I’m trying to do a pagination for a list of “messages” on a calculated field, so my structure is more or like the following one:

Channel Resource

defmodule Organizations.Channel do
  use Ash.Resource,
    data_layer: AshPostgres.DataLayer,
    extensions: [
      AshGraphql.Resource
    ]

  require Ash.Query

  # Some other configs ...
 
  relationships do
    has_many :messages, Channels.ChannelMessage do
      private? true
      destination_attribute :channel_id
      api Channels
  end 

  actions do
    defaults [:create, :update, :destroy]

    # This one creates a PageOfChannels
    read :list do
      pagination countable: true,
                 required?: true,
                 offset?: true,
                 max_page_size: 10
    end

    read :read do
      primary? true
    end
  end

Channel Messages Resource

defmodule Channels.ChannelMessage do
  use Ash.Resource,
    data_layer: AshPostgres.DataLayer,
    extensions: [
      AshGraphql.Resource
    ]

  # Some other configs ...

  actions do
    # This creates a  PageOfChannelMessages
    read :list do
      pagination countable: true,
                 required?: true,
                 offset?: true,
                 max_page_size: 10,
                 default_limit: 10
    end

    read :read do
      primary? true
    end
  end
  
  relationships do
    belongs_to :channel, Channels.Channel do
      allow_nil? false
      primary_key? true
    end
  end

With that said, I want to access my ChannelMessages, from the Channel resource, so I added a calculation for it, but I also want to paginate them using the same Type and structure (in this case PageOfChannelMessages) to share entities on the UI side with ApolloClient

So I did:

calculations do
    calculate :channel_messages, {:array, ChannelMessageUnion}, fn record, %{api: api} ->
      record = api.load!(record, :messages)

      record.messages
      |> Enum.map(&%Ash.Union{type: ChannelMessageUnion.struct_to_name(&1), value: &1})
    end

But with this calculation, my channel_messages is just an array with all the messages or just a trimmed array if I limit it, so I don’t see how I can calculate as a PageOf type since those types are not accessible or I don’t know how, so with this in mind, my question would be can I reuse the actual pagination of AshGraphQL o should I cook my own pagination to be able to re-use it across all my app (calculation and lists)