feat: more complete i18n infrastructure

lib/bds/i18n.ex

@@ -0,0 +1,158 @@
+defmodule BDS.I18n do
+  @moduledoc false
+
+  @supported_languages [
+    %{code: "en", flag: "GB"},
+    %{code: "de", flag: "DE"},
+    %{code: "fr", flag: "FR"},
+    %{code: "it", flag: "IT"},
+    %{code: "es", flag: "ES"}
+  ]
+  @supported_language_codes Enum.map(@supported_languages, & &1.code)
+
+  @format_locales %{
+    "en" => "en-US",
+    "de" => "de-DE",
+    "fr" => "fr-FR",
+    "it" => "it-IT",
+    "es" => "es-ES"
+  }
+
+  @flag_emoji %{
+    "GB" => "🇬🇧",
+    "DE" => "🇩🇪",
+    "FR" => "🇫🇷",
+    "IT" => "🇮🇹",
+    "ES" => "🇪🇸"
+  }
+
+  @default_language "en"
+  @default_format_locale "en-US"
+  @locale_files Path.expand("../../priv/i18n/locales/*.json", __DIR__)
+                |> Path.wildcard()
+                |> Enum.sort()
+
+  for file <- @locale_files do
+    @external_resource file
+  end
+
+  @catalogs Enum.into(@locale_files, %{}, fn file ->
+              locale = file |> Path.basename(".json") |> String.downcase()
+              {locale, Jason.decode!(File.read!(file))}
+            end)
+
+  def supported_languages, do: @supported_languages
+
+  def default_language, do: @default_language
+
+  def normalize_language(language) do
+    language
+    |> normalize_locale_prefix()
+    |> case do
+      value when value in @supported_language_codes -> value
+      _other -> @default_language
+    end
+  end
+
+  def resolve_ui_locale(locale), do: resolve_supported_locale(locale) || @default_language
+
+  def current_ui_locale do
+    (System.get_env("LC_ALL") || System.get_env("LC_MESSAGES") || System.get_env("LANG"))
+    |> resolve_ui_locale()
+  end
+
+  def resolve_render_locale(language), do: resolve_supported_locale(language) || @default_language
+
+  def format_locale(language) do
+    language
+    |> resolve_supported_locale()
+    |> case do
+      nil -> @default_format_locale
+      locale -> Map.get(@format_locales, locale, @default_format_locale)
+    end
+  end
+
+  def locale_mapping(language) do
+    ui_locale = resolve_ui_locale(language)
+
+    %{
+      ui_locale: ui_locale,
+      format_locale: format_locale(ui_locale)
+    }
+  end
+
+  def get_render_translations(language) do
+    language
+    |> resolve_render_locale()
+    |> catalog_for_locale()
+  end
+
+  def get_ui_translations(locale) do
+    locale
+    |> resolve_ui_locale()
+    |> catalog_for_locale()
+  end
+
+  def translate(language, key) do
+    key = key |> to_string() |> String.trim()
+
+    case resolve_supported_locale(language) do
+      nil ->
+        Map.get(catalog_for_locale(@default_language), key, key)
+
+      locale ->
+        Map.get(catalog_for_locale(locale), key, key)
+    end
+  end
+
+  def translate_render(language, key), do: translate(language, key)
+  def translate_ui(locale, key), do: translate(locale, key)
+
+  def flag(language) do
+    language
+    |> resolve_supported_locale()
+    |> case do
+      nil -> @default_language
+      locale -> locale
+    end
+    |> flag_code()
+    |> then(&Map.get(@flag_emoji, &1, &1))
+  end
+
+  def flag_code(language) do
+    language
+    |> resolve_supported_locale()
+    |> case do
+      nil -> @default_language
+      locale -> locale
+    end
+    |> then(fn locale ->
+      @supported_languages
+      |> Enum.find(hd(@supported_languages), &(&1.code == locale))
+      |> Map.fetch!(:flag)
+    end)
+  end
+
+  defp resolve_supported_locale(language) do
+    language
+    |> normalize_locale_prefix()
+    |> case do
+      value when value in @supported_language_codes -> value
+      _other -> nil
+    end
+  end
+
+  defp normalize_locale_prefix(language) do
+    language
+    |> to_string()
+    |> String.trim()
+    |> String.replace("_", "-")
+    |> String.downcase()
+    |> String.split("-", parts: 2)
+    |> List.first()
+  end
+
+  defp catalog_for_locale(locale) do
+    Map.get(@catalogs, locale, Map.get(@catalogs, @default_language, %{}))
+  end
+end