distraction.party/lib/pleroma/pagination.ex
Haelwenn (lanodan) Monnier e83ad12c57
pagination.ex: Drop atom keys in params
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
2019-03-28 17:18:59 +01:00

84 lines
1.8 KiB
Elixir

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) do
options = cast_params(params)
query
|> paginate(options)
|> Repo.all()
|> enforce_order(options)
end
def paginate(query, options) do
query
|> restrict(:min_id, options)
|> restrict(:since_id, options)
|> restrict(:max_id, options)
|> restrict(:order, options)
|> restrict(:limit, options)
end
defp cast_params(params) do
param_types = %{
min_id: :string,
since_id: :string,
max_id: :string,
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, :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