mobilizon/lib/web/plugs/detect_locale_plug.ex

75 lines
2.2 KiB
Elixir

# Portions of this file are derived from Pleroma:
# Pleroma: A lightweight social networking server
# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
# NOTE: this module is based on https://github.com/smeevil/set_locale
defmodule Mobilizon.Web.Plugs.DetectLocalePlug do
@moduledoc """
Plug to set locale for Gettext
"""
import Plug.Conn, only: [get_req_header: 2, assign: 3]
alias Mobilizon.Web.Gettext, as: GettextBackend
@spec init(any()) :: any()
def init(_), do: nil
@spec call(Plug.Conn.t(), Keyword.t()) :: Plug.Conn.t()
def call(conn, _) do
locale = get_locale_from_header(conn)
assign(conn, :detected_locale, locale)
end
@spec get_locale_from_header(Plug.Conn.t()) :: String.t()
defp get_locale_from_header(conn) do
conn
|> extract_accept_language()
|> Enum.find(&supported_locale?/1)
end
@spec extract_accept_language(Plug.Conn.t()) :: list(String.t())
defp extract_accept_language(conn) do
case get_req_header(conn, "accept-language") do
[value | _] ->
value
|> String.split(",")
|> Enum.map(&parse_language_option/1)
|> Enum.sort(&(&1.quality > &2.quality))
|> Enum.map(& &1.tag)
|> Enum.reject(&is_nil/1)
|> ensure_language_fallbacks()
_ ->
[]
end
end
@spec supported_locale?(String.t()) :: boolean()
defp supported_locale?(locale) do
GettextBackend
|> Gettext.known_locales()
|> Enum.member?(locale)
end
@spec parse_language_option(String.t()) :: %{tag: String.t(), quality: float()}
defp parse_language_option(string) do
captures = Regex.named_captures(~r/^\s?(?<tag>[\w\-]+)(?:;q=(?<quality>[\d\.]+))?$/i, string)
quality =
case Float.parse(captures["quality"] || "1.0") do
{val, _} -> val
:error -> 1.0
end
%{tag: captures["tag"], quality: quality}
end
@spec ensure_language_fallbacks(list(String.t())) :: list(String.t())
defp ensure_language_fallbacks(tags) do
Enum.flat_map(tags, fn tag ->
[language | _] = String.split(tag, "-")
if Enum.member?(tags, language), do: [tag], else: [tag, language]
end)
end
end