Implement public actor ICS endpoint and event ICS export

Closes #83 and #84

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/service/export/feed.ex

@@ -1,4 +1,4 @@
-defmodule Mobilizon.Service.Feed do
+defmodule Mobilizon.Service.Export.Feed do
   @moduledoc """
   Serve Atom Syndication Feeds
   """

lib/service/export/icalendar.ex

@@ -0,0 +1,75 @@
+defmodule Mobilizon.Service.Export.ICalendar do
+  @moduledoc """
+  Export an event to iCalendar format
+  """
+
+  alias Mobilizon.Events.Event
+  alias Mobilizon.Events
+  alias Mobilizon.Actors.Actor
+  alias Mobilizon.Actors
+
+  @doc """
+  Export a public event to iCalendar format.
+
+  The event must have a visibility of `:public` or `:unlisted`
+  """
+  @spec export_public_event(Event.t()) :: {:ok, String.t()}
+  def export_public_event(%Event{visibility: visibility} = event)
+      when visibility in [:public, :unlisted] do
+    {:ok, %ICalendar{events: [do_export_event(event)]} |> ICalendar.to_ics()}
+  end
+
+  @spec export_public_event(Event.t()) :: {:error, :event_not_public}
+  def export_public_event(%Event{}), do: {:error, :event_not_public}
+
+  @spec do_export_event(Event.t()) :: ICalendar.Event.t()
+  defp do_export_event(%Event{} = event) do
+    %ICalendar.Event{
+      summary: event.title,
+      dtstart: event.begins_on,
+      dtend: event.ends_on,
+      description: event.description,
+      uid: event.uuid,
+      categories: [event.category] ++ (event.tags |> Enum.map(& &1.slug))
+    }
+  end
+
+  @doc """
+  Export a public actor's events to iCalendar format.
+
+  The events must have a visibility of `:public` or `:unlisted`
+  """
+  # TODO: The actor should also have visibility options
+  @spec export_public_actor(Actor.t()) :: String.t()
+  def export_public_actor(%Actor{} = actor) do
+    with {:ok, events, _} <- Events.get_public_events_for_actor(actor) do
+      {:ok, %ICalendar{events: events |> Enum.map(&do_export_event/1)} |> ICalendar.to_ics()}
+    end
+  end
+
+  @doc """
+  Create cache for an actor
+  """
+  def create_cache("actor_" <> name) do
+    with %Actor{} = actor <- Actors.get_local_actor_by_name(name),
+         {:ok, res} <- export_public_actor(actor) do
+      {:commit, res}
+    else
+      err ->
+        {:ignore, err}
+    end
+  end
+
+  @doc """
+  Create cache for an actor
+  """
+  def create_cache("event_" <> uuid) do
+    with %Event{} = event <- Events.get_event_full_by_uuid(uuid),
+         {:ok, res} <- export_public_event(event) do
+      {:commit, res}
+    else
+      err ->
+        {:ignore, err}
+    end
+  end
+end