forked from AkkomaGang/akkoma
e83ad12c57
Atom keys could also have been transformed to string, or the other way around but this one is more efficient and what we actually expect with the current param_types in Pagination
84 lines
1.8 KiB
Elixir
84 lines
1.8 KiB
Elixir
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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