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