# Pleroma: A lightweight social networking server # Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/> # SPDX-License-Identifier: AGPL-3.0-only defmodule Pleroma.Pagination do @moduledoc """ Implements Mastodon-compatible pagination. """ import Ecto.Query import Ecto.Changeset alias Pleroma.Repo @default_limit 20 def fetch_paginated(query, params, type \\ :keyset) def fetch_paginated(query, params, :keyset) do options = cast_params(params) query |> paginate(options, :keyset) |> Repo.all() |> enforce_order(options) end def fetch_paginated(query, params, :offset) do options = cast_params(params) query |> paginate(options, :offset) |> Repo.all() end def paginate(query, options, method \\ :keyset) def paginate(query, options, :keyset) do query |> restrict(:min_id, options) |> restrict(:since_id, options) |> restrict(:max_id, options) |> restrict(:order, options) |> restrict(:limit, options) end def paginate(query, options, :offset) do query |> restrict(:offset, options) |> restrict(:limit, options) end defp cast_params(params) do param_types = %{ min_id: :string, since_id: :string, max_id: :string, offset: :integer, limit: :integer } params = Enum.reduce(params, %{}, fn {key, _value}, acc when is_atom(key) -> Map.drop(acc, [key]) {key, value}, acc -> Map.put(acc, key, value) end) changeset = cast({%{}, param_types}, params, Map.keys(param_types)) changeset.changes end defp restrict(query, :min_id, %{min_id: min_id}) do where(query, [q], q.id > ^min_id) end defp restrict(query, :since_id, %{since_id: since_id}) do where(query, [q], q.id > ^since_id) end defp restrict(query, :max_id, %{max_id: max_id}) do where(query, [q], q.id < ^max_id) end defp restrict(query, :order, %{min_id: _}) do order_by(query, [u], fragment("? asc nulls last", u.id)) end defp restrict(query, :order, _options) do order_by(query, [u], fragment("? desc nulls last", u.id)) end defp restrict(query, :offset, %{offset: offset}) do offset(query, ^offset) end defp restrict(query, :limit, options) do limit = Map.get(options, :limit, @default_limit) query |> limit(^limit) end defp restrict(query, _, _), do: query defp enforce_order(result, %{min_id: _}) do result |> Enum.reverse() end defp enforce_order(result, _), do: result end