defmodule Pleroma.Web.ActivityPub.ActivityPub do
  alias Pleroma.Repo
  alias Pleroma.Activity
  import Ecto.Query

  def insert(map) when is_map(map) do
    map = Map.put_new_lazy(map, "id", &generate_activity_id/0)

    map = if map["object"] do
      object = Map.put_new_lazy(map["object"], "id", &generate_object_id/0)
      Map.put(map, "object", object)
    else
      map
    end

    Repo.insert(%Activity{data: map})
  end

  def generate_activity_id do
    host =
      Application.get_env(:pleroma, Pleroma.Web.Endpoint)
      |> Keyword.fetch!(:url)
      |> Keyword.fetch!(:host)
    "https://#{host}/activities/#{Ecto.UUID.generate}"
  end

  def generate_object_id do
    host =
      Application.get_env(:pleroma, Pleroma.Web.Endpoint)
      |> Keyword.fetch!(:url)
      |> Keyword.fetch!(:host)
    "https://#{host}/objects/#{Ecto.UUID.generate}"
  end

  def fetch_public_activities(opts \\ %{}) do
    public = ["https://www.w3.org/ns/activitystreams#Public"]
    fetch_activities(public, opts)
  end

  def fetch_activities(recipients, opts \\ %{}) do
    since_id = opts["since_id"] || 0

    query = from activity in Activity,
      limit: 20,
      order_by: [desc: :inserted_at]

    query = Enum.reduce(recipients, query, fn (recipient, q) ->
      map = %{ to: [recipient] }
      from activity in q,
      or_where: fragment(~s(? @> ?), activity.data, ^map)
    end)

    query = from activity in query,
      where: activity.id > ^since_id

    Repo.all(query)
    |> Enum.reverse
  end
end