defmodule Pleroma.Web.ActivityPub.Transmogrifier do
  @moduledoc """
  A module to handle coding from internal to wire ActivityPub and back.
  """
  alias Pleroma.User
  alias Pleroma.Object
  alias Pleroma.Activity
  alias Pleroma.Repo
  alias Pleroma.Web.ActivityPub.ActivityPub

  import Ecto.Query

  require Logger

  @doc """
  Modifies an incoming AP object (mastodon format) to our internal format.
  """
  def fix_object(object) do
    object
    |> Map.put("actor", object["attributedTo"])
    |> fix_attachments
    |> fix_context
    |> fix_in_reply_to
    |> fix_emoji
    |> fix_tag
  end

  def fix_in_reply_to(%{"inReplyTo" => in_reply_to_id} = object)
      when not is_nil(in_reply_to_id) do
    case ActivityPub.fetch_object_from_id(in_reply_to_id) do
      {:ok, replied_object} ->
        activity = Activity.get_create_activity_by_object_ap_id(replied_object.data["id"])

        object
        |> Map.put("inReplyTo", replied_object.data["id"])
        |> Map.put("inReplyToAtomUri", object["inReplyToAtomUri"] || in_reply_to_id)
        |> Map.put("inReplyToStatusId", activity.id)
        |> Map.put("conversation", replied_object.data["context"] || object["conversation"])
        |> Map.put("context", replied_object.data["context"] || object["conversation"])

      e ->
        Logger.error("Couldn't fetch #{object["inReplyTo"]} #{inspect(e)}")
        object
    end
  end

  def fix_in_reply_to(object), do: object

  def fix_context(object) do
    object
    |> Map.put("context", object["conversation"])
  end

  def fix_attachments(object) do
    attachments =
      (object["attachment"] || [])
      |> Enum.map(fn data ->
        url = [%{"type" => "Link", "mediaType" => data["mediaType"], "href" => data["url"]}]
        Map.put(data, "url", url)
      end)

    object
    |> Map.put("attachment", attachments)
  end

  def fix_emoji(object) do
    tags = object["tag"] || []
    emoji = tags |> Enum.filter(fn data -> data["type"] == "Emoji" and data["icon"] end)

    emoji =
      emoji
      |> Enum.reduce(%{}, fn data, mapping ->
        name = data["name"]

        name =
          if String.starts_with?(name, ":") do
            name |> String.slice(1..-2)
          else
            name
          end

        mapping |> Map.put(name, data["icon"]["url"])
      end)

    # we merge mastodon and pleroma emoji into a single mapping, to allow for both wire formats
    emoji = Map.merge(object["emoji"] || %{}, emoji)

    object
    |> Map.put("emoji", emoji)
  end

  def fix_tag(object) do
    tags =
      (object["tag"] || [])
      |> Enum.filter(fn data -> data["type"] == "Hashtag" and data["name"] end)
      |> Enum.map(fn data -> String.slice(data["name"], 1..-1) end)

    combined = (object["tag"] || []) ++ tags

    object
    |> Map.put("tag", combined)
  end

  # TODO: validate those with a Ecto scheme
  # - tags
  # - emoji
  def handle_incoming(%{"type" => "Create", "object" => %{"type" => "Note"} = object} = data) do
    with nil <- Activity.get_create_activity_by_object_ap_id(object["id"]),
         %User{} = user <- User.get_or_fetch_by_ap_id(data["actor"]) do
      object = fix_object(data["object"])

      params = %{
        to: data["to"],
        object: object,
        actor: user,
        context: object["conversation"],
        local: false,
        published: data["published"],
        additional:
          Map.take(data, [
            "cc",
            "id"
          ])
      }

      ActivityPub.create(params)
    else
      %Activity{} = activity -> {:ok, activity}
      _e -> :error
    end
  end

  def handle_incoming(
        %{"type" => "Follow", "object" => followed, "actor" => follower, "id" => id} = data
      ) do
    with %User{local: true} = followed <- User.get_cached_by_ap_id(followed),
         %User{} = follower <- User.get_or_fetch_by_ap_id(follower),
         {:ok, activity} <- ActivityPub.follow(follower, followed, id, false) do
      ActivityPub.accept(%{to: [follower.ap_id], actor: followed.ap_id, object: data, local: true})

      User.follow(follower, followed)
      {:ok, activity}
    else
      _e -> :error
    end
  end

  def handle_incoming(
        %{"type" => "Like", "object" => object_id, "actor" => actor, "id" => id} = _data
      ) do
    with %User{} = actor <- User.get_or_fetch_by_ap_id(actor),
         {:ok, object} <-
           get_obj_helper(object_id) || ActivityPub.fetch_object_from_id(object_id),
         {:ok, activity, _object} <- ActivityPub.like(actor, object, id, false) do
      {:ok, activity}
    else
      _e -> :error
    end
  end

  def handle_incoming(
        %{"type" => "Announce", "object" => object_id, "actor" => actor, "id" => id} = _data
      ) do
    with %User{} = actor <- User.get_or_fetch_by_ap_id(actor),
         {:ok, object} <-
           get_obj_helper(object_id) || ActivityPub.fetch_object_from_id(object_id),
         {:ok, activity, _object} <- ActivityPub.announce(actor, object, id, false) do
      {:ok, activity}
    else
      _e -> :error
    end
  end

  def handle_incoming(
        %{"type" => "Update", "object" => %{"type" => "Person"} = object, "actor" => actor_id} =
          data
      ) do
    with %User{ap_id: ^actor_id} = actor <- User.get_by_ap_id(object["id"]) do
      {:ok, new_user_data} = ActivityPub.user_data_from_user_object(object)

      banner = new_user_data[:info]["banner"]

      update_data =
        new_user_data
        |> Map.take([:name, :bio, :avatar])
        |> Map.put(:info, Map.merge(actor.info, %{"banner" => banner}))

      actor
      |> User.upgrade_changeset(update_data)
      |> User.update_and_set_cache()

      ActivityPub.update(%{
        local: false,
        to: data["to"] || [],
        cc: data["cc"] || [],
        object: object,
        actor: actor_id
      })
    else
      e ->
        Logger.error(e)
        :error
    end
  end

  # TODO: Make secure.
  def handle_incoming(
        %{"type" => "Delete", "object" => object_id, "actor" => actor, "id" => _id} = _data
      ) do
    object_id =
      case object_id do
        %{"id" => id} -> id
        id -> id
      end

    with %User{} = _actor <- User.get_or_fetch_by_ap_id(actor),
         {:ok, object} <-
           get_obj_helper(object_id) || ActivityPub.fetch_object_from_id(object_id),
         {:ok, activity} <- ActivityPub.delete(object, false) do
      {:ok, activity}
    else
      _e -> :error
    end
  end

  def handle_incoming(
        %{
          "type" => "Undo",
          "object" => %{"type" => "Announce", "object" => object_id},
          "actor" => actor,
          "id" => id
        } = data
      ) do
    with %User{} = actor <- User.get_or_fetch_by_ap_id(actor),
         {:ok, object} <-
           get_obj_helper(object_id) || ActivityPub.fetch_object_from_id(object_id),
         {:ok, activity, _, _} <- ActivityPub.unannounce(actor, object, id, false) do
      {:ok, activity}
    else
      e -> :error
    end
  end

  def handle_incoming(
        %{
          "type" => "Undo",
          "object" => %{"type" => "Follow", "object" => followed},
          "actor" => follower,
          "id" => id
        } = data
      ) do
    with %User{local: true} = followed = User.get_cached_by_ap_id(followed),
         %User{} = follower = User.get_or_fetch_by_ap_id(follower),
         {:ok, activity} <- ActivityPub.unfollow(follower, followed, id, false) do
      User.unfollow(follower, followed)
      {:ok, activity}
    else
      e -> :error
    end
  end

  def handle_incoming(
        %{"type" => "Block", "object" => blocked, "actor" => blocker, "id" => id} = data
      ) do
    with %User{local: true} = blocked = User.get_cached_by_ap_id(blocked),
         %User{} = blocker = User.get_or_fetch_by_ap_id(blocker),
         {:ok, activity} <- ActivityPub.block(blocker, blocked, id, false) do
      User.unfollow(blocker, blocked)
      User.block(blocker, blocked)
      {:ok, activity}
    else
      e -> :error
    end
  end

  def handle_incoming(
        %{
          "type" => "Undo",
          "object" => %{"type" => "Like", "object" => object_id},
          "actor" => actor,
          "id" => id
        } = data
      ) do
    with %User{} = actor <- User.get_or_fetch_by_ap_id(actor),
         {:ok, object} <-
           get_obj_helper(object_id) || ActivityPub.fetch_object_from_id(object_id),
         {:ok, activity, _, _} <- ActivityPub.unlike(actor, object, id, false) do
      {:ok, activity}
    else
      e -> :error
    end
  end

  # TODO
  # Accept

  def handle_incoming(_), do: :error

  def get_obj_helper(id) do
    if object = Object.get_by_ap_id(id), do: {:ok, object}, else: nil
  end

  def set_reply_to_uri(%{"inReplyTo" => inReplyTo} = object) do
    with false <- String.starts_with?(inReplyTo, "http"),
         {:ok, %{data: replied_to_object}} <- get_obj_helper(inReplyTo) do
      Map.put(object, "inReplyTo", replied_to_object["external_url"] || inReplyTo)
    else
      _e -> object
    end
  end

  def set_reply_to_uri(obj), do: obj

  # Prepares the object of an outgoing create activity.
  def prepare_object(object) do
    object
    |> set_sensitive
    |> add_hashtags
    |> add_mention_tags
    |> add_emoji_tags
    |> add_attributed_to
    |> prepare_attachments
    |> set_conversation
    |> set_reply_to_uri
  end

  #  @doc
  #  """
  #  internal -> Mastodon
  #  """

  def prepare_outgoing(%{"type" => "Create", "object" => %{"type" => "Note"} = object} = data) do
    object =
      object
      |> prepare_object

    data =
      data
      |> Map.put("object", object)
      |> Map.put("@context", "https://www.w3.org/ns/activitystreams")

    {:ok, data}
  end

  def prepare_outgoing(%{"type" => _type} = data) do
    data =
      data
      |> maybe_fix_object_url
      |> Map.put("@context", "https://www.w3.org/ns/activitystreams")

    {:ok, data}
  end

  def maybe_fix_object_url(data) do
    if is_binary(data["object"]) and not String.starts_with?(data["object"], "http") do
      case ActivityPub.fetch_object_from_id(data["object"]) do
        {:ok, relative_object} ->
          if relative_object.data["external_url"] do
            _data =
              data
              |> Map.put("object", relative_object.data["external_url"])
          else
            data
          end

        e ->
          Logger.error("Couldn't fetch #{data["object"]} #{inspect(e)}")
          data
      end
    else
      data
    end
  end

  def add_hashtags(object) do
    tags =
      (object["tag"] || [])
      |> Enum.map(fn tag ->
        %{
          "href" => Pleroma.Web.Endpoint.url() <> "/tags/#{tag}",
          "name" => "##{tag}",
          "type" => "Hashtag"
        }
      end)

    object
    |> Map.put("tag", tags)
  end

  def add_mention_tags(object) do
    recipients = object["to"] ++ (object["cc"] || [])

    mentions =
      recipients
      |> Enum.map(fn ap_id -> User.get_cached_by_ap_id(ap_id) end)
      |> Enum.filter(& &1)
      |> Enum.map(fn user ->
        %{"type" => "Mention", "href" => user.ap_id, "name" => "@#{user.nickname}"}
      end)

    tags = object["tag"] || []

    object
    |> Map.put("tag", tags ++ mentions)
  end

  # TODO: we should probably send mtime instead of unix epoch time for updated
  def add_emoji_tags(object) do
    tags = object["tag"] || []
    emoji = object["emoji"] || []

    out =
      emoji
      |> Enum.map(fn {name, url} ->
        %{
          "icon" => %{"url" => url, "type" => "Image"},
          "name" => ":" <> name <> ":",
          "type" => "Emoji",
          "updated" => "1970-01-01T00:00:00Z",
          "id" => url
        }
      end)

    object
    |> Map.put("tag", tags ++ out)
  end

  def set_conversation(object) do
    Map.put(object, "conversation", object["context"])
  end

  def set_sensitive(object) do
    tags = object["tag"] || []
    Map.put(object, "sensitive", "nsfw" in tags)
  end

  def add_attributed_to(object) do
    attributedTo = object["attributedTo"] || object["actor"]

    object
    |> Map.put("attributedTo", attributedTo)
  end

  def prepare_attachments(object) do
    attachments =
      (object["attachment"] || [])
      |> Enum.map(fn data ->
        [%{"mediaType" => media_type, "href" => href} | _] = data["url"]
        %{"url" => href, "mediaType" => media_type, "name" => data["name"], "type" => "Document"}
      end)

    object
    |> Map.put("attachment", attachments)
  end

  defp user_upgrade_task(user) do
    old_follower_address = User.ap_followers(user)

    q =
      from(
        u in User,
        where: ^old_follower_address in u.following,
        update: [
          set: [
            following:
              fragment(
                "array_replace(?,?,?)",
                u.following,
                ^old_follower_address,
                ^user.follower_address
              )
          ]
        ]
      )

    Repo.update_all(q, [])

    maybe_retire_websub(user.ap_id)

    # Only do this for recent activties, don't go through the whole db.
    # Only look at the last 1000 activities.
    since = (Repo.aggregate(Activity, :max, :id) || 0) - 1_000

    q =
      from(
        a in Activity,
        where: ^old_follower_address in a.recipients,
        where: a.id > ^since,
        update: [
          set: [
            recipients:
              fragment(
                "array_replace(?,?,?)",
                a.recipients,
                ^old_follower_address,
                ^user.follower_address
              )
          ]
        ]
      )

    Repo.update_all(q, [])
  end

  def upgrade_user_from_ap_id(ap_id, async \\ true) do
    with %User{local: false} = user <- User.get_by_ap_id(ap_id),
         {:ok, data} <- ActivityPub.fetch_and_prepare_user_from_ap_id(ap_id) do
      data =
        data
        |> Map.put(:info, Map.merge(user.info, data[:info]))

      already_ap = User.ap_enabled?(user)

      {:ok, user} =
        User.upgrade_changeset(user, data)
        |> Repo.update()

      if !already_ap do
        # This could potentially take a long time, do it in the background
        if async do
          Task.start(fn ->
            user_upgrade_task(user)
          end)
        else
          user_upgrade_task(user)
        end
      end

      {:ok, user}
    else
      e -> e
    end
  end

  def maybe_retire_websub(ap_id) do
    # some sanity checks
    if is_binary(ap_id) && String.length(ap_id) > 8 do
      q =
        from(
          ws in Pleroma.Web.Websub.WebsubClientSubscription,
          where: fragment("? like ?", ws.topic, ^"#{ap_id}%")
        )

      Repo.delete_all(q)
    end
  end

  def maybe_fix_user_url(data) do
    if is_map(data["url"]) do
      data = Map.put(data, "url", data["url"]["href"])
    end

    data
  end

  def maybe_fix_user_object(data) do
    data
    |> maybe_fix_user_url
  end
end