class UserSerializer < Pb::Serializer::Base
  message YourApp::User

  attribute :id
  attribute :name
  attribute :posts

  define_primary_loader :user do |subdeps, ids:, **|
    User.where(id: ids).preload(subdeps).map { |u| new(u) }
  end

  define_loader :posts, key: -> { id } do |user_ids, subdeps, **|
    PostSerializer.bulk_load(user_id: user_ids, with: subdeps).group_by { |s| s.post.user_id }
  end

  dependency :posts
  computed def post_count
    posts.count
  end
end

class PostSerializer < Pb::Serializer::Base
  message YourApp::Post

  define_primary_loader :post do |subdeps, user_ids:, **|
    Post.where(user_id: user_ids).preload(subdeps).map { |p| new(p) }
  end

  attribute :id
  attribute :title
  attribute :body
end

class UserGrpcService < YourApp::UserService::Service
  # @param req [YourApp::GetUserRequest]
  # @param call [GRPC::ActiveCall::SingleReqView]
  # @return [YourApp::User]
  def get_users(req, call)
    UserSerializer.bulk_load_and_serialize(ids: [req.user_id], with: req.field_mask)[0]
  end

  # @param req [YourApp::ListFriendUsersRequest]
  # @param call [GRPC::ActiveCall::SingleReqView]
  # @return [YourApp::ListFriendUsersResponse]
  def list_friend_users(req, call)
    current_user = User.find(current_user_id)
    YourApp::ListFriendUsersResponse.new(
      users: UserSerializer.bulk_load_and_serialize(ids: current_user.friend_ids, with: req.field_mask)
    )
  end
end

gem 'pb-serializer'