Introduce backend for reports

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

lib/service/activity_pub/converters/flag.ex

@@ -0,0 +1,85 @@
+defmodule Mobilizon.Service.ActivityPub.Converters.Flag do
+  @moduledoc """
+  Flag converter
+
+  This module allows to convert reports from ActivityStream format to our own internal one, and back.
+
+  Note: Reports are named Flag in AS.
+  """
+  alias Mobilizon.Actors
+  alias Mobilizon.Actors.Actor
+  alias Mobilizon.Events
+  alias Mobilizon.Events.Event
+  alias Mobilizon.Reports.Report
+  alias Mobilizon.Service.ActivityPub.Converter
+
+  @behaviour Converter
+
+  @doc """
+  Converts an AP object data to our internal data structure
+  """
+  @impl Converter
+  @spec as_to_model_data(map()) :: map()
+  def as_to_model_data(object) do
+    with params <- as_to_model(object) do
+      %{
+        "reporter_id" => params["reporter"].id,
+        "uri" => params["uri"],
+        "content" => params["content"],
+        "reported_id" => params["reported"].id,
+        "event_id" => (!is_nil(params["event"]) && params["event"].id) || nil,
+        "comments" => params["comments"]
+      }
+    end
+  end
+
+  def as_to_model(%{"object" => objects} = object) do
+    with {:ok, %Actor{} = reporter} <- Actors.get_actor_by_url(object["actor"]),
+         %Actor{} = reported <-
+           Enum.reduce_while(objects, nil, fn url, _ ->
+             with {:ok, %Actor{} = actor} <- Actors.get_actor_by_url(url) do
+               {:halt, actor}
+             else
+               _ -> {:cont, nil}
+             end
+           end),
+         event <-
+           Enum.reduce_while(objects, nil, fn url, _ ->
+             with %Event{} = event <- Events.get_event_by_url(url) do
+               {:halt, event}
+             else
+               _ -> {:cont, nil}
+             end
+           end),
+
+         # Remove the reported user from the object list.
+         comments <-
+           Enum.filter(objects, fn url ->
+             !(url == reported.url || (!is_nil(event) && event.url == url))
+           end),
+         comments <- Enum.map(comments, &Events.get_comment_from_url/1) do
+      %{
+        "reporter" => reporter,
+        "uri" => object["id"],
+        "content" => object["content"],
+        "reported" => reported,
+        "event" => event,
+        "comments" => comments
+      }
+    end
+  end
+
+  @doc """
+  Convert an event struct to an ActivityStream representation
+  """
+  @impl Converter
+  @spec model_to_as(EventModel.t()) :: map()
+  def model_to_as(%Report{} = report) do
+    %{
+      "type" => "Flag",
+      "to" => ["https://www.w3.org/ns/activitystreams#Public"],
+      "actor" => report.reporter.url,
+      "id" => report.url
+    }
+  end
+end