defmodule Mobilizon.Federation.ActivityStream.Converter.Comment do
  @moduledoc """
  Comment converter.

  This module allows to convert events from ActivityStream format to our own
  internal one, and back.
  """

  alias Mobilizon.Actors.Actor
  alias Mobilizon.Discussions
  alias Mobilizon.Discussions.Comment, as: CommentModel
  alias Mobilizon.Discussions.Discussion
  alias Mobilizon.Events.Event
  alias Mobilizon.Federation.ActivityPub
  alias Mobilizon.Federation.ActivityPub.Visibility
  alias Mobilizon.Federation.ActivityStream.{Converter, Convertible}
  alias Mobilizon.Federation.ActivityStream.Converter.Comment, as: CommentConverter
  alias Mobilizon.Tombstone, as: TombstoneModel

  import Mobilizon.Federation.ActivityStream.Converter.Utils,
    only: [
      fetch_tags: 1,
      fetch_mentions: 1,
      build_tags: 1,
      build_mentions: 1,
      maybe_fetch_actor_and_attributed_to_id: 1
    ]

  require Logger

  @behaviour Converter

  defimpl Convertible, for: CommentModel do
    defdelegate model_to_as(comment), to: CommentConverter
  end

  @doc """
  Converts an AP object data to our internal data structure.
  """
  @impl Converter
  @spec as_to_model_data(map) :: {:ok, map} | {:error, any()}
  def as_to_model_data(object) do
    Logger.debug("We're converting raw ActivityStream data to a comment entity")
    Logger.debug(inspect(object))

    with {%Actor{id: actor_id, domain: actor_domain}, attributed_to} <-
           maybe_fetch_actor_and_attributed_to_id(object),
         {:tags, tags} <- {:tags, fetch_tags(Map.get(object, "tag", []))},
         {:mentions, mentions} <-
           {:mentions, fetch_mentions(Map.get(object, "tag", []))},
         discussion <-
           Discussions.get_discussion_by_url(Map.get(object, "context")) do
      Logger.debug("Inserting full comment")
      Logger.debug(inspect(object))

      data = %{
        text: object["content"],
        url: object["id"],
        # Will be used in conversations, ignored in basic comments
        title: object["name"],
        context: object["context"],
        actor_id: actor_id,
        attributed_to_id: if(is_nil(attributed_to), do: nil, else: attributed_to.id),
        in_reply_to_comment_id: nil,
        event_id: nil,
        uuid: object["uuid"],
        discussion_id: if(is_nil(discussion), do: nil, else: discussion.id),
        tags: tags,
        mentions: mentions,
        local: is_nil(actor_domain),
        visibility: if(Visibility.is_public?(object), do: :public, else: :private)
      }

      maybe_fetch_parent_object(object, data)
    else
      {:ok, %Actor{suspended: true}} ->
        :error
    end
  end

  @doc """
  Make an AS comment object from an existing `Comment` structure.
  """
  @impl Converter
  @spec model_to_as(CommentModel.t()) :: map
  def model_to_as(%CommentModel{deleted_at: nil} = comment) do
    to = determine_to(comment)

    object = %{
      "type" => "Note",
      "to" => to,
      "cc" => [],
      "content" => comment.text,
      "mediaType" => "text/html",
      "actor" => comment.actor.url,
      "attributedTo" =>
        if(is_nil(comment.attributed_to), do: nil, else: comment.attributed_to.url) ||
          comment.actor.url,
      "uuid" => comment.uuid,
      "id" => comment.url,
      "tag" => build_mentions(comment.mentions) ++ build_tags(comment.tags)
    }

    object =
      if comment.discussion_id,
        do: Map.put(object, "context", comment.discussion.url),
        else: object

    cond do
      comment.in_reply_to_comment ->
        Map.put(object, "inReplyTo", comment.in_reply_to_comment.url)

      comment.event ->
        Map.put(object, "inReplyTo", comment.event.url)

      true ->
        object
    end
  end

  @doc """
  A "soft-deleted" comment is a tombstone
  """
  @impl Converter
  @spec model_to_as(CommentModel.t()) :: map
  def model_to_as(%CommentModel{} = comment) do
    Convertible.model_to_as(%TombstoneModel{
      uri: comment.url,
      inserted_at: comment.deleted_at
    })
  end

  @spec determine_to(CommentModel.t()) :: [String.t()]
  defp determine_to(%CommentModel{} = comment) do
    cond do
      not is_nil(comment.attributed_to) ->
        [comment.attributed_to.url]

      comment.visibility == :public ->
        ["https://www.w3.org/ns/activitystreams#Public"]

      true ->
        [comment.actor.followers_url]
    end
  end

  defp maybe_fetch_parent_object(object, data) do
    # We fetch the parent object
    Logger.debug("We're fetching the parent object")

    if Map.has_key?(object, "inReplyTo") && object["inReplyTo"] != nil &&
         object["inReplyTo"] != "" do
      Logger.debug(fn -> "Object has inReplyTo #{object["inReplyTo"]}" end)

      case ActivityPub.fetch_object_from_url(object["inReplyTo"]) do
        # Reply to an event (Event)
        {:ok, %Event{id: id}} ->
          Logger.debug("Parent object is an event")
          data |> Map.put(:event_id, id)

        # Reply to a comment (Comment)
        {:ok, %CommentModel{id: id} = comment} ->
          Logger.debug("Parent object is another comment")

          data
          |> Map.put(:in_reply_to_comment_id, id)
          |> Map.put(:origin_comment_id, comment |> CommentModel.get_thread_id())
          |> Map.put(:event_id, comment.event_id)

        # Reply to a discucssion (Discussion)
        {:ok,
         %Discussion{
           id: discussion_id,
           last_comment: %CommentModel{id: last_comment_id, origin_comment_id: origin_comment_id}
         } = _discussion} ->
          Logger.debug("Parent object is a discussion")

          data
          |> Map.put(:in_reply_to_comment_id, last_comment_id)
          |> Map.put(:origin_comment_id, origin_comment_id)
          |> Map.put(:discussion_id, discussion_id)

        # Anything else is kind of a MP
        {:error, parent} ->
          Logger.warn("Parent object is something we don't handle")
          Logger.debug(inspect(parent))
          data
      end
    else
      Logger.debug("No parent object for this comment")

      data
    end
  end
end