ecto.UUID.generate()),
+      "actor" => actor || object["actor"],
+      "type" => "Create",
+      "object" => object,
+      "to" => to || object["to"],
+      "cc" => cc || object["cc"]
+    }
+  end
+
+  @spec object_id(id :: String.t()) :: String.t()
+  def object_id(id) do
+    url = Application.get_env(:clacks, ClacksWeb.Endpoint)[:url]
+
+    %URI{
+      scheme: url[:scheme],
+      host: url[:host],
+      port: url[:port],
+      path: Path.join("/objects", id)
+    }
+    |> URI.to_string()
+  end
+
+  @spec activity_id(id :: String.t()) :: String.t()
+  def activity_id(id) do
+    url = Application.get_env(:clacks, ClacksWeb.Endpoint)[:url]
+
+    %URI{
+      scheme: url[:scheme],
+      host: url[:host],
+      port: url[:port],
+      path: Path.join("/activities", id)
+    }
+    |> URI.to_string()
+  end
+end

lib/clacks/object.ex

@@ -1,5 +1,6 @@
 defmodule Clacks.Object do
   use Ecto.Schema
+  import Ecto.Changeset
 
   @type t() :: %__MODULE__{}
 
@@ -8,4 +9,10 @@ defmodule Clacks.Object do
 
     timestamps()
   end
+
+  def changeset(%__MODULE__{} = schema, attrs) do
+    schema
+    |> cast(attrs, [:data])
+    |> validate_required([:data])
+  end
 end

lib/clacks_web/controllers/objects_controller.ex

@@ -0,0 +1,21 @@
+defmodule ClacksWeb.ObjectsController do
+  use ClacksWeb, :controller
+  alias Clacks.{Repo, Object, ActivityPub}
+  import Ecto.Query
+
+  def get(conn, %{"id" => id}) do
+    object_id = current_url(conn)
+    query = from(o in Object, where: fragment("?->>'id'", o.data) == ^object_id)
+
+    case Repo.one(query) do
+      nil ->
+        conn
+        |> put_status(404)
+
+      object ->
+        conn
+        |> put_resp_header("content-type", "application/activity+json")
+        |> json(object.data)
+    end
+  end
+end

lib/clacks_web/router.ex

@@ -9,8 +9,8 @@ defmodule ClacksWeb.Router do
     plug :put_secure_browser_headers
   end
 
-  pipeline :api do
+  pipeline :activitypub do
-    plug :accepts, ["json"]
+    plug :accepts, ["activity+json", "html"]
   end
 
   scope "/", ClacksWeb do
@@ -19,6 +19,12 @@ defmodule ClacksWeb.Router do
     get "/", PageController, :index
   end
 
+  scope "/", ClacksWeb do
+    pipe_through :activitypub
+
+    get "/objects/:id", ObjectsController, :get
+  end
+
   # Other scopes may use custom stacks.
   # scope "/api", ClacksWeb do
   #   pipe_through :api