# Pleroma: A lightweight social networking server
# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only

defmodule Pleroma.Object.Updater do
  require Pleroma.Constants

  def update_content_fields(orig_object_data, updated_object) do
    Pleroma.Constants.status_updatable_fields()
    |> Enum.reduce(
      %{data: orig_object_data, updated: false},
      fn field, %{data: data, updated: updated} ->
        updated = updated or Map.get(updated_object, field) != Map.get(orig_object_data, field)

        data =
          if Map.has_key?(updated_object, field) do
            Map.put(data, field, updated_object[field])
          else
            Map.drop(data, [field])
          end

        %{data: data, updated: updated}
      end
    )
  end

  def maybe_history(object) do
    with history <- Map.get(object, "formerRepresentations"),
         true <- is_map(history),
         "OrderedCollection" <- Map.get(history, "type"),
         true <- is_list(Map.get(history, "orderedItems")),
         true <- is_integer(Map.get(history, "totalItems")) do
      history
    else
      _ -> nil
    end
  end

  def history_for(object) do
    with history when not is_nil(history) <- maybe_history(object) do
      history
    else
      _ -> history_skeleton()
    end
  end

  defp history_skeleton do
    %{
      "type" => "OrderedCollection",
      "totalItems" => 0,
      "orderedItems" => []
    }
  end

  def maybe_update_history(
        updated_object,
        orig_object_data,
        opts
      ) do
    updated = opts[:updated]
    use_history_in_new_object? = opts[:use_history_in_new_object?]

    if not updated do
      %{updated_object: updated_object, used_history_in_new_object?: false}
    else
      # Put edit history
      # Note that we may have got the edit history by first fetching the object
      {new_history, used_history_in_new_object?} =
        with true <- use_history_in_new_object?,
             updated_history when not is_nil(updated_history) <- maybe_history(updated_object) do
          {updated_history, true}
        else
          _ ->
            history = history_for(orig_object_data)

            latest_history_item =
              orig_object_data
              |> Map.drop(["id", "formerRepresentations"])

            updated_history =
              history
              |> Map.put("orderedItems", [latest_history_item | history["orderedItems"]])
              |> Map.put("totalItems", history["totalItems"] + 1)

            {updated_history, false}
        end

      updated_object =
        updated_object
        |> Map.put("formerRepresentations", new_history)

      %{updated_object: updated_object, used_history_in_new_object?: used_history_in_new_object?}
    end
  end

  defp maybe_update_poll(to_be_updated, updated_object) do
    choice_key = fn data ->
      if Map.has_key?(data, "anyOf"), do: "anyOf", else: "oneOf"
    end

    with true <- to_be_updated["type"] == "Question",
         key <- choice_key.(updated_object),
         true <- key == choice_key.(to_be_updated),
         orig_choices <- to_be_updated[key] |> Enum.map(&Map.drop(&1, ["replies"])),
         new_choices <- updated_object[key] |> Enum.map(&Map.drop(&1, ["replies"])),
         true <- orig_choices == new_choices do
      # Choices are the same, but counts are different
      to_be_updated
      |> Map.put(key, updated_object[key])
    else
      # Choices (or vote type) have changed, do not allow this
      _ -> to_be_updated
    end
  end

  # This calculates the data to be sent as the object of an Update.
  # new_data's formerRepresentations is not considered.
  # formerRepresentations is added to the returned data.
  def make_update_object_data(original_data, new_data, date) do
    %{data: updated_data, updated: updated} =
      original_data
      |> update_content_fields(new_data)

    if not updated do
      updated_data
    else
      %{updated_object: updated_data} =
        updated_data
        |> maybe_update_history(original_data, updated: updated, use_history_in_new_object?: false)

      updated_data
      |> Map.put("updated", date)
    end
  end

  # This calculates the data of the new Object from an Update.
  # new_data's formerRepresentations is considered.
  def make_new_object_data_from_update_object(original_data, new_data) do
    %{data: updated_data, updated: updated} =
      original_data
      |> update_content_fields(new_data)

    %{updated_object: updated_data, used_history_in_new_object?: used_history_in_new_object?} =
      updated_data
      |> maybe_update_history(original_data, updated: updated, use_history_in_new_object?: false)

    updated_data =
      updated_data
      |> maybe_update_poll(new_data)

    %{
      updated_data: updated_data,
      updated: updated,
      used_history_in_new_object?: used_history_in_new_object?
    }
  end
end