defmodule Linear.Pagination do
  @moduledoc """
  Cursor-based auto-pagination for Linear GraphQL connections.

  Linear uses the Relay connection pattern with `nodes`, `pageInfo.hasNextPage`,
  and `pageInfo.endCursor`. This module handles following cursors automatically.
  """

  @spec paginate((String.t() | nil -> {:ok, map()} | {:error, term()})) :: {:ok, [map()]} | {:error, term()}
  def paginate(query_fn) do
    do_paginate(query_fn, nil, [])
  end

  defp do_paginate(query_fn, cursor, acc) do
    case query_fn.(cursor) do
      {:ok, %{"nodes" => nodes, "pageInfo" => page_info}} when is_list(nodes) ->
        updated = acc ++ nodes

        case page_info do
          %{"hasNextPage" => true, "endCursor" => next} when is_binary(next) and next != "" ->
            do_paginate(query_fn, next, updated)

          _ ->
            {:ok, updated}
        end

      {:ok, %{"nodes" => nodes}} when is_list(nodes) ->
        {:ok, acc ++ nodes}

      {:error, reason} ->
        {:error, reason}

      other ->
        {:error, {:unexpected_connection_shape, other}}
    end
  end
end